Материал: Kaplan USMLE-1 (2013) - Anatomy

Chapter 8 • Gastrointestinal System

ChapterSummary

•The gastrointestinal (GI) system includes the digestive tract and its associated glands. The regional comparisons of the digestive tract are given in Table 1-8- 1 .

•The associated glands are salivary glands, pancreas, liver, and the gallbladder. The salivary glands are compared in Table 1-8-2.

•The pancreas has an exocrine portion and an endocrine portion. The exocrine portion is composed of acini and duct cells. Acini secrete enzymes that cleave proteins, carbohydrates, and nucleic acids. Duct cells secrete water, electrolytes, and bicarbonate.

•The liver is the largest gland in the body. The parenchyma is made up of hepatocytes arranged in cords within lobules.

-Hepatocytes produce proteins, secrete bile, store lipids and carbohydrates, and convert lipids and amino acids into glucose.

-They detoxify drugs by oxidation, methylation, or conjugation, and they are capable of regeneration.

Liver sinusoids, found between hepatic cords, are lined with endothelial cells and scattered Kupffer cells, which phagocytose red blood cells.

•The biliary system is composed of bile caliculi, hepatic ducts, the cystic duct, and the common bile duct. The gallbladder is lined by simple tall columnar cells and has a glycoprotein surface coat. It concentrates bile by removing water through active transport of sodium and chloride ions (especially the former).

-Gallbladder contraction is mediated via cholecystokinin, a hormone produced by enteroendocrine cells in the mucosa ofthe small intestine.

MEDICAL 113