205 L3

Question 1

What increases the surface area of the small intestine and therefore absorption?

Answer 1

Folds of kerching
Microvilli
crypts of lieberkuhn
submicroscopic microvili

Question 2

The absorption of non-electrolyte nutrients (such as proteins, fats and carbohydrate, micronutrients and vitamins) occurs almost exclusively in the —– intestine

Answer 2

small intestine

Question 3

small and large intestine (colon) absorb —– and ——

Answer 3

small and large intestine (colon) absorb water and electrolytes

Question 4

what is the key function of the large intestine?

Answer 4

Absorption through micro villi and crypts

Question 5

The large intestine doesn’t have —–

Answer 5

villi

Question 6

How many litres of fluid is presented to the large intestine and how much is reabsorbed per day?

Answer 6

2L/day is presented to the large intestine and 1.9L/day is reabsorbed

Question 7

How much fluid is presented and reabosrbed by the small intestine per day?

Answer 7

8.5L/day is presented to the small intestine and 6.5L/day is reabsorbed

Question 8

how much fluid is lost as fecal fluid per day?

Answer 8

100mL

Question 9

How much fluid is secreted by the small intestine?

Answer 9

1L/day

Question 10

Does the small intestine actively absorb sodium?

Answer 10

yes

Question 11

Does the large intestine actively absorb sodium?

Answer 11

yes

Question 12

Does the small intestine actively secrete potassium?

Answer 12

No

Question 13

Does the large intestine actively secrete potassium?

Answer 13

yes

Question 14

Does the large intestine absorb nutrients?

Answer 14

No

Question 15

Absorption of non-electrolyte nutrients occurs mainly in the —– intestine

Answer 15

Small intestine

Question 16

The —– intestine absorbs water, sodium, chloride and potassium and secretes bicarbonate.

Answer 16

Small intestine

Question 17

The —– intestine absorbs water, sodium and chloride and secretes bicarbonate and potassium.

Answer 17

Large intestine

Question 18

How is water absorbed?

Answer 18

Osmosis

Coupled to solute movement (glucose)

Transcellular or paracellular

Question 19

where does sodium absorption occur?

Answer 19

In villus epithelial cells of the small intestine and the surface epithelial cells of the large intestine

Question 20

Sodium potassium ATPases

There are Na+/K+ atpases in the ———– membrane pushing – sodium — of the cell and into the —– and bringing – potassium – the cell.

This maintains a high ——– sodium concentration and low —— sodium concentration.

There is always less Na in the —, so there is always a drive for Na —- the cell.

This provides a force for sodium diffusion from the ——- across the —– membrane.

The transport is mediated by sodium ——– transporters.

Answer 20

There are Na+/K+ atpases in the apical membrane pushing 3 sodium out of the cell and into the ECF and bringing 2 potassium into the cell.

This maintains a high extracellular sodium concentration and low intracellular sodium concentration.

There is always less Na in the cell, so there is always a drive for Na into the cell.

This provides a force for sodium diffusion from the lumen across the apical membrane.

The transport is mediated by sodium coupled transporters.

Question 21

Na/glucose or Na/amino acid co transporters

The ———- ——– makes sure there is —— sodium within the cell.

There is a —- for sodium to move — the cell.

When sodium moves —- it co transports glucose via ——-.

The glucose moves out of the cell and into the blood via —–.

Answer 21

The Na/K ATPase makes sure there is low sodium within the cell.

There is a gradient for sodium to move into the cell.

When sodium moves in it co transports glucose via SGLT.

The glucose moves out of the cell and into the blood via GLUT2.

Question 22

Na-H exchanger

The ———- ——– makes sure there is —— sodium within the cell.

There is a —- for sodium to move — the cell.

When sodium moves —- there is an exchange of hydrogen —— of the cell.

Theses exchangers are found on both the apical and basolateral membrane

Answer 22

The Na/K ATPase makes sure there is low sodium within the cell.

There is a gradient for sodium to move into the cell.

When sodium moves in there is an exchange of hydrogen out of the cell.

Theses exchangers are found on both the apical and basolateral membrane

Question 23

Parallel Na-H and Cl-HCO3 exchangers

The ———- ——– makes sure there is —— sodium within the cell.

There is a —- for sodium to move — the cell.

When sodium moves —- there is an exchange of hydrogen —— of the cell.

Sodium is positively charged and chloride is negatively charged so when sodium moves — the cell via Na-H exchangers chloride also moves —- the cell via Cl - HCO3 exchangers.

When hydrogen and bicarbonate move into the —- they form ——– which is unstable and breaks into — and —-.

Answer 23

Parallel Na-H and Cl-HCO3 exchangers

The Na/P ATPase makes sure there is low sodium within the cell.

There is a gradient for sodium to move into the cell.

When sodium moves in there is an exchange of hydrogen out of the cell.

Sodium is positively charged and chloride is negatively charged so when sodium moves into the cell via Na-H exchangers chloride also moves into the cell via Cl - HCO3 exchangers.

When hydrogen and bicarbonate move into the lumen they form H2CO3 which is unstable and breaks into H2O and CO2.

Question 24

Epithelial sodium channels

The ———- ——– makes sure there is —— sodium within the cell.

There is a —- for sodium to move — the cell.

Sodium moves —- the cell via specific sodium channels.

Answer 24

The Na/K ATPase makes sure there is low sodium within the cell.

There is a gradient for sodium to move into the cell.

Sodium moves into the cell via specific sodium channels.

Question 25

How is chloride absorbed?

Answer 25

Linked to Na absorption (Na-H and Cl-HCO3 exchangers) Paracellular across tight junctions- passive absorption Cl-HCO3 transporter - active

Question 26

How is potassium absorbed?

Answer 26

Passive paracellular Active - hydrogen potassium exchangers

Question 27

How is potassium secreted?

Answer 27

Passive - paracellular Active (large intestine) - Via BK channels

Question 28

What will happen if you have some disease in your large intestine causing active fluid loss?

Answer 28

BK channels will actively secrete potassium. There is loss of water and potassium ions leading to hypokalemia

Question 29

Chloride secretion In the -------- membrane ------ ------ push -- sodium ---- of the cell and --- potassium ---- the cell. Epthelial channels in the ----- membrane move the ---- ------ ions back --- of the cell. The ------- channel in the -------- membrane brings ---, --- and ---- into the cell. In the ----- membrane the ----- secretes -------- into the lumen. Sodium and water enters the lumen via -------- transport. It is driven by ---- ions and ------ (second messenger) Results in fluid and ion loss from the ----- due to increased activation of ----.

Answer 29

In the basolateral membrane Na/K ATPases push 3 sodium out of the cell and 2 potassium into the cell. Epthelial channels in the basolateral membrane move the 2 potassium ions back out of the cell. The NKCC1 channel in the basolateral membrane brings Na, 2Cl and K into the cell. In the apical membrane the CFTR secretes chloride into the lumen. Sodium and water enters the lumen via paracellular transport. It is driven by calcium ions and cAMP (second messenger - signals CFTR to be placed into the membrane) Results in fluid and ion loss from the ECM due to increased activation of CFTR.

Question 30

What happens during cystic fibrosis?

Answer 30

Lack of CFTR = no secretion of chloride and therefore no secretion of sodium Results in dense secretion and respiratory problems

Question 31

The ----- intestine is a net absorber of water, sodium, chloride and potassium but it is a net secretor of bicarbonates

Answer 31

Small intestine

Question 32

The ------ intestine carries out net absorption of water, sodium and chloride with few exceptions, but it carries out net secretion of potassium and bicarbonate

Answer 32

Large intestine

Question 33

The dysfunction of fluid absorption in the GI tract leads to ----------

Answer 33

Diarrhoea

Question 34

Would the volume of diarrhoea be larger if a dysfunction in the GI tract occurred in the small or large intestine?

Answer 34

Small intestine

Question 35

------ diarrhoea results from disturbances of absorption. The amount of ----- consumed is not able to be processed by the body. ------ is retained in the ----- of the intestine causing an increase in ------- ------ so ----- is retained in the ---------. This is due to ------- intolerance (lack of the enzyme -----). Increased volume of -------- enters the colon and may overwhelm the ability of the colon to absorb ------- from it. Leads to pronounced diarrhoea. An -------- reaction to gluten results in the destruction of the ------ cells and if severe the ----. This causes nutrient malabsorption. There is an ------- in osmotic pressure in the -------- and water is ------ in the lumen. This is due to coeliac disease.

Answer 35

Osmotic diarrhoea results from disturbances of absorption. The amount of sugar consumed is not able to be processed by the body. Sugar is retained in the lumen of the intestine causing an increase in osmotic pressure so water is retained in the lumen. This is due to lactose intolerance (lack of the enzyme lactase). Increased volume of chyme enters the colon and may overwhelm the ability of the colon to absorb water from it. Leads to pronounced diarrhoea. An autoimmune reaction to gluten results in the destruction of the epithelial cells and if severe the villi. This causes nutrient malabsorption. There is an increase in osmotic pressure in the lumen and water is retained in the lumen. This is due to Coeliac disease.

Question 36

-------- diarrhoea results from disturbances in secretion. Elevation of ---------- activity of cells in unidirectional secretory flux may exceed unidirectional --------- flux and net secretion prevails. Cholera toxin permanently activates ------ --------- thereby causing an elevation of -------- which in turn opens the ---- channel in the apical membrane of the crypt epithelial cells. This causes a prolonged secretion of -----, ---- and ----- which can be fatal. Enterotoxins produced by the bacterial microorganism raise intracellular -----, ----- or ----- leading to the stimulation of --- secretion.

Answer 36

Secretory diarrhoea results from disturbances in secretion. Elevation of secretory activity of cells in unidirectional secretory flux may exceed unidirectional absorptive flux and net secretion prevails. Cholera toxin permanently activates adenylate cyclase thereby causing an elevation of cAMP which in turn opens the Cl channel in the apical membrane of the crypt epithelial cells. This causes a prolonged secretion of Cl, Na and water which can be fatal. Enterotoxins produced by the bacterial microorganism raise intracellular cAMP, cGMP or calcium ions, leading to the stimulation of Cl secretion

Question 37

How can we treat diarrhoea?

Answer 37

Oral rehydration solution When you have diarrhoea the glucose transporters are not affected so if a solution with sodium and glucose is given, when sodium moves into the cell it takes glucose with it. Chloride follows and bicarbonate (to combat acidosis)