Posterior Abdominal Wall Anatomy PDF

POSTERIOR ABDOMINAL WALL DPM PROGRAM Learning Objectives: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. Describe the location of the posterior abdominal wall. Describe the bones that make up the posterior abdominal wall. Describe the structure and f...

POSTERIOR ABDOMINAL WALL DPM PROGRAM Learning Objectives: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. Describe the location of the posterior abdominal wall. Describe the bones that make up the posterior abdominal wall. Describe the structure and function of the diaphragm. Describe the openings of the diaphragm and what passes through each. Describe the attachments, innervation, blood supply, and action of the posterior abdominal wall muscles. Describe what psoas major and iliacus form. Describe the location of the kidneys in the posterior abdominal wall. Describe the anterior surface of the kidney’s relationship to other structures in the posterior abdominal wall. Describe the posterior surface of the kidney’s relationship to other structures in the posterior abdominal wall. Describe the renal fat and fascia of the kidneys. Describe the anatomical structures of the external kidneys. Describe the anatomical structures of the internal kidneys. Describe the renal artery. Describe the ureters. Describe the points of constriction of the ureters. Discuss where renal calculi (stones) typically become lodged in the ureter. Describe the suprarenal glands. Describe the innervation of the kidneys. Describe the abdominal aorta. Describe the branches of the abdominal aorta and what they supply. Describe the inferior vena cava and anterior relationships. Describe the tributaries of the inferior vena cava. Describe where lumbar veins drain and their importance. Describe the lymphatic drainage of posterior abdominal wall structures. Describe the lumbar plexus and its relationship to structures in the posterior abdominal wall. Describe the cutaneous innervation of the lumbar plexus. 1 SMU - Internal Data Describe the location of the posterior abdominal wall. The posterior abdominal region is posterior to the abdominal part of the gastrointestinal tract, the spleen, and the pancreas. This area is bounded by: - bones -muscles making up the posterior abdominal wall Contains numerous structures that not only are directly involved in the activities of the abdominal contents but also use this area as a conduit between body regions. Examples include: -the abdominal aorta -nerve plexuses, - the inferior vena cava, -the sympathetic trunks -lymphatics -kidneys -suprarenal glands 2 SMU - Internal Data Describe the bones that make up the posterior abdominal wall. Lumbar vertebrae: -Lumbar vertebrae increase in size from L1 to L5 -Allow for flexion and extension in the vertebral column Sacrum: -Forms the midline boundary of the posterior abdominal wall -Inferior to lumbar vertebrae -Has anterior and posterior sacral foramina for the anterior and posterior rami of spinal nerves to pass through Pelvic bones: -The ilia, attach laterally to the sacrum at the sacro-iliac joints -The medial side of each region of the iliac bone and the related muscles are components of the posterior abdominal wall Ribs: -Ribs 11 and 12 complete the superior bony framework of the posterior abdominal wall -Rib 11 is posterior to part of the superior part of the left kidney -Rib 12 - is posterior to the superior part of both kidneys - serves as an attachment for numerous muscles 3 SMU - Internal Data Describe the structure and function of the diaphragm. The diaphragm is anchored to the lumbar vertebrae by musculotendinous crura, which blend with the anterior longitudinal ligament of the vertebral column: Median arcuate ligament Right crus is the longest and broadest of the crura -attached to the bodies of vertebrae LI to LIII and the intervening intervertebral discs. Left crus is attached to vertebrae LI and LII and the associated intervertebral disc. There are tendinous arches that connect the crura: Median arcuate ligament: Connects the crura across the midline, and passes anterior to the aorta Medial arcuate ligament: Lateral to the crura, formed by upper part of the psoas major muscle. It is attached medially to the sides of vertebrae L1 and L2. Lateral arcuate ligament: Formed by a thickening in the fascia that covers the quadratus lumborum. It is attached medially to the transverse process of vertebra L1 and laterally to rib XII SMU - Internal Data Lateral arcuate ligament Medial arcuate ligament 4 Describe the openings of the diaphragm and what passes through each. Caval opening • Allows passage of the inferior vena cava at vertebral level T8. • It is accompanied by the right phrenic nerve. Esophageal hiatus • Formed from muscle fibers of the right crus of diaphragm • Allows passage of esophagus at T10 • Constricts when the diaphragm contracts acting as a sphincter. • Transmits the vagal trunks. Aortic hiatus • Is formed from right and left crura. • Found posterior to diaphragm at T12 level, midline. • Transmits the thoracic duct. Additional structures: Greater, lesser and least splanchnic nerves pass through the crura on either side Sympathetic trunks pass posterior to the medial arcuate ligament, on either side 5 SMU - Internal Data Describe the attachments, innervation, blood supply, and action of the posterior abdominal wall muscles. Quadratus Lumborum O: transverse process of L5, iliolumbar ligament, iliac crest I: transverse process of L1-L5 and inferior border of rib 12 Innervation: anterior rami T12and L1-L4 Actions: Depress and stabilize rib 12; some lateral bending of trunk Psoas minor O: lateral surface of T12 and L1 I: pectineal line of pelvic brim Innervation: anterior rami L1 Actions: weak flexion of lumbar vertebral column Psoas major O: lateral surface of T12 and L1-L5, transverse processes of lumbar vertebrae I: lesser trochanter of femur Innervation: anterior rami L1-L3 Actions: Flexion of thigh at hip joint Iliacus O: upper 2/3 of iliac fossa, anterior sacroiliac and iliolumbar ligaments, upper surface of sacrum I: lesser trochanter of femur Innervation: femoral nerve (L2-L4) Actions: Flexion of thigh at hip joint Note: all viscera and vessels have been removed from the photo 6 SMU - Internal Data Describe what psoas major and iliacus form. Psoas major and ilacus muscles: • Pass deep to inguinal ligament • As they pass into the thigh, these combined muscles are referred to as iliopsoas muscle Iliopsoas muscle: • Flexes the thigh at the hip joint when the trunk is stabilized • Flexes the trunk against gravity when the body is supine • Innervated by branches of the femoral nerve Psoas major Iliacus Inguinal ligament Iliopsoas muscle Proximal femur SMU - Internal Data Describe the location of the kidneys in the posterior abdominal wall. Kidney Location: • Retroperitoneal in the posterior abdominal region • Lie in the extraperitoneal connective tissue immediately lateral to the vertebral column • In the supine position, the kidneys extend from approximately vertebra T12 superiorly to vertebra L3 inferiorly • Note: the right kidney is somewhat lower than the left because of its relationship with the liver. • Although they are similar in size and shape, the left kidney is a longer and more slender organ than the right kidney, and is nearer to the midline. 8 SMU - Internal Data Describe the kidney’s anterior surface relationships. Anterior surface of right kidney: ▪ A small part of the superior pole is covered by the right suprarenal gland. ▪ Inferiorly, a large part of the rest of the upper part of the anterior surface is against the liver ▪ Medially, the descending part of the duodenum is retroperitoneal and contacts the kidney. ▪ The inferior pole of the kidney, on its lateral side, is directly associated with the right colic flexure and, on its medial side, is covered by a segment of the intraperitoneal small intestine. Anterior surface of left kidney: ▪ A small part of the superior pole is covered by the left suprarenal gland. ▪ The rest of the superior pole is covered by the intraperitoneal stomach and spleen. ▪ Moving inferiorly, the retroperitoneal pancreas covers the middle part of the kidney. ▪ On its lateral side, the lower half of the kidney is covered by the left colic flexure and the beginning of the descending colon, and, on its medial side, by the parts of the intraperitoneal jejunum. 9 SMU - Internal Data Describe the kidney’s posterior surface relationships. Posterior surface of the right and left kidney: ▪ Related to similar structures Superior: -diaphragm Inferior: -psoas major, quadratus lumborum and transversus abdominis muscles Posterior: -Costodiaphragmatic recesses -Subcostal vessels and nerves -Iliohypogastric and ilioinguinal nerves -Right kidney anterior to rib 12 -Left kidney anterior to ribs 11 and 12 10 SMU - Internal Data Describe the renal fat and fascia of the kidneys. The kidneys are enclosed in and associated with a unique arrangement of fascia and fat. There are two kinds of fat surrounding the kidneys: 1) Perinephric fat (perirenal fat) • Outside the renal capsule • Completely surrounds kidneys • Renal fascia • Enclosing the perinephric fat • Membranous condensation of extraperitoneal fat • Must be incised in any surgical approach to this organ 2) Paranephric fat (pararenal fat) • Completes the fat and fascia's associated with the kidney • Accumulates posterior and posterolateral to each kidney 11 SMU - Internal Data Describe the anatomical structures of the external kidneys. Fibrous capsule External kidney structures Fibrous capsule • easily removable except during disease Hilum • medial margin where renal vessels, lymphatics, and nerves enter, and substances leave • continuous with renal sinus • perinephric fat surrounds all structures in hilum and sinus Hilum 12 SMU - Internal Data Describe the anatomical structures of the internal kidneys. Internal kidney structures Outer renal cortex • continuous band of pale tissue that completely surrounds the inner renal medulla • renal columns project into the inner aspect of the kidney, dividing the renal medulla (consists of renal columns & renal pyramids) into discontinuous aggregations of triangular-shaped tissue renal pyramids • Contains renal corpuscles, proximal/distal tubules, and peritubular capillaries • 95% of all blood that enters the kidneys goes to the cortex Renal Pyramid Outer renal cortex Renal Column Inner renal medulla Renal Medulla • Inner portion of kidney • Renal pyramids that have base and apex • Receives 5% of blood supply • If you have a drop in blood pressure or blood volume this element can have ischemic damage • Contains Henle’s loop, vasa recta, collecting ducts for all nephrons Renal pyramids • Apex points inward toward the renal sinus • Apex is called renal papilla and contains the openings of the papillary ducts draining the renal tubules and is surrounded by the minor calyx. 13 SMU - Internal Data Describe the anatomical structures of the internal kidneys. Internal kidney structures Renal papilla Flow of urine: Renal papilla Minor calices (1 per papilla) –receive urine from collecting ducts Major calices Minor calyx Major calyx Renal pelvis Renal pelvis Ureter Bladder Ureter 14 SMU - Internal Data Describe the renal artery. Renal arteries • Lateral branch of the abdominal aorta • Arise inferior to the origin of the superior mesenteric artery (between L1 and L2 vertebrae) • Left renal artery arises higher than the right • Right renal artery is longer and passes posterior to the inferior vena cava • Divide into anterior and posterior branches as they enter the hilum Renal veins • Multiple renal veins contribute to form the left and right renal veins • Right and left are anterior to the renal arteries • The left renal vein is longer • Crosses the midline anterior to the abdominal aorta and posterior to superior mesenteric artery • Can be compressed by an aneurysm in either of these two vessels it crosses Right renal artery Left renal artery Right renal Vein (cut) Left renal vein 15 SMU - Internal Data Describe the ureters. Ureters • muscular tubes that transport urine from the kidneys to the bladder Path from renal pelvis to bladder: • Continuous superiorly with the renal pelvis • Descends retroperitoneally on the medial aspect of the psoas major muscle • At the pelvic brim, the ureters cross either end of the common iliac artery, enter the pelvic cavity, and continue to the bladder Arterial supply: renal arteries, testicular or ovarian arteries, the common iliac arteries, internal iliac arteries Innervation: • Renal, aortic, superior/inferior hypogastric plexuses • Visceral efferent fibers (GSE): from sympathetic and parasympathetic sources • Visceral afferent fibers (GSA): return to T11-L2 spinal cord levels Ureteric pain: • Usually related to distention of the ureter • Referred to cutaneous areas supplied by T11-L2 spinal cord levels SMU - Internal Data Left ureter Right ureter Ovarian/testicular vessels Common iliac artery 16 Describe the points of constriction of the ureters. Ureters are muscular ducts with narrow lumens. They carry urine from the kidneys to the bladder. Normal constrictions (kidney stones can become lodged at these constrictions): 1. The junction of the renal pelvis with the ureter (ureteropelvic junction). 2. The point where the ureters cross the common iliac vessels at the pelvic brim 3. The junction of the ureter with the urinary bladder. 17 SMU - Internal Data Describe the suprarenal glands. Suprarenal glands • Associated with the superior pole of each kidney • Consist of: • Outer cortex • Inner medulla Arterial supply from three primary sources: 1) Inferior phrenic arteries give off superior suprarenal arteries 2) Abdominal aorta gives off middle suprarenal artery 3) Renal arteries give off inferior suprarenal arteries Innervation: • Preganglionic sympathetic fibers from T8-L1 that directly innervate cells of the adrenal medulla 18 SMU - Internal Data Describe the innervation of the kidneys. Renal plexus • Mixed (parasympathetic and sympathetic fibers) • Predominantly sympathetic • Promotes vasoconstriction (decrease glomerulus filtration rate) Renal plexus Input from: • Aorticorenal ganglion • Lesser splanchnic nerve (T10-T11) • Least splanchnic n. (T12) • Innervates renal plexus directly 19 SMU - Internal Data Describe the abdominal aorta. Abdominal aorta • Begins at the aortic hiatus of the diaphragm as a midline structure at approximately the lower level of vertebra T12 • At L4 vertebral level if bifurcates into (bifourcation): • Right common iliac artery • Left common iliac artery • These will branch into external and internal iliac arteries Relationships: Anterior • Pancreas and splenic vein • Left renal vein • Inferior part of duodenum Posterior • Lumbar veins To the right • Cisterna chyli • Thoracic duct • Azygos vein • Right crus of the diaphragm • Inferior vena cava Abdominal aorta Common iliac artery L4 External iliac artery Internal iliac artery 20 SMU - Internal Data Describe the branches of the abdominal aorta and what they supply. 21 SMU - Internal Data 22 SMU - Internal Data Describe the inferior vena cava and anterior relationships. Inferior vena cava • Returns blood from all structures below the diaphragm • Formed by the R/L common iliac veins • These come together at L5 • Pierces central tendon at T8 Anterior surface of the inferior vena cava crossed by: • Right common iliac artery • Root of the mesentery • Right testicular/ovarian artery • Superior part of duodenum • Bile duct • Portal vein • Liver 23 SMU - Internal Data Describe the tributaries of the inferior vena cava. Tributaries to the inferior vena cava include the: ▪ common iliac veins ▪ lumbar veins ▪ right testicular or ovarian vein ▪ renal veins ▪ right suprarenal vein ▪ inferior phrenic veins ▪ hepatic veins Reminder: there are no tributaries from the abdominal part of the gastrointestinal tract, the spleen, the pancreas, or the gallbladder, because veins from these structures are components of the portal venous system, which first passes through the liver. 24 SMU - Internal Data Describe where lumbar veins drain and the importance. Lumbar veins: • Unique in their connections • Not all of the lumbar veins drain directly into the inferior vena cava ▪ The fifth lumbar vein generally drains into the iliolumbar vein, a tributary of the common iliac vein. ▪ The third and fourth lumbar veins usually drain into the inferior vena cava. ▪ The first and second lumbar veins may empty into the ascending lumbar veins. -ascending lumbar veins connect the common iliac, iliolumbar, and lumbar veins with the azygos and hemi-azygos veins of the thorax -If the inferior vena cava becomes blocked, the ascending lumbar veins become important collateral channels between the lower and upper parts of the body. 25 SMU - Internal Data Describe the lymphatic drainage of posterior abdominal wall structures. Lymphatic drainage from the deep structures below the diaphragm converge mainly on lymph nodes associated with the blood vessels. Lymph then predominately drains into the thoracic duct. Posterior abdominal wall lymph nodes: Pre-aortic • Anterior to abdominal aorta • Form the intestinal trunk • All receive lymph from: • Foregut, midgut, hindgut viscera • Spleen • Pancreas • Gallbladder • Liver Lateral aortic/Lumbar nodes (para-aortic nodes) • On either side of abdominal aorta • Form the right and left lumbar trunks • Receive lymph from: • Body wall • Kidneys • Suprarenal glands • Testes/ovaries Reminder: cisterna chyli (formed by intestinal trunk and lumbar trunks); found anterior to L1 and L2 SMU - Internal Data 26 Describe the lumbar plexus and its relationship to structures in the posterior abdominal wall. Subcostal (T12) Iliohyposgastric (L1) -anterior to quadratus lumborum muscle -above iliac crest gives a branch to supply the posterolateral gluteal skin -cutaneous branches to pubic region Ilio-inguinal nerve (L1) -inferior to iliohypogastric n. -usually crosses part of iliacus muscle on its way to the iliac crest -near the anterior iliac crest it pierces the transversus abdominis muscle and then pierces the internal oblique muscle -emerges through the superficial inguinal ring -cutaneous innervation to upper medial thigh, the root of the penis, anterior surface of the scrotum in men, mons pubis, and labium majus 27 SMU - Internal Data Describe the lumbar plexus and its relationship to structures in the posterior abdominal wall. Genitofemoral nerve (L1 and L2) -passes downward in the psoas major muscle and emerges on the anterior surface of the psoas major m. -passes posterior to the ureter -divides into genital and femoral branches -Genital branch: enters the inguinal canal through the deep inguinal ring. Innervates cremasteric muscle terminates in the scrotum or mons pubis and labia majus. -Femoral branch: descends on the lateral side of the external iliac artery and passes posterior to the inguinal ligament, entering the femoral sheath lateral to the femoral artery. Pierces the anterior femoral sheath and the fascia lata to supply the skin of the upper anterior thigh. Lateral cutaneous nerve of thigh (L2 and L3) -arises from the anterior rami of nerves L2 and L3 -emerges from the lateral border of the psoas major muscle, passing obliquely downward across the iliacus muscle toward the anterior superior iliac spine -passes posterior to the inguinal ligament and enters the thigh -supplies the skin on the anterior and lateral thigh to the level of the knee Femoral nerve (L2 to L4) -descends through the substance of the psoas major muscle, emerging from the lower lateral border of the psoas major -the femoral nerve lies between the lateral border of the psoas major and the anterior surface of the iliacus muscle -is deep to the iliacus fascia and lateral to the femoral artery as it passes posterior to the inguinal ligament and enters the anterior compartment of the thigh. Cutaneous branches of the femoral nerve include: ▪ medial and intermediate cutaneous nerves supplying the skin on the anterior surface of the thigh, and ▪ the saphenous nerve supplying the skin on the medial surface of the leg 28 SMU - Internal Data Describe the lumbar plexus and its relationship to structures in the posterior abdominal wall. Obturator nerve (L2 to L4) -descends in the psoas major muscle, emerging from its medial side near the pelvic brim -continues posterior to the common iliac vessels, passes across the lateral wall of the pelvic cavity, and enters the obturator canal, through which the obturator nerve gains access to the medial compartment of the thigh. -in the area of the obturator canal, the obturator nerve divides into anterior and posterior branches. On entering the medial compartment of the thigh, the two branches are separated by the obturator externus and adductor brevis muscles. Throughout their course through the medial compartment, these two branches supply: ▪ articular branches to the hip joint, ▪ muscular branches to the obturator externus, adductor longus, gracilis, adductor brevis, and adductor magnus muscles, and may provide a small branch to pectineus muscle. ▪ cutaneous branches to the medial aspect of the thigh, and ▪ in association with the saphenous nerve, cutaneous branches to the medial aspect of the upper part of the leg and articular branches to the knee joint Lumbosacral trunk (L4, L5) -passes over the ala (wing) of the sacrum and descends into the pelvis to participate in the formation of the sacral plexus along with the anterior rami of the S1-S4 nerves 29 SMU - Internal Data 30 SMU - Internal Data Describe the cutaneous innervation of the lumbar plexus. 31 SMU - Internal Data