Human Digestive System

Glucose is absorbed via active transport (specifically secondary active transport coupled with sodium) in the small intestine. Alcohol is absorbed via passive diffusion, and water is absorbed via osmosis.

The folds of Kerkring (plicae circulares) are permanent folds of the mucosa and submucosa, most prominent in the duodenum and jejunum, which increase the surface area for absorption.

The entire small intestine has circular folds of the mucous membrane, the valves' of kerkring These folds are more prominent in the jejunum.

The sphincter of Oddi (or hepatopancreatic sphincter) controls the flow of bile and pancreatic juice into the duodenum. When closed, bile is diverted back to the gallbladder.

Intrinsic factor is a glycoprotein produced by the parietal cells of the stomach, which is essential for the absorption of Vitamin B12 in the ileum.

The mucosa of the duodenum contains absorptive cells (enterocytes), goblet cells (secreting mucus), and argentaffin (enteroendocrine) cells, which produce hormones like secretin and CCK.

The ileum is characterized by the presence of Peyer's patches and club-shaped villi. Brunner's glands are a characteristic feature of the duodenum, not the ileum.

The semi-digested, acidic food mass that moves from the stomach into the duodenum is called chyme.

Cholecystokinin (CCK) and secretin are produced by enteroendocrine cells located in the mucosa of the duodenum.

The stomach is divided into the cardia, fundus, body, and the distal pylorus, which connects to the duodenum.

Active absorption in the small intestine involves energy-dependent transport mechanisms for various nutrients, including glucose, amino acids, and sodium ions.

Secretin is produced by the S-cells in the mucosa of the small intestine, specifically the duodenum.

Both secretin and cholecystokinin are hormones secreted by the duodenal mucosa in response to chyme entering the small intestine.