Gastrointestinal transit

Gastrointestinal Physiology refers to the study of the physical and biochemical functions of the gastrointestinal tract. This includes the processes of digestion, absorption, secretion, and motility.

Overview

The gastrointestinal tract (GI tract) is a series of hollow organs joined in a long, twisting tube from the mouth to the anus. It includes the mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus. The liver, pancreas, and gallbladder are also part of the GI tract.

Digestion

Digestion is the process by which food is broken down into smaller components that can be absorbed into the bloodstream. This involves both mechanical digestion, such as chewing and churning in the stomach, and chemical digestion, involving enzymes and other substances.

Absorption

Absorption in the gastrointestinal tract involves the uptake of nutrients from the lumen of the GI tract into the bloodstream. This process occurs primarily in the small intestine, which has a large surface area for absorption due to the presence of villi and microvilli.

Secretion

Secretion in the GI tract involves the release of substances such as enzymes, hormones, and mucus, which aid in digestion and protect the lining of the GI tract. The stomach, for example, secretes hydrochloric acid and pepsinogen, which aid in the digestion of proteins.

Motility

Motility refers to the movement of food through the GI tract. This is achieved through the coordinated contractions and relaxations of the smooth muscle in the walls of the GI tract, a process known as peristalsis.

Regulation

The functions of the GI tract are regulated by both the autonomic nervous system and the enteric nervous system, a network of neurons in the walls of the GI tract. Hormones such as gastrin, secretin, and cholecystokinin also play a role in regulation.

See also

• Digestive system
• Human gastrointestinal tract
• Digestion
• Absorption (biology)
• Secretion
• Motility

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