The small intestine , which consists of three different regions, begins with the exit from the stomach (pyloric sphincter) and ends with the entrance to the large intestine (ileocecal valve). It is attached by mesentery to the posterior body wall of the abdominal cavity.
Mesentery Thin walls of small intestine with blood supply
Most of the arterial blood supply to the small intestine is via the superior mesenteric artery
Venous drainage of the small intestine is via the hepatic portal vein
The duodenum is the first portion of the small intestine and it is mostly located retroperitoneally. The duodenum receives secretions from the liver and the pancreas .
The duodenum is continuous with the jejunum at the duodenojejunal flexure
The major duodenal papilla is a projection the protrudes into the duodenum the allows the exit of bile and pancreatic fluid
The jejunum is about 7.5 feet long and is the portion of the small intestine where the most absorption takes place.
Some absorption occurs in the duodenum and ileum, but most occurs in the jejunum.
Bruising on abdomen where the jejunum and greater omentum were crushed against the spine by an impact with the steering wheel during an automobile collusion.
The ileum (about 10 feet long) is the final portion of the small intestine and it empties into the cecum via the ileocecal valve
Note the circular folds (plicae circulares) of the small intestine.
Inflammation or blockage of the appendix can lead to appendicitis . The main concern is that if the appendix ruptures it will spill bacteria and feces into the peritoneal cavity causing peritonitis. Read the clinical view in the text.
Anterior superior iliac spine Umbilicus McBurney’s point is one third the distance from the anterior superior iliac spine towards the umbilicus
Hordes of bacteria normally found in feces of large intestine . If they escape into the peritoneal cavity, potentially lethal peritonitis may follow.
Fatal peritonitis . Note swollen intestines and pus on inner surface of parietal peritoneum.
Peritonitis can also follow penetrating abdominal injury
A hemorrhoid can be grasped and have a ligating rubber band slipped over its base to cut off its blood supply so it will necrose and fall off.
This elderly man felt that inserting a glass Mason jar into his rectum would “loosen up his plumbing”. Unfortunately, he could not retrieve it and went to the local ER for assistance. If the jar should break during its removal, severe lacerations to the rectum and anus might occur!
An ER doctor came up with this solution for such slippery jar removal!
Note the longitudinal bands ( tenia coli ), the many sacs ( haustra ), and the lobules of fat ( epiploic appendages ) of the large intestine.
Read the clinical view about how polyps may develop into colorectal cancer.
A plastic bag is taped over the colostomy opening to catch the feces gradually expelled by peristalsis.
Read the clinical view in the text about inflammatory bowel disease
The liver is positioned immediately below the diaphragm and is the largest organ in the body.
The falciform ligament divides the liver into two major lobes
Venous blood is brought to the liver by the hepatic portal vein and arterial blood is brought to the liver by the hepatic artery .
The liver contains thousands of hepatic lobules , which are the structural and functional units of the liver. These lobules contain hepatocytes .
Not the portal triads at the periphery of each hepatic lobule.
The sinusoids of liver lobules allow both arterial and venous blood from the periphery to mix as the blood travels towards the central vein at the center . Note that separate bile canaliculi produce bile which travels from the center to the periphery where it is collected into the bile duct.
Chronic alcoholism will typically lead to damage of the liver characterized by scarring of the hepatic sinusoids so they no longer permit easy blood flow. The damaged liver often turns an orange color. This damage of the liver is called “ cirrhosis ”. Cirrhosis is less commonly caused by viruses and some toxic chemicals.
This person has fluid accumulation in the abdominal cavity because of alcoholic cirrhosis . Note that since the blood flow to the liver is partially obstructed, the venous blood will seek alternate routes to return to the heart by traveling through superficial skin veins. This process is called “collateral circulation”.
One route that collateral circulation can occur in cirrhosis is via the esophageal veins. The increased blood flow leads these veins to weaken and bleed (become varicose). These esophageal varicosities will bleed extensively!
The esophageal veins provide an alternate route for venous return (collateral circulation) when hepatic portal hypertension exists because of cirrhosis.
Esophageal varicose veins in patient with alcoholic cirrhosis
Stomach and esophagus turned inside out to reveal numerous varicose veins. Now you know why patients with cirrhosis become chronic gastrointestinal bleeders (chronic G.I. bleeders). Since they lose blood, they also lose iron. Iron deficiency anemia soon develops.
The inner esophageal veins can be surgically closed to help control bleeding . However, this does nothing to solve the underlying cirrhosis.
This cirrhotic patient is vomiting blood from the esophagus, has turned yellow because of accumulated bile pigments, and is suffering brain damage (encephalopathy) because natural toxins in ingested foods are NOT being detoxified by the liver.
The gallbladder is attached to the inferior surface of the liver. It stores and concentrates bile that is produced by the liver for later release.
Liver Gallbladder Endoscopic view of liver and gallbladder
Read about cholelithiais (presence of gallstones in gallbladder or nearby ducts) in the clinical view in the text.
Blockage of the common bile duct by gallstones may lead to accumulated bilirubin ( obstructive jaundice ).
Note that the cystic duct connects the gallbladder to the common bile duct .
The pancreas is a mixed gland because it exhibits both endocrine (produces insulin and glucagon) and exocrine functions (produces digestive enzymes that are released into the duodenum. It has a head , body , and tail . The tail leads towards the spleen. Note the main pancreatic duct
The pancreas is adjacent to the stomach and is retroperitoneal
Sphincter of Oddi controls release of secretions from the hepatopancreatic ampulla into the duodenum.
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The gallbladder concentrates bile produced by the liver and stores it for later release.
The small intestine receives secretions from the liver and pancreas, breaks down food from the stomach, absorbs most of the nutrients , and transports the remaining undigested material to the large intestine.
Peristalsis propels food through the G.I. tract
The large intestine is supplied by the superior and inferior mesenteric arteries and drained by the hepatic portal vein
The defecation reflex is triggered by stretch receptors in the rectum