GIT

Question 1

GIT wall layers

Answer 1

serosa - connective tissue and peritoneum (continuous with parietal peritoneum)

muscularis - alternating direction → peristalsis

submucosa - small glands, BV, N

mucosa - epithelium

Question 2

which salivary glands are the main producer of saliva

Answer 2

sublingual and parotid - 1.5L/day

Question 3

what does the submandibular gland do?

Answer 3

produces mucin

Question 4

what does saliva contain

Answer 4

serous fluid - 99% water → to dissolve bolus for taste (chemoR taste buds only responds to dissolved substances)

muscin - lubricant and glue

Question 5

which branch of ANS innervate inc saliva production

Answer 5

PNS

Question 6

what is the nervous control of peristalsis

Answer 6

controlled by enteric NS

- interstitial cells of cajal (the pacemaker cells)

Question 7

what does the rate of emptying (of food from the stomach) depend on

Answer 7

amount/type of food in stomach

- usually completely empty in 2-6 hours

Question 8

what is the function of HCl in the stomach?

Answer 8

• levels peaks within 1-2hrs after meal
• activate pepsinogen → pepsin
• stimulates duodenum to secrete hormones → release bile + pancreatic juices

Question 9

where are gastric glands found and what cells do they have?

Answer 9

below gastric pits

• chief cells
• parietal cells
• endocrine cells

Question 10

chief cells

Answer 10

secretes pepsinogen → pepsin (breaks down protein)

Question 11

parietal cells

Answer 11

secretes HCl and intrinsic factor

• HCl turns pepsinogen → pepsin
• intrinsic factor → req for abs for vit B12

Question 12

endocrine cells

Answer 12

secretes gastrin → stimulates parietal cells when stomach stretched

secretes ghrelin → stimulates appetite, slow metabolism when stomach not stretched

Question 13

what problems may low dose aspirin cause?

Answer 13

aspirin irreversibly inhibits platelet COX1 → causes peptic ulcers and GI bleeding

Question 14

what is crohn’s disease and which part of the GIT is crohn’s disease associated with?

Answer 14

is an autoimmune disease → inflam of mucosa and associated with illeum

Question 15

plicae

Answer 15

folds containing villi in SI

Question 16

villi

Answer 16

contians BV and lymphatics

- also contain microvilli

Question 17

microvilli

-sucrase, maltase, lactase

• enteropeptidase
• alkaline phosphatase

Answer 17

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

Question 18

crypts of lieberkuhm

Answer 18

deep pits at the base of villi

- produces → new cells and bacterial enz

Question 19

goblet cells

Answer 19

secrete intestinal juices and mucus

Question 20

difference in function of prox and distal halves of LI

Answer 20

prox → reabs remaining water, na, glucose

distal → prepares and stores solid wastes for elimination

Question 21

unique features of LI

Answer 21

• fat tags (epiploic appendices)
• no villi
  mucus producing glands → lubricate faeces
• uneven layer of muscle fibres → taenia coli

Question 22

appendix

Answer 22

• accessory organ of digestive system
• breeding ground for non-pathogenic bacteria
• contains masses of lymphoid tissue (MALT)

Question 23

how of CO does the liver use

Answer 23

33%

Question 24

sinusoids

Answer 24

extend from hepatic veins → drains into central veins
- flow from: lobe → lobule → sinusoids

contains ‘kupffer’ cells
- hepatic macrophages

Question 25

CCK relation to gallbladder

Answer 25

stimulates gallbladder contraction

Question 26

what are calcified gall stones called

Answer 26

cholelithiasis

Question 27

function of the liver

Answer 27

• store and prod bile
• detox
• metabolise protein, fats, CHO
• stores substances
• maintain oncotic pressure (prod albumin)
• haematopoiesis in fetal dev

Question 28

3 stages of deglutination

Answer 28

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

Question 29

hormonal mech from fats in stomach

Answer 29

gastric inhibitory peptide released in response to fat in duodenum
→ dec peristalsis → slow chyme into duo

Question 30

nervous mech for gastro-motility

Answer 30

enterogastric reflex
- stretch R in duo → sensitive to presence of acid and distension → impulse to medulla → inh PNS, stim SNS → inh gastric peristalsis

Question 31

fat digestion

Answer 31

lipid mixes with water and lecithin → forms micelles → fat becomes water soluble

lipase also form micelles

Question 32

site of CHO digestion

Answer 32

by amaylase (in saliva and pancreatic juices)

by sucrase/lactase/maltase → intestinal brush border

Question 33

site of protein digestion

Answer 33

pepsin → gastric juice

trypsin and chymotrypsin → pancreatic juices

peptidase → intestinal brush border

Question 34

site of fat digestion

Answer 34

bile (emulsifier) → liver to gallbladder to pancreas

pancreatic lipase → pancreas

Question 35

physiology of constipation

Answer 35

slow peristalsis in distal colon → extra water abs in intestine → hardened stool

Question 36

physiology of diarrhoea

Answer 36

inc peristalsis → fast movement of chyme → dec water and electrolyte abs → watery stool

Question 37

newborn and GI

Answer 37

• v small stomach (frequent feeds)

- peristalsis inefficient → freq vomit

Question 38

old and GI

Answer 38

• 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