Processes and Phases of Digestion Explained

Mouth

Site of mastication and initial digestion.

Gingiva

Gums surrounding the teeth in the mouth.

Palates

Roof of the mouth, separates oral and nasal cavities.

Hard Palate

Bony anterior section of the roof of the mouth.

Soft Palate

Muscular posterior section of the roof of the mouth.

Submandibular Gland

Salivary gland located beneath the jaw.

Sublingual Gland

Salivary gland located under the tongue.

Parotid Gland

Largest salivary gland located near the ear.

Central Incisors

Front teeth used for cutting food.

Lateral Incisors

Teeth adjacent to central incisors.

Canines

Pointed teeth for tearing food.

Premolars

Teeth used for grinding food.

Molars

Large teeth for crushing and grinding.

Bolus

Chewed food mixed with saliva.

Amylase

Enzyme that begins starch digestion in the mouth.

Lingual Lipase

Enzyme that starts fat digestion in the mouth.

Epiglottis

Flap that prevents food from entering the trachea.

Esophagus

Tube connecting pharynx to stomach.

Peristalsis

Involuntary muscle contractions moving food through GI tract.

Gastric Reflux

Backflow of stomach contents into esophagus.

Cardia

Upper region of the stomach below the esophagus.

Fundus

Dome-shaped top part of the stomach.

Chyme

Semi-liquid mixture of food and gastric juices.

Duodenum

First part of the small intestine.

Jejunum

Middle section of the small intestine, main absorption site.

Ileum

Final section of the small intestine.

Cecum

First part of the large intestine.

Haustrum

Pouches in the large intestine for chyme storage.

Defecation Reflex

Process triggered by stretch receptors in the intestine.

Pancreas

Produces pancreatic juices for digestion.

Liver

Processes nutrients and detoxifies substances.

Gallbladder

Stores and concentrates bile for fat digestion.

Bile

Emulsifies fats for easier digestion.

Gluconeogenesis

Production of glucose from non-carbohydrate sources.

Hormones

Regulatory substances released by endocrine glands.

Gastrin

Hormone stimulating gastric juice secretion.

Cholecystokinin (CCK)

Hormone that stimulates bile release and satiety.

Secretin

Hormone that regulates pancreatic juice secretion.

Somatostatin

Hormone that inhibits gastric secretions.

Nutrient Absorption

Process of nutrients entering the bloodstream.

Pancreatic Amylase

Enzyme that breaks down starches into disaccharides in the small intestine.

Maltase

Enzyme in the small intestine that breaks down maltose into glucose.

Sucrase

Enzyme in the small intestine that breaks down sucrose into fructose and glucose.

Lactase

Enzyme in the small intestine that breaks down lactose into glucose and galactose.

Pepsin

Enzyme in the stomach that begins breaking down proteins into polypeptides.

Pancreatic Proteases

Enzymes that break down polypeptides into smaller peptides in the small intestine.

Peptidases

Enzymes that break down peptides into amino acids in the small intestine.

Bile

Emulsifies fats into smaller droplets in the small intestine.

Pancreatic Lipase

Enzyme that breaks down triglycerides into monoglycerides and fatty acids.

Pancreatic Nucleases

Enzymes that break down DNA and RNA into nucleotides.

Nucleotidases

Enzymes that break down nucleotides into nitrogenous bases, sugars, and phosphates.

Interdigestive Phase

Digestive tract is quiet; somatostatin inhibits gastrin and HCl secretion.

Cephalic Phase

Sight/smell/taste activates vagal efferents, stimulating digestive secretions.

Gastric Phase

Stomach working; highest acid secretion and plasma gastrin levels occur.

Intestinal Phase

Amino acids/peptides/digested fats stimulate CCK release, slowing chyme entry.

CCK

Hormone that slows chyme entry and stimulates pancreatic juice and bile release.

Gastric Inhibitory Peptide

Decreases stomach secretions, motility, and emptying.

Secretin

Stimulates pancreatic juice flow and inhibits gastric juice secretion.

GI Tract

Tube that opens at both ends for food processing.

Mechanical Digestion

Physical movement of the GI tract aiding chemical digestion.

Chemical Digestion

Catabolic/hydrolysis reactions breaking down large food molecules.

Absorption

Passage of nutrients from GI tract into blood or lymph.

Defecation

Elimination of feces from the GI tract.