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Gastro > Physiology and Pharmaxology of the small and large intestine > Flashcards

Physiology and Pharmaxology of the small and large intestine Flashcards

1
Q

Describe the length of the different parts of the small intestine

A

Duodenum - 25cm
Jejunum - 2.5m
Ileum - 3m

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2
Q

What happens in the small intestine

A

Major site for digestion and absoprtion

Receives chyme from the stomach, pancreatic juice from pancreas and bile form the gall bladder

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3
Q

How does the small intestine move remaining residues to the large intestine

A

Through the ileocaecal valve

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4
Q

In which part of the small intestine does most of the absorption and digestion occur?

A

Duodenum

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5
Q

How do pancreatic secretions and bile secretions enter the small intestine?

A

Through the sphincter of Oddi

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6
Q

What moves into the large intestine?

A

Unabsorbed electrolytes, water and indigestible residue (cellulose)

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7
Q

What is the sphincter between the small intestine and the large intestine

A

Ileocaecal valve

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8
Q

What controls the opening of the ileocaecal valve

A

The hormone Gastrin

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9
Q

In what 3 ways is the surface area of the small intestine increased?

A

Circular folds of Kerckring
Villi
Microvilli

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10
Q

What is the name of the absorptive cells?

A

Enterocytes

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11
Q

What 7 peptide hormones are secreted from endocrine cells within the mucosa

A 
Gastrin
Cholexystokinin (CKK)
Secretin
Motilin
Glucaogon-like insulinotropic peptide (GIP)
Glucagon like peptide 1 
Ghrelin
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12
Q

Where is gastrin secreted from

A

From G cells of gastric antrum and duodenum

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13
Q

Where is CCK secreted from?

A

From I cells of duodenum and jejunum

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14
Q

Where is secretin secreted from?

A

S cells of duodenum

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15
Q

WHere is motilin secreted?

A

From M cells of duodenum and jejunum

It has a special purpose in migrating the motor complex

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16
Q

Where is GIP secreted

A

an incretin from K cells of duodenum and jejunum

It causes an increase in gastric motility and serves as an incretin (feedforward signal)

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17
Q

Where is GLP-1 secreted

A

an incretin from L cells of the gut

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18
Q

Where is Ghrelin secreted

A

from Gr cells of the gastric antrum, small intestine and elsewhere (pancreas)

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19
Q

Where do all peptide hormones act on

A

G protein couple receptors

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20
Q

What is the role of Ghrelin

A

To release a hunger signal as a feedforward mechanism to prepare the body for food

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21
Q

What is the name given to the jucie of the small intestine

A

Succus entericus

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22
Q

What will cause the release off the intestinal juice

A

Any stimulatory act on the GI tract

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23
Q

What are some of the control mechanisms related to the secretions of the small intestine

A

Distension / irritation if acid is present

Parasympathetic activity - change in ACh

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24
Q

Secretions of the small intestine include:

A

Mucus - for protection/ lubrication
Aqueous salt - for enzymatic digestion
No digestive enzymes

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25
Q

What does excessive activity cause?

A

Secretory diarrhoea (cholera)

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26
Q

What is the function of the ATPase in the basolateral membrane

A

To maintain a low intracellular concentration of sodium

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27
Q

Cysitic fibrosis patients may suffer from what in GI

A

a decrease in secretion of succus entericus

28
Q

Segmentation in the duodenum is primarily due to what?

A

distension due to Chyme entering

29
Q

What is triggered by gastrin from the stomach

What is the alternative name for this?

A

Segmentation in the empty ileum

Gastroileal reflex

30
Q

How many segmentation contraction are there in the duodenum?
In the ileium

A

Duodenum: 12/min
Ileum: 9/min

31
Q

What enhances the strength of segmentation

A

Parasympathetic nervous system

32
Q

What decreases the strength of segmentation

A

Sympathetic system

33
Q

Describe the 2 main activities which occur in the interdigestive or fasting state

A

A few localised contractions

The mirgrating motor complex (MMC)

34
Q

What happens to the small intestine when chyme enters

A

therefore it is inhibited by feeding, vagal activity, gastrin and motility and poylystic kinin. ]

35
Q

What are the 2 main types of pancreatic secretions

A

Endocrine and Exocrine

36
Q

Give two examples of endocrine hormones

A

Insulin and Glucagon

37
Q

Give 2 examples of exocrine cells

A

acquous NaHCO3, dyct cells)

38
Q

What do acini cells eventually form? and where dies it join?

A

Pancreatic duct which joins the common bile duct.

39
Q

What are the 3 main types of pancreatic enzyme

A

Proteases, amylases and lipases

40
Q

Name the 3 phases of pancreatic secretion control

A

Cephalic
Gastrin
Intestinal

41
Q

What is cephalic control

A

The feedforward mechanism which is stimulated by vagal sitmulation of acinar cells

42
Q

What is gastric control

A

Evokes a vagovagal reflex resulting in parasympathetic stimulation of acinar and duct cells

43
Q

What is intestinal control

A

Chyme enterinf the stomach is acidic which triggers the release of secretin

44
Q

What is secreten

A

It is carried in the blood and effects the pancreatic duct cels causing an increased in the secretion of aqueous NaHCO3 solution into duodenal lumen . This results in the neutralisation of acid in the duodenual lumen

45
Q

Name the different parts of the large intestine

A 
Appendix
Caecum 
Ascending Colon
Transverse Colon
Descending Colon
Sigmoid colon
Rectum
46
Q

How much does the large intestine receive of ileocaecal material

A

1L per day

47
Q

What are the four primary functions of the large intestine

A

Absorption of H20, Na and Cl with secretion of K, HCO3 and mucus - proximal colon
Absorption of short chain fatty acids
Reservoir - distal colon
Periodic elimination of faeces

48
Q

What is faeces composed of

A

H20, 50g solid, including cellulose, bacteria, bilirubin and a small amount of salt

49
Q

What is the only product which is truly excretory

A

Bilirubin

50
Q

What occurs in the first 2rds of the large intestine

A

Fluid reabsorption and bacterial fermentation

51
Q

What occurs in the last part of the large intestine

A

Final drying and storage

52
Q

What are the 3 patterns of motility in the large intestine

A

Haustration
Peristaltic propulsive movements
Defaecation

53
Q

How does haustration occur?

A

It is caused by contraction of the circular muscle - similar to segmentation in function, but much lower frequency
It occurs in the proximal colon
Generated by slow wave activity and mixes content allowing time for fluid and electrolyte reabsorption

54
Q

What is the outer longtitudinal muscle layer comprised of?

A

3 bands - the taenia coli

55
Q

What is mass movement

A

Simultaneous contraction of large section of the circular muscle of the ascending and transverse colon

56
Q

When is mass movement triggered?

A

triggered by a meal

It can also occur in the distal colon, propelling faeces in to the rectum

57
Q

Where else does mass momvemtn occur?

A

Int he distal colon, propelling faeces in to the rectum triggering the defaecation reflex

58
Q

What happens when it IS convenient to defaecate

A

The anal sphincter which turns to the rectum causing contraction assisted by abdominal muscles. These cause an increase in pressure in the abdomen so the diaphragm moves down

59
Q

What is Hirschsprung disease

A

A condition in which rectal filling does not cause internal anal sphincter to relax

60
Q

What happens if it is safe and convenient to defaecate?

A

Afferent signals are sent back tot he spinal cord and cause relaxation

61
Q

What happens if it is not safe and convenient to defaecate?

A

The skeletal muscle of the external anal sphincter contracts strongly until there is another mass movement

62
Q

What do the bacteria in the colon do?

A

increase intestinal immunity by competition with pathogenic microbes
promote motility and help maintain mucosal integrity
synthesise vitamin K and free fatty acids that are absorbed
activate some drugs (used in treatment of IBD)

63
Q

What does the anus permit

A

Expulsion of intestinal gas (flatus) as well as faeces

64
Q

Where do gasses arise from

A

swallowed air
bacteria in the colon which attack forms of carbs that are indigestible to humans
gas that is not absorbed in the large intestine

65
Q

What happens when we want to expel gas

A

The abdominal muscles contract to cause pressure but both the external and internal anal sphincters contract strongly to produce a slit like exit to prevent liquid material escaping and only gas is expelled

66
Q

Why is turbulence produced?

A

Gas escapes at a high pressure

Gastro (67 decks)

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