Exchange and the lymphatic system

Question 1

What properties of the capillaries means they are efficient in exchange

Answer 1

Lots of them - short distance for exchange 
Small diameter therefore large surface area to volume ratio
Thin walled (one cell thick)

Question 2

What are the endothelia cell junctions called in the capillaries

Answer 2

clefts

Question 3

What can be present within the walls of the endothelia

Answer 3

fenestrations - produce channel

Question 4

What is the structure of continuous capillaries in the brain

Answer 4

No clefts or channels

Question 5

What is the structure of fenestrated capillaries

Answer 5

Clefts and channels present

Question 6

What is the structure of discontinuous capillaries

Answer 6

Clefts and massive channels present

Called - sinusoids

Question 7

Where would continuous/fenestrated/discontinuous capillaries be found

Answer 7

Continous = muscle
Fenestrated = Intestine
Discontinuous = Liver

Question 8

Why is sinusoids present in the liver

Answer 8

to allow the passage of big molecule e.g. protein

Question 9

What is the structure of the continuous capillaries in muscle

Answer 9

Clefts only

Question 10

Why is there no clefts and channels present in the brain

Answer 10

To maintain an tight blood brain barrier

Question 11

What is the two processes occurring in clotting

Answer 11

formation of a platelet plug

formation of a fibrin clot

Question 12

How is the platelet plug formed

Answer 12

Platelets recognise collagen

Therefore signal and attract more platelets

Question 13

What enzyme is responsible for activating precursor fibrinogen

Answer 13

Thrombin converts to fibrin

Question 14

What is the 6 mechanism of the epithelium to prevent clotting

Answer 14

Stops blood contacting collagen
Produces prostacyclin and NO
Produces tissue factor pathway inhibitor (TFPI)
Expresses thrombomodulin
Expresses heparin
Secretes tissue plasminogen activator (t-PA)

Question 15

What two mechanisms of the epithelium prevent platelet aggregation

Answer 15

The Stoping of blood contacting collagen

The Production of prostacyclin and NO

Question 16

What two mechanisms of the epithelium inactivate thrombin

Answer 16

Expresses thrombomodulin

Expresses heparin

Question 17

How does thrombodulin inactivate thrombin

Answer 17

Bind to it

Question 18

The epitheliums production of tissue factor pathway inhibitor (TFPI) prevents clotting by

Answer 18

Stoping thrombin production

Question 19

What is the purpose of the tissue plasminogen activator secreted by the epithelium

Answer 19

Breaks the clot down

Question 20

What is the main mechanism of exchange in the capillaries

Answer 20

Diffusion

Question 21

What is the exception of another exchange present in the capillaries and why it this important

Answer 21

The carrier mediated transport of glucose needed by the brain, as the tight blood brain barriers prevents diffusion

Question 22

Why is the diffusion in the capillaries a self regulating process

Answer 22

Increasing the oxygen levels, increases the diffusion rate of oxygen

Question 23

Why is the diffusion in the capillaries a non saturable process

Answer 23

Increasing the concentration Oxygen, increases conentration gradient, and allows continually movement of oxygen across the capillaries as nothing can prevent the movement so cant be saturated

Question 24

How do non polar substances cross the capillaries

Answer 24

across the membrane

Question 25

How do polar substances cross the capillaries

Answer 25

Through the cleft/channels of capillary membrane

Question 26

What causes the bulk flow movement on the capillaries

Answer 26

The hydrostatic pressure pulling fluid out of the capillaries opposed by the osmotic pressure pulling fluid into the capillaries

Question 27

Where does the hydrostatic pressure decrease

Answer 27

from the arterioles to the venules

Question 28

Where does the osmotic pressure increase

Answer 28

from the arterioles to the venules

Question 29

How much fluid is lost due to bulk flow due to how much is gained

Answer 29

20L is lost in the capillaries due to hydrostatic pressure

17L is retained in the capillaries due to osmotic pressure

Question 30

Where does the remaining 3L, due to bulk flow end up

Answer 30

In the lymphatic system

Question 31

What two factors ensure lymph is pumped upwards towards the heart

Answer 31

Smooth muscle in the lymph periodically contracts pushing the fluid
and valves ensure the fluid is pushed up the way towards the heart

Question 32

What pushes the fluid forward in the capillary system

Answer 32

valves

Question 33

Define oedema

Answer 33

accumulation of excess fluid

Question 34

What is four reasons that cause oedema

Answer 34

Lymphatic obstruction
Raised CVP
Hypoproteinemia

Increased capillary permeability

Question 35

What are two factors that causes lympathic obstruction

Answer 35

filariasis - tropical disease caused by worms

surgery

Question 36

What can cause an increase in central venous pressure

Answer 36

ventricular failure

Question 37

What are the various factors that cause hypoproteinemia - low protein levels in the blood

Answer 37

nephrosis - kidney disease
liver failure,
nutrition

Question 38

What is an example of an autoimmune disease causing increased capillary permeability due to inflammation

Answer 38

rheumatism - inflammation and pain in the joints

Question 39

How does low protein levels result in oedema

Answer 39

Low protein levels reduces osmotic concentration therefore reducing reabsorption causing this accumulation of fluid

Question 40

What is the differing structure of capillaries and lymph vessels

Answer 40

Lymph vessles have blind ends

Question 41

Where does lymph return to in the heart

Answer 41

The low presure part of systemic circulation