Physiology

Question 1

four layers of the GI tract

Answer 1

mucosa
submucosa
muscularis externa
serosa/adventitia

Question 2

where is the muscularis mucosae located?

Answer 2

mucosa

Question 3

where is the submucous plexus located?

Answer 3

submucosa

Question 4

where is the myenteric plexus located

Answer 4

muscularis externa

Question 5

which layer is made up of the circular and longitudinal muscle layers?

Answer 5

muscularis externa

Question 6

function of the circular muscle layer?

Answer 6

makes the lumen longer and narrower

Question 7

function of the longitudinal muscle layer

Answer 7

makes the lumen shorter and fatter

Question 8

what initiates slow wave activity in the GI tract?

Answer 8

interstitial cells of Cajal (pacemaker cells between the two muscle layers)

Question 9

major patterns of motility in the stomach and small intestine

Answer 9

1. peristalsis
2. segmentation
3. colonic mass movement (faeces into rectum)
4. migrating motor complex (stomach to terminal ileum)
5. tonic contractions

Question 10

gastric factors affecting stomach emptying

Answer 10

volume and consistency of chyme

Question 11

patterns of motility in the large intestine

Answer 11

• haustration (slow wave)
• peristalsis propulsion
• defecation

Question 12

two areas of secretion in the stomach

Answer 12

• oxyntic gland area

- pyloric gland area

Question 13

cells in the oxyntic gland area

Answer 13

• chief cells (pepsinogen)
• parietal cells (HCl, intrinsic factor and gastroferrin)
• enterochromaffin (histamine)

Question 14

cells in the pyloric gland area

Answer 14

• D cells (somatostatin)

- G cells (gastrin)

Question 15

role of intrinsic factor and gastroferrin

Answer 15

bind B12 and Fe2+

Question 16

role of somatostatin

Answer 16

inhibit HCl secretion

Question 17

how does the mucosa protect itself from being digested?

Answer 17

secretes PGE2 and PGI2

Question 18

two motility regions in the stomach

Answer 18

• orad: tonic contractions- vagus

- caudad: slow wave (retropulsion)

Question 19

two types of secretions in the pancreas

Answer 19

1. endocrine: islets of Langerhans

2. exocrine: acinar cells

Question 20

five pancreatic enzymes (precursors)

Answer 20

1. trypsinogen
2. chymotrypsinogen
3. carboxypeptidase
4. pancreatic amylase
5. pancreatic lipase

Question 21

how is Cl- secreted

Answer 21

through CFTR on apical membranes (overstimulated causes secretory diarrhoea- loss of K+)

Question 22

describe luminal digestion

Answer 22

pancreatic enzymes secreted into the duodenum

Question 23

describe membrane digestion

Answer 23

mediated by enzymes at the brush border of epithelial cells

Question 24

in carbohydrate digestion what is the role of alpha-amylase

Answer 24

breaks alpha-1,4-links

Question 25

in carbohydrate digestion what is the role of isomaltase?

Answer 25

breaks alpha-1,6 links

Question 26

what are oligosaccharidases

Answer 26

integral membrane proteins with a catalytic domain that faces the lumens

Question 27

examples of oligosaccharidases

Answer 27

lactase, maltase, sucrase and isomaltase

Question 28

substances involved in protein digestion

Answer 28

- HCl and pepsin in stomach | - pancreatic enzymes function as either endopeptidases or exopeptidases in the small intestine

Question 29

describe lipid digestion

Answer 29

converted to an emulsion by lipases which is reduced by pancreatic lipase

Question 30

what does failure to secrete bile salts result in?

Answer 30

lipid malabsorption (steatorrhoea and vitamin deficiency- A, D, E and K)

Question 31

how are glucose and galactose absorbed?

Answer 31

secondary active transport mediated by SGLT1 (Na+)

Question 32

how is fructose absorbed

Answer 32

facilitated diffusion mediated by GLUT5

Question 33

how do all monosaccharides exit enterocytes

Answer 33

facilitated diffusion by GLUT2

Question 34

how are peptides absorbed at the brush border?

Answer 34

by PepT1 (co-transport with H+)

Question 35

how is cholesterol absorbed

Answer 35

NPC1L1 (ezetimibe)

Question 36

what is the taeniae coli

Answer 36

longitudinal smooth muscle in the colon is divided into three strands to cause the production of haustra

Question 37

how is the appendix connected to the caecum?

Answer 37

appendiceal orifice

Question 38

three major functions of the large intestine

Answer 38

- secretion of K+, HCO3- and mucus - absorption of Na+, Cl- and H2O (& short chain fatty acids) - reservoir for periodic elimination

Question 39

what enhances Na+ absorption and K+ secretion

Answer 39

aldosterone

Question 40

is the absorption of water a passive process?

Answer 40

yes, it follows solutes (usually Na+)

Question 41

three mechanisms of water absorption in the jejunum

Answer 41

- Na+/glucose co-transport - Na+/amino acid co-transport - Na+/H+ exchange

Question 42

mechanism of water absorption in the ileum and proximal colon

Answer 42

Na+/H+ and Cl-/HCO3- exchange (reduced NaCl absorption causes diarrhoea)

Question 43

mechanism of water absorption in the distal colon

Answer 43

epithelial Na+ channels (enhanced by aldosterone)

Question 44

define assimilation

Answer 44

overall process of digestion and absorption

Question 45

major functions of the liver

Answer 45

- metabolism - deactivation of hormones (insulin, glucagon, ADH, steroids) - storage of A, D, E, K vitamins, iron, copper and glycogen - synthesis of protein (acute phase proteins, coagulation, albumin, etc.) - protection: Kupffer cells - detoxification - secretion of bile

Question 46

describe the secretion of bile by the liver

Answer 46

secreted by hepatocytes into canaliculi which drains into bile ducts, neutralising chyme an forms micelles

Question 47

two phases of drug metabolism in the liver

Answer 47

Phase 1: oxidation (CYP450s), reduction and hydrolysis. | phase 2: conjugation e.g. glucuronidation

Question 48

what is the enteric nervous system

Answer 48

it is the autonomic nervous system that supplies the GI tract

Question 49

parasympathetic neurotransmitter in the ENS

Answer 49

both preganglionic and postganglionic synapse with ACh

Question 50

role of the parasympathetic in the ENS

Answer 50

'rest and digest' - increases blood flow, secretion and smooth muscle contraction - relaxation of sphincters

Question 51

neurotransmitters in the sympathetic of the ENS

Answer 51

preganglionic release ACh and postganglionic release NA

Question 52

role of the sympathetic in the ENS

Answer 52

- increased sphincter tone | - decreased motility, secretion and blood flow

Question 53

define retching

Answer 53

rhythmic reverse peristalsis with forceful contraction of abdominal muscles and the diaphragm

Question 54

define emesis

Answer 54

forceful expulsion of gastric-intestinal contents out of the mouth

Question 55

what stimuli act directly on the VC

Answer 55

- pain, repulsive sights, smells and emotional factors | - motion (signals via the vestibular nucleus)

Question 56

what stimuli act on the NTS

Answer 56

pharyngeal stimulation, gastric/duodenal distension or irritation

Question 57

what stimuli act on the CTZ (no BBB)

Answer 57

- pharyngeal stimulation, gastric/duodenal distension or irritation - toxins, drugs and vagal afferents

Question 58

consequences of severe vomiting

Answer 58

- dehydration - metabolic alkalosis - hypokalaemia - oesophageal damage e.g. Mallory-Weiss tear

Question 59

which area of the brain 'causes' obesity

Answer 59

lesioning ventromedial hypothalamus (leptin and insulin report fat status)

Question 60

define satiety

Answer 60

period of time between termination of one meal and the next (gherlin is the hunger signal)