GI System 2/3 Flashcards
Oral Phase Digestion
- mechanical digestion (chewing)
- digestion of starches (salivary amylase)
- lipid hydrolysis (lingual lipase)
Oral Antibacterial Actions
Lysozyme: antibacterial enzyme
Immunoglobulins: antibodies
Gastric Phase Digestion
- contractions & gastric acid/secretions digest food
- produces chyme
Gastric Phase Protection
- acidic environment destroys pathogens
- mucus & bicarbonate protect stomach lining
Gastric Phase Storage
- chyme release into SI is regulated
Mucus-Bicarbonate Layer
- Gastric mucous cells secrete bicarboante to neutralize gastric juice (acidic) which protects gastric epithelium
Gastric Protein Digestion
pepsinogen is activated by acidic environments, turning into pepsin
- HCL denatures folded proteins
- Pepsin cleaves peptide bonds
Gastric Chemical Digestion Overview
Protein - HCL denatures protein, pepsin breaks peptide bonds
Fats - Gastric motility & Gastric Lipase
Carbohydrate - none (salivary amylase is inactivated at low pH
Gastric Motility
forms an emulsion of lipids (fat droplets) and gastric lipase
Gastric Lipase
hydrolyses triglycerides into monoglycerides and free fatty acids
Pariteal Cells
secrete HCL upon acetylcholine stimulation
Chief Cells
secrete Pepsinogen/gastric lipase upon ACh stimulation
SI Functions: regulation of gastric emptying
chyme release is regulated by what materials enter
- simple carbs increase release
- protein decreases release
SI Functions: Secretions
- Epithelial Cells: mucus, brush border enzymes
- Pancreas: Bicarbonate, digestive enzymes (pancreatic lipase/protease/amylase)
- Liver & Gallbladder: Bile
SI Functions: Digestion
carbs/proteins/fats
SI Lacteals
transport absorbed fat via lympatic system because fats are hydrophobic and need to be packaged at the liver
Exocrine Pancreas
- most secretions for digestion are from pancreas
- pancreatic protease/amylase/lipase
- duct cells secrete NaHCO3- to neutralize acidic chyme from the stomach
Bilary Secretions
Bile is produced by the liver and stored in the gallbladder
- used to digest and absorb fats
Carbohydyrate Digestion
Oral: mechanical by chewing, chemical by salivary amylase
Gastric: mechanical by peristaltic contractions, no chemical
Intestinal: mechanical by segmental contractions, chemical by pancreatic amylase/sucrase/lactase/maltase
Protein Digestion
Oral: mechanical by chewing, no chemical
Gastric: mechanical by peristaltic contractions, chemical by pepsin/HCl
Intestinal: mechanical by segmental contractions, chemical by pepsin/trypsin
Fat Digestion
Oral: mechanical by chewing
Gastric: mechanical by peristaltic contractions, chemical by gastric lipase/emulsification
Intestinal: mechanical by segemental contractions, chemical by pancreatic lipase/colipase
Lipid Transport
requried course emulsification in the stomach (fat droplets) and fine emulsification (micelles) in the small intestine
The Large Intestinal Phase
- furthur absorption of water and electrolytes
- environment for microflora
- digests some fiber
- storage of waste in rectum
Microflora Functions
- digest dietary fibre
- produce vitamin K
- limit growth & invasion of pathogenic microorganism’s
Steatorrhea
undigested fat in feces, sign of intestinal dysfunction
