UNIT 8

Digestion

The process of breaking down food into smaller components that can be absorbed by the body.

Absorption

The process of taking digested nutrients from the digestive tract into the bloodstream.

Ingestion

The intake of food through the mouth.

Peristalsis

Alternating muscle contractions that propel food through the digestive tract.

Chemical digestion

The breakdown of large organic molecules into smaller compounds by enzymes.

Mechanical digestion

The physical breakdown of food into smaller pieces.

Alimentary Canal

The digestive tube where digestion and absorption take place.

Upper Alimentary Canal

The portion of the digestive system including the mouth, pharynx, and esophagus.

Lower Alimentary Canal

The part of the digestive system including the stomach, small intestine, and large intestine.

Enzymatic Hydrolysis

The process of breaking down large food molecules into monomers using enzymes and water.

Absorption of Nutrients

Most nutrients are absorbed through the mucosa of the intestinal villi by active transport processes driven by metabolic energy.

Protein Digestion

Proteins are digested in the gastrointestinal tract by various enzymes like pepsin, trypsin, and chymotrypsin into amino acids and peptides.

Carbohydrate Digestion

Carbohydrates are broken down into monosaccharides like glucose, fructose, and galactose by enzymes like salivary and pancreatic amylase.

Lipid Digestion

Lipids are digested in the small intestine by lipases with the help of bile salts, forming micelles for absorption into the epithelial cells.

Micelles

Micelles are clusters of fatty elements with bile salts that aid in the absorption of fat-soluble vitamins and lipids in the small intestine.

Chylomicrons

Water-soluble lipoprotein droplets formed in epithelial cells to transport lipids, which enter the lymphatic stream and eventually the bloodstream.

Absorption of Micronutrients

Fat-soluble vitamins are absorbed with dietary fats, while water-soluble vitamins are absorbed by diffusion, except for vitamin B12 which requires intrinsic factor for uptake.

Chloride ions

Anions actively transported in the small intestine and secreted into the lumen in exchange for bicarbonate ions.

Potassium ions

Cations moving across the intestinal mucosa by simple diffusion in response to osmotic gradients.

Iron

Essential for hemoglobin production, actively transported into mucosal cells and stored as iron-ferritin complexes.

Calcium

Absorption closely related to blood levels of ionic calcium, regulated by active vitamin D and parathyroid hormone.

Water

Approximately 9L enters the small intestine daily, with 95% absorption occurring by osmosis, affecting the absorption rate of other substances.