9/19/22 Flashcards
mucus
composed of mucin, H2O, and bicarbonate (HCO3-), lubricates foods and protects mucosa (against super acids)
protects stomach w/ protein and water
intrinsic factor
needed for vitamin B12 absorption
enzymes
pepsin; gastric lipase
hydrochloric acid (HCl)
facilitates digestion, protein degradation, and absorption of micronutrients
oxyntic gland
located in body and fundus
secretion: HCl, pepsinogen, intrinsic factor, histamine, somatostatin
pyloric gland
located in pyloric antrum (near pylorus, entry to duodenum)
secretion: mainly mucus. Also gastrin and somatostatin
parietal cell
secretes HCl, intrinsic factor
enterochromatin-like cell
secretes histamine (allergens, inflammation)
D cell
secretes somatostatin
chief cells
secrete pepsinogen
pepsinogen
a zymogen (inactive protease)
if not a zymogen, would digest everything
turned into pepsin (active form) in stomach lumen in response to H+
proteases role
break peptide bonds
gastric acid pH
2
same as lemon juice
gastric acid aka
HCl
gastric acid functions
- converting or activating pepsinogen to form pepsin
- denaturing proteins
- releasing various nutrients such as vitamins and minerals from organic complexes so absorption can occur
- acting as a bactericide agent (needed to kill bacteria ingested with food
- contains mucins
mucins
bind water and form gel: provide lubrication and protection
no parietal cells would lead to
no intrinsic factor, no vitamin B12 absorption
parietal cell purpose
regulate acid secretion
parietal cell phases
- Cephalic
- Gastric
- Intestinal
cephalic phase of acid secretion
- think/smell/see food
- release ACh which sends signal to stomach to release Gastrin
gastric phase of acid secretion
- stretching of stomach signals release of Gastrin
intestinal phase of acid secretion
SST inhibits HCl
Secretin activates bicarbonate release
chief cells secretions
pepsinogens I and II are secreted in granules into the gastric lumen by chief cells
main stimuli for secretion: acetylcholine, HCl, low pH
pepsin role
chops proteins into aa
GERD mechanism
increase pressure in stomach
opens lower vasovagal sphincter
esophagus pH is typically 7 but lowers to around 2 with GERD
GERD causal factors
carminatives (spearmint, peppermint)
fatty foods
alcohol
smoking
GERD pathway
- GERD
- Heartburn
- Esophagitis
- Ulcer
GERD treatments
- smaller meals
- higher protein
- dairy
- antiacids
- fluid between meals
- avoid causal factors
ACh pathway
- ACh causes gastrin release
- gastrin enters circulation and goes to bile cell
- acid release in stomach
cause of stomach peptic ulcer
disruption of mucosa (very pH sensitive) of GI tract
peptic ulcer causal factors
- gastric acid
- pepsin
- H. pylori (normal stomach bacteria)
- chronic uses of aspirin, alcohol, NSAIDs (ibuprofen)
peptic ulcer treatments
- diet
- H2 receptor blockers (cimetidine, ranitidine)
- PPIs (omeprazole, esomeprazole)
no gut microbiota =
no immune system
gut microbiota functions
- maturation and education of host immune response
- protection against pathogen overgrowth
- influence host-cell proliferation and vascularization (create new and repair old blood vessels)
- regulate intestinal endocrine functions
- source of energy biogenesis (5-10% of daily host energy requirements
other gut microbiota functions
- neurologic signaling and bone density
- biosynthesis of vitamins, NTs, and other bioactive compounds
- metabolism of bile salts, drugs and elimination of exogenous toxins
microbial composition in GI tract
> 1000 different species, largely bacteria
1. bacteria
2. archaea
3. viruses
4. fungi/yeast
5. protozoa
2 main phyla of gut bacteria
firmicutes
bacteriodetes
make up 90% of gut bacteria
effects of maternal exposure on microbiome
environment
antisepsis
antibiotics
diet
vertical transmission in early life of microbiome
- oral (pre-mastication of food)
- mammary (through brestfeeding, selection)
- cutaneous (contact with skin)
- vaginal (passage through birth canal
where do most bacteria live in the body?
the colon!
why?
train immune system, breakdown food
