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Journey through GI > Physiology of the GI Tract > Flashcards

Physiology of the GI Tract Flashcards

1
Q

Describe the General organisation of the GI

A 
Mouth
Esophagus
Stomach
Liver
Duodenum
Pancreas
Jujenum
Transverse colon
Descending colon
Ascending colon
Ileum
Appendix
Rectum
Anal Canal
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2
Q

Label the GI wall

A

Label the Gi wall

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3
Q

Describe the structure of the pharynx that allows movement through it

A

smooth muscle electrically coupled
segmented
peristaltic contractions

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4
Q

what is the main control of motility

A

intrinsic innervation enteric nervous system

IIENS

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5
Q

what is the role of the myenteric plexus vs the submucosal plexus

A

myenteric plexus is mainly motility whereas the submucosal is mainly formation of secretions and blood flow

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6
Q

can the IIENS act independently from other signals

A

yes it is part of the autonomic nervous system

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7
Q

what does parasympathetic increase

A

mobility and secretion as ach acts on muscarinic receptors increasing salivation mucosa and constriction

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8
Q

what does sympathetic do

A

reduces GI function as the noradrenaline relaxes the smooth muscle in GIT

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9
Q

what in addition to neurotransmitter influence the GI

A

hormones

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10
Q

what are two examples of hormones that affect the GI

A

Endocrine hormones e.g. gastrin

Paracrine e.g. histamine

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11
Q

what is motility

A

“Motility” is a term used to describe the contraction of the muscles that mix and propel contents in the gastrointestinal (GI) tract.”

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12
Q

what does saliva aid in

A

swallowing
beginning digestion
killing bacteria

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13
Q

what type of process is saliva controlled by

A

autnomic process

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14
Q

what does the parasympathetic watery saliva do

A

increases secretion and blood flow

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15
Q

what does the sympathetic mixed saliva do

A

increase secretion and reduces blood flow

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16
Q

describe the three steps of swallowing

A

voluntary swallow

peristalsis - distention triggered under autonomic control, mucous aids movement

enters stomach via esophageal sphincter

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17
Q

label the parts of a stomach

A

label the parts of a stomach

18
Q

what is the stomach lined with

A

gastric glands

19
Q

what is the role of the gastric glands

A

they secrete gastric juice

parietal cells secrete acid

chief cells produce pepsinogens and other digestive enzymes

20
Q

what is contained in gastric juice

A

salts
HCL
pepsinogens
water

21
Q

how much gastric juice is produced per day

A

2-3 litres produced per day

22
Q

what does the low pH of 1-3 of the stomach help with

A

aids breakdown of tissue

activates pepsinogen and optimizes pepsin function

absorption of calcium and iron

protects against microorganisms / pathogens

23
Q

Describe the formation of stomach acid

A

parietal cell carbonic anhydrase generates H+ and HCO3- from carbon dioxide and water

Cl enters the partietal cell in exchange of the HCO3-
and is transported out via the K+ CL- symport

Proton pump secretes H+ into the stomach lumen

24
Q

describe the regulation of acid secretion

A

Gastrin is released from a G cell in response to nerve, hormonal and food stimuli

This activates the CCk2 receptors on ECL cells stimulating histamine release

this is then released from the entero chromaffin cell (ECL)

and it binds to the H2 receptors on parietal cells stimulating acid secretion

meanwhile acetylcholine stimulates the parietal cells from cholinergic nerves

25
Q

what is the role of gastric mucosa

A

protects stomach wall from acid and gastric enzymes

26
Q

what properties allow the gastric mucosa to protect the stomach wall

A

gel like

alkaline

bicarbonate

27
Q

what type of secretory cells does the gastric mucosa contain

A

epithelial cells

neck cells of gastric pits

28
Q

what is a prostaglandins

A

a group of lipids made at sites of tissue damage or infection that are involved in dealing with injury and illness. They control processes such as inflammation, blood flow, the formation of blood clots and the induction of labor.

29
Q

what do prostaglandins promote

A

mucosal secretion as it increase blood supply bicarbonate and mucosal gel secretion

30
Q

what can a reduction in mucosa function lead too

A

gi disorders

31
Q

what role does the stomach play in gastric propulsion

A

stomach mixes and stores food for digestion in the intestine

peristaltic waves propel content to the duodenum via the plyoric sphincter

32
Q

what is emesis

A

vomitting which is the sudden forceful evacuation of stomach and sometimes duodenum

33
Q

what is vomiting often preceeded by

A

loss of appetite

nausea

vasoconstriction with pallor

sweating

dizziness excess salivation

34
Q

what happens during vomiting

A

respiration inhibited

stomach relaxes
duodenum contracts

diaphragm and abdominal muscles contract powerfully

gastro oesophagal sphincter relaxes, gastric contents expelled

35
Q

where is vomiting controlled

A

medulla of the brainstem in the chemoreceptor trigger zone and the vomiting center

36
Q

what is the role of the liver

A

secretion of bile

lipid transport

37
Q

what is the role of hte pancreas

A

endocrine gland function insulin and glucagon into blood stream

exocrine digestion digestive, alkaline fluid reduces the pH in the Duodenum

proteolytic aid breakdown of proteins

lipolytic aid fat digestion

38
Q

what is propulsion regulated as

A

major area for nutrient and drug adsorption

Monosaccharides and amino acids absorbed by Na dependent co-transport

Fats and fat soluble vitamins absorbed by micelles+bile salts (see liver lecture)

Water soluble vitamins absorbed by facilitated transport

39
Q

what is the role of the large intestine

A

stores indigestible food residues before elimination by defecation

absorbs water and electrolytes

40
Q

what does mucous do in the large intestine

A

secretion aids motility of faeces

Journey through GI (30 decks)

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