D3 - Digestive Structures Flashcards
Ingestion
The process of taking substances into the body.
Example: Swallowing food
Digestion
The process of breaking down food into smaller components.
Two types:
- Physical digestion → Mechanical breakdown of food
- Chemical digestion → Breaking chemical bonds in food molecules
Physical Digestion
Mechanical breakdown of food (chewing, churning, segmentation).
Chemical Digestion
Breaking chemical bonds in food molecules.
Uses enzymes and acids.
Absorption
Nutrients from food enter the bloodstream.
Occurs mostly in the small intestine.
Bolus
Chewed food mixed with saliva.
Formed in the mouth and swallowed.
Salivary Glands
Produce saliva, which contains salivary amylase.
Salivary Amylase
Enzyme that begins digestion of carbohydrates.
Breaks polysaccharides → disaccharides.
Epiglottis
Flap of tissue that covers the trachea when swallowing.
Prevents choking.
Esophagus
Muscular tube that connects the mouth to the stomach.
Moves food using peristalsis.
Peristalsis
Wave-like muscle contractions that push food through the digestive tract.
Esophageal Sphincter
Circular muscle at the bottom of the esophagus.
Prevents stomach acid from going back up (acid reflux).
Stomach
Sac-like muscular organ that continues digestion.
Contains gastric juice (HCl, enzymes, mucus) and absorbs water, alcohol, and some drugs.
Gastric Juice
pH 1-3, contains water, HCl, mucus, salts, enzymes.
Helps digest food and kill bacteria.
Chyme
Partially digested food mixed with gastric juice.
Pepsin
Enzyme in the stomach that digests proteins.
Works only in the presence of HCl.
Pyloric Sphincter
Muscle at the bottom of the stomach.
Controls the release of chyme into the small intestine.
Small Intestine
6 meters long, divided into duodenum, jejunum, ileum.
Most digestion and absorption occur here.
Duodenum
First 25 cm of the small intestine.
Receives enzymes from the pancreas and liver.
Segmentation
Sloshing movement of food back and forth in the small intestine.
Villi
Tiny ridges and folds in the small intestine.
Increase surface area for absorption.
Microvilli
Even smaller projections on villi.
Site of nutrient absorption.
Carbohydrases
Enzymes that digest carbohydrates.
Examples: Sucrase, maltase, lactase.
Nucleases
Enzymes that digest nucleic acids (DNA & RNA).
Nucleosidases
Enzymes that further break down nucleic acids.
Peptidases
Enzymes that digest proteins into amino acids.
Large Intestine
Absorbs water and salts from waste.
Contains bacteria that produce vitamins and stores and eliminates waste.
Colon
Main part of the large intestine.
Absorbs water and salts.
Rectum
Stores feces before elimination.
Anus
Opening where waste leaves the body.
Controlled by two sphincters (one voluntary, one involuntary).
