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Region 16: Kidneys and Retroperitoneal Structures Abdominal aorta --appears in abdomen at aortic hiatus of diaphragm at T12 vertebrae --ends in front of L4 by dividing into left and right common iliac arteries --Unpaired branches from its anterior surface *unpaired celiac trunk *unpaired superior mesenteric artery *unpaired inferior mesenteric artery --paired branches from its lateral side --unpaired branch from dorsolateral side *unpaired median sacral artery Renal Fascia --anterior and posterior lamellae fuse lateral, superior, and medial to kidneys *separate extraperitoneal fat into perirenal fat (adjacent to kidneys) and pararenal fat (behind posterior lamella of renal fascia Suprarenal Glands --located at superior medial aspect of kidneys --since cortical part of suprarenal glands produce steroids, gland appears fatty and may pass for some of fat that surrounds kidney --Blood supply to suprarenal glands *three sets of aa. supply the glands a. superior suprarenal aa: branch from inferior phrenic aa. b. middle suprarenal aa.: brach directly off aorta c. inferior suprarenal aa: branches of renal aa. *one major suprarenal vein drains suprarenal gland a. right side: vein drains directly into inferior vena cava b. left side: vein usually joined by inferior phrenic vein before emptying into left renal vein --suprarenal medulla: innervated directly by preganglionic sympathetic fibers Kidneys --external features *medial border is indented by a hilum --internal anatomy a. hilus opens into renal sinus contains renal vessels, nerve, lymphathics, major and minor calyces, and renal pelvis (enlarged upper end of ureter) b. medulla: characterized by pyramids whose apexes project into minor calyx as a papilla and its base lies at corticomedullary junction c. pyramids are separated by cortical tissue designated as renal columns (some of the collecting ducts of the pyramids continue into cortex called medullary rays) --Blood Supply *renal arteries: branch from aorta at level of L1 a. right renal a.: passes posterior to inferior vena cava --divides as it approaches the kidney to form segmental aa. --inferior suprarenal aa: branches of renal aa. *renal veins: tributaries of inferior vena cava a. left renal vein: passes in front of aorta immediately below origin of superior mesenteric a. Ureters --Minor calyces: join to form major calyces, which form the renal pelvis (upper expanded part of ureter) --relationships of the ureter *through most of their course, the ureters lie on the psoas muscles, then cross the bifurcation of the common iliac vessels to enter the pelvis Inferior Vena Cava --begins at elvel of L5 by confluence of the left and right common iliac vein --ends at level of T8 where it passes through the diaphragm --lies to the right of the aorta --has tributaries --important collateral routes b/w superior and inferior vena cava include *thoracoepigastric veins *ascending lumbar veins: change to azygos vein on right and hemiazygos on left Lymphatics --Cisterna Chyli *lies on bodies of L1 and L2 *dilated sac that receives lymph gathered from lower part of the body *it is the inferior end of the thoracic duct --Thoracic Duct *leaves the abdomen by way of the aortic hiatus and travels b/w the aorta and azygos vein Autonomic Nervous system of the Abdomen --while the chain ganglia of the sympathetic system are well defined anatomically, the collateral ganglia on the vental side of the aorta are not --Sympathetic system *white communicating ramus (L1-2) *postganglionic fibers enter the gray communicating rami to follow spinal nerves of the lumbar plexus --collateral ganglia *preganglionic fibers enter them via the thoracic splanchnice nerves (greater, lesser, least) and the lumbar splanchnic nerves *celiac ganglion: receives preganglionic fibers from the thoracic splanchnic nerves *ganglion impar/coccygeal ganglion: terminal convergence of sympathetic trunks, anterior to coccyx and single --Parasympathetic System a. preganglionic parasympathetic supply to the structures derived from foregut (stomach, duodenum, liver, gallbladder, pancreas) and midgut (jejunum, ileum, ascending and transverse colons) via the vagus nerves b. preganglionic parasympathetic fibers to the hindgut structures (descending and sigmoid colon, rectum) and the pelvic organs arise in segments S2,3,4 of the spinal cord c. fibers enter pelvis plexus via pelvic splanchnic nerve (parasympathetic) d. nervus erigentes *preganglionic parasympathetic fibers of the pelvic splanchnic nerves going to terminal pelvic ganglia