Unit 3: Abdominal Viscera

layers of the GI tract

1) tunica mucosa lining lumen

2) tunica submucosa

3) tunica muscularis

4) tunica serous outer layer

tunica mucosa

- simple columnar epithelium

- lines GI tract lumen and its underlying loose CT tissue

- lamina propria contains vessels (blood & lymphatics) and nerves

- specialized plica, villi, and microvilli increase surface area of tract

tunica submucosa

- highly vascular loose CT layer

tunica muscularis

- inner, circular and outer, longitudinal smooth muscle layer

tunica serosa

- outer visceral peritoneal layer

esophagus

- approx 10 inches long

- distal-most inch lies inferior to esophageal hiatus, angling slightly to the left

- lined by stratified squaous epithelium

- muscular layer changes from skeletal to smooth along its length

stomach

- muscular sac of 1500 to 2000 mL (normal capacity)

regions of the stomach

- cardia : region around gastroesophageal junction

- fundus : region superior to the gastroesophageal junction

- body : main part

- pylorus : region from the angular incisures to the pyloric sphincter

- pyloric sphincter : the thickened region of circular smooth muscle to the right of midline

duodenum

- initial 10 inches of small intestine, forming a C shape toward the left side

- lies from the level of T12/L1 to L3, crossing from right to left of midline posterior to small intestine mesentery and its superior mesenteric artery

- divided into 1st (superior), 2nd (descending), 3rd (horizontal), 4th (ascending) parts

duodenum extras

- head and uncinate process of the pancrea lie on the surface of the C shaped curvature

- hepatopancreatic duct system joins the descending part

jejunum

- duodenojejunal flexure supported by the suspensory ligament of the duodenum (ligament of Treitz)

- typically ~8 inches long

- normally occupies the LUQ

ileum

- typically about 12 inches long

- typically occupies the RLQ

- normally ends in the right iliac fossa at the iliocecal junction

cecum

- initial portion of the large intestine

- ileocecal valve : superior and inferior lips held together by distension of the cecal walls

appendix

- blind-end extension from the inferomedial cecal wall

- typically about 3 inches long

- might lie retrocecal (21%) but is commonly pelvic (78%)

colon

- typically 4-5 feet in length

- three bands of longitudinal muscle form the taenia coli, which start in wall of cecum (bands converge on appendix) and extend to the junction of the sigmoid colon and rectum

- sacculated (formed by haustra)

ascending colon

- typically about 5-8 inches in length

- from cecum to the right colic/hepatic flexure closee to the right lobe of the liver

transverse colon

- typically about 18-20 inches in length

- hangs down as a loop between colic flexures

- largest and most mobile part of colon

- attached to the deep surface of the greater omentum

descending colon

- typically about 9-12 inches in length

- from left colic/splenic flexure to left iliac fossa

- normally narrower than the ascending and transverse colon

sigmoid colon

- typically about 15-20 inches in length

- forms S-shaped loop from left iliac fossa to the 3rd sacral segment in the true pelvis where it continues on as the rectum

- position variable depending on the size of the mesentery

rectum

- 5-6 inches in length

- ends at the inferior tip of the coccyx

anus

- internal (smooth) and external (skeletal) sphincters

- epithelium changes back to stratified squamous

liver

- surrounded by fibrous CT capsule

- divided into lobes

liver lobes

- large right and left anatomic lobes (based on external appearance) or functional/portal lobes (based on internal blood and bile flow)

- lobes divided into segments

liver segments

- separate functional units with their own system of vessels

- segments can be removed without impacting function of other segments

liver ligaments

- falciform ligament : divides the anatomic lobes anteriorly

- ligamentum teres & ligamentum venosum : divides anatomical lobes posteriorly

functional lobes of liver

- divided by a line joining the left sides of the gall bladder and the IVC

- caudate lobe (superior) and quadrate lobe (inferior) are small lobes which are parts of the right anatomic or left functional lobes

porta hepatis

- area on the inferior surface where all structures pass through, entering or exiting liver

- contain hepatic arteries, hepatic portal vein, hepatic ducts, nervous and lymphatic tissue (but NOT the hepatic veins, which drain into the IVC directly)

gall bladder

- sac-like structure of about 30-60 mL of capacity

- stores and concentrates bile

pancreas

- typically 5-7 inches in length, lying posterior to the body of the stomach

- head in curvature of duodenum

- body extends slightly superiorly across the midline and tail lies close to the hilum of the spleen

hepatic ducts

- right and left hepatic ducts drain the right and left functional lobes of the liver and join to form the common hepatic duct

cystic duct

- connects the neck of the gall bladder to the common hepatic duct

common bile duct

- union of the cystic and common hepatic ducts passing posterior to the first part of the duodenum

pancreatic ducts

- main pancreatic ducts joins the common bile duct to form the hepatopancreatic ampulla

- accessory pancreatic duct also drains head and may empty separately into the duodenum (~10%) through minor duodenal papilla

hepatopancreatic sphincter

- smooth muscle forming the major duodenal papilla

spleen

- lies at the level of the 9th to 11th ribs on left posteriolateral wall

- surrounded by fibrous CT capsule

- hilum lies medially

kidneys

- lie in a separation of transversalis fascia (renal fascia) surrounded by the fibrous capsule and perirenal fat

- outside of the renal fascia is the PARArenal fat

- contains renal pyramids, renal columns, & renal cortex

location of kidneys

- right : lies a bit lower than the left, deep to the 12th rib

- left: lies deep to the 11th and the 12th ribs

minor calyces

- each minor calyx receives urine excreted through the papilla of the renal pyramid

major calyces

- formed by minor calyces joining

- transmit urine to renal pelvis

- 2-3 major calyces collect urine from 2-3 minor calyces in the renal sinus

renal pelvis

- proximal expansion of ureter that exits the hilum and collects urine from the major calyces in the fat-filled renal sinus

ureter

- extends inferiorly anterior to psoas major into the true pelvis

suprarenal glands

- lie on the superior pole of each kidney and are surrounded by a CT capsule

suprarenal artery supply

- by the suprarenal arteries :

- superior comes off inferor phrenic artery

- middle comes off aorta

- inferior comes off renal artery

suprarenal venous drainage

- usually drained by a single large suprarenal vein

- the shorter, right suprarenal vein drains into the IVC

- the larger, left suprarenal vein drains into the renal vein

intraperitoneal

- organs that are covered by visceral peritoneum and project completely into the peritoneal cavity

mesentery

- reflection of the peritoneum towards the viscera from the posterior abdominal wall

extraperitoneal / retroperitoneal

- structures which only bulge into the peritoneal cavity such that the peritoneum only covers part of their surface

mesentery of the small intestine

- root is approx 6 inches long, lying diagonally from the left of L2 to the sacroiliac joint

- contains jejunal, ileal, ileocecal a/vs, nerves, and lymphatics

mesoappendix

- mesentery of the appendix

transverse mesocolon

- adheres to the posterior wall of the greater omentum

sigmoid mesocolon

- mesentery of the sigmoid colon

coronary ligament

- peritoneal reflection from diaphragm to liver

- liver surface posterior to reflection is the bare area of the liver

falciform ligament

- from abdominal wall to the liver (remnant of the ventral mesentery of the liver)

- has the ligamentum teres hepatis (round ligament of the liver) (obliterated umbilical vein) in its inferior margin

lesser omentum

- composed of hepatogastric and hepatoduodenal ligaments

- btwn visceral surface of liver and lesser curvature of stomach / first part of duodenum

- contains common bile duct, proper hepatic artery, hepatic portion vein (portal triad!!)

epiploic foramen (omental foramen)

- space btwn lesser omentum free border on right and posterior abdominal wall

- separates the greater (general abdominal cavity) and lesser sacs of the abdomen

gastrophrenic ligament

- connects fundus of stomach to diaphragm

gastrosplenic/splenorenal ligament

- connects stomach to spleen and spleen to kidney

primary retroperitoneal

- structures develop on the posterior wall and remain there in extraperitoneal tissue covered on anterior surface by parietal peritoneum

- include kidneys, ureters, aorta, IVC, sympathetic trunks

secondarily retroperitoneal

- structures that develop in the mesentery but are later drawn to the posterior abdominal wall and become attached to it

- includes 2,3,4 part of duodenum, pancreas, ascending colon, descending colon, rectum

intraperitoneal structures

- liver, gall bladder, stomach, spleen, 1st part of duodenum, jejunum, ileum, cecum, appendix, transverse colon, sigmoid colon

lesser sac (omental bursa)

- posterior to stomach and lesser omentum

- permit movement of stomach across nearby structures

- communicates with greater sac through omental (epiploic) foramen

greater sac

- main/largest part of peritoneal cavity

- includes supracolic compartment (stomach, liver, spleen)

- includes infracolic compartment (small intestine, ascending/descending colon, paracolic gutters, is posterior to greater omentum)

right & left lateral gutters & left medial gutter

- open inferiorly

- any fluid in them can drain into the pelvic cavity if a person rises from a supine position

right medial gutter

- not open inferior because of the attachments of the gut mesentery

- fluid tends to stay there regardless of body position

right lateral gutter

- continuous superiorly with the infrahepatic recess/hepatorenal pouch

-> space between the right, kidney, right colic flexure, and right lobe of liver

-> lowest part of peritoneal cavity when the body is supine, fluid from a ruptured gall bladder or appendix will normally collect there