MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Ya.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

CHAPTER 7. THE PROCESS OF NUTRITION AND ITS PATHOLOGY

The Digestive System is divided into the digestive tract and glands. It ensures the ingestion, mechanical and chemical Processing of food, the absorption of its breakdown products, and the elimination of indigestible residues.

In humans, the digestive tract is 8-10 m long and consists of the Oral Cavity, Pharynx, Esophagus, Stomach, Small Intestine, and Large Intestine.

The digestive glands include large and small Salivary Glands, the Pancreas, and the Liver.

Digestion is a complex physiological process during which food entering the digestive tract undergoes mechanical and chemical transformations, while the nutrients it contains, following depolymerization, are absorbed into the Blood AND Lymph. Digestion involves the functional digestive system, which represents the digestive Organs and neurohumoral regulatory mechanisms. Each section of the digestive system sequentially performs all three Functions: secretory, motor, and absorptive. Food is gradually modified in each section, with functional interconnections existing between them. Impairments in any of these sections lead to impaired DIGESTION IN THE subsequent ones.

Nutrients—Proteins, fats, CARBOHYDRATES, mineral salts, Water, and Vitamins that make up food—are essential for the body's vital activity. They serve as a source of energy and building material.

Nutrients in the form they are consumed with food cannot be absorbed and utilized by the body. Only water, mineral salts, and vitamins are absorbed and assimilated in their original form.

In the digestive tract, proteins, fats, and carbohydrates undergo physical transformations, which include mechanical processing, grinding, Swelling, and dissolution. Nutrients also undergo chemical changes caused by Enzymes found in the secretions of the digestive glands: salivary, gastric, pancreatic, and intestinal juices. This constitutes the secretory function of the gastrointestinal tract. Enzymes that break down proteins are proteases, fats are lipases, and carbohydrates are carbohydrases. The amount and ratio of enzymes in secretions correspond to the quantity and Nature of the consumed food. For example, when consuming a protein-rich diet, pancreatic secretion contains more proteases. As a result of enzymatic breakdown, proteins yield Amino Acids; fats yield Fatty acids, glycerin, and monoglycerides; and carbohydrates yield Monosaccharides. The End products of chemical food processing are absorbed into the blood and lymph and utilized by body Cells as energy and structural material. This function of the gastrointestinal tract is called absorption. In addition to the end products of nutrient Hydrolysis, water, vitamins, and salts are also absorbed. The motor function is performed in every section of the digestive tract. It is carried out by the Muscle fibers of the tract and ensures chewing, swallowing, mixing food with secretions, moving it forward, as well as eliminating indigestible food residues, certain toxic substances, and Bacteria from the body.