Digestion Flashcards
Describe the 4 processes performed by the Dig. System
Motility: Muscular contractions that mix/move material in Dig. tract
Secretion: Of Dig. enzymes, mucus, hormones etc.
Digestion: Chemical breakdown of large molecules into smaller subunits for absorption.
Absorption: Base monomers from digestion transported from Dig. tract into blood/lymph.
Protein subunits
Amino Acid < Peptide < Polypeptide < Protein
Carbohydrate subunits
Monosaccharide < Disaccharide < Polysaccharide
Lipid subunits
Trigylcerides = Glycerol backbone with 3 fatty acid chains
Digestion of Polymers
Dehydration Synthesis ->
Monomer + Monomer+ … = Polymer (+H2O)
<- Hydrolysis
(Digestion is hydrolysis, but accelerated by dig. enzymes
Enzymes that break down Carbohydrates
Salivary Amylase (Oral Cavity)
Pancreatic Amylase (Small Intestine)
Disaccharidases (Small Intestine) (Maltase, Sucrase, Lactase)
Enzymes that break down lipids
Lingual lipase (oral cavity)
Pancreatic Lipase (Sm Intestine)
Gastric Lipase (Stomach)
Enzymes that break down Proteins
Pepsin (Stomach)
Proteases (Carboxypeptidase, trypsin, chymotrypsin, elastase) (Sm Intestine)
Peptidases & Dipeptidases (Sm Intestine)
Absorption of Proteins & Carbs
Proteins and Carbs are broken down on the brush border of Sm Intestine Epith. cells. -> then leave the cells via facilitated diffusion into blood capillaries.
Absorption of Lipids
Lipids form Micelles (hydrophobic molecules surrounded by bile salts) pass through membrane of intestinal epithelial cell via simple diffusion. Then surrounded by a protein coat, and leave cell via exocytosis to enter lymphatic system and eventually circulatory system.
Digestive hormones and what they do (6)
Gastrin: causes more gastric secretions and increases stomach muscle activity.
Secretin: Causes the pancreas to release bicarbonate ions to neutralize the acidic chyme, and stimulates the liver to secrete bile
GIP: Gastric Inhibitory Peptide. Inhibits acid production and peristalsis in stomach, and stimulates release of insulin from pancreas.
CCK: Cholecystokinin. Stimulates gall bladder to contract, releasing stored bile and stimulates pancreas to release digestive enzymes
VIP: Vasoactive intestinal Peptide. Stimulates secretions of sm intestine and inhibits acid production in the stomach.
Enterocrinin: Stimulates mucin production by submucosal glands.
Central reflex control of Dig. system
Gastroenteric reflex: Receptors in stomach stimulate CNS to tell SM intestine to increase motility and secretion.
Gastroileal reflex: Receptors in stomach stimulate CNS to tell ileum to open to allow material to transfer from Sm intestine to Lg intestine
Three phases of Gastric secretion
Cephalic Phase: Starts with sight, smell, taste or thought of food. Tells CNS to prepare stomach for arrival of food.
Gastric Phase: Starts with arrival of bolus in stomach which stimulates increase in gastric secretion, contraction of muscularis externa, release of Gastrin.
Intestinal Phase: Starts with arrival of chyme in duodenum. Slows down activity in stomach to ensure sm intestine has enough time to process chyme efficiently.
