GI Anatomy & Physiology [McNeish] Flashcards Preview

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Flashcards in GI Anatomy & Physiology [McNeish] Deck (35):
1

List the organisation of the gut wall

Serosa
Longitudinal smooth muscle
Circular smooth muscle
Submucosa
Muscularis mucosa
Laminara propria
Epithelium
Lumen

2

What is the enteric nervous system?

Main control of motility in wall of GI tract
Integrates autonomic nervous system and local signals
Can function independently of any other signals

3

Which parts of the GIT wall are involved with the enteric nervous system?

The myenteric plexus = mainly motility
The submucosal plexus = mainly formation of secretions/blood flow

4

How does the parasympathetic nervous system affect the GI tract?

Increases motility and secretion
ACh acting on muscarinic receptors
Increased salivation and mucosa constriction
(via vagus nerve)

5

How does the sympathetic nervous system affect the GI tract?

The SNS reduces GI function
Noradrenaline relaxes smooth muscle in GIT

6

Which hormones regulate the GIT?

Endocrine hormones:
Released into bloodstream
Made in mucosal endocrine cells
Paracrine hormones:
Relatively short distance - local action
Made in cell walls of GIT

7

How do hormones affect the GIT?

Often modulate nerve action
Affect secretion and motility

8

Give 2 examples of endocrine hormones which are present in the GIT

Gastrin
Cholesystokinin (CCK)

9

Give 2 examples of paracrine hormones which are found in the GIT

Histamine
Somatostatin

10

List 3 roles of saliva

Aids swallowing
Begins digestion
Kills bacteria

11

What effect does the parasympathetic nervous system have on saliva production?

Watery saliva
(INcreased secretion and blood flow)

12

What effect does the sympathetic nervous system have on saliva production?

Mixed response
(Increased secretion, reduced blood flow)

13

List the 3 stages of swallowing

1st step = voluntary
2nd step = peristalsis - distention triggered under autonomic control, mucous aids movement
3rd step = enters stomach via oesophageal sphincter

14

What is the role of gastric glands and where are they found?

Gastric glands are found in the stomach
They secrete gastric juice

15

Name the 2 types of gastric gland and their specific roles

Parietal cells = secrete acid
Chief cells = produce pepsinogens (and other digestive enzymes)

16

List 5 substances that gastric juice contains

Salts
HCl
Pepsinogens
Water
Intrinsic factor (glycoprotein necessary for the absorption of vitamin B12)

17

List 4 roles of HCl in the stomach

Aids breakdown of tissue
Activates pepsinogen and optimises pepsin function
Allows absorption of calcium and iron
Protects against micro-organisms/pathogens

18

How is stomach acid formed?

Parietal cell:
Carbonic anhydrase generates H+ and HCO3-
Cl- enters parietal cell in exchange for HCO3- and transported out via the K+/Cl- symport
Proton pump H+/K+ ATPase secretes H+ into stomach lumen

19

How is gastrin regulated?

Released from G cell in response to nerve, hormonal and food stimuli
Activates CCK2 receptors on ECL cells stimulating histamine release

20

How is acetylcholine regulated?

ACh released from cholinergic nerves
Stimulates parietal cells

21

How is histamine regulated?

Released from entero-chromaffin like (ECL) cells
Agonist on H2 receptor on parietal cells = stimulates acid secretion

22

What is the role of the gastric mucosa?

Protects stomach wall from acid and gastric enzymes
Gel-like and alkaline

23

What kind of cells does the gastric mucosa contain?

Secretory cells:
Epithelial cells
Neck cells of gastric pits

24

What is the role of prostaglandins in the GIT?

Promote mucosal secretion
by increasing blood supply

25

List 3 disorders associated with increased acid production

Gastro-Oesophageal Reflux Disease (GORD) - heartburn, acid reflux, indigestion
Gastric bleeding - often due to NSAID treatment
Ulceration - may be caused by stress

26

List 4 things that happen in the GIT during vomiting (emesis)

Respiration inhibited (larynx and nasopharynx closed)
Stomach relaxes, duodenum contracts
Diaphragm and abdominal muscles contract powerfully
Gastro-oesophageal sphincter relaxes, gastric contents expelled

27

Which part of the brain controls vomiting?

The medulla of the brainstem
- The chemoreceptor trigger zone (CTZ)
- Vomiting centre

28

What is the main function of the pancreas?

Endocrine: Releases insulin and glucagon into the bloodstream
Exocrine: Releases alkaline fluid (reduces pH in duodenum) and digestive enzymes

29

Which 2 types of digestive enzyme which is released from the pancreas?

Proteolytic enzymes = aid breakdown of proteins
Lipolytic enzymes = aid fat digestion

30

How are monosaccharides and amino acids absorbed in the small intestine?

They are absorbed by Na-dependent co-transport

31

How are fats and fat-soluble vitamins absorbed in the small intestine?

They are absorbed by micelles and bile salts

32

How are water-soluble vitamins absorbed in the small intestine?

They are absorbed by facilitated transport

33

Name 2 disorders of absorption in the small intestine

Coeliac disease
Chrohn's

34

What happens in the large intestine?

Indigestible food residues are stored before elimination
Mucous secretion aids motility of faeces
Absorbs water and electrolytes
Resident bacteria from some vitamins (riboflavin, vitamin K, vitamin B12)

35

How does dietary fibre increase motility/defecation?

Bulk stimulates movement
Dietary fibre hydrates the bulk allowing greater propulsion and softer faeces