Abdominal Wall

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Abdominal Wall
2011-10-20 14:42:04
anatomy abdominal wall

anatomy abdominal wall
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  1. abdominal wall regions
    • epigastric
    • umbilical
    • hypogastric
    • R&L hypochondriac, flank, groin
  2. External Abdominal Oblique m.
    • first muscle layer below the superficial fascia
    • Note the fiber direction - which is sometimes referred to as �hands in pocket� or �hands down� position.
    • Medially, the connective tissue of this muscle continues as a broad, flat sheet of (white, dense) connective tissue called �the external abdominal oblique aponeurosis.�
    • ACTION: compresses the abdominal contents and can flex the trunk.
    • INNERVATION: ventral rami of T7-L1 spinal nerves.
  3. Superficial Fascia Veins
    • anastomoses of veins
    • Veins above the umbilicus (e.g., thoracoepigastric and lateral thoracic vs.) will bring blood into the SVC system.
    • Veins below the umbilicus eventually (e.g., superficial epigastric v.) bring blood into the IVC system.
    • In the umbilical region, the parumbilical veins (not depicted here) anastomose with superficial epigastric veins. This is one of the portacaval anastomoses.
    • Clinical Note: When the veins around the umbilical region are dilated, this is called caput medusa � which is a symptom of conditions like cirrhosis which results in blood backing up in the portal system and into the caval system.
  4. caput medusa
    When the veins around the umbilical region are dilated, a symptom of conditions like cirrhosis which results in blood backing up in the portal system and into the caval system.
  5. internal abdominal oblique m.
    • deep to external abdominal oblique.
    • fiber direction as being �hands up� or perpendicular to that of the 1st layer.
    • Medially, it continues as the internal abdominal oblique aponeurosis.
    • Action: compress the abdominal contents and flex the trunk.
    • Innervation:ventral rami of T7-L1 spinal nerves.
  6. transversus abdominis m.
    • deep to internal ab oblique
    • fiber direction as being �horizontal.�
    • Medially, it continues as the transversus abdominis aponeurosis.
    • ACTION: compresses the abdominal contents.
    • Innervation: ventral rami of T7-L1 spinal nerves.
  7. rectus abdominis m
    • deep to rectus sheath anterior wall
    • extends from the subcostal margin medially to the pubic bone of the pelvis.
    • INNERVATION: ventral rami of T7-T12 spinal nerves.
    • ACTION: together can flex the trunk.
  8. rectus abdominis blood supply
    • posterior surface between muscle and posterior rectus sheath
    • superior epigastric a. & v. (from the internal thoracic vessels).
    • The inferior vessels are the inferior epigastric a. & v. (from the external iliac vessels).
    • These anastomose along the posterior surface of the rectus abdominis.
  9. retroperitoneal space
    • These structures include various organs, the IVC, aorta, associated visceral nerve plexuses, muscles, and somatic nerves.
    • The peritoneum of the posterior wall of the peritoneal cavity must be removed in order to reveal these structures.
    • The retroperitoneal space is that part of the abdominal cavity posterior to the peritoneum of the posterior wall of the peritoneal cavity.
  10. Organs in Situ (post abdominal wall)
    • When the peritoneum of the posterior abdominal wall is removed (along with the duodenum and pancreas),
    • kidneys, ureters, suprarenal glands, aorta and its branches, IVC and its tributaries, muscles, and nerves of the lumbar plexus can be visualized.
  11. Quadratus Lumborum
    • Origin: iliac crest
    • Insert: lumbar vertebrae, rib 12
    • Nerve: T12-L4 ventral rami ns.
    • Action: depresses & stabilizes rib 12; some lateral bending of trunk
  12. psoas major
    • Origin: T12-L5 vertebrae
    • Insert: femur (lesser trochanter)
    • Nerve: L1-3 ventral rami ns.
    • Action: main flexor of hip (acts together with iliacus as a single muscle �iliopsoas)
  13. Iliacus
    • Origin: iliac fossa
    • Insert: femur (lesser trochanter)
    • Nerve: femoral n. (L2-4)
    • Action: main flexor of hip (acts together with psoas as a single muscle � iliopsoas)
  14. lumbar plexus
    • involved in the innervation of the lower anterior abdominal wall and lower limb muscles
    • nerves of this plexus consist of ventral rami nerves of the L1-L4 spinal nerves.
    • somatic nerve plexus (formed of ventral rami nerves) whose branches may be seen in and around the psoas muscle in the posterior abdominal wall.
    • These branches are somatic afferent (sensory) or somatic efferent (motor) to body wall structures such as skin and skeletal muscle (of the lower limb in particular).
    • In addition to the lumbar plexus branches, in this general area you may also see other nerve structures such as the sympathetic trunk and subcostal nerve.
  15. lumbar plexus branches
    • iliohypogastric n. (L1)
    • ilioinguinal n. (L1)
    • genitofemoral n. (L1-2)
    • lateral femoral cutaneous n. (L2-3)
    • obturator n. (L2-4)
    • femoral n. (L2-4)
  16. iliohypogastric n.
    • (lumbar plexus)
    • L1 spinal nerve ventral ramus
    • It is motor to abdominal musculature and cutaneous to the skin of the suprapubic region.
    • Relationship: It emerges from the psoas m. & crosses the quadratus lumborum and then pierces the transversus abdominis muscle
  17. ilioinguinal n.
    • (lumbar plexus)
    • L1 spinal nerve ventral ramus.
    • It is sensory to the medial upper hip region and anterior genital area.
    • Relationship: It emerges from the psoas m. & crosses the quadratus lumborum inferior to the iliohypogastric and traverses the inguinal canal.
  18. lateral femoral cutaneous n.
    • (lumbar plexus)
    • L2-3 spinal nerve ventral ramus.
    • It is sensory to the lateral upper hip region.
    • Relationship: It emerges from the psoas m. & crosses the middle of the iliacus m.
  19. genitofemoral n.
    • (lumbar plexus)
    • L1-2 spinal nerve ventral ramus.
    • It divides into a genital branch (which enters the inguinal canal and is motor to cremaster muscle) and femoral branch (sensory to anterior upper thigh region).
    • The branches will not be studied during this block.
    • Relationship: It emerges on the anterior surface of the psoas m. & passes inferiorly.
  20. femoral n.
    • (lumbar plexus)
    • L2-4 spinal nerve ventral rami.
    • Its branches are motor to anterior thigh muscles and sensory to the knee and skin of the thigh and leg. Relationship: It emerges between the psoas & iliacus muscles& passes inferiorly deep to the inguinal ligament to enter the anterior thigh.
  21. obturator n.
    • (lumbar plexus)
    • L2-4 spinal nerve ventral rami.
    • It is motor to medial thigh muscles and sensory to the skin of the medial thigh.
    • Relationship: It is found deep betwee the psoas & vertebral column.
    • It passes inferiorly into the pelvis, through the obturator canal, and into the medial thigh.
  22. supraarenal blood supply
    • superior middle inferior suprarenal arteries
    • superior-About 6-8 little suprarenal arteries originate from the inferior phrenic arteries (which branch from the aorta to supply the diaphragm).
    • middle-orginate from aorta
    • inferior originate from the renal arteries (which branch from the aorta).
  23. suprarenal venous drainage
    • principle venous drainage of the suprarenal glands is by way of the right and left suprarenal veins.
    • The right suprarenal vein drains directly into the IVC.
    • The left suprarenal vein drains into the left renal vein (which then drains into the IVC).
  24. suprarenal gland
    • comprised of an outer cortex and inner medulla.
    • The medulla is derived from neural crest cells and are functional sympathetic postganglionic cells.
    • Thus the medulla is innervated by sympathetic preganglionic fibers from the thoracic splanchnic nerves which pass through the celiac plexus and renal plexus without synapsing and then travel to the suprarenal glad to synapse on chromaffin cells of the medulla.
    • Blood vessels of the cortex are supplied by sympathetic postganglionic fibers.
  25. Renal Fat & Fascia
    • kidney is embedded in protective layers of fat and fascia.
    • These layers are:
    • (1) perirenal fat - which is the adipose tissue surrounding the fibrous capsule of the kidney,
    • (2) renal fascia - which is a membranous connective tissue layer superficial to the perirenal fat, and
    • (3) pararenal fat - which is the adipose tissue between the renal fascia and the parietal peritoeneum.
  26. Renal Hilum
    structures of the renal hilum include (from anterior to posterior): the renal vein, renal artery, and renal pelvis. The renal pelvis narrows to form the ureter which empty into the bladder.
  27. Ureter
    • ureters descend from the kidneys over the psoas muscle and are crossed by the gonadal vessels.
    • They then cross into the pelvis right at the bifurcation of the common iliac artery into external and internal iliac arteries.
    • They will continue in the pelvis to join the bladder.
    • The ureters are innervated by fibers (VA, VE) which extend from the renal plexus.
  28. abdominal aorta
    • descends on the vertebral column to the left of the inferior vena cava and gives off a number of branches
    • (3 unpaired branches, paired branches to viscera, paired branches to the body wall, and the median sacral artery).
    • It then divides into two common iliac arteries at the level of vertebrae L4.
    • The common iliac arteries, in turn, divide into the internal iliac arteries which supply the pelvis and the external iliac arteries (which pass into the anterior thigh) and become the femoral arteries.
  29. Abdominal Aorta: Paired branches body wall
    There is one pair of inferior phrenic arteries will supply the diaphragm and 4 pairs of lumbar arteries (to the body wall) which branch from the aorta.
  30. Abdominal Aorta: Paired branches viscera
    There are 3 paired branches: the middle suprarenal as., the renal arteries, and gonadal (testicular or ovarian arteries.
  31. Median Sacral Branch
    • Descending from the aortic bifurcation is a single median sacral artery which extends into the pelvis over the sacrum and down to the coccyx.
  32. Hepatic Veins
    • The hepatic veins drain blood from the liver into the IVC. (right, middle,left)
  33. Renal Veins
    drain blood from kidneys into IVC
  34. right inferior phrenic vein
    drain from diaphram into IVC (left phrenic is variable)
  35. lumbar veins
    dran from lower body wall into IVC
  36. right gonadal vein
    • drains either the testes or ovary IVC
    • NOTE: left gonadal and suprarenal drain into left renal.
  37. ascending lumbar veins
    • simply interconnect the lumbar veins.
    • Inferiorly they connect with the common iliac vein and superiorly with the azygous vein on the right and hemiazygous on the left.
  38. Renal Veins
    • The renal veins are anterior to the renal arteries.
    • The left renal vein is longer than the right and crosses anterior to the aorta.
    • It receives the left phrenic vein, left suprarenal vein, and left gonadal vein.
    • The right renal vein is relatively short.
    • Note that on the right side, the right gonadal (testicular or ovarian) vein usually drains into the IVC, not into the right renal vein.
  39. Renal Arteries
    • Note how the superior mesenteric artery crosses over the left renal vein.
    • Clinical Note: The left renal vein can potentially be compressed by a dilated superior mesenteric artery.
  40. Abdomen Surface
  41. Posterior Rectus Sheath