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GI (Y1) > Physiology of Digestion 1 - Week 1 > Flashcards

Physiology of Digestion 1 - Week 1 Flashcards

1
Q

What is the purpose of the small intestine?

A

Major site for digestion and absorption

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2
Q

What is the approximate length of the small intestine?

A

6m

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3
Q

What is the approximate diameter of the small intestine?

A

3.5cm

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4
Q

What are the 3 parts of the small intestine?

A

Duodenum, jejunum, ileum

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5
Q

What are the 3 substances that the small intestine receives?

A

Chyme from the stomach, pancreatic juice from pancreas, bile from gall bladder

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6
Q

Intestinal juice is also known as…

A

succus entericus

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7
Q

The small intestine moves remaining residues to the large intestine via…

A

The ileocaecal valve

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8
Q

Which 3 adaptations are in place to increase the surface area of the small intestine?

A

circular folds (of Kerckring)
villi
microvilli (the brush border)

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9
Q

List the hormones secreted into the lumen by the mucosa of the small intestine.

A

Gastrin, Cholecystokinin (CCK), Secretin, Motilin, gastric inhibitory peptide, Glucagon-like peptide-1, Ghrelin

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10
Q

Where is gastrin produced?

A

G cells of gastric antrum (mainly) and duodenum

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11
Q

Where is Cholecystokinin (CCK) produced?

A

I cells of duodenum and jejunum

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12
Q

Where is Secretin produced?

A

from S cells of duodenum

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13
Q

Where is Motilin produced?

A

from M cells of duodenum and jejunum

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14
Q

Where is gastric inhibitory peptide produced?

A

K cells of duodenum and jejunum

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15
Q

Where is GLP-1 produced?

A

L cells of the gut

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16
Q

Where is Ghrelin produced?

A

Gr cells of the gastric antrum, small intestine and elsewhere (e.g. pancreas)

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17
Q

By which molecular mechanism do hormones secreted in the small intestine work?

A

G-protein coupled receptors

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18
Q

How much succus entericus is produced per day?

A

2L/day

19
Q

Give some factors which increase secretions by the small intestine.

A

Distension/irritation, gastrin, CCK, secretin, parasympathetic nerve activity

20
Q

Give a factor which reduces secretions by the small intestine.

A

sympathetic nerve activity

21
Q

Succus entericus contains…

A

Mucous, aqueous salt, no digestive enzymes

22
Q

How is segmentation initiated in the small intestine?

A

Initiated by small intestine pacemaker cells causing the BER which is continuous. At threshold activates segmentation which in the duodenum is primarily due to distension by entering chyme

23
Q

What is the effect of the gastroileal reflex on segmentation?

A

Release of gastrin by the stomach triggers segmentation in the ileum

24
Q

How many segmentation contractions does the ileum have?

A

9 per min

25
Q

How many segmentation contractions does the duodenum have?

A

12 per min

26
Q

What is meant by the migrating motor complex (MMC)?

A

occurs between meals every 90 – 120 min
strong peristaltic contraction passing length of the intestine (stomach  ileocaecal valve)
clears small intestine of debris, mucus and sloughed epithelial cells between meals – ‘housekeeper function’

27
Q

MMC is inhibited by…

A

Feeding & vagal stimulation, gastrin and CCK

28
Q

MMC is triggered by…

A

motilin

29
Q

Name 2 endocrine secretions of the pancreas.

A

Insulin and Glucagon

30
Q

Name an exocrine secretion of the pancreas.

A

Pancreatic juice

31
Q

What are the 2 main components of pancreatic juice?

A

digestive enzymes , aqueous NaHCO3- solution

32
Q

What is the purpose of HCO3- rich fluid in pancreatic juice?

A

Neutralises acidic chyme to create optimum pH for pancreatic enzymes and prevent erosion by acid

33
Q

How do Pancreatic duct cells secrete HCO3-?

A

Combines CO2 and H20 to create carbonic acid (by carbonic anhydrase). H+ dissociates creating HCO3-. HCO3- enters lumen by Cl-/HCO3- pump.

34
Q

Which condition may cause reduced secretion by pancreatic duct cells?

A

Cystic Fibrosis

35
Q

Which enzyme produced by duodenal mucosal cells can covert pancreatic enzymes to their active form?

A

Enterokinase

36
Q

How are pancreatic secretions controlled?

A

Cephalic – mediated by the vagal stimulation of mainly the acinar cells (20% total secretion)
Gastric – gastric distension evokes a vagovagal reflex resulting in parasympathetic stimulation of acinar and duct cells (5-10% total secretion)
Intestinal (70-80% of total secretion)

37
Q

What are the 3 main constituents of food?

A

Carbohydrates, lipids and proteins

38
Q

How much carbohydrate should be consumed per day?

A

approx. 400 g per day

39
Q

How much lipids should be consumed per day?

A

approx. 25-160 g per day

40
Q

How much protein is digested per day?

A

approx. 70-100 g per day ingested, plus 35-200 g from endogenous sources e.g. digestive enzymes and dead cells from GI tract

41
Q

What are the 2 digestive enzymes which take place in the small intestine?

A

Luminal digestion, membrane digestion

42
Q

Luminal digestion is mediated by…

A

pancreatic enzymes secreted into the duodenum

43
Q

Membrane digestion is mediated by…

A

enzymes situated at the brush border of epithelial cells

44
Q

What is meant by absorption?

A

processes by which the absorbable products of digestion are transferred across both the apical and basolateral membranes of enterocytes

GI (Y1) (79 decks)

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