Digestive System Flashcards
Digestive system order (from food intake to excretion)
Oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, rectum
Enteric nervous system
collection of 100 million neurons that govern function of gastrointestinal system. Triggers peristalsis.
Hormones that drive thirst, hunger, and satiety
- Thirst: ADH, Aldosterone
- Hunger: Glucagon, Ghrelin
- Satiety: Leptin, Cholecystokinin
Ptyalin
Salivary amylase. Breaks sugar into smaller sugars (maltose and dextrins)
Esophagus: what muscles comprise it
- Top: somatic (voluntary) control, mostly skeletal
2. Bottom: autonomic (involuntary) control, mostly smooth
Swallowing: where initiated and where end
- Initiated at upperesophageal sphincter (at oropharynx)
2. End with lower esophageal sphincter (cardiac sphincter)
Emesis
Vomiting
Gastric gland: 3 cells and their roles
- Mucous cells: secrete mucus, bicarbonate. Protect muscular wall from acidic conditions
- Chief cells: produce pepsinogen. Pepsin digests peptides near aromatic amino acids
- Parietal cells: produce H+ that cleave pepsinogen to pepsin, produce intrinsic factor. Intrinsic factor helps absorb vitamin B12
Gastric gland
Gland in fundus and body of stomach that respond to signals from vagus nerve (parasympathetic)
Pylori glands
contain G-cells that secrete gastrin
Gastrin
Induce parietal cells to secrete more HCl, signal stomach to mix contents
Small intestine order
Duodenum, Jejunum, Ileum
Enzymes and hormones in duodenum
Enzymes: brush-border enzymes, enteropeptidase
Hormones: secretin, Cholecystokinin
Brush-border enzymes
In luminal surface.
- Disaccharidases (maltase, isomaltase, lactase, sucrase)
- Aminopeptidase: removes N-terminal AA. Di- and tripeptides can be absorbed back into the intestinal wall
Enteropeptidase
Activation of other digestive enzymes from accessory organs.
- Secretes hormones (secretin, CCK)
- Critical for trypsinogen activation
- Can activates procarboxypeptidases A and B
Secretin
peptide hormone, causes pancreatic enzymes to be released into duodenum
- Regulates pH of digestive tract by reducing HCl production (by parietal cells)
- Increases bicarbonate secretion from pancreas
Enterogastrone - hormone that slows motility through digestive tract
Cholecystokinin (CCK)
Stimulates bile & pancreatic juice secretion. Secreted with entry of chyme
Bile
Fluid of bile salts, cholesterol, and pigments.
Bile salts
Cholesterol derivatives that make lipids form micelles, easier for pancreatic lipase for digestion
Pancreatic juice
complex mixture of several enzymes in bicarbonate-rich alkaline solution. Neutralizes acidic chyme, provides good environment that digests nutrients.
Accessory organs of digestion
- Pancreas
- Liver
- Gallbladder
Pancreas role in digestion
- Release insulin, glucagon, somatostatin
- Made of acinar cells, producing pancreatic juices
- Secrete products into ducts that enter duodenum
Liver functions
- Processing nutrients (glycogenesis and glycogenolysis)
- Production of urea from ammonia
- Detoxification of chemicals
- Production of bile
- Synthesis of albumin and clotting factors
Albumin
Protein that maintains plasma oncotic pressure, carrier for drugs, and hormones
Bile ducts
Connect liver w/ gallbladder and small intestine.
- Bile produced in liver, stored in gallbladder
- Bile pigment: bilirubin (byproduct of Hg breakdown). Bilirubin travels to liver - conjugated then secreted into bile for excretion
- Jaundice when liver malfunctions
Gallbladder role in digestion
Stores & concentrates bile.
- Contracts and pushes bile out to biliary tree upon CCK
- Common site of cholesterol or bilirubin stone formation
Lacteal
lymphatic channel that takes up fats for transport into lymphatic system
What is absorbed via 2ndary active transport and facilitated diffusion
Simple sugars (glucose, fructose, galactose), amino acids. Small fatty acids.
Packaging larger fatty acids
Reformed into triglycerides, then packaged into chylomicrons. Enter circulation via lacteals.
