Gastrointestinal Anatomy

Gastrointestinal Skeleton of the Abdomen The skeleton of the abdomen is represented in the adjacent figure. Starting from the from we have: xiphoid process X costal cartilages (ribs 7-10) tips of ribs 11 and 12 vertebrae L1-L5 iliac crests IC tubercle of the crest TC anterior superior iliac spine ASIS anterior inferior iliac spine AIIS inguinal ligament IL pubic tubercle PT pubic crest PC pubic symphysis PS the separation of the abdomen from the pelvis, the pelvic brim PB

The inguinal ligament extends from the anterior superior iliac spine ASIS to the pubic tubercle PT and is used as one of the lower borders of the abdomen. This ligament is really a turned under edge of the aponeurosis of the external abdominal oblique muscle. We will mention it again when we cover the inguinal region of the abdomen. The thoracic diaphragm separates the abdominal cavity from the thoracic cavity.

Abdominal Wall Surface Anatomy of the Abdomen • Before getting into the nitty gritty of the abdomen, keep in mind that you want to be able to use your knowledge to project the anatomy onto the surface of the abdomen. You will want to be able to visualize the relative positions of abdominal organs as they lie within the abdomen. Clinicians might use several different ways of subdividing the surface of the anterior abdominal wall but I will only present two of them here. By subdividing the surface into regions, one person can tell another person exactly where to look for possible problems.

The easiest is to separate the surface into 4 quadrants: upper left quadrant ULQ lower left quadrant LLQ upper right quadrant URQ lower right quadrant LRQ These quadrants are developed by dropping a vertical line down the middle of the sternum MSP and a horizontal line across and through the umbilicus TUP

The second way of dividing the abdominal surface is into 9 regions: left hypochondriac LH left lumbar LL left iliac LI epigastric E umbilical U hypogastric H right hypochondriac RH right lumbar RL right iliac RI These regions are formed by two vertical planes and two horizontal planes. The two vertical planes are the lateral lines LLL and RLL. These lines are dropped from a point half way between the jugular notch and the acromion process. The two horizontal planes are the transpyloric plane TPP and the transtubercular plane TTP. The tubercles are the tubercles of the iliac crests.

As a student of anatomy, it is sometimes fun to pretend that you are going to be a surgeon and are, at this point, considering entering the abdominal cavity to remove or reconstruct something in the abdominal cavity. It would helpful if you knew what makes up the wall of the abdomen so that you would be able to judge how deep you have gone with each knife cut. This brings us to the discussion of the abdominal wall. When considering the abdominal wall, you will need to know where, specifically it is that you want to enter.

Layers of the Abdominal Wall •

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The layers of the abdominal wall vary, depending on where it is you are looking. For instance, it is somewhat different along the lateral sides of the abdomen than it is at the anterior side. It is also somewhat different at its lower regions. Lets start out along the lateral side of the abdomen: skin superficial fascia deep fascia muscle subserous fascia peritoneum

At the lateral side of the abdomen (1) there is a dotted line passing through the abdominal wall. Note the layers a surgeons knife, a criminal knife or a anatomy student's knife must pass through to get to the peritoneal cavity: 1.skin 2.superficial fascia (this may be as thin as or less than a half inch or as thick as 6 inches or more) 3.deep fascia (all skeletal muscle is surrounded within its own deep fascia). The deep fascia of the abdominal wall is different than that found around muscles of the extremities, however. It is of the loose connective tissue variety. It is necessary in the abdominal wall because it offers more flexibility for a variety of functions of the abdomen. At certain points, this fascia may become aponeurotic and serve as attachments for the muscle to bone or to each other, as is the case at the linea alba. 4.subserous fascia also known at extraperitoneal fascia (a layer of loose connective tissue that serves as a glue to hold the peritoneum to the deep fascia of the abdominal wall or to the outer lining of the GI tract. It may receive different names depending on its location (i.e. transversalis fascia when it is deep to that muscle, psoas fascia when it is next to that muscles, iliac fascia, etc.) 5.peritoneum (a thin one cell thick membrane that lines the abdominal cavity and in certain places reflects inward to form a double layer of peritoneum) Double layers of peritoneum are called mesenteries, omenta, falciform ligaments, lienorenal ligament, etc.)

At the anterior wall of the abdomen, in the midline there is no muscle so a knife would only go through the: 1.skin 2.superficial fascia 3.deep fascia (in this case a thickened area of deep fascia called the linea alba) 4.subserous fascia 5.peritoneum

If we look at the wall inferior to the level of the belly button (umbilicus), you will see that the superficial fascia has become divided into to parts: a superficial fatty part that is continuous with the same layer over the rest of the body (Camper's fascia) a deep membranous layer that is continuous down into the perineum to surround the penis and to form a layer of the scrotum. (Scarpa's fascia)

As you examine the abdomen in thin subjects, you may be able to see the superficial veins that drain the abdominal wall. These veins drain into one of two major veins: subclavian (not shown) femoral (F) and also into a minor, but important vein, the paraumbilical vein PU. The paraumbilical vein drains into the portal vein and then through the liver. This is an important clinical connection. The lower abdominal wall is drained by way of the superficial epigastric SE and superficial circumflex iliac SCI veins into the femoral vein. The upper abdominal wall is drained by way of the thoracoepigastric TE and lateral thoracic LT veins into the subclavian.

Muscles of the Abdominal Wall • It is now time to consider the muscles that make up the anterior and anterolateral abdominal wall. There are 4 pairs of muscles to consider. We will remove layers carefully to see the deeper levels. As we go deeper through the layers, you should be aware of the cutaneous veins and nerves that travel in the layers.

The most superficial layer of anterolateral muscles are the: external abdominal obliques EAO Notice on the right side of the specimen that the lower part of the superficial fascia has been left behind so that you might see its two layers, the fatty layer (Camper's fascia) CF and the membranous layer (Scarpa's fascia) SF. Running through the fatty layer are the superficial veins, the superficial epigastric SE, the paraumbilical veins radiating out from the umbilicus and the thoracoepigastric vein TE. The cutaneous nerves to the abdomen are mainly continuations of the lower intercostal nerves (T7 - T12). An important level to remember is that the umbilical region is supplied by the 10th intercostal nerve. The lowermost part of the abdominal wall is supplied by a branch of L1, the iliohypogastric IH nerve. Its other branch is the ilioinguinal II nerve. You should also identify the linea alba LA. This white line is where the aponeuroses of the external abdominal oblique, internal abdominal oblique, and transverse abdominis muscles converge at the midsagittal part of the abdominal wall.

In the image, the left external abdominal oblique has been cut away at the white dotted line and removed in order to show the internal abdominal oblique IAO. You can also see lower cut edge of the external abdominal oblique at the inguinal ligament IL The anterior wall of the rectus sheath RS has also been removed on the right side in order to see the underlying right rectus abdominis RA muscle. Note that the rectus abdominis muscle is subdivided into small sections by so called tendinous inscriptions TI. This arrangement is what forms the wash-board abs in well-exercised people. We will discuss the formation of the rectus sheath in a moment. You may also see a small muscle overlying the inferior end of the rectus abdominis muscle, the pyramidalis muscle PY. This small muscles tenses the lower part of the linea alba.

In this specimen, the rectus abdominis muscle, internal abdominal oblique and anterior rectus sheath have been removed. You can identify the posterior rectus sheath and its lower free margin, the arcuate line AL. What you see below this line is the transversalis fascia and running in the fascia is the inferior epigastric artery IEA, a branch of the external iliac artery. This artery enters the rectus sheath posterior to the rectus abdominis muscle and supplies the anterior abdominal wall. Extending from the top, is a branch of the internal thoracic (or mammary) artery, the superior epigastric artery. Also note that the cutaneous nerves are found to lie between the internal abdominal oblique and the transversus abdominis muscles.

Makeup of the Rectus Sheath at Different Levels • The rectus sheath consists of two lamina, the anterior sheath and the posterior sheath. The sheath is made up of the aponeuroses of the three anterolateral abdominal muscles (external abdominal oblique, internal abdominal oblique and the transversus abdominis) as they converge at the linea alba. The makeup of the anterior and posterior sheaths vary depending on the level of the abdominal wall you examine.

The three levels that we will examine are: above the costal margins there is only an anterior sheath made up of the aponeurotic fibers of the external abdominal oblique EAO between the costal margin and the arcuate line anterior sheath is made up of a combination of the aponeurosis of the external abdominal oblique EAO and the internal abdominal oblique IAO. posterior sheath is made up of a combination of the aponeuroses of the internal abdominal oblique IAO and the transversus abdominis muscles TA. Notice that the aponeurosis of the internal abdominal oblique splits around the two sides of the rectus abdominis muscle. below the arcuate line the anterior sheath is made up of the aponeuroses of all three abdominal muscles EAO, IAO, and TA. there is no posterior sheath below the arcuate line. The transversalis fascia makes up the posterior aspect of the rectus abdominis muscle.

Inguinal Region, Spermatic Cord and Testis • Start examining the inguinal region by identifying the external oblique aponeurosis which forms the anterior boundary to the canal. In the first image, identify the external abdominal oblique muscle EAO and its aponeurosis. Notice that the lower margin of the external oblique forms the inguinal ligament IL. There is a weakness in the aponeurosis of the external oblique called the superficial inguinal ring SIR and is shown as a white dotted line. The superficial ring has a medial crus (or superior)MC and a lateral crus (or inferior)LC. Passing through the superficial ring are the spermatic cord SC and the ilioinguinal nerve IIN which is a branch of L1 nerve.

In the second image, the external oblique has been removed and you see the internal abdominal oblique IAO. Notice the cut margin of the external oblique at the inguinal ligament IL. Note that some of the fibers of the internal oblique continue down and around the spermatic cord to become the creamasteric layer of the spermatic cord. These muscle fibers perform an important reflex called the cremasteric reflex, a test performed in most routine physical exams in males.

In the third image, the internal oblique has been removed and you see the transversus abdominis muscle TA. If you look just below the lower fibers of the tranversus abdominis you will see the spermatic cord SC as it passes through the deep inguinal ring DIR. Identify the ilioinguinal nerve as it runs deep to the inguinal ligament. Notice that it does not enter the inguinal canal along with the spermatic cord. The deep inguinal ring is nothing more than a thickening of the transversalis fascia at the point where the structures that make up the spermatic cord converge.

Cremasteric reflex. A reflex is a reaction to some kind of stimulus (stroke, pin prick, etc.). A stimulus is picked up by sensory (afferent) nerves and carried to the spinal cord (central nervous system) where it forms a synapse with motor (efferent) neurons that pass out to a muscle to perform an action. In the case of the cremasteric reflex, the afferent limb of the reflex is by way of the genitofemoral nerve and the efferent limb is by way genitofemoral fibers to the cremasteric muscle. The result is that by stroking the skin on the medial side of the thigh next to the scrotum, the scrotum is pulled up on that side. The spinal cord segments involved are L1 - L2.

Three layers of the spermatic cord are picked up from three layers of the abdominal wall: 1)internal spermatic fascia, 2)cremaster muscle and fascia, and 3)external spermatic fascia. As the structures within the spermatic cord pass through the transversalis fascia they pick up one of the layers of the spermatic cord, the internal spermatic fascia. As it continues through the canal, it picks up the cremasteric layer of muscle and fascia from the internal oblique muscle and finally, when it passes through the superficial ring, it picks up an external spermatic fascia layer, derived from the aponeurosis of the external oblique. Surgeons utilize their knowledge of these layers in the repair of inguinal hernias. Notice the conjoined tendon (or falx inguinalis) X superior to and behind the spermatic cord SC.

As a final exercise, you should learn the walls of the inguinal canal. anterior wall laterally - muscles fibers of the external oblique medially - aponeurosis of the external oblique most medially there is not wall but instead there is a deficiency called the superficial inguinal ring. superior -- arching fibers of the internal oblique and sometimes transverse abdominis. These fibers start anterior and lateral, pass over the spermatic cord and the medially forms part of the posterior wall of the canal. posterior -- lateral the posterior wall is deficient at the deep inguinal ring. Medially the posterior wall is made up of the fused aponeuroses of the internal oblique and transverse abdominis, called the conjoined tendon X. inferior (or floor) -- inguinal ligament. Medially, some of the fibers of the inguinal ligament curve under the spermatic cord and fasten into the pectineal line of the pubis, this is the lacunar ligament which forms part of the floor of the inguinal canal.

Once you know where the inguinal region is and what makes up its boundaries and contents, you might want to know what inguinal hernias are. A hernia is a protrusion of part of the intestinal tract, greater omentum or just fat through a weakened part of the abdominal wall. In our case, we are talking about a weakness in the inguinal region of the abdominal wall. There are two weakened parts of the lower abdominal wall in the inguinal region: 1)at the deep inguinal ring and 2)at the conjoined tendon. There are two types of inguinal hernias: 1)indirect and 2)direct. When a hernia occurs at the deep inguinal ring, it is called an indirect inguinal hernia. This type of hernia will carry all the same layers as the spermatic cord and if foreceful enough will end showing through the superficial inguinal ring. This type of hernia is definitively diagnosed at surgery by being lateral to the inferior epigastric artery. When a hernia occurs at the conjoined tendon, it is called a direct inguinal hernia. If the force and weakness is great enough, the herniated material will also appear through the superficial ring, but it will not carry all of the layers that the spermatic cord has. At surgery it is definitively diagnosed as direct by being medial to the inferior epigastric artery.

After the spermatic cord traverses the inguinal canal, it leads into the scrotum and to the testes. In order to free the testes and its coverings from the scrotum, the remains of the embryonic gubernaculum testis has to be cut. At this point the testes can be withdrawn from the scrotum. What you see is the outer side of a closed sac called the tunica vaginalis. This must be cut in order to view the parts of the testis.

Once the tunica has been opened, identify the: parietal layer of the tunica vaginalis ptv visceral layer of the tunical vaginalis vtv head of the epididymus h body of the epididymus b tail of the epididymus t sinus of epididymis s appendix epididymis ae testis ductus (vas) deferens dd The anterior border of the testis is to your right. Hydrocele is a condition in which fluid collects in the space c of the tunica vaginalis

Spermatic Cord • If you examine a cross sectional area of the spermatic cord, you will see the following layers: • external spermatic fascia • cremasteric muscle and fascia • genitofemoral nerve gfn • internal spermatic fascia • ductus deferens dd • lymph vessels lv • pampiniform plexus of veins ppv. These veins will become the testicular vein. • testicular artery

The anterior surface of the spermatic cord is toward the top. During physical examination, the ductus deferens can be felt as a rope-like cord. Surgeons who perform vasectomies can roll the spermatic cord over the pubic bone so that they know exactly where make their incisions.

Peritoneum and Peritoneal Reflections • The best way to try to visualize the peritoneum and its reflections is to examine sagittal and cross sections through the abdomen. After looking at images of these sections, students who have a cadaver available can then follow the road map that I will be giving as a way to classify various organs in the abdominal cavity before actually displaying them.

First, we will take a look at a sagittal section through the abdomen just to the right of the midline of the body. The parietal peritoneum is colored bright blue and the visceral peritoneum is colored magenta.

After cutting through the abdominal wall, if you put your hand under the wall, you will be touching parietal peritoneum. If you start by putting your finger as high as possible 1, then run it along the inner aspect of the abdominal wall 2 until you reflect onto the superior surface of the urinary bladder 3, then over the uterus in the female 4, then down into the pouch of Douglas 5, again in the female, up along the anterior surface of the rectum onto the posterior abdominal wall 6 until you reach the root of the mesentery of the small intestine. From here you follow the mesentery of the small intestine 7 going around its coils until you reach the other side of the mesentery back down to the posterior abdominal wall where you will cross over the horizontal part of the duodenum 8. Your finger will then travel along the inferior aspect of the gastrocolic ligament 9, down the posterior surface of the greater omentum (go) to its lower border and back up along its anterior surface 11. Your finger then passes over the anterior surface of the stomach 12, along the anterior lamina of the lesser omentum 13. At this time you probably couldn't continue the trip because you would have to enter the epiploic foramen (ef) to enter the lesser peritoneal cavity (lpc) where visceral peritoneum lines this space anteriorly and parietal peritoneum posteriorly.

Second, we will take a look at a couple of cross sections taken through the abdomen: 1)one through the level of the liver, stomach and spleen and 2)another through a lower level. These levels are shown at A and B on the sagittal section above.

Again, start at 1 and follow around the peritoneal cavity. Once on the back of the abdomen, 2 you will reflect onto the anterior surface of the right kidney, pass through the epiploic foramen, along the posterior wall of the lesser peritoneal cavity, 3 then up along the renal lienal ligament 4 onto the posterior surface of the stomach 5. Your finger will continue through the epiploic foramen again to turn around the free margin of the lesser omentum 6, then over the anterior surface of the stomach again 7. Continue to follow around the greater curvature of the stomach 8 until you reflect again along the gastrolienal ligament 9. Your finger will now pass around the spleen, onto the left kidney to the parietal peritoneum and back to the falciform ligament fl.

In the second cross section, start out anteriorly in the abdomen 1. Trace around to the posterior abdominal wall until you reach the lateral paracolic gutter 2, over the anterior surface of the ascending colon ac, down into the medial paracolic gutter 3then onto the large vesselsvessels posterior abdomen. Over the front of the vessels, your finger will travel along the right part of the mesentery of the small intestine 4. You then travel around the coils of the small intestine until you reach the posterior abdominal wall again 5. Continue along the left side, over the descending colon dc and finally, up to the anterior part of the abdominal wall.

In the above discussion, you followed the peritoneal lining of the abdominal cavity in two different directions and classified organs and specialities of the periperitoneum along the way. The peritoneal cavity is a closed cavity made up of a thin, one-cellthick serous membrane. The word serous denotes that this membrane can produce fluid;slidinghe intestinal tract is highly moveable within the abdominal cavity, there is a need to have some lubrication between the sliding surfaces and this is produced by the peritoneum. On the other hand infections and other pathologies might result in an overproduction of fluid, which is not what one would like. There are certain pathological conditions that produce extra fluid in the peritoneal cavity and this results in what is called ascites.

The peritoneum has the following properties: 1.it becomes double in certain areas. This double layer of peritoneum is given different names: mesentery, ligament, fold, or omentum. 2.as already mentioned, it lines the abdominal cavity 3.it almost completely surrounds some parts of the intestinal tract. These parts are called intraperitoneal structures. 4.it only covers the anterior part of some structures. These structures are called retroperitoneal. Retroperitoneal structures include: urinary system, ascending colon, descending colon, horizontal part of duodenum, pancreas (except for its tail). 5.it produces a covering around some of the intestines. The covering is called its serous coat. 6.peritoneal folds are usually caused by underlying blood vessels, ducts or embryonic remnants.

General Inspection of the Abdominal Cavity and its Contents • This image shows the peritoneum following the removal of the abdominal wall. When the abdominal wall aw is removed, what you have remaining is the transversalis fascia covering the peritoneum. It is thicker and fatty in some areas and it contains some of the blood vessels supplying the anterior abdominal wall (i.e., the inferior epigastric artery iea in this case).

After the peritoneum is opened, identify the major organs as they lie within the abdominal cavity. In this dissection, the lower part of the peritoneum has been reflected downward in order to display the peritoneal folds in this region: lateral peritoneal fold lpf produced by the inferior epigastric artery. medial peritoneal fold mpf produced by the the embryonic umbilical arteries median peritoneal fold mepf produced by the closed embryonic urachus which arose from the apex of the urinary bladder in the embryo.

You will frequently read that the peritoneal folds are called ligaments. In this case, only the folds formed by leftover embryonic structures are named ligaments. The embryonic urachus is the median umbilical ligament and the embryonic umbilical arteries are the lateral umbilical ligament.

Structures that should be identified at this stage are: .liver in the upper right quadrant of the cavity. It is separated into right rlli and left llli lobes by the falciform ligament fl. .the tip of the gall bladder gb hanging down under the margin of the liver .stomach st in the upper left quadrant .a small edge of the spleen sp in the upper left quadrant .greater omentum go covering most of the abdominal structures .small intestines (ileum) il in the lower right quadrant .sometimes the transverse colon tc can be seen through a thin portion of the greater omentum.

The free margin of the falciform ligament fl contains the remnant of the embryonic umbilical vein, now called the ligamentum teres (round ligament) lt of the liver. The paraumbilical veins run along either side of the ligament and empty into the portal vein, a clinically important connection discussed later. At this point, you might want to take a tour of the abdominal cavity by following the peritoneum around and identifying structures as you go. Take a look at this page and follow the instructions. It would be nice if this could be done at the cadaver, but not everyone has that opportunity so you have to imagine what is going on.

When the greater omentum is pulled up and to the right side, you can see more of the small intestine si. Most of this small intestine is jejunum. The transverse colon tc is attached to the under side of the greater omentum and can also be seen.

By pulling the small intestine from the left side of the abdomen up and to the right, you can see the structures under it. The descending colon dc, a piece of the sigmoid colon sc and the upper part of the rectum rec. You can also see the root of the mesentery of the small intestine dotted line.

Summary of Ligaments attached to the Umbilicus •

The falciform ligament is a double fold of peritoneum which extends from the umbilicus to the antero-superior surface of the liver. In its free edge, you will see that it contains a cord-like structure which passes to the inferior border of the liver. This is the round ligament of the liver, which is formed by the remains of the left umbilical vein of the fetus. Running adjacent to the ligament are small veins the connect the paraumbilical veins around the umbilicus to the portal vein. On the deep surface of the lower abdominal wall, note that there are three cord-like structures seen through the peritoneum and extending upwards towards the umbilicus. These are the median umbilical ligament (or median umbilical fold), and the lateral umbilical ligaments (or medial umbilical folds). The median umbilical ligament extends from the tip of the bladder to the umbilicus and is the remains of the fetal urachus. The lateral umbilical ligaments arise from the pelvis as a continuation of the internal iliac artery and extend to the umbilicus. These are the obliterated parts of the fetal umbilical arteries that carried blood from the fetus back to the placenta of the mother.

Reflections of the Peritoneum • On the adjacent sagittal section of the body, you can identify the following parts of the peritoneum and its reflections. The parietal peritoneum is colored greenish blue and the visceral peritoneum is dark purple. Just imagine that you have a cadaver available. Insert your fingers between the diaphragm d and the top of the liver and push until you are stopped by a reflection of the peritoneum from the diaphragm onto the diaphragmatic surface of the liver. This reflection forms the superior limb of the coronary ligament cl. If you could push your fingers up behind the liver, you would encounter another reflection, this would be the inferior part of the coronary ligament. The two superior parts come forward and unite to become continuous with the falciform ligament.

If you continue to move your fingers along the diaphragmatic surface of the liver to its lower border and then onto the visceral surface of the organ, your fingers will be directed towards the lesser curvature of the stomach. This layer is the lesser omentum lo and extends from the visceral surface of the liver (specifically the porta hepatis region of the liver) to the lesser curvature of the stomach and then over the anterior surface of the stomach. The lesser omentum has a free margin near the gall bladder and behind this margin is the epiploic foramen ef which connects the greater peritoneal sac to the lesser peritoneal sac ls which is also known as the omental bursa. If you place your fingers within the epiploic foramen and grasp the free margin of the lesser omentum, you will feel several structures: bile duct, hepatic artery and portal vein. We will talk about these later. If you place your fingers superiorly, you will feel the caudate lobe of the liver. If you feel posterior, you will feel the inferior vena cava and if you feel inferiorly, you will touch the first part of the duodenum.

You should constantly look at enough cross sections so that you feel comfortable with them. Remember that your left is the cross section's right since you are looking upwards towards the body. In this image, you can identify some of the peritoneal ligaments that you couldn't see on the sagittal section above. Identify the: .falciform ligament FL .lienorenal ligament LR .gastrolienal ligament GL .lesser omentum LO Also, identify the epiploic foramen EF and the relationships of the lesser sac LS (or omental bursa).

Here is a summary of the all of the various names used to describe different parts of the peritoneal reflections: 1. coronary ligament .superior border .inferior border .right triangular ligament - from liver to right kidney .left triangular ligament 2. falciform ligament - from anterior abdominal wall to liver ligamentum teres - in free margin of the falciform ligament paraumbilical veins 3. lesser omentum - extends from liver to lesser curvature of stomach and first part of duodenum .hepatogastric part - from liver to lesser curvature of stomach .hepatoduodenal part - free margin of lesser omentum from liver to first .part of duodenum .portal vein .bile duct .proper hepatic artery

4. greater omentum .gastrocolic part - from greater curvature of stomach to point where transverse colon attaches to the back side of the greater omentum .gastrosplenic part - from greater curvature of stomach to spleen .gastrophrenic part - from the fundus of the stomach to the diaphragm 5. transverse mesocolon - from transverse colon to posterior abdominal wall 6. mesentery of the small intestinee - from jejunum and ileum to the root of the mesentery on the posterior wall of the abdominal cavity. The root extends obliquely across the posterior abdominal wall from the beginning of the jejunum to the end of the ileum at the cecum. 7. lienalrenal ligament - double layer of peritoneum extending from the spleen to the anterior surface of the left kidney 8. sigmoid mesocolon - from sigmoid colon to posterior abdominal wall over the psoas muscle 9. mesoappendix - from base of appendix to its apex

The Oesophagus -is a narrow muscular tube, forming the food passage between the pharynx and stomach. -It extends from the lower part of the neck to the upper part of the abdomen. -The oesophagus is 25cm(10inches) long. -The tube is flatened anteroposteriorly, and the lumen is kept collapsed;it dialtes only during the passage of food bolus. -The pharyngooesophageal junction is the narrowest part of the alimentary canal except for the vermiform appendix.

. The oesophagus begins in the neck at the lower border of the cricoid cartilage where is is continuation with the lower end of the pharynx. -It descends in front of the vertebral column through the superior and posterior part of the mediastinum,and pierces the diaphragm at the level of vertebra T1o. -It ends by opening into the stomach( cardiac end) at the level of vertebraeT11.

CURVATURES In general, the oesophagus is vertical,but shows slight curvatures in two sides-both in left side. -one is at the root of the neck and the other near the lower end. Constrictions Normally, the oesophagus shows 4 constriction at the following levels 1.At its beginning ( 6 inches from the incisor teeth) 2.Where it is crossed by the aortic arch(9 inches from the incisor teeth) 3.Where it is crossed by the left bronchus(11inches from the incisor teeth) 4.Where it pierces the diaphragm(15 inches from the incisor teeth)

Relations of the thoracic part of the oesophagus A.Anterior:a. trachea b.right pulmonary artery c. left bronchus d. pericardium with left atrium e.diaphragm B.Posteriorly:a.vertebral column b.right posterior intercostal arteries,c. thoracic duct, d.. azygos vein with the terminal parts of the hemiazygos vein. E. thoracic aorta ,f. right pleural recess ,g.diaphragm.

C.To the right:a. right lung and pleura,b.azygos vein, c. the right vagus D.To the left:a. thoracic duct,b. left subclavian artery.c.aortic arch ,d. left lung and left pleura ,e. left recurrent laryngeal nerve,all in the superior mediatinum. In posterior medistinum it os related to1.the descending thoracic aorta ,2.the left lung and pleura. Abdominal part of oesophagus -- is only about half an inch long. --Enters the abdomen through the oesophageal opening of the diaphragm situated at the level of vertebraeT10,slightly situated at the left of the median plane.

The opening also transmits the anterior and posterior gastric nerves, oesophageal branches of the left gastric artery artery and accompanying veins. -The oesophagus runs downward and to the left in front of the crus of the diaphragm and of the left inferior phrenic artery.Anteriorly, it lies in agroove on the posterior surface of the left lobe of the liver, and ends by openieng into the cardiac end of the stomach at the level of T11, about an inch to the left median plane.Its right border is continous with the lesser curvature of the stomach, but the left border is seperated from the fundus of the stomach by the cardiac notch. Peritoneum covers the oesophagus only anteriorly and on the left side.

Blood supply 1.The cervical part ( including the segment up to the arch of aorta) is supplied by the inferior thyroid arteries. 2. The thoracic part is supplied by the oesophageal branches of the aorta. 3. The abdominal part is supplied by the oesophageal branches of the left gastric artery.

Venous drainage -Upper part of oesophagus— brachiocephalic veins. .Middle part of oesophagus—azygos vein .Lower part of oesophagus—left gastric vein. Lymphatic Drainage . Cervical part----deep cervical nodes. .Thoracic part---posterior mediastinal nodes. .Abdominal part—left gastric nodes.

Nerve supply of the oesophagus. A. Parasympathetic nerves---upper half of the oesophagus—recurrent laryngeal nerve. --lower half of the oesophagus plexus formed mainly by the two vagi.parasympathetic nerves are sensory, motor, and secretomotor to the oesophagus. B.Sympathetic nerves---upper half of the oesophagus ---middle cervical ganglion Lower half of the oesophagus—directly upper thoracic ganglia.They are vasomotor.

Applied Anatomy 1.oesophageal varices. 2.The normal constrictions should be kept in mind during oesophagoscopy. 3.Achalasia 4.Tracheo-oesophageal fistula 5.Mediastinal syndrome--- dysphagia 6.Lower end is the commonest site of oesophageal carcinoma.

Dr. ARUN KUMAR GUPTA MBBS, MD(2ND Year) Department of Respiratory Medicine, MCZU.

The Stomach • In the living and in the upright posture, the stomach is usually J-shaped. The lowest part of the body can even extend into the greater pelvis. The pylorus lies at the level of the lower border of of the body of the L1 vertebra. • When partially distended—piriform inshape. • Obese person---horizontal – steerhorn stomach

Size • The stomach is a very distensible organ. It is about 10 inch long , and the mean capacity is 30ml at birth,1000ml at puberty at and 1500ml—2000ml or more in adults.

The parts of the stomach that you should identify are: • connection to the esophagus E • cardiac notch CN • fundus F • body B • angular notch AN • pyloric antrum Py • area of pyloric sphincter PS • 1st part of the duodenum D • lesser curvature LC • greater curvature GC

Inside Structures of the Stomach • When the stomach is opened, you can identify these structures: • esophagus coming into the stomach • cardiac notch • fundus • body • gastric folds or rugae • angular notch • pylorus of stomach • pyloric sphincter • first part of the duodenum

Relations of stomach A.Peritoneal relations .The stomach is lined by peritoneum on both its surface.At the lesser curvature the layers of peritoneum lining the anterior and posterior surfaces meet and become continous with the lesser omentum. .Along the greater part of the greater curvature the two layers meet to form the greater omentum.Near the cardiac end of the greater curvature the two layers meet to form the gastrosplenic ligament. .Near the cardiac end of the peritoneum on the posterior surface is reflected on to the diaphragm as the gatrophrenic ligament. .Cranial to this ligament a small part of the posterior surface of the stomach is in direct contact with the diaphragm. This is the bare area of the stomach.

B.Visceral relations .The anterior surface of the stomach is related to the liver, diaphragm and the anterior abdominal wall. .The diaphragm seperates the stomach from the left pleura,the pericardium,and 6th to 9th ribs. .The costal cartilages are seperated from the stomach by the transversus abdominis. .The posterior surface of the stomach is related to the structures forming bed ,all of which are seperated from the stomach by the cavity of the lesser sac.

Arteries of the Stomach • The arteries that supply the stomach are branches of the celiac trunk or artery. This is the first unpaired branch of the abdominal aorta, arising just after the aorta passes behind the diaphragm. The branches of the celiac artery are three: • left gastric • splenic • common hepatic

The branches to the stomach arise from the above: celiac C left gastric LG - supplies the lesser curvature of the stomach and lower esophagus esophageal E splenic S which gives rise to: short gastric SG - supplies area of the fundus left gastroepiploic LGE - supplies the left part of greater curvature of the stomach common hepatic CH gastroduodenal GD right gastric RG - supplies right side of lesser curvature of the stomach right gastroepiploic RGE - supplies the right part of the greater curvature of the stomach

Venous Drainage of the Stomach • The stomach drains either directly or indirectly into the portal vein as follows: • short gastric veins SGfrom the fundus to the splenic vein S • left gastroepiploic LGE along greater curvature to superior mesenteric vein SM • right gastroepiploic RGE from the right end of greater curvature to superior mesenteric vein SM • left gastric vein LG from the lesser curvature of the stomach to the portal vein PV • right gastric vein RG from the lesser curvature of the stomach to the portal vein PV

Lymphatic Drainage • All of the lymphatic vessels drain into nodes scattered along the arteries and named accordingly. The final group of nodes that receive lymph from the stomach is the preaortic (celiac) nodes located around the celiac trunk as it arises from the abdominal aorta.

Nerve supply of stomach • The stomach is supplied by both the parasympathetic and sympatethic parts of the autonomic nervous system. • parasympathetic – preganglionic from right (posterior vagal trunk) and left (anterior vagal trunk) vagus nerves. – postganglionic neurons are very short and lie within the wall of the stomach.

• sympathetic – preganglionic fibers mainly from the thoracic splanchnic nerves. – postganglionic arise in the ganglia of the celiac plexus

The direction of lymph flow and the position of the major lymph nodes are essential in understanding the possible spread of malignancy from the stomach.

Functions 1.The stomach acts primarly as a reservoir of food. 2.By its peritaltic movements it softens and mixes the food with the gastric juice. 3.The gastric glands produce the gastric juice which contains enzymes that play an important role in digestion of food. 4.The gastric glands also produce HCL which destroys many organisms present in food and drink. 5. The lining cells of the stomach produce abundant mucous which protects the gastric mucosa against the corrosive action of HCL. 6.Some substances are absorbed in the stomach.

Applied Anatomy 1.Gastric pain is felt in the epigastrium becz. The stomach is supplied from segmentsT6 toT10 of the spinal cord,which alos supply the upper part of the abdominal wall.Pain is produced either by spasm of muscle, or by overdistension. 2.The interior of the stomach can be visualized by taking a skiagram after giving a barium meal.It can also be examined directly with the use of a gastroscope,which can be passed into the stomach through the mouth.

Duodenum • The duodenum, into which the stomach opens, is about 25 cm long, C-shaped and begins at the pyloric sphincter. It is almost entirely retroperitoneal and is the most fixed part of the small intestine.

The duodenum is described as having four parts: 1. Part one, superior part (SD) 2. Part two, descending part (DD) 3. Part three, horizontal part (HD) 4. part four, ascending part (AD) The fourth part of the duodenum terminates at the duodenojejunal flexure DJF with the jejunum. The ligament of Treitz is a musculofibrous band that extends from the upper aspect of the ascending part of the duodenum to the right crus of the diaphragm and tissue around the celiac artery.

As you can see, the head of the pancreas sits in the Cshaped duodenum, so as long as we are here, we may as well point out the structures here: .head of the pancreas PH .uncinate process of the head of the pancreas PUP .neck of the pancreas PN where the superior mesenteric artery and vein pass behind the pancreas .body of the pancreas PB .tail of the pancreas PT. This part is within peritoneum and abuts the spleen The other structures in the area are the: .inferior vena cava IVC .portal vein PV .aorta aorta .celiac trunk C .kidneys

Part one, superior part (SD) A. Peritoneal Relations

1.The proximal 1 inch is movable. It is attached to the lesser omentum above,and to the gretaer omentum below. 2. The distal 1 inch is fixed. It is retroperitoneal. It is covered with peritoneum only on its anterior aspect. B.Visceral relations: 1.Anteriorly: quadrate lobe of liver,and gall bladder. 2.posteriorly:gastroduodenal artery, bile duct and portal vein. 3.Superiorly: epiploic foramen. 4.inferiorly: head of and the neck of the pancreas.

Part two, descending part (DD) .this is about three inches long. .It begins at the superior duodenal flexure, passes downwards to reach the lower border of the third lumbar vertebra,where is curves towards the left( at the inferior duodenal flexure) to become continuous with the third part.its relations are as follows: A.Peritoneal relations .It is retroperitoneal and fixed, its anterior surface is covered with peritoneum, except near the middle,where it is directly related to the colon. B.Visceral relations: 1.Anteriorly:(a)right lobe the liver; (b) transverse colon;© root of the transverse mesocolon; (d) small intestine. 2. Posteriorly:(a) anterior surface of the right kidney near the medial border; (b) right renal vessels; © right edge of the inferior vena cava;(d) right psoas major. 3.Medially: (a) head of the pancreas;and (b) the bile duct. 4.Laterally: right colic flexure. The interior of the second part of the duodenum shows the following special features. 1. The major duodenal papilla is an elevation present posteromedially,8 to 10 cm distal to the pylorus. The hapatopancreatic ampulla opens at the summit of the papilla. 2.the minor duodenalpapilla is present 6 to 8 cm distal to the pylorus,and presents the opening of the accessory pancreaticduct.

Third part of the duodenum This part is about four inches long. -it begins at the inferior duodenal flexure,on the right side of the lower border of the third lumber vertebra. - it passes alomost horizontally and slightly upwards in front of the inferior vena cava,and ends by joining the fourth part infront of the abdominal aorta. -Its relations are as follows: A.Peritoneal relations .It is retroperitoneal and fixed .its anterior surface is covered with peritoneum,except in the median plane,where it is crossed by the superior mesenteric vessels and by the root of the mesentery. B.Visceral relations 1.Anteriorly: (a) superior mesenteric vessels;and (b) root of mesentery. 2.posteriorly:(a) right ureter,(b) right psoas major,© right testicular or ovarian vessles; (d) inferior vena cava (e) abdominal aorta with origin of inferior mesenteric artery. 3. Superiorly: head of the pancreas with uncinate process. 4. Inferiorly: coils of jejunum

Fourth part of the duodenum This part is one inch long . It runs upwards on or immediately to the cleft of the aorta,up to the upper border of the second lumbar vertebra,where it turns frowards to become continuous with the jejunum at the duodenojejunal flexure.its relation are as follows: A.Peritoneal relations It is mostly retroperitoneal, and covered with peritoneum only by anteriorly.The terminal part is suspended by the uppermost part of the mesentery,and is mobile. B.visceral relations 1.Anteriorly: (a) transverse colon;(b)transverse mesocolon; © lesser sac; and (d) stomach 2. Posteriorly:(a) left sympathetic chain. (b) left psoas major;© left renal veeels(d) left testicular vessels(e) inferior mesenteric vein. 3. To the right: Attachment of the upper part of the root of the mesentery. 4.to the left:(a) left kidneys; and (b) left ureter 5.superiorly:Body of pancreas.

Suspensory muscle of duodenum ( ligament of treitz) This is afibromuscular band which suspends and supports the duodeno-jejunal flexure. It arises from the right crus of the diaphragm, close to the right side of the oesophagus, passes downwards behind the pancreas,and is attached to the posterior surface of the duodenojejunal flexure and the third parts of the duodenum. .It is made up of:(a) striped muscle fibres in its upper part; (b) elastic fibres in its middle part;and © plain muscle fibres in its lower part. .Normally its contraction increases the angle of the duodeno-jejunal flexure. Sometimes it is attached only to the flexure,and then its contraction may narrow the angle of the flexure, causing partial obstruction of the gut.

Blood Supply of the Duodenum • • • •

superior pancreaticoduodenal anterior and posterior branches inferior pancreaticoduodenal anterior and posterior branches Most duodenal ulcers occur within 5 cm of the pylorus and most frequently on the anterior wall.

Venous Drainage .The veins of the duodenum drain into the splenic, superior mesenteric and portal veins. Lymphatic drainage .Most of the lymph vessles from the duodenum end in the pancreaticoduodenal nodes present along the inside of the curve of the duodenum.From here the lymph passes partly to the hepatic nodes,and through them to the coeliac npdes;and partly to the superior mesenteric nodes. .Some vessels drain into the hepatic nodes directly. .All the lymph reaching the hepatic nodes drains into the coeliac nodes.

Nerve supply .Sympathetic nerves from the spinal segments T9 TO 10, and parasympathetic nerves from the vagus, pass through the coeliac plexus and reach the duodenum along its arteries.

Applied anatomy 1. In skiagrams taken after giving a barium meal, the first part of the duodenum is seen as a triangular shadow called the duodenal cap. 2.The first part of the duodenum is one of the commonest sites for peptic ulcer, possibly becz. Of direct exposure of this part to the acidic contents reaching it from the stomach. 3.Duodenal diverticula are fairly frequent.They are seen along its concave border, generally at points where arteries enter the duodenal wall. 4.Congenital stenosis and obstruction of the second part of the duodenum may occur at the site of the opening of the bile duct.Other causes of obstruction are(I) an annular pancreas;(ii)Pressure by the superior mesenteric artery; or (iii)contraction of the suspensory muscle of the duodenum.

The duodenum, jejunum and ileum make up the small intestine. We have already discussed the duodenum.

Jejunum and Ileum

• The jejunum and ileum is slung from the posterior abdominal wall by the mesentery of the small intestines and, therefore, is extremely mobile. The mesentery of the small intestine arises from the root of the mesentery which extends from the duodenojejunal flexure to the ileocecal junction. • The jejunum is about 2.5m (8ft) long and passes imperceptibly into the ileum, which is about 4m (12ft) long. this part of the small intestine occupies a central position in the abdominal cavity, below the liver and the stomach, and behind the transverse mesocolon, the transverse colon and the greater omentum. The lowest coils of the intestine lie in the pelvic cavity. The purple dotted line in the lower image is an arbitrary line that can be used to separate the jejunum which is to the upward left of the line and the ileum which is to the downward and right of the line.

Blood Supply to Ileum and Jejunum • The ileum and jejunum are supplied by the superior mesenteric artery and its intestinal branches. The branches are rather special in that small arcades are formed and from the arcades, the straight vessels, vasa recta arise and supply the intestine. These straight vessels are end arteries and if they should be occluded, the part of the intestine supplied by them will die. One way to tell the ileum from the jejunum, other than by general location, is that there are more layers of arcades before the vasa recta are given off, in the ileum.

Lymphatic drainage .Lymph from lacteals drain into plexuses in the wall of the gut.From there it passese into lymphatic vessels in the mesentery and along the superior mesentery artery .Drains into nodes present infront of the aorta at the origin of the superior mesenteric artery.

Large Intestine • The large intestine extends from the ileocecal junction to the anus and is about 1.5m long. On the surface, you can identify bands of longitudinal muscle fibers called taeniae coli, each about 5mm wide. There are three bands and they start at the base of the appendix and extend from the cecum to the rectum. Along the sides of the taeniae, you will find tags of peritoneum filled with fat, called epiploic appendages (or appendices epiploicae). The sacculations, called haustra, are characteristic features of the large intestine, and distinguish it from the rest of the intestinal tract.

The large intestine consists of the following parts: 1. cecum 2. ascending colon 3. transverse colon 4. descending colon 5. sigmoid colon 6. rectum Not seen in diagram. 7. anal canal Not seen in diagram. 8. anus Not seen in diagram.

There are two flexures associated with the colon: 1. right colic flexure or hepatic flexure 2. left colic flexure or splenic flexure

Caecum a large blind sac forming the commencement of the large intestine. -it is situated in the right iliac fossa, above the lateral half of the inguinal ligament. -it communicates superiorly with the ascending colon,medially at the level of the caecocolic junction with the ileum,and posteromedially with the appendix. - it is 6cm long and 7.5 cm broad. -it is one of those organs of the body that have greater width than the length.(another example is the prostate.)

Relations A.Anterior- coils of the intestine and anterior abdominal wall B.posterior- right psoas and iliacus, genitofemoral,femoral and lateral cutaneous nerve of the thigh( all of the right side) vessels: testicular or ovarian, and often the external iliac( of the right side),and the appendix in the retrocaecal recess.

Types .the

caecum and appendix develop from the caecal bud arising from the postarterial segment of the midgut loop. The proximal part of the bud dilates to from the caecum. .the distal part remains narrow to form the apex of the caecum. However,due to rapid growth of the lateral wall of the caecum, attachment of the appendix shifts medially. Developmental arrest in the shift of the appendix forms the basis of the types of caeca. 1.conical type(13%),where the appendix arises from the apex of the caecum. 2.intermediate type(9%) where the right and left caecal pouches are equal in size,and the appendix arises from a depression between them. 3.ampullary type(78%),where the right caecal pouch is much larger than the left,and the appendix arises from the medial side.

Vessels and nerves .the arterial supply of the caecum is derived from the caecal branches of the ileocolic artery. .The veins drain into the superior mesenteric vein. .the nerve supply is same as that of the midgut( sympathetic,T11to L1; parasympathetic,vagus

Ileocaecal valve .The lower end of the ileum opens on the posteromedial aspect of the caeco-colic junction. The ileocaecal opening is guarded by the ileocaecal valve. Structure The valve has two lips and two f renula. (1)The upper lip is horizontal and lies at the ileocolic junction. (2) The lower lip is longer and concave,and lies at the ileocaecal junction. The two frenula are formed by the fusion of the lips at the ends of the aperture.these are the left and right frenula.the left end of the aperture is rounded;and the right end narrow and pointed.

Control and mechanism 1.The valve is actively closed by sympathetic nerves,which causes tonic contraction of the ileocaecal sphincter. 2. It is mechnically closed by distension of the caecum.

Functions 1. It prevents reflux from caecum to ileum. 2. It regulates the passage of ileal contents into the caecum,and prevents them from passing too quickly.

Ascending colon .IT is about 5 inches long and extends from the caecum to the inferior surface of the right lobe of the liver.. Here,it bends to the left to form the right colic flexure.usually it is retroperiotoneal. Anteriorly, it is related to the coils of small intestine, the right edge of the greater omentum,and the anterior abdominal wall. Posteriorly,it is related to the iliacus, the iliolumbar ligament,the quadratus lumborum,the transversus abdominis,the diaphragm at the tip of the last rib; the lateral cutaneous nerve,ilio-inguinal and ilio-hypogastric nerves;the iliac branches of the iliolumbar vessels, the fourth lumbar artery; and the right kidney.

Right colic flexure(hepatic flexure) .This flexure lies at the junction of the ascending colon and transverse colon. Here,the colon bends forwards,downwards and to the left. .The flexure lies on the lower part of the right kidney. .Anterosuperiorly,it is related to the colic impresssion on the inferior surface of the right lobe of the liver.

Transverse colon • .IT is about 20 inches long and extend across the abdomen from the right colic flexure to the left colic flexure . .Actually it is not transverse,but hangs down as aloop to avariable extent,sometimes reaching the pelvis. .It is suspended by the transverse mesocolon,and has a wide range of mobility. Anteriorly,it is related to the greater omentum and to the anterior abdominal wall.Posteriorly,it is related to the second part of the duodenum,the head of the pancreas,and to coils of small intestine.

Left colic flexure(splenic flexure) • .This flexure lies at the junction of the transverse colon and the descending colon.here,the colon bends downwards and backwards. .the flexure lies on the lower part of the left kidney and diaphragm,behind the stomach,and below the anterior end of the spleen .the flexure is attached to the 11th rib by a horizontal fold if peritoneum,called the phrenico colic ligament. . The ligament supports the spleen and forms a partial upper limit of the left paracolic gutter.

Descending colon • .It is about 10 inches long and extend from the left colic flexure to the sigmoid colon. .It runs vertically up to the iliac crest,and then inclines medially on the iliacus and psoas major to reach the pelvic brim,where its continous with the sigmoid colon. The descending colon is narrower than the ascending colon.usually,it is retroperitoneal. .Anteriorly,it is related to the coils of small intestine.Posteriorly,it is related to the transversus abdominis,the quadratus lumborum,the iliacus and psoas muscles;the ilio0hypogastrc,ilio-inguinal,lateral cutaneous,femoral and genitofemoral nerves, iliac branches of the ilio lumbar vessels,and the testicular and external iliac vessels.

Sigmoid colon( pelvic colon) • .It is about 15 inches long,and extends from the pelvic brim to the third piece of the sacrum, where it becomes the rectum. .IT Forms a sinous loop,and hangs down in the pelvic over and uterus. .Ocassionaly ,it is very short,and takes a straight course. .It is suspended by the sigmoid mesocolon and is covered by the coils of small intestine.

vermifomAppendix • -worm like diverticulum arising from the posteromedial wall of the caecum,about 2 cm below the ileocaecal orrifice. Dimensions Length-2-20cm( 1-9inch) width- 9cm .It is longer in children than in adults. Diameter- 5mm positions—clockwise position. Appendicular Orrifice 1. It is situated on the posteromedial aspect of the caecum 2cm below the ileocaecal orifice. 2. The appendicular orrifice is occasionally guraded by an indistinct semilunar fold of mucous membrane,known as valve of gerlach. 3. The orifice is marked on the surface by a point situated 2 cm below the junction of the transtubercular and right lateral planes.

Peritoneal relations • -suspended by a small , trangular fold of a peritoneum – mesoappendix or appendicular mesentery Blood supply .appendicular artery—lower division of ileocolic artery. Nerve supply—sympathetic nerves T9to T10 ,Parasympathetic from vagus lympahtic drainage .directly into ileocolic nodes,,,,appendicular nodes. Applied anatomy .appendicitis .MC Burneys point

Arterial Supply of the Colon • • •

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The colon is supplied by branches of the superior mesenteric and inferior mesenteric arteries. Superior mesenteric artery ileocolic artery – superior branch that joins the right colic – cecal branch – appendicular branch – ileal branch right colic artery – descending branch to join the superior branch of the ileocolic – ascending branch that joins the right branch of the middle colic middle colic artery – right branch – left branch that joins with the ascending branch of the left colic artery Inferior mesenteric artery left colic – ascending branch that joins the middle colic – descending branch that joins the highest sigmoid branch sigmoid arteries (2-3) – superior sigmoid branch join the left colic – inferior sigmoid branch joins the superior rectal superior rectal artery - not shown in the image

Venous Drainage of the Gastrointestinal Tract • The venous drainage of the gastrointestinal tract, from the lower esophagus to the upper rectum is by way of the portal venous system. This system also drains the spleen and pancreas.

• • • • • • •

The portal vein is usually described as being formed by the splenic and superior mesenteric veins. The inferior mesenteric vein then joins the splenic vein. However, there are variations to this pattern and might exist. Two of these are that the inferior mesenteric vein may join at the junction of the splenic with the superior mesenteric or the inferior mesenteric veins may join the superior mesenteric vein before it merges with the splenic. Identify the: superior rectal vein inferior mesenteric vein splenic vein superior mesenteric vein esophageal veins left gastric vein portal vein

The numbered stars represent the areas where the portal venous system anastomoses with the caval venous system and are clinically important in portal or caval hypertension. 1. esophageal plexus - caval drainage into azygos veins, portal drainage into the left gastric vein 2. rectal plexus - caval drainage into middle and inferior rectal veins and then into the pudendal and internal iliac veins back to inferior vena cava, portal drainage into the superior rectal, the inferior mesenteric and the splenic 3. paraumbilical veins - caval drainage downward to the superficial inferior epigastri c vein to the femoral vein, to the external iliac, to the inferior vena cava, upward to the thoracoepigastric vein, the lateral thoracic vein, subclavian vein, superior vena cava, portal drainage through the paraumbilical vein to the portal vein.

Clinical Consideration •

Portal obstruction. In cases of liver disease where the portal blood can no longer pass through the liver, the blood will try to get back to the heart any way it can and this usually involves the superior or inferior venae cavae. One possible cause of liver disease is chronic alcoholism. When the liver becomes impassable, it will pass backwards through the portal vein into the left gastric, paraumbilical or superior rectal. At each of these sites, the veins become enlarged and will result in other clinical signs and symptoms. In case of the esophageal plexus (*1), esophageal varices will develop and massive hemorrhage may occur resulting in death. In case of the rectal plexus (*2), hemorrhoids occur, resulting in pain and bleeding. In case of the paraumbilical veins (*3), visible signs of venous enlargement and tortuosity occur on the abdomen and these are referred to the caput medusae. Caval blockage. In cases where tumors or other pathologies compress the vena cava, the blood will utilize the above connections to return blood to the heart but this time through the caval system.

The rectum and Anal canal •

.The rectum is the distal part of the large gut. .It is placed between the sigmoid colon above and the anal canal below. .Distension of the rectum causes the desire to defaecate. .The rectum in man is not straight as the name implies.infact it is curved in an anteroposterior direction and also from side. .The rectum is situtated in the posterior part of the lesser pelvis,infront of the lower three pieces of tha sacrum and the coccyx. IT begins as acontinuation of the sigmoid colon at the level of vertebra S3. .The rectosigmoid junction is indicated by the lower end of the sigmoid mesocolon. The rectum ends by becoming contionous with the anal canal at the anorectal junction. .THE junction lies 2 to 3 cm in front of and a little below the tip of the coccyx. .The rectum is 12 cm(5inch) long.in the upper part it has the same diameter(4cm) as that of the sigmoid colon,but in the lower part is dilated to form the rectal ampulla.

Course and direction • 1.In its course,the rectum runs first downwards and backwards,then downwards,and finally downwards and forwards. 2. The beginning and the end of the rectum lie in the median plane,but it shows two types of curvatures in its course. A.Two anteroposterior curve(1) the sacral flexure of the rectum follows the concavity of the sacrum and coccyx; and (2) the perineal flexure of the rectum is the backward bend at the anorectal junction. B. Three lateral curves:(1) the upper lateral curve is convex to the right;(2) the middle lateral curve is convex to the left and is most prominent; and (3) the lower lateral curve is convex to the right

Relations A.Peritoneal realtions • (1) The upper one third of the rectum is covered with the peritoneum in front and on the sides. (2) the middle one third is covered only infront; (3) the lower one third,which is dialted to form the ampulla is devoid of peritoneum,and lies below the rectovesical pouch in male and below the rectouterine pouch in females. . The distance between the anus and the floor of the pouch is 7.5 cm in males but only 5.5 cm in females.

B.visceral relations •

a.Anteriorly in males:(1) the upper two thirds of the rectum are related to the rectovesical pouch( with coils of intestine and sigmoid colon),(2) the lower one third of the rectum is related base of the urinary bladder,the terminal parts of the ureters,the seminal vesicles, the deferent ducts and the prostate. Anteriorly in females:(1) the upper two thirds of the rectum are related to the rectouterine pouch( with coils of intestine and sigmoid colon). The pouch seperates the rectum from the uterus,and form the upper part of the vagina.(2) the lower one third of the rectum is related to the lower part of the vagina. B. Posteriorly- the relations are same in the male and female.they are (1) lower 3 pieces of the sacrum,the coccyx and the anococcygeal ligament.(2) piriformis,the coccygeus and the levator ani; (3) the median sacral,the superior rectal and the lower lateral sacral vessels. (4) the sympathetic chain with the ganglion impar;the anterior primary rami of S3.4,5.col,and the pelvic splanchnic nerves; lymph nodes, lymphatics and fat.

Mucosal folds • . The mucous membrane of an empty rectum shows two types of folds, longitudinal and transverse. A. THE longitudinal folds are transitory. They are present in the lower part of an empty rectum,and are obliterated by diatension. B. the transverse of horizontal folds( houston’s valves or plicae trans versales) are permanent and most marked when the rectum is distended.(1) the upper fold lies near the upper end of the rectum,and projects from the right or the left wall. Sometimes it may encircle and partially constrict the lumen.(2) the middle fold ( largest and most constants) lies at the upper end of the rectal ampulla,and projects from the anterior and right walls.(3) the lowest fold( inconstant) lies 2.5 cm below the middle fold,and projects from the left wall.(4) sometimes a fourth fold may be present on the left wall 2.5 cm above the middle fold.

Functional parts of the rectum • According to some authorities, the rectum has two functional parts. The upper part( related to the peritoneum) develops from the hindgut and lies above the middle of fold of the rectum. It acts as faecal reservoir which can freely distended anteriorly. The lower part ( devoid of peritoneum) develops from the cloca and lies below the middle fold. It is empty in normal individuals,but may contain faeces in cases of chronic constipation, or after death.being sensitive causes the desire to defaecate. However, according to other authorities the sigmoid colon is the faecal reservoir and the whole of the rectum is empty in normal individuals,being sensitive to distension,therefore, causes the desire to dafaecate.

ARTERIAL SUPPLY • 1.Superior rectal artery---chief artery of the rectum,,continuation of the inferior mesenteric artery. 2. Middle rectal artery– anterior division of the internal iliac artery 3. Median sacral artery.– arising from the back of the aorta. Venous drainage 1. Superior rectal vein 2. Middle rectal vein—open into the internal iliac veins. lymphatic drainage 1. Lymphatics from more than the upper half of the rectum pass along the superior rectal vessels to the inferior mesenteric nodes after passing through the pararectal and sigmoid nodes. 2. Lymphatics from the lower half of the rectum pass along the middle rectal vessels to the internal iliac nodes.

Nerve supply • The rectum is supplied by both sympathetic(L1,2) and parasympathetic(S2,3,4) nerves through the superior rectal( inferior mesenteric) and inferior hypogastric plexuses. Sympathetic nerves are vasoconstrictor, inhibitory to the rectal musculature and motor to the internal sphincter.Parasympathetic nerves are motor to the musculature of the rectum and inhibitory sphincter.Sensations of distension of the rectum pass through the parasympathetic nerves,while pain sensations are carried by both the sympathetic and parasympathetic.

Supports of rectum • 1. Pelvic floor 2. Fascia of walder– it attaches the lower part of the rectal ampulla to the sacrum. It is formed by condensation of the pelvic fascia behind the rectum.it encloses the superior rectal vessels and lymphatics. 3. Lateral ligaments of the rectum– they are formed by condensation of the pelvic fascia on the each side of the rectum. They enclose the middle rectal vessels, and branches of the pelvic plexuses,and attach the rectum to the posterolateral walls of the lesser pelvis. 4. Rectovesical fascia( of denovilliers). It extends from the rectum behind to the seminal vesicles and prostate in front. 5. The pelvic peritoneum and the related vascular pedicles also help in keeping the rectum in position.

Applied anatomy • 1. Digital examination per rectum(PR) In a normal person, the following structures can be palpated by a finger passed per rectum A. In males: • (1) posterior surface of the prostate; • (2) seminal vesicles; and vasa deferentia B.In females: • (1) perineal body; • (2) cervix;and • (3) occasionally the ovaries C.In both sexes: • (1) anorectal ring; • (2) coccyx and sacrum;and • (3) ischiorectal fosaae and ischial spines. 2. Proctoscopy and sigmoidoscopy. 3.Prolapse of recrum.

ANAL CANAL • The anal canal is the terminal part of the large intestine. .It is situated below the level of the pelvic diaphragm. It lies in the perineum ( anal triangle) in between the right and left ischiorectal fossae. .The anal canal is 3.8 cm long.it extends from the anorectal junction to the anus. .It is directed downwards and backwards.the anal canal is surrounded by sphincters which keep the lumen closed in the form of an anteroposterior. .the anorectal junction is marked by the forward convexity of the perineal flexure of the rectum and lies 2-3 cm infront of and slightly below the tip of the coccyx. .the anus is the surafce opening of the analcanal,situated about 4 cm below and infront of the tip of the coccyx in the cleft between the buttocks. .The surrounding skin is pigmented and thrown into radiating folds,and contains a ring of large apocrine glands.

Relations of the anal canal • .Anteriorly.(a) in both sexes: perineal body.(b) in males: membraneous urethra and bulb of the penis.© in females: lower end of vagina. B. Posteriorly.(1) Anococcygeal ligament; and (2) tip of the coccyx. C. Laterally. Ischiorectal fossa. Interior of the anal canal The interior of the anal canal shows many important features and can be divided into three parts.;(A ） The upper [art,about 15mm long;(B)the middle part,about 15mm long and ©the lower part 8 mm long.Each part is lined by a characteristic epithelium and reacts diffferently to various diseases of this region.

Upper part ( mucous) • This part is about 15mm long. It is lined by mucous membrane,and if of ectodermal origin.the mucous membrane shows 6 to 10 vertical folds: folds are called the anal columns( of moragagni). The lower ennds of the anal columns are united to each other by short transverse folds of mucous membrane: these are called the anal valves.Above each valve there is depression( in mucosa) which is called anal sinus. The anal valves together form atransverse line that all round the anal canal. This is pectinate line. Occasionally,the anal valves show epithelial projections called anal papillae.

Middle part( transitional zone or pecten) • .the next 15mm or so of the anal canal is alos lined by mucous membrane,but anal columns are not present here. The mucosa has a bliush appearance of dense venous plexus that lies between it and the muscle coat. The mucosa is less mobile than in the uper part of the anal canal. This region is referred to as the pecten or transitional zone. The lower limit of the pecten often has a whitish appearance because of which it is referred to as the white line( of hilton)

Lower part( cutaneous) • .IT is about 8 mm lomg and is lined by true skin containing sweat and sebaceous glands. The epithellium lining the upper 15 mm of the canal is columnar; that lining the middle part( pecten) is stratified squamous,but is distinguished from the skin in that there are no sebaceous or sweat glands,or hair, in relation to it. The epithellium of the lowest part resembles that of true skin in which sebaceous and sweat glands are present.

Musculature of the anal canal • A.Anal sphincters 1. the internal anal sphincter is involuntary in nature. It is formed by the thickend circular muscle coat of this part of the gut.it surrrounds the upper three fourths(30mm) of the anal canal extending from the upper end of the anal canal to the white line of hilton. 2.The external anal sphincter is under voluntary control. It is made up of striated muscle and is suppled by inferior rectal nerve and the perineal branch of the fourth sacral nerve.it surrounds the whole length of the anal canal and has three parts,subcutaneous,superficial and deep. The subcuatneous part lies below the the level of the internal sphincter and surrounds the lower part of the anal canal.

.it is in the form of a flat band about 15mm broad. It has no bony attachement.the superficial part is elliptical in shape and arises from the posterior surtace of the terminal segment of the coccyx as the anococcygeal ligament. The fibres surround the lower part of the internal sphincter and are inserted into the perineal body. The deep part surround the upper part of the internal sphincter and is fused with the puborectalis. It arises from the anoccygeal ligamnet,and is inserted into the perineal body where the fibres decussate and become continous with those of the superficial tranaverse perineal muscles.

B.Conjoint longitudinal coat. • It is formed by fusion of the puborectalis with the longitudinal muscle coat of the rectum at the anorectal junction. It lies between the external and internal sphincters. When traced downwards it becomes fibroelastic and at the level of the white line it breaks up into a number of fibroelastic septa which spread fanwise, pierce the subcuqatneous part of the external sphincter,and are attached to the skin around the anus.The most lateral of these septa forms the perianal fascia. The most medial septum forms,the anal intermuscular septum,which is attached to the white line. In addition, some strands pass obliquely through the internal sphincter and end in the submucosa below the anal canal valves.

C.Anorectal ring • .This is a muscular ring present at the anorectal junction. It is formed by the fusion of the puborectalis,deep external sphincter and the internal sphincter.it is easily felt by a finger in the anal canal.Surgical division of this ring results in rectal incontinence. The ring is less marked anteriorly where the fibres of the puborectalis are absent.

D.Surgical spaces related to the anal canal • 1.The ischiorectal space lies on each side of the anal canal. 2. the perineal space surrounds the anal canal below the white line. It contains the subcutaneous external sphincter rectal ,the external rectal venous plexus,and the terminal branches of the inferior rectal vessels and nerves.Pus in this space tends to spread to the anal canal at the white line or to the surface of the perianal skin rather than to the ischiorectal space. 3. The submucous space of the canal lies above the white line between the mocous membrane and the internal sphincter. It contains the internal rectal venous plexus and lymphatics

Liver • The liver is the largest gland of the body. It normally weighs about 1.5kg. The sharp inferior border of the liver does not normally extend below the right costal margin. If it does, it is enlarged. In order to free the liver for study, you must cut the falciform ligament, superior and inferior parts of the coronary ligament, the right and left triangular ligaments, the lesser omentum and the structures in its free margin (common bile duct, proper hepatic artery and portal vein) and the hepatic veins at the point where they empty into the inferior vena cava.

This is an anterior view of the liver. You should identify the: •right lobe •cut edge of the falciform ligament •left lobe •diverging cut edges of the superior part of the coronary ligament •fundus of the gall bladder

This an image of the visceral surface of the liver. Make sure you can orient yourself properly. Check out to see where the fundus of the gall bladder is located. Identify the following structures: .right lobe .fundus of the gall bladder .cystic duct .portal vein .hepatic arteries .common bile duct .quadrate lobe .ligamentum teres .left lobe .ligamentum venosum and its groove .caudate lobe .groove for the inferior vena cava and the cut hepatic veins within it .porta hepatis outline in yellow. The area where the arteries, ducts and portal vein enter and leave the liver.

Finally we take a look at the superior aspect of the liver. This part of the liver is separated from the heart by the domes of the diaphragm. In this image, the anterior (diaphragmatic) surface of the liver is upward and the visceral surface is downward on the page. This aspect allows you to identify the: .right lobe .cut edge of the falciform ligament .the cut edges of the superior and inferior parts of the coronary ligament .the left triangular ligament .the right triangular ligament .bare area of the liver (where there is no peritoneum covering the liver .groove for the inferior vena cava and the hepatic einvs .caudate lobe of the liver more or less wrapping around the groove of the inferior vena cava

Separation of the four lobes of the liver: •right sagittal fossa - groove for inferior vena cava and gall bladder •left sagittal fissure contains the ligamentum venosum and round ligament of liver •transverse fissure (also porta hepatis) - bile ducts, portal vein, hepatic arteries Relationship of the visceral aspect of the liver to other abdominal viscera.

Biliary System • The biliary system is made up of the ducts arising in the liver, the gall bladder and its duct and the common bile duct. Starting in the liver, the small biliary ducts converge to form the larger right and left hepatic ducts. These, in turn, join to form the common hepatic duct which joins with the cystic duct to form the common bile duct. Remember, when we studied the duodenum, that the common bile duct joins the major pancreatic duct to empty into the ampulla which then empties into the second part (descending part) of the duodenum. The gall bladder receives bile from the liver by way of the common hepatic duct into the cystic duct. The gall bladder stores and concentrates its contents and also excretes its bile back through the cystic duct to join the common hepatic duct to become the common bile duct which then carries the bile into the duodenum. The location of the tip of the fundus can be approximated on the surface of the abdomen at the point where the lateral edge of the rectus abdominis crosses the cartilage of the 9th rib.

.Clinical Considerations Cirrhosis of the liver is the result of atrophy of the liver parenchyma and a hypertrophy of the connective tissue. Over time, there will be jaundice and portal hypertension. .Jaundice is an accumulation of bile pigment in the blood stream. This is frequently a result of obstruction of the duct system. .The liver is frequently a site for secondary metastasis of cancer from almost any part of the body because of its great vascularity.

List of Items to Know • Liver • • • • • •

•

right lobe left lobe quadrate lobe caudate lobe falciform ligament – ligamentum teres of liver coronary ligament – right triangular ligament – left triangular ligament porta hepatis – common hepatic duct – portal vein – proper hepatic artery • left hepatic • right hepatic – cystic – gall bladder • fundus • cystic duct – ligamentum venosum or groove for the ligament

Celiac Trunk .common hepatic artery .proper hepatic artery .left hepatic .right hepatic .cystic artery

Pancreas • The pancreas has two functions: • 1. digestive - produces digestive enzymes • 2. hormonal - islets of Langerhans produce insulin needed to control blood sugar levels

Parts and relations 1. Head .lies within the curve of the duodenum .uncinate process is a prolongation of the head. The superior mesenteric artery and vein crosses this process. 2. uncinate process .the part of the head that wraps behind the superior mesenteric artery and vein and comes to lie adjacent to the ascending part of the duodenum. 3. Neck .a constricted portion to the left of the head. It abuts the pylorus above and the beginning of the portal vein behind. 4. Body .anterior surface separated from the stomach by the omental bursa .posteriorly related to the aorta, splenic vein, left kidney and renal vessels, left suprarenal, origin of superior mesenteric artery and crura of diaphragm. 5. Tail .extends into the lienorenal ligament and abuts the spleen.

Dorsal Aspect of the Pancreas and its Ducts • When the pancreas and duodenum are flipped over and the pancreas dissected, you will be able to identify the ducts of the pancreatic system. In order to see the complete system, you must open the descending part of the duodenum.

Identify the following: . major pancreatic duct of Wirsung . accessory pancreatic duct of Santorini . common bile duct . major duodenal papilla . minor duodenal papilla Note that the major pancreatic duct merges with the common bile duct to form a swelling in the duodenal wall called the ampulla (of Vater). The muscular wall of the ampulla may be thickened, forming the sphincter of Oddi. This ampulla then empties into the descending part of the duodenum at the major duodenal papilla. There may not be an accessory pancreatic duct but if there is, its opening is located a couple of centimeters above the major papilla at the minor duodenal papilla.

Blood Supply of Pancreas • Arteries • small branches from the splenic • superior pancreaticoduodenal - from the gastroduodenal • inferior pancreaticoduodenal - from the superior mesenteric • Veins • splenic vein to portal vein • superior mesenteric vein which then becomes the portal vein

Clinical Considerations .hypertrophy of the head may cause portal or bile duct obstruction .degeneration of the islets of Langerhans leads to diabetes mellitus .pancreatitis is a serious inflammatory condition of the exocrine pancreas .cancer of the head of the pancreas is many time a fatal pathology