Foramina Diaphragm

1 Anatomy – Hour A (1-2pm) Class of 2009 Co-Op November 16, 2005 Dr. Kuhlmann Writer: Jacob Clark Pelvis & Perineum 2 As we all know, Dr. K talks pretty fast and it’s hard to take notes, but I did what I could using multiple old Co-Ops and relistening to the lecture (it wasn’t easy). Have a great Thanksgiving break (and if you are looking at this while you’re on break, STOP and enjoy yourself)! Dr. K started by showing a hemisected pelvis 1. 2 areas located posteriorly a. The greater and lesser sacrosciatic notch 1. Sacrospinous and spinous ligament are oriented with the notches to create greater and lesser sacrosciatic foramen 2. Anteriorly and Inferiorly a. Obturator membrane 1. Obturator internus muscle a. Defect in this muscle and the obturator membrane called obturator canal Anterior view looking down into the pelvis 1. The Sacrospinous ligament runs between the sacrum and the ischial spine. It forms the inferior border of the Greater Sacrosciatic foramen and the superior border of the Lesser Sacrosciatic foramen. 2. The Sacrotuberous Ligament runs between the sacrum and the ischial tuberosity. It forms the inferior border of the Lesser Sciatic foramen. Male / Female Pelvis 1. Greater (false) pelvis a. Area of bony pelvis superior to the plane of the pelvic inlet b. Contains abdominal viscera 2. Lesser (true) pelvis a. Area of bony pelvis inferior to the plane of the pelvic inlet b. Contains the pelvic viscera Female Pelvic Inlet Pelvic Outlet Pelvic Cavity Pubic Arch

Oval Longer transverse diameter Longer A-P diameter Longer transverse diameter Divergent as proceed from the inlet to the outlet (cylindrical) > 90 degrees

Different types of pelvis:

Male Heart-shaped Shorter A-P diameter Shorter transverse diameter Convergent (funnel-shaped) < 90 degrees

2 NOTE: You don’t need to remember the various measurements but know that there are four types of pelvises. 1. Gynecoid a. Most common female shape 2. Android a. Most common male shape 3. Anthropoid a. Long A-P diameter and short transverse diameter. b. Higher risk for occiput posterior deliveries (babies face up). 4. Platypelloid a. Very dysfunctional pelvis when it comes to obstetrics b. Gestational age dependent c. Often require C-section for delivery Muscular Pelvis: 1. Piriformis 1. Originates from the lateral aspect of the sacrum 2. Passes (“exits”) through the greater sacrosciatic foramen 3. Interdigitations through which the nerves and arteries pass a. Correlate well with the foramina 2. Obturator Internus 1. Passes (“exits”) through the lesser sacrosciatic foramen 3. Greater Canter of the Femur 1. Place of attachment for both the piriformis and the obturator internus 2. We should be able to see this clearly with the gluteal dissection 4. Intrinsic Musculature of the Pelvis 1. Pelvic diaphragm • Creates 2 spaces: 1. Intra-pelvic (visceral) space  superior to the pelvic diaphragm a. Structures (such as uterus, rectum, urethra) are within this space 2. Ischiorectal (ischioanal) space (fossa)  inferior to the pelvic diaphragm a. Filled primarily with fat and covered by the gluteus maximus b. Running through this area are structures including branches of the pudendal nerves and arteries, and the hemeroidal arteries • Muscles of the pelvic diaphragm: a) Levator ani muscles (main part of the pelvic diaphragm) 1. Pubococcygeus m. a. Originates by the pubis, comes back to the coccyx b. Bilateral

3 2. Puborectalis m. a. Part of Pubococcygeus m. b. Described as a condensation or the formation of a sling c. Pulls rectum anteriorly, helping to maintain rectal continence 3. Iliococcygeus m. b) Coccygeus m. (also known as Ischiococcygeus m.) (This muscle is NOT a component of Levator ani muscles) **Remember: The pelvic diaphragm is the primary support for the pelvic viscera!! 5. Urogenital Diaphragm – is also known as the deep pouch (space) and it fills in an anterior defect in the pelvic diaphragm 1. Comprised of muscle, so there is a fascia on either side a. Fascia of the UG diaphragm is composed of 2 layers: 1. Superior fascia 2. Inferior fascia (also known as perineal membrane) **Anything inferior to the inferior fascia and just deep to the skin is part of the Superficial Pouch (Space)!** a) Continuous with Scarpa’s fascia along the anterior abdominal wall 2. The urethra and the vagina pass through the UG diaphragm 3. In the male, just the urethra passes through ** The UG diaphragm does NOT contain the rectum!** 5. Muscles of UG diaphragm are between the superior & inferior fascia: 1. Sphincter urethrae m. (there is some question as to whether it actually works as a sphincter) 2. Deep transverse perineal m. 6. The Superficial Space (pouch) is composed of: 1. Ischiocavernosus m. – (bilaterally symmetric) 2. Bulbocavernosus m. (also known as Bulbospongiosus m.) – (bilaterally symmetric) 3. Vestibular bulb - a pamipiniform (vine-like) plexus of veins that is extremely vulnerable to bleeding during trauma in this region (Straddle injury) 4. Bartholen’s gland 5. Superficial transverse perineal m. – (bilaterally symmetric) ** The fascia of the superficial pouch is contiguous with Scarpa’s fascia on the anterior abdominal wall. Thus, a male who damages the urethra in a “straddle injury” will have a uroma (pool of urine) that can extend up the anterior abdominal wall. Similarly, a female who has a “straddle injury” can have blood extend up the anterior

4 abdominal wall.** 7. Building up of the layers of the pelvic diaphragm and UG diaphragm (notes p. 17) The Neural Pelvis 1) Obturator nerve (know the course of the nerve) * This nerve originates from L2-L4 and accompanies the obturator artery and vein. It runs along the superior pelvic aperture, crosses the sacroiliac joint and passes through the obturator canal, sending branches to the Obturator internus muscle and the Adductor muscles of the thigh. 2) Lumbosacral trunk * L4-L5, joins up with S1-S3. 3) Pudendal n. – from S2-4 1. More easily seen in the gluteal region when perineum is dissect out a. Common area for this to be tagged 2. Leaves pelvis through Greater Sacrosciatic foramen, wraps around and is encompassed in its own canal, Alcock’s (Pudendal) Canal a. Pudendal canal contains Pudendal n., a., and v. 3. Provides main sensory innervation to perianal and perineum region [384] a. Don’t spend any time looking for the perforating cutaneous because you won’t find it, probably not even clinically 4. Gives off branches through the deep pouch, such as the inferior rectal n. (also known as hemorrhoidal n.), and terminates as the dorsal n. of the penis/clitoris **Majority of perineum innervation is from Pudendal nerve!** 4) Other nerves play a minor role in sensory innervation to the perineum: 1. Posterior femoral cutaneous n. (perineal branch) 2. Perforating cutaneous n. (never seen by Dr. Kuhlmann) 3. Ilioinguinal n. 5) Pudendal anesthesia 1. Dealt with very easily during the second stage of labor 2. Done through a catheter or a sleeve by palpating the sacrosciatic area (notch), going into the sacrospinous ligament and then you can actually get the anesthetic back near the pudendal n. The Vascular Pelvis A. Aorta terminates as the common iliac arteries that bifurcate into the external and internal iliac aa. (int. iliac a. = hypogastric a.) B. The external iliac is going to give rise to the deep circumflex a. and the inferior epigastric a. 1. Inferior epigastric is one of the first branches you see as an

5 anastomosis C. Internal iliac a. (hypogastric a.) splits into anterior and posterior divisions: 1) Anterior Division: a. Umbilical a. a) Runs until the level of the pubic symphysis, then becomes obliterated as the medial or lateral umbilical ligament b) Also sends branches to the bladder b. Obturator a. a) Follows the obturator n. through the obturator canal and supplies the medial area of the thigh b) Also gives off vesicular branches to the bladder c. Pudendal a. a) Hemmorhoidal aa. d. Inferior and posterior gluteal aa. e. Vaginal a. f. Uterine a. g. Middle rectal a. In the abdomen, blood flows from medial to lateral (aorta is medial) In the pelvis, blood flows from lateral to medial (iliacs are lateral) **Also, “Water runs under the bridge” (Males: ureter runs under Vas Deferens, females: ureter runs under Uterine artery) 2) Posterior Division (easier to remember this and know others come from ant.): a. Iliolumbar a. b. Lateral sacral a. c. Superior gluteal a. Pelvic Viscera 1. Female pelvis A. The Uterus (has 3 parts: cervix, body, and fundus) 1) Visceral peritoneum is thrown up on the uterus and goes behind the uterus a. Called the broad ligament 1. Fold of visceral peritoneum 2) Ligaments: 1. Broad ligament a. Composed of an anterior and posterior leaf 1. It is a sheet of visceral peritoneum folded over (remember the uterus and fallopian tubes are covered with peritoneum – they are retroperitoneal) 2. Suspensory ligament of uterus 3. Round ligament – extends laterally from the uterus anterior to the fallopian tube (which is anterior to the ovary). This is important to remember so that you won’t tie off the wrong structure in a tubal ligation!

6 4. Uterosacral ligament (also known as sacrouterine ligament or sacrocervical ligament) – extends from cervix to sacral area; supports the uterus and vagina 3. Blood supply a. Uterine a. – primary source of blood to the uterus 1. Bifurcates at the level of the uterus into: a. Descending branch 1. Anatomoses with vaginal a. b. Ascending branch 1. Joins the ovarian artery to become the uteroovarian a. 4. Support for the pelvis (on scale of 1 –> 10 w/ 10 = greatest support) a. Round ligament (2) b. Uterosacral ligament - extends from uterus to the sacral region (8) c. Transverse cervical ligament (Machenrodt’s, or cardinal ligament) a) contains the ureter, uterine a., and uterine v. (10) d. Suspensory ligament – mustn’t offer support, since he gave it a (-1) e. Pubocervical ligament – originates from the pubic area and attaches to the cervix and perhaps a lower segment of the uterus **f. Pelvic diaphragm - main support for pelvic viscera! (10) a) If support is lost, the urethra can become prolapsed out into the vagina 5. Spaces or Pouches 1. When doing gynecology, the goal is to create these spaces a. Once one creates these spaces, dissection and surgery can be done with relative impunity 1. Paravescicular space a. Surrounding the bladder b. Create this space when trying to identify the blood vessels to the uterus 1. Particularly true in radical surgery when you’ve got to remove a patient’s bladder, cervix, uterus, and rectum in cases that are referred to as exoneration for various gynelogical malignancies such as cervical cancer and advanced uterine cancer 2. Retro space of Sylvius (Retropubic space) a. Can cause you problems at the time of caesarian when you’re trying to dissect down and identify the direction to go. It is quite vascular and bleeds a lot 1. Most common cause of bleeding in this area is from the retractor. 3. Space of Douglas a. Space between the cervix and the rectum 4. Pararectal Space a. Important for colorectal surgeons (cancer, etc.)

7 Bladder A. Males: the prostate gland is inferior to the bladder Females: the pelvic diaphragm is inferior to the bladder B. Levator ani and pubic symphysis rest on the anterior border of bladder C. Areas of the bladder emphasized: 1. Dome - superior portion of the bladder 2. Trigone - area of bladder shaped like a triangle. The corners are the 2 ureteric orifices on the lateral sides and the urethra a. In surgery, cuts into the dome of the bladder heal easily b. However, cuts in the trigone heal poorly and may cause problems D. The muscle of the bladder is the detrusor m. (smooth muscle) 1. 3-4 layers of muscle that can distend quite readily, especially in pregnancy when there is significant relaxation going on. a. With a woman in labor, getting lots of fluids, one can palpate the bulge of the bladder up past the umbilicus E. Pretty much sitting anteriorly and inferiorly within the pelvis -parasympathetic stimulation contracts the bladder! ** Prostate hypertrophy or cancers may result in significant urinary retention because the neck of the bladder may be constricted. ** However, since females have a shorter urethra, they are more vulnerable to incontinence. The Urethra A. In males, the urethra has three components: 1. Prostatic urethra - passes through prostate gland (first part of urethra) 2. Membranous urethra - passes through UG diaphragm (second part of the urethra) 3. Spongy urethra - runs through the corpus spongiosum of the penis (last part of the urethra) B. In females, there is only a membranous urethra C. Prostatic utricle is the homologue to the upper vagina and the uterus Rectum Note: **Distal 1/3 of rectum not covered by peritoneum and rectum does not go through the UG diaphragm.** 1. Contains 3-4 incomplete valves that are important for maintaining continence 2. Anal region has blood vessels (responsible for hemorrhoids) 3. External Anal Sphincter (voluntarily controlled): a. Deep, Internal, Superficial components 4. Internal Anal Sphincter (involuntarily controlled) **Continence controlled by sphincteric control, puborectalis muscle (sling), and additionally deep, superficial, and subcutaneous components.

8