Human Digestive System

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

The duodenum is an endocrine organ that produces hormones such as secretin, cholecystokinin (CCK), and enterogastrone to regulate digestion.

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.

The hepatopancreatic duct (formed by the common bile duct and pancreatic duct) opens into the duodenum at the major duodenal papilla.

The small intestine is the primary site for both the chemical digestion of food and the absorption of nutrients into the bloodstream. While the stomach begins protein digestion, the vast majority of nutrient uptake occurs in the small intestine.

Vomiting is a reflex action typically triggered by irritation or distension of the stomach or the upper small intestine (duodenum). It is controlled by the vomiting center in the medulla oblongata, not the hypothalamus.

Secretin is a hormone released by the S cells of the duodenum in response to low pH (acidic chyme) entering from the stomach. It stimulates the pancreas to release bicarbonate-rich fluid to neutralize the acid.

Peyer's patches are organized lymphoid follicles found in the submucosa of the ileum, which is the distal portion of the small intestine. They play a critical role in immune surveillance of the intestinal lumen.

Enterokinase (also known as enteropeptidase) is an enzyme that activates trypsinogen into trypsin. Without trypsin, other pancreatic proteases cannot be activated, leading to a severe failure in protein digestion.

The small intestine is divided into three parts in order: the duodenum (first), the jejunum (middle), and the ileum (last). The duodenum receives chyme from the stomach.