Posterior Abdominal Wall I. Removal of intraperitoneal structures allows access to retroperitoneal viscera and posterior abdominal wall, all of which are covered by peritoneum.

Peripheral attachments to the posterior abdominal wall and the diaphragm. The duodenum and pancreas… Rosse & Gaddum-Rosse, 1997 Retroperitoneal viscera of the digestive tract: Duodenum Pancreas Ascending Colon Descending Colon Rectum Other components: Kidney and Ureters Aorta Inferior Vena Cava Nerve Plexuses regulating the function of the abdomen

Dissection of posterior abdominal wall showing great vessels, spleen, kidneys, and suprarenal glands. Moore & Agur, 1996

Moore & Agur, 1996

II. Kidneys and Suprarenal Glds. Position – Left kidney – superior margin at the level of the 11th rib Right kidney – superior margin at the level of the 12th rib Relation to liver A. Kidney Structure Hilus Cortex Medulla Pyramids Calyces Pelvis Ureters Blood supply B. Suprarenal glds. Blood supply Inf. Phrenic Suprarenal Renal Note: Number of arteries to endocrine glds.

THE KIDNEYS AND ADRENAL GLANDS, ANTERIOR VIEW. The gland on the left is more rounded, while that on the right is more in the shape of a three-cornered-hat. The three potential sources of blood supply for each gland are shown here. Mathers et al., 1996

THE KIDNEYS. Transverse section at approximately L2, through the middle of the two kidneys. Separate layers of fat are found between the surface of the kidney and the renal capsule (the perirenal fat) and between the renal capsule and the transversalis fascia (pararenal fat). The renal capsule itself is a special extension of the transversalis fascia. Mathers et al., 1996

Coronal section of kidney Moore & Agur, 1996 _____________________________________________ THE KIDNEYS AND ADRENALS, BLOOD SUPPLY, ANTERIOR VIEW. The right renal artery is longer than the left because the aorta lies to the left of the midline of the body. The renal arteries arise at approximately the same level as the superior mesenteric artery and just below the celiac axis. Each renal artery typically gives off an inferior suprarenal artery as well. The adrenal glands also get a direct middle suprarenal branch from the aorta and often a third source of arterial blood, a superior suprarenal branch of the inferior phrenic artery. The pattern of supply is tremendously variable.

III. Abdominal aorta (Review) Position To the left of the IVC Vertebral column Branches Inferior phrenic (2) Celiac trunk Superior mesenteric Renal (2) Gonadal (2) Inferior mesenteric Lumbar (4 pairs) Common iliac (2) Internal and External Median sacral IV. Inferior Vena Cava Tributaries of IVC corresponding to branches of aorta Note: Left gonadal ! left renal Right gonadal ! IVC

V. Muscles of the Posterior Abdominal Wall Psoas major and minor Iliacus Quadratus lumborum Transversus abdominis Diaphragm – discussed separately (see below)

Pansky, 1996

Moore and Agur, 1996 VEINS OF THE POSTERIOR ABDOMINAL WALL. Like the thorax, the abdominal wall is segmental, although there are no ribs to emphasize the point. There are five pairs of lumbar veins, comparable in every way to the intercostal vessels of the thorax. The lumbar veins arise in the anterolateral body wall and drain blood posteriorly and directly into the IVC. On each side there is a vertical ascending lumbar vein, which passes behind the diaphragm and connects with the azygos (on the right) or hemiazygos (on the left) system of veins in the thorax. The inferior phrenic veins drain blood from the inferior surface of the diaphragm, and empty, at least in part, into the renal veins. They also connect superiorly with the superior epigastric veins, which drain into the internal thoracic and eventually into the subclavian veins on each side. Recall that the gonadal veins (testicular or ovarian) drain into the IVC on the right and renal vein on the left. -Mathers et al., 1996

VI. Innervation 1. Sympathetic A. Sympathetic Trunks Enters peritoneal cavity posterior to medial arcuate ligament Descends along sides of vertebral column to end at Ganglion Impar on coccyx B. Thoracic Splanchnic nerves Greater, lesser and least – penetrate ipsilateral crus of diaphragm and synapse in ciliac, superior mesenteric, aorticorenal and inferior mesenteric ganglia 2. Parasympathetic Foregut and midgut – CNX Enters celiac and superior mesenteric plexuses to serve GI tract as far as the left colic flexure Hindgut and pelvic viscera – S2-4 Serves remainder of GI tract, descending colon ! anus Note: (A) Sympathetic fibers and parasympathetic fibers intermix with one another to form a complicated plexus that is associated with the abdominal aorta. Different portions of this plexus are referred to as the celiac, superior mesenteric, renal and intermesenteric plexuses, terms which are given to portions of the plexus in association with arteries and viscera. Their boundaries are not exact. (B) At the level of the common iliac a. the plexus forms the superior hypogastric plexus. From this plexus are derived the Hypogastric n. which descend into the pelvic cavity and innervate the pelvic viscera. (C) Function – Regulation of visceral function Sympathetics – fight, flight, fright responses Parasympathetics – conservation and restoration of body responses

Autonomic nerve supply of abdomen. Orange, sympathetic; green, parasympathetic; blue, plexus; yellow, nerves of sacral plexus. Moore and Agur, 1996

Schematic representation of the distribution of the vagus nerves. -Gardner et al., 1975

3. Afferents (sensory) – these are carried with the sympathetic and parasympathetic nerves described above. 4. Somatic A. Phrenic – mixed (motor and sensory) to diaphragm (discussed later) B. Thoraco-abdominal – T7-11 (intercostal) C. Subcostal (T12) D. Lumbar Plexus Ventral rami of L1-4 a. Iliohypogastric n. (L1) – mixed; interval oblique and transversus and hypogastric skin b. Ilioinguinal n. (L1) – mixed; external oblique, internal oblique and inguinal region. Ilioinguinal and iliohypogastric n. are reciprocal in size c. Genitofemoral n. (L1,2) Genital branch – mixed; cremastic and scrotal/mons skin Femoral branch– femoral region d. Lateral femoral cutaneous (L2,3) – anterior and lateral thigh e. Femoral n. (L2-4) – mixed; thigh muscles f. Obturator n. (L2-4) – mixed; adductors and mid. thigh g. Lumbosacral trunk (L4,5) – contributes to sacral plexus h. Muscular branches (T12,L1-4) – innervation of quadratus lumborum, psoas and iliacus NERVES OF LUMBAR PLEXUS 1 and 2. The ilioinguinal and iliohypogastric nerves (L1) arise from the ventral ramus of L1 and enter the abdomen posterior to the medial arcuate ligaments and pass inferolaterally, anterior to the quadratus lumborum muscle, the pierce the transversus abdominis muscle near the anterior superior iliac spine and pass through the internal and external oblique muscles to supply the skin of the suprapubic and inguinal regions. 3. The lateral femoral cutaneous nerve (L2,L3) runs inferolaterally on the iliacus muscle and enters the thigh posterior to the inguinal ligament, just medial to the anterior superior iliac spine; it supplies the skin on the anterolateral surface of the thigh. 4. The femoral nerve (L2-L4) emerges from the lateral border of the psoas and innervates the iliacus muscle and the extensor muscles of the knee. 5. The genitofemoral nerve (L1,L2) pierces the anterior surface of the psoas major muscle and runs inferiorly on it deep to the psoas fascia; it divides lateral to the

common and external iliac arteries into femoral and genital branches. 6. The obturator nerve (L2,L4) emerges from the medial border of the psoas to supply the adductor muscles of the thigh. 7. The lumbosacral trunk (L4,L5), passes over the ala (wing) of the sacrum and descends into the pelvis to take part in the formation of the sacral plexus along with the ventral rami of S1-S4 nerves.

Moore and Agur, 1996

Gray’s Anatomy, 1995

VII. Posterior Aspect of Anterior Abdominal Wall Median umbilical ligament [urachus (obliterated allantois)] Medial umbilical ligament (umbilical a.) Lateral umbilical ligament (inferior epigastric a.) Umbilicus Rectus Sheath/Arcuate Line Ligamentum teres (umbilical v.) Falciform ligament VIII. Diaphragm – function discussed in later lecture on thorax 1. Dome-shaped 2. Skeletal muscle (periphery) inserts onto central tendon 3. Muscle origins A. Sternal – xiphoid process ! central tendon

The inguinal portion of the anterior abdominal wall as seen from behind. -Woodburne and Burkel, 1988

B. Costal – cartilages and bone of ribs 7-12 ! central tendon C. Lumbar – lumbar vertebrae 2 and 3 ! central tendon Right and Left Crura 4. Innervation Phrenic n. – C3,4,5 T7-T12 – sensory 5. Ligaments (A) Superior and (B) inferior views of the diaphragm. Median arcuate – aorta Rosse and Gaddum-Rosse, 1997

Medial arcuate – psoas Lateral arcuate – quadratus lumborum 6. Aperatures a. Vena caval foramen – inf. vena cava; T8 b. Esophageal hiatus – esophagus and CNX; T10 c. Aortic – aorta, thoracic duct and azygos v.; T12

Moore and Agur, 1996