Physiology of Intestinal Lining

Duodenal (Brunner) Glands

• Secrete alkaline secretions with a pH range of 8.1-9.3
• Serve two purposes:
  • Protect the duodenal mucosa from gastric acids
  • Provide the optimal pH for pancreatic enzyme action

Lymph Vessels of the Intestine

• Begin as blind tubes in the core of villi
• Referred to as lacteals

Histophysiology of the Intestine

• Presence of plicae, villi, and microvilli increases the surface area of the intestinal lining
• This increased surface area results in a 600-fold increase in the intestinal surface

Lipid Digestion and Absorption

• Lipid digestion occurs mainly due to the action of pancreatic lipase and bile
• Most lipid absorption occurs in the duodenum and upper jejunum in humans

Intestine (L.I.)

• Consists of appendix, cecum, colon, rectum, and anal canal, with the colon divided into ascending, transverse, descending, and sigmoid parts
• Mucosal membrane has no folds except in the rectal portion, and no villi are present
• Intestinal glands are long and contain many goblet cells, absorptive cells, and few enteroendocrine cells

Functions of the Intestine

• Absorption of water
• Formation of fecal mass
• Production of mucus

Lamina Propria

• Rich in lymphoid cells and nodules
• Richness is due to the extremely abundant bacterial population of the L.I.

Cell Renewal in the Gastrointestinal Tract

• Epithelial cells of the entire G.I. tract are constantly being replaced by new ones formed through mitosis of stem cells

This quiz covers the structure and function of the intestinal lining, including the role of Brunner glands and villi in digestion.