Lecture 29: Capillaries and Veins

Question 1

What are Capillaries ?

Answer 1

Tubes of endothelial cells that branch from the arterioles-sites of O2,CO2 and nutrient exchange between the blood and cells.

Question 2

How much volume of blood is found in the capillary beds?

Answer 2

Only 250ml of 5000ml total blood volume is found in the capillary beds

Question 3

What does the decrease in velocity help with once blood reaches the capillaries?

Answer 3

the velocity slowing down allows for nutrient exchange or dropping O2 and picking CO2. flow remains the same but the velocity slows down

Question 4

what are capillary pores and what do they do?

Answer 4

-Water filled cleft
-enable passage of K,Na,and amino acids
-pores are present at cellular junctions between endothelial cells
-pore size differs with tissue type: liver capillary pores are large and brain capillary pores are non-existent .

Question 5

What is a precapillary sphincter and a metarteriole?

Answer 5

Precapillary sphincters surround capillaries.
Metarterioles is a thoroughfare channel from an arteriole to a venule

Question 6

What happens during passive exchange?

Answer 6

Passive exchange of glucose,CO2 and O2 between IF and plasma membranes of cells

Question 7

What happens during bulk flow?

Answer 7

Movement of water and solutes across the capillary wall via pores of things like Na, K, glucose and amino acids .

Question 8

What is Ultrafiltration?

Answer 8

Fluid moves from the capillary lumen to the low pressure IF outside the capillary

Question 9

How does the hydrostatic pressure change across the capillary ?

Answer 9

It starts at arteriole side Pc(37) and when it goes to the venue side the pressure drops to Pc(17)

Question 10

What is reabsorption?

Answer 10

Reverse bulk flow: inward driving pressure exceeds an outward opposing pressure across the capillary wall.and this happens at the venule side

Question 11

What forces drive bulk flow?

Answer 11

Capillary blood(hydrostatic fluid) pressure
Colloid osmotic pressure (oncotic pressure): product of the dissolved proteins within the plasma blood

Question 12

What does the term Pc mean?

Answer 12

Capillary blood pressure is the hydrostatic pressure exerted on the inside of capillary walls by the blood

Question 13

What does the term PI.p mean?

Answer 13

Plasma colloid osmotic pressure(oncotic pressure) exerted by dispersed plasma proteins .Encourages fluid movement into the capillary lumen (inward pressure ). More protein in plasma compared to IF. Plasma proteins attract water

Question 14

What does the term P.IF mean?

Answer 14

Interstital fluid hydrostatic pressure=1 mmHg

Question 15

What does the term Pi.IF mean?

Answer 15

Interstitial oncotic pressure =due to proteins in the IF-this is usually negligible. This is usually 0 but if unhealthy it could change

Question 16

What is the significance of bulk flow?

Answer 16

It regulates the distribution of ECF between plasma and IF.
It can also help maintain BP

Question 17

At the arteriolar end of the capillary what is the outward pressure?

Answer 17

The outward pressure is high

Question 18

At the venular end of the capillary, what is the inward and outward pressure comparison?

Answer 18

The inward pressure is greater than the outward pressure

Question 19

what is lymph?

Answer 19

It is a IF that enters a lymphatic vessel and contains plasma proteins that are not reclaimed by the blood plasma and fats. Wherever you have regular capillaries you will have lymph capillaries as well

Question 20

What are the functions of the lymphatic system?

Answer 20

-Defense against disease by the lymph nodes
-Transport of absorbed fat from thew digestive tract

Question 21

When does edema occur?

Answer 21

Occurs when there is excessive interstitial fluid in tissues

Question 22

What causes Edmea?

Answer 22

Reduced concentration of plasma proteins(starvation)

Increased permeability of the capillary walls

Increased venous pressure

Blockage of lymph vessels

Question 23

What is the velocity in veins compared to capillaries ?

Answer 23

Blood velocity is higher than the capillaries and veins have very thin walls unlike arteries that have very thick walls.

Question 24

Veins have ______ radii and offer _____ resistance to flow

Answer 24

Large,Low

Question 25

How much of the blood do the veins hold?

Answer 25

60% of the blood is stored in veins

Question 26

What is venous return ?

Answer 26

It is the volume of blood entering each atrium per minute

Question 27

What is another name for veins?

Answer 27

Capciatan vessels

Question 28

review the five factors for enhanced venous return