Physiology and Pharmaxology of the small and large intestine

Question 1

Describe the length of the different parts of the small intestine

Answer 1

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

Question 2

What happens in the small intestine

Answer 2

Major site for digestion and absoprtion

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

Question 3

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

Answer 3

Through the ileocaecal valve

Question 4

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

Answer 4

Duodenum

Question 5

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

Answer 5

Through the sphincter of Oddi

Question 6

What moves into the large intestine?

Answer 6

Unabsorbed electrolytes, water and indigestible residue (cellulose)

Question 7

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

Answer 7

Ileocaecal valve

Question 8

What controls the opening of the ileocaecal valve

Answer 8

The hormone Gastrin

Question 9

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

Answer 9

Circular folds of Kerckring
Villi
Microvilli

Question 10

What is the name of the absorptive cells?

Answer 10

Enterocytes

Question 11

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

Answer 11

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

Question 12

Where is gastrin secreted from

Answer 12

From G cells of gastric antrum and duodenum

Question 13

Where is CCK secreted from?

Answer 13

From I cells of duodenum and jejunum

Question 14

Where is secretin secreted from?

Answer 14

S cells of duodenum

Question 15

WHere is motilin secreted?

Answer 15

From M cells of duodenum and jejunum

It has a special purpose in migrating the motor complex

Question 16

Where is GIP secreted

Answer 16

an incretin from K cells of duodenum and jejunum

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

Question 17

Where is GLP-1 secreted

Answer 17

an incretin from L cells of the gut

Question 18

Where is Ghrelin secreted

Answer 18

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

Question 19

Where do all peptide hormones act on

Answer 19

G protein couple receptors

Question 20

What is the role of Ghrelin

Answer 20

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

Question 21

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

Answer 21

Succus entericus

Question 22

What will cause the release off the intestinal juice

Answer 22

Any stimulatory act on the GI tract

Question 23

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

Answer 23

Distension / irritation if acid is present

Parasympathetic activity - change in ACh

Question 24

Secretions of the small intestine include:

Answer 24

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

Question 25

What does excessive activity cause?

Answer 25

Secretory diarrhoea (cholera)

Question 26

What is the function of the ATPase in the basolateral membrane

Answer 26

To maintain a low intracellular concentration of sodium

Question 27

Cysitic fibrosis patients may suffer from what in GI

Answer 27

a decrease in secretion of succus entericus

Question 28

Segmentation in the duodenum is primarily due to what?

Answer 28

distension due to Chyme entering

Question 29

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

Answer 29

Segmentation in the empty ileum | Gastroileal reflex

Question 30

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

Answer 30

Duodenum: 12/min Ileum: 9/min

Question 31

What enhances the strength of segmentation

Answer 31

Parasympathetic nervous system

Question 32

What decreases the strength of segmentation

Answer 32

Sympathetic system

Question 33

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

Answer 33

A few localised contractions | The mirgrating motor complex (MMC)

Question 34

What happens to the small intestine when chyme enters

Answer 34

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

Question 35

What are the 2 main types of pancreatic secretions

Answer 35

Endocrine and Exocrine

Question 36

Give two examples of endocrine hormones

Answer 36

Insulin and Glucagon

Question 37

Give 2 examples of exocrine cells

Answer 37

acquous NaHCO3, dyct cells)

Question 38

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

Answer 38

Pancreatic duct which joins the common bile duct.

Question 39

What are the 3 main types of pancreatic enzyme

Answer 39

Proteases, amylases and lipases

Question 40

Name the 3 phases of pancreatic secretion control

Answer 40

Cephalic Gastrin Intestinal

Question 41

What is cephalic control

Answer 41

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

Question 42

What is gastric control

Answer 42

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

Question 43

What is intestinal control

Answer 43

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

Question 44

What is secreten

Answer 44

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

Question 45

Name the different parts of the large intestine

Answer 45

``` Appendix Caecum Ascending Colon Transverse Colon Descending Colon Sigmoid colon Rectum ```

Question 46

How much does the large intestine receive of ileocaecal material

Answer 46

1L per day

Question 47

What are the four primary functions of the large intestine

Answer 47

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

Question 48

What is faeces composed of

Answer 48

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

Question 49

What is the only product which is truly excretory

Answer 49

Bilirubin

Question 50

What occurs in the first 2rds of the large intestine

Answer 50

Fluid reabsorption and bacterial fermentation

Question 51

What occurs in the last part of the large intestine

Answer 51

Final drying and storage

Question 52

What are the 3 patterns of motility in the large intestine

Answer 52

Haustration Peristaltic propulsive movements Defaecation

Question 53

How does haustration occur?

Answer 53

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

Question 54

What is the outer longtitudinal muscle layer comprised of?

Answer 54

3 bands - the taenia coli

Question 55

What is mass movement

Answer 55

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

Question 56

When is mass movement triggered?

Answer 56

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

Question 57

Where else does mass momvemtn occur?

Answer 57

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

Question 58

What happens when it IS convenient to defaecate

Answer 58

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

Question 59

What is Hirschsprung disease

Answer 59

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

Question 60

What happens if it is safe and convenient to defaecate?

Answer 60

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

Question 61

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

Answer 61

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

Question 62

What do the bacteria in the colon do?

Answer 62

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)

Question 63

What does the anus permit

Answer 63

Expulsion of intestinal gas (flatus) as well as faeces

Question 64

Where do gasses arise from

Answer 64

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

Question 65

What happens when we want to expel gas

Answer 65

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

Question 66

Why is turbulence produced?

Answer 66

Gas escapes at a high pressure