GIT Flashcards
GIT wall layers
serosa - connective tissue and peritoneum (continuous with parietal peritoneum)
muscularis - alternating direction → peristalsis
submucosa - small glands, BV, N
mucosa - epithelium
which salivary glands are the main producer of saliva
sublingual and parotid - 1.5L/day
what does the submandibular gland do?
produces mucin
what does saliva contain
serous fluid - 99% water → to dissolve bolus for taste (chemoR taste buds only responds to dissolved substances)
muscin - lubricant and glue
which branch of ANS innervate inc saliva production
PNS
what is the nervous control of peristalsis
controlled by enteric NS
- interstitial cells of cajal (the pacemaker cells)
what does the rate of emptying (of food from the stomach) depend on
amount/type of food in stomach
- usually completely empty in 2-6 hours
what is the function of HCl in the stomach?
- levels peaks within 1-2hrs after meal
- activate pepsinogen → pepsin
- stimulates duodenum to secrete hormones → release bile + pancreatic juices
where are gastric glands found and what cells do they have?
below gastric pits
- chief cells
- parietal cells
- endocrine cells
chief cells
secretes pepsinogen → pepsin (breaks down protein)
parietal cells
secretes HCl and intrinsic factor
- HCl turns pepsinogen → pepsin
- intrinsic factor → req for abs for vit B12
endocrine cells
secretes gastrin → stimulates parietal cells when stomach stretched
secretes ghrelin → stimulates appetite, slow metabolism when stomach not stretched
what problems may low dose aspirin cause?
aspirin irreversibly inhibits platelet COX1 → causes peptic ulcers and GI bleeding
what is crohn’s disease and which part of the GIT is crohn’s disease associated with?
is an autoimmune disease → inflam of mucosa and associated with illeum
plicae
folds containing villi in SI
villi
contians BV and lymphatics
- also contain microvilli
microvilli
-sucrase, maltase, lactase
- enteropeptidase
- alkaline phosphatase
secrete digestive enz
- sucrase: sucrose → glucose + fructose
- maltase: maltose → glucose x2
- lactose: lactose → glucose + galactose
- enteropeptidase: activates trypsinogen → trypsin
- alkaline phosphatase: removes phosphates from organic molecules
crypts of lieberkuhm
deep pits at the base of villi
- produces → new cells and bacterial enz
goblet cells
secrete intestinal juices and mucus
difference in function of prox and distal halves of LI
prox → reabs remaining water, na, glucose
distal → prepares and stores solid wastes for elimination
unique features of LI
- fat tags (epiploic appendices)
- no villi
mucus producing glands → lubricate faeces - uneven layer of muscle fibres → taenia coli
appendix
- accessory organ of digestive system
- breeding ground for non-pathogenic bacteria
- contains masses of lymphoid tissue (MALT)
how of CO does the liver use
33%
sinusoids
extend from hepatic veins → drains into central veins
- flow from: lobe → lobule → sinusoids
contains ‘kupffer’ cells
- hepatic macrophages
CCK relation to gallbladder
stimulates gallbladder contraction
what are calcified gall stones called
cholelithiasis
function of the liver
- store and prod bile
- detox
- metabolise protein, fats, CHO
- stores substances
- maintain oncotic pressure (prod albumin)
- haematopoiesis in fetal dev
3 stages of deglutination
1) oral
- vol and forms bolus
2) pharyngeal stage
- invol → bolus pushed down to eso
3) eso stage
- invol → skeletal and SM move bolus down via peristalsis
hormonal mech from fats in stomach
gastric inhibitory peptide released in response to fat in duodenum
→ dec peristalsis → slow chyme into duo
nervous mech for gastro-motility
enterogastric reflex
- stretch R in duo → sensitive to presence of acid and distension → impulse to medulla → inh PNS, stim SNS → inh gastric peristalsis
fat digestion
lipid mixes with water and lecithin → forms micelles → fat becomes water soluble
lipase also form micelles
site of CHO digestion
by amaylase (in saliva and pancreatic juices)
by sucrase/lactase/maltase → intestinal brush border
site of protein digestion
pepsin → gastric juice
trypsin and chymotrypsin → pancreatic juices
peptidase → intestinal brush border
site of fat digestion
bile (emulsifier) → liver to gallbladder to pancreas
pancreatic lipase → pancreas
physiology of constipation
slow peristalsis in distal colon → extra water abs in intestine → hardened stool
physiology of diarrhoea
inc peristalsis → fast movement of chyme → dec water and electrolyte abs → watery stool
newborn and GI
- v small stomach (frequent feeds)
- peristalsis inefficient → freq vomit
old and GI
- dec GIT activity
- dec digestive juices → less efficient abs
- slow peristalsis → constipation
- changes acinar cells in exocrine pancreas → dec enz
- taste/smell changes → loss appetite → elderly citizens poorly nourished
