Abdominal Wall Landmarks: Bony & Soft

Abdominal Wall Landmarks: bony & soft

• costal arch: formed by #7-10 costal cartilages – a. infrasternal angle - sharp upward angle at midline, xiphoid process at the apex – b. epigastric fossa - depression just inferior to xiphoid

Coxal bones

• Three bones fused together • ilium: anterior superior iliac spine; iliac crest • ischium • pubis: pubic symphysis, • inguinal ligament (below): indicated at surface by depression separating leg from abdomen

Abdominal wall

• Linea alba: midline from xiphoid to pubic bone, umbilicus - at level of L4 • Linea semilunaris: parallels linea alba on each side; marks lateral border of rectus abdominis • Tendinous intersections: 3 horizontal divisions of rectus abdominis between linea semilunaris

Regions Superficial vessels

• thoracoepigastric veins: drain laterally from umbilical level up • anterior perforating veins: closer to midline • umbilical venous plexus (caput medusae may seen in portal hypertension) • superficial epigastric artery, vein • superficial circumflex iliac artery vein

Nerves • Thoracoabdominal nerve: continuations of intercostals 7-11 & subcostal from thorax to abdomen, between internal oblique & transverse abdominis • Anterior, lateral cutaneous nerve: terminal branches of thoracoabdominal nerve to the surface – T7-9 to skin superior to umbilicus – T10 to skin surrounding umbilicus – T11-12, L1 to skin inferior to umbilicus • Iliohypogastric nerve: to skin over inguinal region • Ilioinguinal nerve: just inferior to iliohypogastric to skin of superior, medial thigh

Muscles

• External oblique muscle • Internal oblique muscle • Transversus abdominis • Rectus abdominis EXTERNAL ABDOMINAL OBLIQUE • Origin – Anterior fibers: external surfaces of ribs five through eight interdigitating with serratus anterior – lateral fibers: external surface of ninth rib, interdigitating with serratus anterior; and external surfaces of 10th, 11 th ans 12th ribs, interdigitating with latissnus dorsi • Insertion – Anterior fibers: into a board, flat aponeurosis, terminating in the linea alba, which is a tendinous rephe which extends from the xiphoid – Lateral fibers: as the inguinal ligament, into anterior superior spine and public tubercle, and into the external lip of anterior one half of iliac crest. EXTERNAL ABDOMINAL OBLIQUE • Action – Anterior fibers: acting bilaterally, the anterior fibers flex the vertebral column approximating the thorax and pelvis anteriorly, support and compress the abdominal viscera, depress the thorax, and assist in respiration. Acting unilaterally with the anterior fibers of the Internal Oblique on the opposite site, the anterior fibers of External Oblique rotate the vertebral column, bring the thorax forward (when the pelvis is fixed), or the pelvis backward (when the thorax is fixed). For example, with the pelvis fixed, the right external oblique rotates the thorax counterclockwise, and the left external oblique rotates the thorax clockwise. EXTERNAL ABDOMINAL OBLIQUE • Action – Lateral fibers: acting bilaterally, the lateral fibers of the external oblique flex the vertebral column, with major influence on the lumbar spine, titling the pelvis posteriorly. Acting unilaterally with the lateral fibers of the internal oblique on the same side, these fibers of the external oblique laterally flex the vertebral column, approximating the thorax and iliac crest. These external oblique fibers also act with the internal oblique on the opposite side to rotate the vertebral column. The external oblique, in its action on the thorax, is comparable to the sternocleidomastoid in its action on the head. EXTERNAL ABDOMINAL OBLIQUE

• Nerve – Anterior fibers: T5, 6, T7-T12 – Lateral fibers: T5, 6, T7-T12 • Direction of the fibers: – Anterior fibers: the fibers extend obliquely downward and medialward with the uppermost fibers from the xiphoid – Lateral fibers: fibers extend obliquely downward and medialward, more downward than the anterior fibers INTERNAL ABDOMINAL OBLIQUE

• Origin – Lower anterior fibers: middle one third of intermediate line of iliac crest, and thoracolumbar fascia – Upper anterior fibers: anterior one third of intermediate line of iliac crest – Lateral fibers: middle one third of intermediate line of iliac crest, and thoracolumbar fascia • Insertion – Lower anterior fibers: inferior borders of 10th, 11th, and 12th ribs and linea alba by means of aponeurosis – Upper anterior fibers: linea alba by means of aponeurosis – Lateral fibers: inferior borders of 10th, 11th, and 12th ribs and linea alba by means of aponeurosis INTERNAL ABDOMINAL OBLIQUE

• Action – Lower anterior fibers: acting bilaterally, the lateral fibers flex the veterbral column, approximating the thorax and pelvis anteriorly, and depress the thorax. Acting unilaterally with the lateral fibers of the external oblique on the same side, these fibers of the internal oblique laterally flex the vertebral column, approximating the thorax and pelvis. These fibers also act with the external oblique on the opposite side to rotate the vertebral column. INTERNAL ABDOMINAL OBLIQUE

• Action – Upper anterior fibers: acting bilaterally, the upper anterior fibers flex the vertebral column, approximating the thorax and pelvis anteriorly, support and compress the abdominal viscera, depress the thorax, and assist in respiration. Acting unilaterally, in conjuction with the anterior fibers of the external oblique on te oppisite side, the ipper anterior fibers of the internal oblique rotate the vertebral column, bringing the thorax backward (when the pelvis is fixed), or the pelvis forward (when the thorax is fixed). For example, the right internal oblique rotates the thorax clockwise and the left internal oblique rotates the thorax couinterclockwise on a fixed pelvis. INTERNAL ABDOMINAL OBLIQUE

• Action – Lateral fibers: acting bilaterally, the lateral fibers flex the veterbral column, approximating the thorax and pelvis anteriorly, and depress the thorax. Acting unilaterally with the lateral fibers of the external oblique on the same side, these fibers of the internal oblique laterally flex the vertebral column, approximating the thorax and pelvis. These fibers also act with the external oblique on the opposite side to rotate the vertebral column. INTERNAL ABDOMINAL OBLIQUE

• Nerve – Lower anterior fibers: T7-11, T12, iliohypogastric and ilioinguinal, ventral rami – Upper anterior fibers: T7-11, T12, iliohypogastric and ilioinguinal, ventral – Lateral fibers: T7-11, T12, iliohypogastric and ilioinguinal, ventral rami • Direction of fibers: – Lower anterior fibers: fibers extend obliquely upward and medialward, more upward than the anterior fibers – Upper anterior fibers: fibers extend obliquely medialward and upward – Lateral fibers: fibers extend obliquely upward and medialward, more upward than the anterior fibers • TRANSVERSUS ABDOMINIS • Origin – inner surfaces of cartilages of lower six ribs, interdigitating with the diaphragm; thoracolumbar fascia; anterior three fourths of internal lip of iliac crest; and lateral one third of inguinal ligament • Action – Acts likes a girdle to flatten the abdominal wall and compress the abdominal viscera; upper portion helps to decrease the infrasternal angle of the ribs as in expiration. This muscle has no action in lateral trunk flexion except that it acts to compress the viscera and stabilize the linea alba, thereby permiting better action by anteriolateral trunk muscles • Insertion – linea alba by means of a board aponeurosis, pubic crest and pectin publis • Nerve – T7-T12, iliohypogastric, ilioinguinal, ventral divisions Direction of fibers: transverse (horizontal) RECTUS ABDOMINIS

• Origin – pubic crest and symphysis • Action – flexes the vertebral column by approximating the thorax and pelvis anteriorly. With the pelvis fixed, the thorax will move toward the pelvis; with the thorax fixed, the pelvis will move toward the thorax. • Insertion – costal cartilages of fifth, sixth, and seventh ribs, and xiphiod process of sternum • Nerve – T5-T12, ventral rami

Inguinal triangle

• bounded by – lateral border of rectus abdominis muscle medially – inguinal ligament inferiorly – inferior epigastric artery laterally

Inguinal canal

• roof: – internal oblique & transversus abdominis muscle • posterior wall: – transveralis fascia, reinforced medially by conjoint tendon (internal oblique & transversus abdomilis muscle) •Floor: – Superior surface of inguinal ligament • Anterior wall: – aponeurosis of the external oblique muscle • Superficial & deep ring