Human Digestive System

The digestive system is responsible for breaking down food into nutrients and minerals that the body can absorb and use. The other systems listed serve different primary functions like transport, gas exchange, or waste removal.

The hypothalamus is the region of the brain that acts as the control center for many homeostatic processes, including the regulation of hunger and satiety.

The primary function of the digestive system is to break down food into nutrients that the body can absorb for energy, growth, and repair, while expelling indigestible waste.

Chyme is the semi-fluid mass of partially digested food and gastric secretions that is formed in the stomach and passed into the duodenum.

The pyloric valve, or pyloric sphincter, is a ring of smooth muscle that regulates the passage of partially digested food from the stomach into the duodenum. Mitral and pulmonary valves are found in the heart, while the diencephalon is a region of the brain.

Trypsin is a pancreatic enzyme secreted into the small intestine where it hydrolyzes proteins into smaller peptides and peptones. Other enzymes like ptyalin and amylase digest carbohydrates, while lipase digests fats.

Hydrochloric acid (HCl) is secreted by the parietal cells in the stomach lining, creating an acidic environment necessary for the activation of pepsin and the digestion of food.

Ghrelin is a hormone produced primarily by the stomach that signals hunger to the brain, thereby increasing appetite and hunger pangs. Leptin, on the other hand, is produced by fat cells and acts to decrease appetite.

The digestive system breaks down food into nutrients, which are then absorbed into the bloodstream of the circulatory system to be transported to cells throughout the body. Making food is not a human biological process, saliva is produced by salivary glands, and waste disposal is primarily handled by the excretory system.

Pancreatic amylase digests starch into the disaccharide maltose (and dextrins) in the small intestine. Maltose is subsequently broken down into glucose by maltase, which is an enzyme bound to the microvilli of the small intestine (not a pancreatic enzyme).

Villi and microvilli are structural adaptations of the small intestine that vastly increase the surface area available for the absorption of digested nutrients. Assimilation is the subsequent integration of these nutrients into body tissues, which occurs after absorption.