Exchange and the Lymphatic System

Question 1

How are capillaries suited to diffusion?

Answer 1

• Lots of them so a lot of exchange can go on

- Very small and a large surface area to volume ratio so diffusion increases

Question 2

What are the two bypass structures in a cap bed?

Answer 2

• Arteriovenous bypass

- Metarterioles

Question 3

What is the distance between two epithelial cells known as?

Answer 3

Cleft

Question 4

Which capillaries have large pores?

Answer 4

Fenestrated capillaries

Question 5

Describe continous capillaries

Answer 5

• Leaky celfts between cells

- No channels

Question 6

Where would you find specialised continuous capillaries that have no clefts of channels?

Answer 6

• Blood brain barrier

- Blood testes/ovary barrier

Question 7

Where would you find specialised continuous capillaries that have larger clefts?

Answer 7

Muscle

Question 8

Where would you find fenestrated capillaries?

Answer 8

Intestine

Question 9

What are discontinuous capillaries?

Answer 9

Have massive channels and clefts

Question 10

Where would you find discontinuous capillaries?

Answer 10

Liver

Question 11

Why are the capillaries in the liver discontinuous?

Answer 11

To allow lots of proteins to enter the bloodstream

Question 12

What two aspects does clotting involve?

Answer 12

• Formation of a platelet plug

- Formation of a fibrin clot

Question 13

What is the basement membrane that the capillary sits on made of?

Answer 13

• Collagen

Question 14

What happens for a clot to begin to form?

Answer 14

Endothelium ruptures

Question 15

What is the process of a blood clot forming after the endothelium ruptures?

Answer 15

• Collagen that is revealed attracts platelets
• This forms a platelet plug
• Fibrinogen floating in the blood is converted to fibrin by thrombin
• Fibrin plug created

Question 16

When is the clotting mechanism dangerous?

Answer 16

If it occurs in capillaries where the blood flow is slow and has a higher chance of clotting

Question 17

What 6 methods does the epithelium use to stop blood clotting from happening?

Answer 17

• Stops blood contacting collagen
• Produces prostacyclin and nitric oxide
• Produces tissue factor pathway inhibitor (TFPI)
• Expresses thrombomodulin
• Expresses heparin
• Secretes tissue plasminogen activator (t-PA)

Question 18

How does stopping the blood contacting the collagen stop clotting?

Answer 18

No platelet aggregation

Question 19

How does prostacyclin and NO stop clotting?

Answer 19

Both inhibit platelet aggregation

Question 20

What does tissue factor pathway inhibitor (TFPI) stop the production of?

Answer 20

Thrombin

Question 21

What does thrombomodulin do to stop clotting?

Answer 21

Binds to thrombin deactivating it

Question 22

What does heparin act on to stop clotting?

Answer 22

Also inactivates thrombin in the same way as thrombomodulin

Question 23

What does tissue plasminogen factor do?

Answer 23

• Converts plasminogen to plasmin

- Plasmin digests clot

Question 24

What is self regulation in reference to diffusion?

Answer 24

• If cells use more oxygen the conc. gradient increases so more of it diffuses into the cell

Question 25

What is non saturable in reference to diffusion?

Answer 25

- If oxygen required channel they'd have a maximum rate where they all become saturated - Diffusion stops this

Question 26

How do polar substances get through the capillary?

Answer 26

Through clefts/channels

Question 27

What channels exist in the brain capillaries to allow glucose to cross the blood-brain barrier?

Answer 27

Glucose transporters

Question 28

What is hydrostatic pressure?

Answer 28

- Think of a hose with holes in it - As water moves through it some of it moves out - The higher the pressure in the hose the more that will move out

Question 29

What is osmotic pressure?

Answer 29

- Created by plasma proteins unable to leave capillaries | - Osmotic pressure draws water into the capillary

Question 30

What is the osmotic pressure created by plasma proteins called?

Answer 30

Oncotic pressure

Question 31

On average how much water is lost through hydrostatic pressure each day?

Answer 31

20L

Question 32

On average how much water is regained through oncotic pressure each day?

Answer 32

17L

Question 33

What happens to the remaining 3L that is lost?

Answer 33

Taken up by the lymphatic system

Question 34

How does the fluid that enters the lymph vessels stay there?

Answer 34

Enters through 1 way valves

Question 35

How is lymph able to move through the system back to the blood?

Answer 35

- Squeezed by smooth muscles contracting - Eventually enters thoracic duct/right lymphatic duct - Passes through lymph nodes on the way

Question 36

In what ways can oedema come about?

Answer 36

- Lymph obstruction - Raised central venous pressure - Hypoproteinemia - Increased capillary permeability

Question 37

What can lymphatic obstruction be a result from?

Answer 37

- Filariasis (similar to elephantisis) - Surgery - Elephantisis (parasitic worms grow and multiply in lymph)

Question 38

What can result in a raised central venous pressure?

Answer 38

Ventricular failure

Question 39

How can a raised central venous pressure result in oedema?

Answer 39

Increases hydrostatic pressure

Question 40

What can hypoproteinamia be due to?

Answer 40

- Nephrosis - Liver failure - Nutrition

Question 41

Name a condition caused by hypoproteinemia

Answer 41

- Kwashiorkor | - Reduces oncotic gradient