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GIT Revision > Normal GIT Physiology > Flashcards

Normal GIT Physiology Flashcards

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1
Q

What are the common structural layers of the GIT and which of these is the most varied? What is the role and general structure of each?

A

Mucosa (most diverse): epithelium, lamina propria, mucularis mucosae
Submucosa: dense CT for strength and elasticity with nerve, small ganglia and blood vessels
Mucularis externa: inner circumferential and outer longitudinal smooth muscle for gut movement, with myenteric ganglia in between
Serosa/adventitia: fluid-secreting simple squamous epithelium, thin layer of CT (adventitia is thicker CT joining GIT with surrounding structures)

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2
Q

What does the ENS regulate?

A

Absorption and secretion via submucous ganglia

Smooth muscle activity via myenteric ganglia

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3
Q

What kind of epithelium is present throughout the different segments of the GIT?

A

Oesophagus: non-keratinised stratified squamous
Stomach: simple columnar
Small intestine: simple columnar with villi
Colon: simple columnar
Rectum: simple columnar
Anus: non-keratinised stratified squamous

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4
Q

What are the 2 types of muscle in the oesophagus? Where are they located and what is their significance?

A

Striated in top 1/3 of oesophagus: under somatic control

Smooth in lower 2/3 of oesophagus: under autonomic control

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5
Q

What are the distinctive features of the stomach mucosa?

A

Gastric glands with mucous, parietal, chief and enteroendocrine cells
3rd oblique layer of smooth muscle

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6
Q

What is the role of the mucous cells?

A

Produce mucus

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7
Q

What is the role of the parietal cells?

A

Secrete HCl

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8
Q

What is the role of the chief cells?

A

Produce pepsinogen

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9
Q

What is the role of the enteroendocrine cells?

A

Release gastrin

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10
Q

Which cells are found in the cardia, antrum and pylorus of the stomach?

A

Mucous

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11
Q

What glands are found in the oesophagus?

A

Mucous glands

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12
Q

What cells are found in the body (corpus) of the stomach?

A

Parietal

Chief

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13
Q

How is the SA of the small intestine increased to aid absorption?

A

Plicae circulares: folded surface
Villi: extensions of mucosa
Microvilli: projections on enterocytes on villi

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14
Q

What are the crypts of Lieberkuhn?

A

Lumen between villi where glands of the small intestine empty

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15
Q

What is special about the lamina propria and muscularis mucosae in the small intestine?

A

Extends into the villi

Contains blood and lymph vessels, and immune cells

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16
Q

List the 5 epithelial cells of the small intestine and their roles

A 
Enterocytes: fluid transport, absorption
Goblet cells: mucus secretion
EE cells: hormone release
Paneth cells: anti-microbial secretions
Stem cells: to renew epithelium
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17
Q

What are the distinctive features of the duodenum?

A

Highly coiled Brunner’s glands in submucosa

Low plicae circulares and long villi

18
Q

What is the role of Brunner’s glands?

A

Release alkaline mucus to inactivate stomach enzymes and neutralise acid

19
Q

Describe the histological structure of the entire GIT and all the important features

A

Oesophagus: non-keratinised stratified squamous epithelium, submucosal seromucinous glands
Stomach: simple columnar epithelium, mucus cells, parietal cells, chief cells, EE cells, oblique smooth muscle
SI: plicae circulares, villi, microvilli, crypts of Lieberkuhn, enterocytes, Paneth cells
Duodenum: Brunner’s glands, low plicae circularis, long villi
Ileum: Peyer’s patches, short villi, more goblet cells
Colon: taeniae coli, more goblet cells than SI
Rectum: more goblet cells
Anus: stratified squamous epithelium

20
Q

What are the distinctive features of the ileum?

A

Peyer’s patches
Short villi
More goblet cells

21
Q

What are the distinctive features of the large intestine?

A

Muscularis externa has 3 bundles of longitudinal muscle called taeniae coli
Straight tubular glands
More goblet cells than SI (esp in rectum)

22
Q

What are the 4 main cell types in the large intestine?

A

Enterocytes
Goblet cells
EE cells
Stem cells

23
Q

Describe the transition between the oesophagus and stomach

A

Abrupt junction between non-keratinised stratified squamous and columnar epithelium

24
Q

Describe the transition between the rectum and anus

A

Abrupt junction between columnar and non-keratinised stratified squamous epithelium

25
Q

What is the role of vago-vagal reflexes in GI control?

A

Coordinate movements in upper GI (control of swallowing)
Regulates acid secretion in stomach
Coordinates contractions of stomach and duodenum

26
Q

What is the role of intestino-intestinal reflexes in GI control?

A

Reflex inhibition of proximal regions when distal regions are distended (controls motility)

27
Q

What is the role of the interstitial cells of Cajal (ICC)?

A

Act as muscle pacemakers (modulated by neural activity)

28
Q

What happens during the cephalic phase of digestion?

A

Sight, smell and taste of food acts via the vagus nerve to cause salivation, gastric acid (30%) and pepsin secretion, and relaxation of gastric corpus and fundus

29
Q

How is HCl secretion regulated in the stomach?

A

Stimulated by ACh from enteric neurons excited by vagal efferent neurons
Stimulated by gastrin from G cells in antrum and duodenum
Stimulated by histamine from ECL cells
Inhibited by somatostatin from D cells

30
Q

What is the effect of somatostatin on gastric cells? What stimulates its release?

A

Release stimulated by acid in duodenum or gastrin

Inhibits HCl secretion by acting on parietal, ECL and G cells

31
Q

What are G cells located?

A

Antrum of stomach

Duodenum

32
Q

Where are D cells located?

A

Stomach

Duodenum

33
Q

What are the disaccharides of the human diet?

A

Lactose

Sucrose

34
Q

What are the monosaccharides of the human diet?

A

Glucose

Fructose

35
Q

What is lactose?

A

Disaccharide composed of galactose and glucose

36
Q

What is sucrose?

A

Disaccharide composed of glucose and fructose

37
Q

What is maltose?

A

Disaccharide composed of 2 glucose

38
Q

What is maltotriose?

A

Trisaccharide composed of 3 glucose

39
Q

How are maltase and sucrase synthesised? How are they activated?

A

As a single large glycoprotein

Separated and activated by pancreatic proteases

40
Q

What organs are covered by adventitia and what organs are covered by serosa?

A

Adventitia: retroperitoneal (pancreas, duodenum, ascending and descending colon, adrenals, kidneys)
Serosa: intraperitoneal (stomach, first part of duodenum, jejunum, ileum, caecum, transverse and sigmoid colon, rectum, liver, spleen)

GIT Revision (37 decks)

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