Lecture 75: Gross Anatomy - Posterior Abdominal Wall & Diaphragm PDF

Lecture 75: Gross Anatomy - Posterior Abdominal Wall & Diaphragm Musculoskeletal framework: posterior to abdominal GI tract, liver, pancreas, & spleen; includes muscles that move the trunk & lower limbs, limited superiorly by the diaphragm Bones: ribs XI & XII, crest & fossa of ilium, bodies & trans...

Lecture 75: Gross Anatomy - Posterior Abdominal Wall & Diaphragm Musculoskeletal framework: posterior to abdominal GI tract, liver, pancreas, & spleen; includes muscles that move the trunk & lower limbs, limited superiorly by the diaphragm Bones: ribs XI & XII, crest & fossa of ilium, bodies & transverse processes of LV1-LV5 (prominent due to forward convexity of spine), and upper margin (ala) of sacrum Muscles: erector spinae group is located posterior to abdominal wall assist in trunk extension Psoas minor: TV12-LV1 → iliopubic eminence of pelvis; assists in trunk flexion Psoas major: TV12-LV4 → lesser trochanter of femur; assists in trunk & thigh flexion Iliacus: iliac fossa of pelvis → lesser trochanter of femur; assists in trunk & thigh flexion Quadratus lumborum: rib 12 & TV12-LV5 → iliac crest of pelvis; assists in lateral flexion of trunk Clinical correlation: psoas abscess occurs when pus accumulates b/w psoas muscle & its fascia, causing severe pain during thigh flexion; associated symptoms = fever, weight loss, & malaise Diaphragm: Anatomy: two crura (R attached to LV1-LV3, L attached to LV1-LV2) connected at midline w/ 3 tendinous arches: median arcuate ligament (contains aorta & thoracic duct), medial arcuate ligament (contains psoas major & sympathetic trunk), lateral arcuate ligament (contains quadratus lumborum) Esophageal hiatus: at TV10, esophagus passes through w/ anterior &c posterior vagal trunks & esophageal branches from the L gastric artery & vein Caval opening: at T8, IVC passes through w/ R phrenic nerve L phrenic N, azygos & hemiazygos veins, & thoracic splanchnics pass directly through muscle Developmental considerations: diaphragm develops from septum transversum (forms central tendon), pleuroperitoneal folds (close R/L pericardioperitoneal canals), posterior esophageal mesentery (forms R/L crura), & peripheral rim (infiltrating myocytes from somites C3-C5) Congenital diaphragm hernia: failure of pleuroperitoneal fold to close canal → gut enters thorax Clinical correlation: hiatal hernia occurs when diaphragm is weak near esophageal hiatus, permitting passage of the stomach into the thorax Abdominal aorta: Unpaired branches: celiac trunk (TV12), SMA (LV1), IMA (LV3) Paired branches: inferior phrenic (emerge near celiac), middle suprarenal & renal arteries (emerge near SMA), gonadal (~LV2), lumbar (4 pairs, LV1-LV4) Clinical correlations: Nutcracker syndrome: compression of the L renal v. b/w SMA & aorta, causes flank pain, blood in urine (hematuria), & L-sided varicocele SMA syndrome: compression of 3rd part of duodenum b/w SMA & aorta, causes intermittent intestinal pain, especially after eating Abdominal aortic aneurysm (AAA): bulge/swelling of the abdominal aorta, often fatal if ruptured IVC: lies to the R of the abdominal aorta, formed by the convergence of the 2 common iliac vv. Tributaries: common iliac, lumbar, R gonadal, renal, R suprarenal, inferior phrenic, & hepatic veins Ascending lumbar veins: long venous channels that provide collateral circulation if IVC is blocked Clinical correlations: IVC filters: prevent the passage of DVT clots into the heart/lungs May-Thurner syndrome: compression of the L common iliac v. by the R common iliac a. against the body of LV5, resulting in the pain & swelling of the L lower limb, often in young adult women Abdominal lymphatics: 2 channels form trunks that converge at the R posterior surface of the aorta near LV1-LV2, forming the cisterna chyli that marks the beginning of the thoracic duct Pre-aortic channel: nodes along the abdominal aorta receive lymph from the GI tract & accessory organs (liver, gallbladder, pancreas, spleen) Para-aortic channel: nodes lateral to the abdominal aorta & IVC, receive lymph from the body wall, kidneys, suprarenal glands, & testes/ovaries Clinical correlations: in retroperitoneal lymph node dissection (RPLND), surgery is required to clear cancerous retroperitoneal lymph nodes; can be done open (requires long incision of anterior abdominal wall) or laparoscopically (small incision cites w/ shorter recovery time, but has limitations) Nerves: understand the nerves of the lumbar plexus: Subcostal n: from T12, associated w/ the 12th rib & quadratus lumborum muscle, dermatome = suprapubic Iliohypogastric & ilioinguinal nn: from L1, cross the quadratus lumborum muscle as they course laterally; send motor branches to the anterior abdominal wall, sensory branches distribute to the L1 dermatome of the pubic region & accompany the spermatic cord to innervate the anterior scrotum & upper medial thigh Genitofemoral n: from L1-L2, exits anteriorly out of the main belly of the psoas major Genital branch: motor innervation to the cremasteric muscle & sensory to anterior scrotum Femoral branch: provides cutaneous innervation to the upper anterior thigh Lateral femoral cutaneous n: from L2-L3, follows the contour of the iliac fossa & iliacus muscle & travels into the lateral thigh deep do the lateral attachment of ing lig; innervates skin of proximal lateral thigh Femoral n: from L2-L4, courses lateral to the inferior part of the psoas major (review innerv from HBF-I) Obturator n: from L2-L4, courses medial to the psoas major (review innerv from HBF-I) ANS abdomen: lumbar sympathetic trunks lie anterolateral to lumbar vertebral bodies, ganglia are flat & difficult to distinguish Prevertebral plexus: prevertebral ganglia surround the aorta & its large branches (celiac, SMA, IMA, renal), continues inferiorly as the sup hypogastric plexus, & divides into L/R hypogastric nn. Organ relationships: