Gross Anatomy II - Week 6 Lecture Notes.pdf

Abdominal Aorta Begins at the level of T12 (aortic hiatus of diaphragm) as a continuation of descending thoracic aorta à descends anterior to lumbar vertebral column, posterior to peritoneum (it is a retroperitoneal structure), and to the left of IVC à terminates...

Abdominal Aorta Begins at the level of T12 (aortic hiatus of diaphragm) as a continuation of descending thoracic aorta à descends anterior to lumbar vertebral column, posterior to peritoneum (it is a retroperitoneal structure), and to the left of IVC à terminates at level of L4 by dividing into right and left common iliac arteries Visceral branches: Unpaired: celiac trunk, superior mesenteric artery, inferior mesenteric artery Paired: middle suprarenal arteries, renal arteries, testicular/ovarian arteries Parietal branches: Unpaired: median sacral artery Paired: inferior phrenic arteries, lumbar arteries (4 pairs) https://sites.google.com/view/grossanatomyii/week-6-lecture-notes 6/21/24, 2 06 PM Page 2 of 19 :  Celiac Trunk Originates from abdominal aorta at the level of T12 Lies posterior to stomach and lesser sac Immediately divides into 3 branches: Left gastric artery Splenic artery Common hepatic artery Left gastric artery: smallest branch of celiac trunk à passes superiorly and to the left, toward cardial region of stomach, posterior to lesser sac à gives off esophageal branches (supply lower part of esophagus) and then descends along lesser curvature of stomach à anastomoses with right gastric artery Splenic artery: largest branch of celiac trunk à runs to the left, along superior border of pancreas, posterior to stomach and lesser sac (it follows a wavy course) à reaches hilum of spleen within splenorenal ligament https://sites.google.com/view/grossanatomyii/week-6-lecture-notes 6/21/24, 2 06 PM Page 4 of 19 :  Branches of splenic artery Pancreatic branches à supply neck, body and tail of pancreas Left gastroepiploic (gastroomental) artery à originates near hilum of spleen à reaches greater curvature of stomach in gastrosplenic ligament and runs along greater curvature from left to right à anastomoses with right gastroepiploic artery Short gastric arteries à originate close to hilum of spleen à reach stomach in gastrosplenic ligament and supply its fundus Terminal branches à enter spleen through its hilum Common hepatic artery runs anteriorly and to the right to reach superior aspect of 1st part of duodenum, where it divides into 2 branches: proper hepatic artery and gastroduodenal artery Proper hepatic artery Ascends between 2 layers of hepatoduodenal ligament toward hilum of liver (porta hepatis) and divides into right and left branches that enter liver through porta hepatis. The right branch usually gives off cystic artery (supplies gallbladder) Within lesser omentum, proper hepatic artery lies anterior to (hepatic) portal vein and to the left of common bile duct Right gastric artery à usually originates from proper hepatic artery à descends to pyloric end of stomach à runs to the left along lesser curvature of stomach à anastomoses with left gastric artery Gastroduodenal artery Descends posterior to 1st part of duodenum à it gives off right gastroepiploic and superior pancreaticoduodenal arteries Right gastroepiploic (gastroomental) artery à runs along greater curvature of stomach from right to left à anastomoses with left gastroepiploic artery Superior pancreaticoduodenal arteries (anterior and posterior) à supply duodenum and head of pancreas à anastomose with inferior pancreaticoduodenal arteries (branches of superior mesenteric artery) https://sites.google.com/view/grossanatomyii/week-6-lecture-notes 6/21/24, 2 06 PM Page 6 of 19 :  Superior Mesenteric Artery (SMA) Unpaired visceral branch of abdominal aorta that originates from anterior aspect of abdominal aorta at level of L1, posterior to neck of pancreas Runs inferiorly and to the right à at its origin it passes anterior to the left renal vein, then it passes anterior to uncinate process of pancreas and 3rd part of duodenum and continues along root of mesentery of small intestine (aneurysms of initial part of SMA can compress left renal vein or 3rd part of duodenum) Supplies lower part of head of pancreas, distal part of duodenum, jejunum, ileum, cecum, appendix, ascending colon and proximal ⅔ of transverse colon https://sites.google.com/view/grossanatomyii/week-6-lecture-notes 6/21/24, 2 06 PM Page 7 of 19 :  Branches of Superior Mesenteric Artery (SMA) Inferior pancreaticoduodenal artery à divides into anterior and posterior branches, which pass to the right supplying lower part of head of pancreas and distal half of duodenum à anastomose with superior pancreaticoduodenal branches of gastroduodenal artery (anastomosis between CT and SMA) Jejunal and ileal (intestinal) arteries à 12 to 15 in number à originate from left side of SMA à run between 2 layers of mesentery of small intestine to reach coils of jejunum and ileum à form arterial arcades that increase in number from jejunum to ileum à terminal arcades give rise to straight arteries that supply intestinal wall Ileocolic artery à lowermost of branches that originate from right side of SMA à runs inferiorly and to the right, toward ileocecal junction, behind peritoneum à its branches supply terminal ileum, cecum, appendix and beginning of ascending colon Right colic artery à runs to the right, behind peritoneum, to supply ascending colon and beginning of transverse colon à exhibits considerable variability (may originate from SMA, ileocolic artery, middle colic artery or it may be absent) Middle colic à runs between 2 layers of transverse mesocolon à its branches supply proximal ⅔ of transverse colon à anastomoses with left colic artery (branch of IMA) https://sites.google.com/view/grossanatomyii/week-6-lecture-notes 6/21/24, 2 06 PM Page 10 of 19 :  Inferior Mesenteric Artery (IMA) Lowest unpaired visceral branch of abdominal aorta à originates from anterior aspect of abdominal aorta at level of L3 Runs inferiorly, posterior to peritoneum, in left infracolic space à crosses left common iliac vessels and continues into pelvis as superior rectal artery Supplies distal ⅓ of transverse colon, descending colon, sigmoid colon, rectum and upper half of anal canal Branches: Left colic artery à runs to the left, behind peritoneum à its branches supply distal ⅓ of transverse colon and descending colon à anastomoses with middle colic artery (branch of SMA) Branches: Sigmoid arteries à 2 or 3 in number à run between 2 layers of sigmoid mesocolon à supply sigmoid colon Superior rectal artery à inferior continuation of IMA à descends into pelvis posterior to rectum à supplies rectum and upper half of anal canal à anastomoses with middle and inferior rectal arteries (branches of internal iliac and internal pudendal arteries, respectively) https://sites.google.com/view/grossanatomyii/week-6-lecture-notes 6/21/24, 2 06 PM Page 11 of 19 :  Development of the Digestive System Objectives 1. List the divisions of the gut tube and identify their associated vasculature and their derivatives 2. Identify the origins of the tissues which make up the digestive system 3. Describe the process of rotation of the gut tube 4. Describe the formation of the anorectal canal https://sites.google.com/view/grossanatomyii/week-6-lecture-notes 6/21/24, 2 06 PM Page 13 of 19 :  Divisions of the Gut Tube With cephalocaudal and lateral folding of embryo, part of endoderm-lined yolk sac cavity is incorporated into embryo to form primitive gut In cephalic and caudal parts of embryo, primitive gut is a blind-ended tube (foregut and hindgut, respectively) à middle part (midgut) remains temporarily connected to yolk sac by vitelline duct (stalk of yolk sac) Pharyngeal gut (cephalic part of foregut) extends from buccopharyngeal (oropharyngeal) membrane to respiratory diverticulum (lung bud) Remaining part of foregut lies caudal to pharyngeal gut and extends inferiorly as far as hepatic diverticulum (liver bud) à abdominal part of foregut is supplied by celiac trunk Midgut begins caudal to liver bud and extends to a point that corresponds with junction of proximal ⅔ and distal ⅓ of transverse colon in the adult à supplied by SMA Hindgut extends from distal ⅓ of transverse colon to cloacal membrane à supplied by IMA Endoderm forms epithelial lining of digestive tract and gives rise also to parenchyma (specific cells) of glands (hepatocytes, endocrine and exocrine cells of pancreas) Muscle, connective tissue and peritoneal components of gut tube are derived from visceral (splanchnic) mesoderm à stroma of glands is also derived from visceral mesoderm Upper part of anal canal is derived from hindgut endoderm and lower part is derived from ectoderm of anal pit (proctodeum) which is an invagination of surface ectoderm à rupture of anal membrane establishes continuity between two parts of anal canal (boundary between 2 parts is indicated by pectinate line) https://sites.google.com/view/grossanatomyii/week-6-lecture-notes 6/21/24, 2 06 PM Page 14 of 19 :  Stomach Appears as a fusiform dilatation of foregut in 4th week of development Positional changes are most easily explained by assuming that stomach rotates around a longitudinal axis and an anteroposterior axis Stomach rotates 90°clockwise around its longitudinal axis and left side faces anteriorly and right side faces posteriorly and left vagus nerve now innervates anterior wall of stomach and right vagus nerve now innervates its posterior wall. during this rotation, original posterior wall grows faster than anterior one, forming the greater and lesser curvatures, respectively Cephalic and caudal ends of stomach are originally in midline with further growth stomach rotates around anteroposterior axis and caudal (pyloric) end moves right and upward and cephalic (cardial) end moves left and downward Rotation around longitudinal axis pulls dorsal mesogastrium to the left and ventral mesogastrium to the right and it also creates a space behind stomach (omental bursa or https://sites.google.com/view/grossanatomyii/week-6-lecture-notes 6/21/24, 2 06 PM Page 15 of 19 :  Functions Stores food Mixes food with gastric secretions to form semi-fluid mass (chyme) Controls rate of delivery of chyme to small intestine 2 surfaces (walls): anterior and posterior 2 borders: lesser curvature (shorter and on the right) and greater curvature (longer and on the left) Incisura angularis (angular notch) à indentation located in lower part of lesser curvature 2 orifices: cardial and pyloric orifices Cardial orifice: communicates esophagus with stomach https://sites.google.com/view/grossanatomyii/week-6-lecture-notes 6/21/24, 2 06 PM Page 17 of 19 :  Cardial notch: indentation located between left border of esophagus and fundus of stomach Pyloric orifice: communicates stomach with duodenum à it is surrounded by a sphincter (pyloric sphincter), formed by a thickening of circular muscle layer of stomach Parts https://sites.google.com/view/grossanatomyii/week-6-lecture-notes 6/21/24, 2 06 PM Page 18 of 19 :  Cardia (cardial part) à area immediately adjacent to cardial orifice Fundus: dome-shaped, upper part of stomach à limited inferiorly by horizontal line drawn across stomach starting at cardial notch à usually is full of gas Body: extends from the level of cardial notch to the level of angular notch Pyloric part: distal, funnel-shaped region of stomach à extends from angular notch to pyloric orifice à its proximal, wider part is known as pyloric antrum à its distal, narrower part is known as pyloric canal Anatomical relations: Anteriorly: anterior abdominal wall, left costal margin, diaphragm, left lobe of liver Posteriorly: lesser sac, diaphragm, spleen, upper part of left kidney, left suprarenal gland, splenic artery, pancreas, transverse mesocolon Summary of the Blood Supply of the Stomach Arteries: Left gastric artery (branch of celiac trunk) Right gastric artery (branch of proper hepatic artery) Left gastroepiploic artery (branch of splenic artery) Right gastroepiploic artery (branch of gastroduodenal artery) Short gastric arteries (branches of splenic artery) All arteries are accompanied by veins of same name à all venous blood from stomach drains (directly or indirectly) into portal vein https://sites.google.com/view/grossanatomyii/week-6-lecture-notes 6/21/24, 2 06 PM Page 19 of 19 :