The Abdominal Wall

The Abdominal Wall

Lectured by Bien Eli Nillos, MD

PRE-TEST: Identify

Where is the Abdomen? The region of the trunk that lies between the diaphragm above and the inlet of the pelvis below

Xiphoid Process • Thin cartilaginous lower part of the

sternum • Easily palpated in the depression where the costal margins meet in the upper part of the anterior abdominal wall • Xiphisternal junction – lies opposite the body of the ninth thoracic vertebra.

Costal Margin • The curved lower margin of the

thoracic wall, formed in front by the cartilages of the seventh, eighth, ninth and tenth ribs and behind by the cartilages of the eleventh and twelfth ribs • Reaches its lowest level at the tenth costal cartilage, which lies opposite the body of the third lumbar vertebra

Iliac Crest • May be felt along its entire length

and ends in front at the Anterior Superior Iliac Spine (ASIS). • Its highest point lies opposite the body of the fourth lumbar vertebra. • About 2 inches posterior to the ASIS, the outer margin projects to form the tubercle of the crest – lies at the level of the body of 5th Lumbar Vertebra.

Inguinal Ligament • Rolled-under inferior

margin of the external oblique muscle • Attached laterally to the ASIS, curves downward and medially to be attached to the pubic tubercle

Symphysis Pubis • Cartilaginous joint that lies in the

midline between the bodies of the pubic bones • Felt as a solid structure beneath the skin in the midline at the lower extremity of the anterior abdominal wall • Pubic crest – ridge on the superior surface of the pubic bones medial to the pubic tubercle

Superficial Inguinal Ring • Triangular aperture in the

aponeurosis of the external oblique muscle situated above and medial to the pubic tubercle • In males – the margins can be felt by invaginating the skin of the upper part of the scrotum with the tip of the little finger • In females – smaller and difficult to palpate

Scrotum • Pouch of skin containing the testes,

the epididymides, lower ends of the spermatic cord. • Testis on each side is a firm ovoid body surrounded on its lateral, anterior and medial surfaces by two layers of tunica vaginalis. • Testis should lie free and not tethered to the skin or subcutaneous tissue.

Linea Alba • Fibrous band that extends from

symphysis pubis to the xiphoid process and lies in the midline. • Fusion of the aponeuroses of the muscles of the anterior abdominal wall and is represented on the surface by a slight median groove

Umbilicus • Lies in the linea alba and is

inconstant in position • Puckered scar and is the site of attachment of the umbilical cord in the fetus

Linea Semilunaris • Lateral edge of the rectus abdominis

muscle, crosses the costal margin at the tip of the ninth costal cartilage • To accentuate, the patient is asked to lie on his back and raise his shoulders off the couch without using his arms

Abdominal Regions

The Superficial Fascia • Divided into: superficial fatty layer and

deep membranous layer • Fatty layer – continuous with the superficial fat over the rest of the body and may be extremely thick in obese patients. • Membranous layer – fades out over the thoracic wall above and along the midaxillary line laterally, inferiorly it passes onto the front of the thigh where it fuses with the deep fascia

Clinical Notes • Camper’s Fascia – a.k.a. Superficial fatty layer • Scarpa’s Fascia – a.k.a. deep membranous layer • Colles fascia – extension of the Scarpa’s in the perineum

External Oblique • Origin – lower eight ribs • Insertion – xiphoid process, linea

alba, pubic crest, pubic tubercle, iliac crest • Nerve supply – lower 6 thoracic nerves • Action – supports abdominal contents, assists in forced expiration, micturition, defecation, partuition,

Clinical Notes • Triangular shaped defect in the

external oblique aponeurosis, lies immediately above and medial to the pubic tubercle (hmmm….sounds familiar?) • The lower border of the aponeurosis is folded backward on itself, forming the inguinal ligament.

Internal Oblique • Origin – lumbar fascia, iliac crest,

lateral two thirds of the inguinal ligament • Insertion – Lower three ribs and costal cartilages, xiphoid process, linea alba, symphysis pubis • Nerve supply – lower six thoracic nerves • Action – same with external obliques

1. 2. 3. 4. 5. 6. 7. 8.

Inguinal ligament Muscular part of transversus abdominis Transversus abdominis aponeurosis Muscular part of internal oblique Internal oblique aponeurosis Transversalis fascia Cremasteric fascia forming middle coating of spermatic cord Pubic tubercle

Transversus Abdominis • Origin – lower six costal cartilages,

lumbar fascia, iliac crest, lateral third of inguinal ligament • Insertion – xiphoid process, linea alba, symphysis pubis • Nerve supply – lower six thoracic nerves • Action – compresses abdominal contents

Rectus Abdominis • Origin – symphysis pubis and pubic

crest • Insertion – fifth, sixth and seventh costal cartilages and xiphoid process • Nerve supply – lower six thoracic nerves • Action – compresses abdominal contents and flexes vertebral column

• When it contracts, its lateral margin

forms a curved ridge that can be palpated and often seen (hmmm…sounds familiar again)

• It is enclosed between the

aponeuroses of the external oblique, the internal oblique and the transversus, which form the rectus sheath.

Pyramidalis • Origin – anterior surface of pubis • Insertion – Linea alba • Nerve supply – Twelfth thoracic nerve • Action – tenses the linea alba It is often absent

Rectus Sheath

Arteries of the Anterior and Lateral Abdominal Walls • Superior epigastric artery – terminal

branch of the internal thoracic artery; supplies the upper central part of the anterior abdominal wall • Inferior epigastric artery – branch of the external iliac artery, just above the inguinal ligament; supplies the lower central part of the anterior abdominal wall

• Deep circumflex iliac artery – branch of the external iliac artery; supplies the lower lateral part of the abdominal wall. • Posterior Intercostal arteries – 2, branches of the descending thoracic aorta; supply the lateral part of the abdominal wall.