ANATOMY OF THE ABDOMEN

THE ABDOMINThe Abdomen is the region of the trunk that lies between the diaphragm above & the inlet of the pelvis below.The abdominal wall:Superiorly , the abdominal wall is formed by the diaphragm ,which separates the abdominal cavity from the thoracic cavity .Inferiorly the abdominal cavity is continuous with the pelvic cavity through the pelvic inlet.Anteriorly ,the abdominal wall is formed by the lower part of thoracic cage & below by the rectus abdominus M ,,ext. oblique ,int. oblique & transverse abdominus M.& fasciae.

The abdominal wallPosteriorly ,the abdominal wall is formed in the midline by the 5 lumbar vertebrae & their intervertebra discs,laterally,by the 12th ribs ,upper part of bony pelvis ,the psoas M.,the quadratus lumborum M.,& the aponeuroses of origin of transversus abdominus M.The anterior abdominal wall is divided by 2 midclavicular lines longitudanally & subcostal & inter tubercular lines transeversly to 9 regions:right & left hypochondrium& epigastric area in between., right & left lumbar areas & umbilicus area in between & right & left iliac fossae(inguinal) & hypogastric area in between.

The abdominal wallThe abdominal wall formed from 1- the skin : which supplied by the ant. Rami of the lower 6 thoracic & 1st lumber Nn. (which is the ilio-hypogastric & ilio-inguinal Nn.).T7 supply the skin of epigastric area,T10 supply the umbilicus&L1supply area above the inguinal lig.& the symphysis pubis.2- The superficial fascia :which divided to superficial fatty layer & deep membranous layer.,the fatty layer changed in the scrotum to dartos M.

The abdominal wall3- the deep fascia :it is a thin layer of aleolar tissue covering the mm. 4- the muscular layer : consist of 3 broad thin sheets that are aponeurotic in front (ext. oblique , int. oblique & trasversus abdominus )also there is a wide vertical M( the rectus abdominus M.) which enclosed by the sheet to form the rectus sheath .5- The fascia transversalis :thin layer of fascia that lines the trasversus abdominus M.& extend down to form the femoral sheath.

The abdominal wall6- the extra-peritoneal fat .7- the parietal peritoneum THE INGUINAL CANAL : It is an oblique passage ( canal ) through the lower abdominal wall & it allows to pass structures to & from the testis to abdomen in male,& the round lig .of the uterus to labium majus in female.& it transmits the ilio-inguinal N. in both sexes. The canal is 4 cm long lies above & parallel to the inguinal lig. Extend from the deep inguinal ring (a hole in transversalis fascia) down ward & medially to superficial inguinal ring( a hole in the aponeurosis of the ext. oblique M.

THE INGUINAL CANALThe walls of inguinal canal :The ant. wall :apooneurosis of ext. oblique M. The post.wall :the fascia transversalis .The inf. wall (the floor) : the inguinal lig.The sup. wall (the roof ): the lowest Ff. of int. oblique & transversus abdominis Mm.

THE INGUINAL CANALThe spermatic cord : is a collection of strs. that pass through the inguinal canal to & from the testis , it is formed from : 1- The vas deferens .2- the testicular artery .3- The testicular veins (pampiniform plexus).4- Testicular lymph nodes .5- autonomic Nn.6-processus vaginalis .7- Cremasteric A.8- Artery to vas deferens .9- Genital br. Of genito-femoral N .

The spermatic cordThe spermatic cord covered by 3 concentric layers of fascia derived from the layers of ant. Abdominal wall :1- The external spermatic fascia derived from the ext. oblique aponeurosis.2- Cremastric fascia derived from the int. oblique M.3- Internal spermatic fascia derived from the fascia transversalis .

The scrotumIt is an outpouching of the lower part of the ant. Abd. Wall . It contains the testes , the epididymides & the lower end of spermatic cord.The wall of the scrotum has the fallowing layers: the skin ,superficial fascia( dartos M. replace the fatty layer) , The external spermatic fascia , Cremastric fascia , Internal spermatic fascia & tunica vaginalis .

THE ABDOMINAL CAVITYThe peritoneumIt is a serous membrane lining the wall of the abdomen & the pelvic cavities (= parietal P.) & clothing the abdominal & pelvic viscera (=visceral P) , the space between them called the peritoneal cavity which contain small amount of fluid .Between the parietal P. & the fascia covering the abd. Is a layer of connective tissue called the extra-peritoneal tissue. The organs which are covered totally with visceral P. called intraperitoneal organs while those covered partially or lying behind the P. called retroperitoneal organs.

The omentum: is 2- layers folds of P. that connects the stomach to other viscus.The greater omentum connects the stomach to transverse colon ,The lesser omentum connect the stomach to liver.The mesentery is a 2-layers folds of P. connecting parts of intestine to the post. abd. wall. e.g. mesentery of small int., the transverse colon, The sigmoid colon.The Parietal P. is sensitive to pain,temp.,touch & pressure & supplied by lower 6 thoracic & 1st lumber Nn. while the visceral P. sensitive to strech& tearing& supplied by autonomic N.S.

The gastrointestinal tractThe osophagus : is a muscular collapsible tube ,25 cm long, joins the pharynx to the stomach, its major part in the thorax, enters the abdomen through an opening in the right crus of the diaphragm &enter the stomach on its right side.The stomach :It is J-shape organ lies under cover of the lower ribs, has cardiac orifice above & pyloric orifice below,& has greater & lesser curvitures , & ant. & post. Surfaces.It devided to :fundus,body ,incisura angularis , antrum , pyloric canal & pyloric sphincter.

The StomachThe lesser curvature :forms the right border & extends from the cardiac orifice to the pylorus. It is suspended from the liver by the lesser omentum.The greater curvature :forms the left border, the greater omentum extends from the lower part to the transverse colon & the gastro-splenic omentum extend from the upper part to the spleen .The mucus membrane forms many folds called rugae that are longitudinal in direction.It has 3 muscular layers:longitudinal , circular & oblique.The stomach function is :storage of food ,mix the food with gastric secretions to form chyme, & the delivery of the chyme to the small intestine.

The small intestineIt extends from the pylorus to the ileo-cecal valve & divided to duodenum , the jejunum & the ileum.The duodenum : is a C- shape tube ,25 cm long, joins the stomach to the jejunum . It receives the opening of the bile & pancreatic ducts & curves around the head of pancreas. It divided to 4 parts :1st part is 5cm long, begins at pylorus & runs upward & backward on the right side of L1 vertebra.

The duodenumThe 2nd part: is 8 cm long runs vertically downward in front of the right kidney & on right side of L1,2 vertebrae. Its medial border receives the bile duct & the main pancreatic ducts in major duodenal papilla & receive the accessory panc. Duct higher up in the minor duod. Papilla .The 3rd part: is 8 cm long ,runs horizontally to the left, in front of the vertebral column& the lower margin of the head of panc.The 4th part: is 5 cm long, runs upward & to the left to the duodeno-jejunal flexure.The mucus memb. Is formed in circular folds called Plicae circularis .

The Jejunum & The IleumIt is 6 m long. The jejunum is the upper 2/5th of this length start in duodeno-jejunal junction to merge with the ileum which end in the ileo-cecal junction.The coils of them are freely mobile & attached to the post. abd. wall by fan shape fold of peritoneum called Mesentery of the small intestine.The jejunum has wider-bored, thicker-walled , redder & less fat than the ileum ,also the plicae circulares are larger ,more numerous & closely set.

The Large IntestineIt extends from the end of the ileum to the anus. It divided to Cecum , Appendix ,ascending colon ,Transverse colon ,Descending colon ,Sigmoid colon , Rectum & Anal canal.Its function is absorption of water & electrolytes& the storage of undigested material until it can be expelled from the body as feces .The Cecum : It is a blind-ended pouch located in the right iliac fossa , attached to its postero-medial surface is the appendix. The longutudinal Mm. folded in 3 strips called the teniea coli which covered the base of the appendix.The ileum enter the large int. at the junction of the cecum with the ascending colon in the ileo-cecal valve.

The Large IntestineThe Appendix :is a narrow muscular tube contain large amount of lymphoid tissue ,its base lies below the ileo-cecal junction & attached by the meso-appendix to the mesentery of the small int.The tip lies in many positions like retrocecal, pelvic, paracecal, subhepatic & retro-ileal sites.

The Large IntestineThe Ascending Colon :It is 13 cm long ,extend upward from the cecum to inf. surface of the liver where it turns to the left forming the hepatic flexure & become continuous with the transverse colon.The Transverse Colon : It is 40 cm long , begins at hepatic flexure extend across the abd. suspended by the transverse meseocolon, to the splenic flexure where turns downward to start the descending colon.

The Large IntestineThe Descending Colon : It is 25 cm long , extend from the splenic flexure downward to pelvic brim to continue with sigmoid colon,The Sigmoid Colon :It is 35cm long ,begins at the pelvic brim to continue with the rectum at S3 vertebra .Its attached to post. pelvic wall by sigmoid mesocolon where the left external iliac Vv. & the left ureter pass..

The Large IntestineThe rectum :It is 13 cm long begins in front of S3 as continuation of sigmoid colon to pass downward fallowing the curve of the sacrum & coccyx to the tip of the coccyx where pierce the pelvic diaphragm & become continuous with the anal canal . The dialated lower part called the rectal ampulla.The Anal Canal :is 5 cm long extend from the pelvic diaphragm to the anus opening & surrounded by the anal sphincters.

The blood supply of GIT.The arterial supply of the GIT related to the development of deferent parts of the gut . The celiac A. is the A. of the foregut & supplies from the lower 1/3 of the osophagus to the middle of the 2nd part of the duodenum.The sup. Mesenteric A .is the A. of the midgut & supplies from the middle of the 2nd part of the duodenum to distal 1/3 of the transverse colon.The inf. Mesenteric A. is the A. of the hindgut &supplies the large int. from distal 1/3 of the transverse colon down to half of the anal canal .

The celiac arteryIt arise from the abdominal aorta at T12 level, It gives 3 branches :1- The left gastric A. to lesser curvature of the stomach &lower Esophagus to anastamose with the right gastric A..2- The splenic A: run on the upper border of the pancreas & behind the stomach to enters the spleen . It gives:2-1- pancreatic branches.2-2- left gastro-epiploic A. on the greater curvature of the stomach to anastamose with the right gastro-epiploic A.

The celiac artery2-3- Short gastric Aa. to the fundus of the stomach.3- The Hepatic A. which gives :3-1- right gastric A. runs on the lesser curvature to anastamose with the left gastric A.3-2- Gastro-duodenal A. runs behind the 2nd part of the duod. to divide to right gastro-epiploic A (on the greater curvature) & superior pancreatico-duodenal A. which descend between the 2nd part of the duod. & the head of pancreas.3-3- Right & left hepatic Aa. that enter the porta hepatis. The right hepatic A. gives the cystic A. to the gall bladder

The superior mesenteric arteryIt is the A. of the midgut . It arise from the abd. aorta below the celiac A. to run downward behind the neck of the panc.& in front of the 3rd part of the duod. Its branches are :1- the inf. Pancreatico-duodenal A.2- middle colic A to supply the trans. colon3- right colic A. to supply the ascen. colon.4- Ileo-colic A. which supply the small int. ,cecum (by cecal br.) & appendix( by appendicular A.)5- jejunal & ileal branches .

The inferior mesenteric A.It is the A. of the hindgut,arise from the aorta 4 cm above its bifurcation to pass downward & to the left.Its branches are:1- left colic A.2- sigmoid Aa.3- superior rectal A.The marginal A.: form from the anastamosis of the colic Aa. Aroud the concave margin of the large int. It starts at the ileo-cecal junction to the sup rectal A.

Venous Drainage of GIT:The greater part of the GIT & its accessory organs drain to the liver by the portal venous system.THE PORTAL VEIN: is 5 cm long formed behind the neck of the panc. by the union of sup. Mesenteric vein & the splenic vein then it ascend to the right behind the 1st part of the duod. to enter the lesser omentum then to porta hepatis where divided to right & left terminal branches.The portal circulation start as a capillary plexus in the organ it drains & ends by emptying in the liver.

The tributaries of the portal vein:1- the splenic vein which receive the short gastric ,left gastroepiploic ,inf. Mesenteric & pancreatic veins. 2- the inf. Mesen. V. which joins the splenic V. & receive the sup. Rectal V. ,sigmoid V. & left colic V.3-The sup. Mesen. V .it pass in front of the 3rd part of duod. to join the splenic V. behind the neck of the panc. It receives the jejunal , ileal, lieocolic ,right colic, middle colic, inf. pancreaticoduodenal & right gastroepiploic Vv.

The tributaries of the portal vein4- left gastric vein.5- right gastric vein.6- cystic veins : which drains the gall bladder.Portal systemic anastamosis:1- at the lower end of eosophagus:(left gastric V & eosophageal V) . 2- at anal canal (sup. rectal Vv &middle& inf. Rectal Vv) .3-paraumbilical V.(left br. Of portal vein& veins of ant. Abd. Wall ).4- the veins of asc.colon , desc. colon, duod., panc.& liver with renal , lumbar & phrenic veins.

THE LIVERThe largest gland in the body. It divided to large right lobe & small left lobe by the attachment of the peritoneum of the falciform lig. The right lobe divided to qudrate lobe & cuadate lobe by the presence of gall bladder.The porta hepatis (=hilum of the liver )lies between the cuadate & quadrate lobes. It receives the R. & L.hepatic ducts,R.&L. br. Of hepatic A.,portal vein ,symp.& parasymp.N Ff.& hepatic lymph nodes.The arterial supply of the liver by the hepatic A(br. Of celiac A.),& the portal vein (enter the porta hepatis) & the venous drainage by the hepatic veins (2 veins emerge from the post. surface to the inf. Vena cava.

The Bile DuctsThe bile ducts of the liver consists of the right & left hepatic ducts which unite outside the liver to form the common hepatic duct which descend to receive the cystic duct to form the common bile duct then descend behind the 1st part of the duod to enter the medial wall of the 2nd part after joining with the main panc. duct to open in the ampulla of vater which opens in the lumen of the duod. by the major duod papilla. The ampulla of vater surrounded by circular M called the sphincter of oddi .

THE GALL BLADDER: is a pear-like sac lying on the under surface of the liver, divided to fundus ,body , neck which continue with the cystic duct.THE PANCREAS: It is an exocrine( produce enzymes& secreted by the main panc.duct & accessory duct) & endocrine (islets of lungerhans produce insulin & glucagon) gland lies on the post. abd. wall behind the peritoneum, divided to head , neck , body & tail .

THE SPLEEN: It is the largest single mass of lymphoid tissue, lies under the left diaphragm close to the 9th ,10th & 11th ribs . The peritoneum surround the spleen condensated to the greater curvature of the stomach forming the gastro-splenic lig. & to the left kidney forming the lieno-renal lig. THE KIDNEYS :reddish-brown str. lies behind the peritoneum high up on the post. abd. wall, the right K. is lower than the left because of the liver. they covered by fibrous capsule ,perirenal fat, renal fascia then pararenal fat.The kidney divided to cortex & medulla.

THE URETERS : It is 25 cm long muscular tube extend from the kidney downward on the Psoas M . In the retro peritoneal space to enter the pelvis then to the post. surface of the urinary bladder. THE SUPRA RENAL GLAND :yellowish retroperitoneal organs on the upper pole of the kidney, surrounded by the renal fascia divided to cortex & medulla.

ARTERIES ON THE POST. ABD.WALLTHE AORTA : It enters the abd. through the aortic opening of the diaphragm at T12 level. It descends behind the peritoneum on the ant. surface of the bodies of lumbar vert. then at L4 level it divided to 2 common iliac Aa. It gives branches:1- three ant. Visceral br. :celiac , sup. Mesenteric & inf. Mesenteric Aa.2- three lateral br.:supra renal , renal & testicular or ovarian Aa.3- three terminal br.: two common Iliac Aa& median sacral A.

ARTERIES ON THE POST. ABD.WALLThe common iliac Aa.: are the terminal br. of the aorta, at L4 level ,runs downward & laterally along the med. border of the Psoas M. each A. ends in front of sacro-iliac jt. by dividing to ext.& int. iliac Aa. The ureter pass in front of the bifurcation.The ext. iliac A.: pass on the medial border of Psoas M. it gives : inf. Epigastric & deep circumflex iliac Aa. Then enters the thigh behind the inguinal lig. to form the femoral A.The int. iliac A. :pass in front of sacro-iliac joint to pass to the pelvis.

Veins on the posterior abdominal wallThe inferior Vena Cava :It conveys most of the blood of the body below the diaphragm to the right atrium of the heart. It is formed by the union of the common iliac veins at L5 level . It ascend on the right side of the aorta pierces the diaphragm at T8 level.& drains to the right atrium. Its tributaries are :1-Ant. Visceral trib. the hepatic veins .2- three lateral visceral trib.: right supra renal ( left vein to the left renal vein) , renal veins & right testicular or ovarian vein( the left vein drains to left renal vein).

3- five lateral abd. Wall tributaries : the inf .phrenic vein & 4 lumbar veins.4-three veins of origin :2 common iliac veins & median sacral vein.