Peritoneal Canal and Peritoneum

• Cristina V. Dieni, PhD can be contacted at phone number 942-421, ext 2248 and email dienic@newmanu.edu

Peritoneal Canal

• It's an extension from the respiratory diaphragm inferiorly to the floor of the pelvis

The Peritoneum

• The serosa, also known as the visceral peritoneum, adheres to the organs and is continuous with the parietal peritoneum
• The parietal peritoneum lines the walls of the abdominal cavity

Organs

• Intraperitoneal organs lie within the peritoneal cavity
• Organs are completely surrounded by the visceral peritoneum
• Examples include the stomach and liver
• Retroperitoneal organs are covered by the parietal peritoneum on their anterior surface
• Examples include the kidneys, ureters, and abdominal aorta

Mesenteries

• These are fused, double sheets of visceral peritoneum
• They stabilize the position of organs and blood vessels/nerves
• All small intestine with the exception of the duodenum is suspended in a sheet of mesentery called the mesentery proper
• The mesocolon is the mesentery attached to the large intestine
• The mesentery between the stomach and the liver is the lesser omentum
• The mesentery from the stomach to the transverse colon that hangs down anterior to the small intestine is the greater omentum

Esophagus

• The esophagus is a hollow musculoelastic tube posterior to the trachea
• It transports foods and liquids to the stomach
• It passes along dorsal wall of the mediastinum in the thoracic cavity
• The esophagus enters the peritoneal cavity through an opening in the diaphragm, the esophageal hiatus

The Stomach

• It is a dilated, saclike portion of the Gastro Intestinal tract
• It exhibits significant variation in size and configuration
• The stomach is divided into these regions: cardiac, fundus, body, and Pyloric (antrum and canal)
• Right border of stomach is the lesser curvature; the lesser omentum attaches here and extends to liver as hepatogastric ligament
• Convex inferior border with greater omentum suspended from its margin
• Area of stomach that communicates with esophagus superiorly is the cardiac part
• Superior part just under left dome of diaphragm is the fundus
• Main part between fundus and pyloric antrum is the body
• Portion divided into proximal antrum and distal canal is the pyloric part
• Site of pyloric sphincter smooth muscle; joins 1st part of duodenum is the pylorus

Duodenum Features

• First part; attachment site for hepatoduodenal ligament of lesser omentum; technically not retroperitoneal for the first inch (2.5 cm) is the superior part
• Second part; site where bile and pancreatic ducts empty is the descending part
• Third part; crosses inferior vena cava and aorta and is crossed anteriorly by mesenteric vessels is the inferior part
• Fourth part; tethered by suspensory ligament at duodenojejunal flexure is the ascending part

Small Intestine Measurements

• Duodenum: about 25 cm long and largely secondarily retroperitoneal
• Jejunum: about 2.5 meters long and suspended by a mesentery
• Ileum: about 3.5 meters long and suspended by a mesentery
• The jejunum is recognizable from the ileum because the jejunum occupies the left upper quadrant of the abdomen, is larger in diameter that the ileum, has thicker walls, has mesentery with less fat, has arterial branches with fewer arcades and longer vasa recta and internally has mucosal folds that are higher and more numerous, which increases the surface area for absorption
• The small intestine ends at the ileocecal junction
• At the ileocecal junction is the ileocecal valve, a smooth muscle sphincter that controls the passage of ileal contents into the cecum

Arterial Supply To Small Intestine

• Small intestine receives its arterial supply from the superior mesenteric artery and its branches, with the exception of the first part of the duodenum
• The first part of the duodenum receives arterial blood from the gastroduodenal branch from the common hepatic artery of the celiac trunk

Large Intestine

• The large intestine is about 1.5 meters long
• The cecum is a pouch connected to the ascending colon and the ileum
• It extends below the ileocecal junction, it is surrounded by, but not suspended by a mesentery
• A narrow muscular tube of variable length containing numerous lymphoid nodules that is suspended by a mesentery called the mesoappendix, is the appendix
• The ascending colon is secondarily retroperitoneal that ascends on the right flank to reach the liver, and it bends into the right colic (hepatic) flexure
• The transverse colon is suspended by a mesentery, the transverse mesocolon, and runs transversely from the right hypochondrium to the left, where it bends to form the left colic (splenic) flexure
• The descending colon is secondarily retroperitoneal and descends along the left flank to join the sigmoid colon in the left groin region
• The sigmoid colon is suspended by a mesentery, the sigmoid mesocolon, and forms a variable loop of bowel that runs medially to join the midline rectum in the pelvis
• The superior two thirds of the rectum is retroperitoneal
• The rectum and anal canal extend from the middle sacrum to the anus

Large Intestine Blood Supply

• The superior mesenteric artery supplies blood to the cecum, the ascending colon, the appendix, and most of the transverse colon
• The inferior mesenteric artery supplies blood to the distal transverse colon, the descending colon, the sigmoid colon, and the rectum
• The internal iliac and internal pudendal arteries supply blood to the distal rectum, the anal canal, and the rectal branches

The Liver

• Largest solid organ on the body which is anatomically divided into four lobes
• The right lobe is the largest lobe
• The left lobe lies to the left of the falciform ligament
• The quadrate lobe lies between the gallbladder and round ligament of the liver
• The quadrate lobe lies between the inferior vena cava (IVC), ligamentum venosum, and porta hepatis
• The liver receives the venous drainage from the Gl tract, its accessory organs and the spleen via the portal vein
• Functions of the liver include storage of energy sources (glycogen, fat, protein, and vitamins)
• Other functions include production of cellular fuels (glucose, fatty acids, and ketoacids), production of plasma proteins and clotting factors, and lymph production, metabolism of toxins and drugs, Modiication of many hormones, production of bile acids, excretion of substances (bilirubin), storage of iron and many vitamins; and Phagocytosis of foreign materials that enter the portal circulation from the bowel

Gallbladder and Extrahepatic Ducts

• The gallbladder is composed of a fundus, body, infundibulum, and neck
• The function of the gallbladder is to receive, store, and concentrate bile
• Bile is secreted by the hepatocytes of the liver, passing through the extrahepatic duct system Bile collects in the right and left hepatic ducts after draining the right and left liver lobes
• The bile enters the common hepatic duct
• It enters the cystic duct and is stored and concentrated in the gallbladder
• Upon stimulation, largely by vagal eferents and cholecystokinin (CCK), bile leaves the gallbladder and enters the cystic duct
• The bile passes inferiorly down the common bile duct
• The bile enters the hepatopancreatic ampulla (of Vater), which is surrounded by a smooth muscle sphincter (of Oddi) which empties into the second part of the duodenum (major duodenal papilla)

The Pancreas

• The pancreas is an exocrine and endocrine organ
• It lies posterior to the stomach in the posterior wall of the lesser sac (omental bursa)
• The pancreas is a secondarily retroperitoneal organ with the exception of the distal tail which is in contact with the spleen
• The head is nestled within the C-shaped curve of the duodenum and overlying the abdominal aorta, the right renal vessels, the left renal vein(s), and the IVC, in which its uncinate process lies posterior to the superior mesenteric vessels
• The neck lies anterior to the superior mesenteric vessels, the aorta, and the IVC and deep to the pylorus of the stomach
• The body extends above the duodenojejunal flexure and across the superior part of the left kidney
• The tail extends from the left kidney, which it crosses, and terminates at the hilum of the spleen in the splenorenal ligament

The Spleen

• The spleen lies in the left upper quadrant (hypochondriac region) of the abdomen
• It's tucked posterolateral to the stomach
• Its tucked under the protection of the lower left rib cage and diaphragm
• The spleen is a large lymph node which becomes larger during infections
• Functions include Lymphocyte proliferation (B and T cells), immune surveillance and response, and blood filtration
• The spleen destroys old or damaged red blood cells (RBCs), destroys damaged platelets, recycles iron and globin, provides a reservoir for blood, and provides a source of RBCs in early fetal life

The Kidneys and Adrenal Glands

• These are retroperitoneal organs that receive a rich arterial supply
• Each kidney is enclosed in the following layers of fascia and fat: Renal capsule, Perirenal (perinephric) fat, Renal (Gerota's) fascia and Pararenal (paranephric) fat

GI Tract Development

• The Gl tract is derived from the following three embryonic gut regions
• Foregut: gives rise to the abdominal esophagus, stomach, proximal half of the duodenum, liver, gallbladder, and pancreas
• Midgut: gives rise to the distal half of the duodenum, jejunum, ileum, cecum, appendix, ascending colon, and proximal two thirds of the transverse colon
• Hindgut: gives rise to the distal third of the transverse colon, descending colon, sigmoid colon, rectum, and proximal anal canal

Major Branches of SMA

• Major branches include the inferior pancreaticoduodenal artery, jejunal and ileal branches, the middle colic artery, the right colic artery, and ileocolic artery

Major Branches of IMA

• Major branches include the left colic artery, sigmoid arteries, and superior rectal artery