Physiology and Pharmaxology of the small and large intestine Flashcards Preview

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Flashcards in Physiology and Pharmaxology of the small and large intestine Deck (66):
1

Describe the length of the different parts of the small intestine

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

2

What happens in the small intestine

Major site for digestion and absoprtion
Receives chyme from the stomach, pancreatic juice from pancreas and bile form the gall bladder

3

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

Through the ileocaecal valve

4

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

Duodenum

5

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

Through the sphincter of Oddi

6

What moves into the large intestine?

Unabsorbed electrolytes, water and indigestible residue (cellulose)

7

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

Ileocaecal valve

8

What controls the opening of the ileocaecal valve

The hormone Gastrin

9

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

Circular folds of Kerckring
Villi
Microvilli

10

What is the name of the absorptive cells?

Enterocytes

11

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

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

12

Where is gastrin secreted from

From G cells of gastric antrum and duodenum

13

Where is CCK secreted from?

From I cells of duodenum and jejunum

14

Where is secretin secreted from?

S cells of duodenum

15

WHere is motilin secreted?

From M cells of duodenum and jejunum
It has a special purpose in migrating the motor complex

16

Where is GIP secreted

an incretin from K cells of duodenum and jejunum
It causes an increase in gastric motility and serves as an incretin (feedforward signal)

17

Where is GLP-1 secreted

an incretin from L cells of the gut

18

Where is Ghrelin secreted

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

19

Where do all peptide hormones act on

G protein couple receptors

20

What is the role of Ghrelin

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

21

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

Succus entericus

22

What will cause the release off the intestinal juice

Any stimulatory act on the GI tract

23

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

Distension / irritation if acid is present
Parasympathetic activity - change in ACh

24

Secretions of the small intestine include:

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

25

What does excessive activity cause?

Secretory diarrhoea (cholera)

26

What is the function of the ATPase in the basolateral membrane

To maintain a low intracellular concentration of sodium

27

Cysitic fibrosis patients may suffer from what in GI

a decrease in secretion of succus entericus

28

Segmentation in the duodenum is primarily due to what?

distension due to Chyme entering

29

What is triggered by gastrin from the stomach
What is the alternative name for this?

Segmentation in the empty ileum
Gastroileal reflex

30

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

Duodenum: 12/min
Ileum: 9/min

31

What enhances the strength of segmentation

Parasympathetic nervous system

32

What decreases the strength of segmentation

Sympathetic system

33

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

A few localised contractions
The mirgrating motor complex (MMC)

34

What happens to the small intestine when chyme enters

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

35

What are the 2 main types of pancreatic secretions

Endocrine and Exocrine

36

Give two examples of endocrine hormones

Insulin and Glucagon

37

Give 2 examples of exocrine cells

acquous NaHCO3, dyct cells)

38

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

Pancreatic duct which joins the common bile duct.

39

What are the 3 main types of pancreatic enzyme

Proteases, amylases and lipases

40

Name the 3 phases of pancreatic secretion control

Cephalic
Gastrin
Intestinal

41

What is cephalic control

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

42

What is gastric control

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

43

What is intestinal control

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

44

What is secreten

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

Name the different parts of the large intestine

Appendix
Caecum
Ascending Colon
Transverse Colon
Descending Colon
Sigmoid colon
Rectum

46

How much does the large intestine receive of ileocaecal material

1L per day

47

What are the four primary functions of the large intestine

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

What is faeces composed of

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

49

What is the only product which is truly excretory

Bilirubin

50

What occurs in the first 2rds of the large intestine

Fluid reabsorption and bacterial fermentation

51

What occurs in the last part of the large intestine

Final drying and storage

52

What are the 3 patterns of motility in the large intestine

Haustration
Peristaltic propulsive movements
Defaecation

53

How does haustration occur?

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

What is the outer longtitudinal muscle layer comprised of?

3 bands - the taenia coli

55

What is mass movement

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

56

When is mass movement triggered?

triggered by a meal
It can also occur in the distal colon, propelling faeces in to the rectum

57

Where else does mass momvemtn occur?

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

58

What happens when it IS convenient to defaecate

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

What is Hirschsprung disease

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

60

What happens if it is safe and convenient to defaecate?

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

61

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

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

62

What do the bacteria in the colon do?

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

What does the anus permit

Expulsion of intestinal gas (flatus) as well as faeces

64

Where do gasses arise from

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

What happens when we want to expel gas

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

Why is turbulence produced?

Gas escapes at a high pressure

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