HUBS192 Lecture 7 - Cardiovascular System, Circulatory System Anatomy, Capillaries and Lymphatics

Question 1

what is the function of capillaries?

Answer 1

site of exchange between blood and tissues

Question 2

what 3 things does the function of capillaries demand?

Answer 2

1) very thin walls
2) large total CSA of capillary bed
3) slow & smooth blood flow

Question 3

what determines slower blood flow of capillaries?

Answer 3

large total CSA area of the capillary bed compared to arterioles means much slower blood flow

Question 4

what is a capillary composed of?

Answer 4

endothelial cells

Question 5

what are endothelial cells?

Answer 5

specialised cells that form the barrier between the blood and the tissues that wrap around to form junctions creating the thin cellular tube

Question 6

what is the lumen?

Answer 6

the inside space of a tubular structure (an opening)

Question 7

what is the size of a lumen of a capillary?

Answer 7

8-10μm

Question 8

how do you get from the lumen to the surrounding tissue?

Answer 8

by passing through the endothelial cell either by passive diffusion or active transport (continuous capillary because the cell forms a continuous interface barrier)

Question 9

what happens when pre-capillary sphincters constrict?

Answer 9

they stop blood going into the side branches forcing the blood to shot through the central channel and straight out the other side

Question 10

what is a vascular shunt?

Answer 10

a thoroughfare channel from an arteriole to a venule controlled by involuntary muscle

Question 11

how does the structure of capillaries vary according?

Answer 11

varies according to the rate of exchange needed and how controlled the exchange must be

Question 12

what are the 3 types of capillaries and how leaky are each of them?

Answer 12

1) continuous (tight=controlled)
2) fenestrated (leaky)
3) sinusoidal (very leaky)

Question 13

what is the diameter of a continuous capillary?

Answer 13

8-10μm (lumen is the the diameter of a red blood cell)

Question 14

what are endothelial cells?

Answer 14

specialised type of epithelial cell

Question 15

what is another name for the basement membrane?

Answer 15

basal laminar

Question 16

what is the basement membrane?

Answer 16

layer of connective tissue that is produced by the epithelial cells to help stick themselves down to the underlying connective tissue

Question 17

what are the 3 components of a continuous capillary?

Answer 17

1) basement membrane
2) endothelial layer (tunica intima)
3) intercellular cleft

Question 18

where are continuous capillaries found?

Answer 18

in skeletal muscle and cardiac muscle

Question 19

what is the diameter of fenestrated capillaries?

Answer 19

8-10μm

Question 20

what are fenestrations?

Answer 20

small openings/holes

Question 21

where are fenestrated capillaries found?

Answer 21

in the kidney and in the small intestine

Question 22

what is the diameter of a sinusoidal capillary

Answer 22

30-40μm

Question 23

what 2 components make up a sinusoidal capillary?

Answer 23

1) incomplete basement membrane

2) intercellular gap

Question 24

what is the function of an incomplete basement membrane?

Answer 24

to allow cells in the surrounding tissues can be wedged up in the sinusoidal openings

Question 25

what is different about sinusoidal capillaries compared to continuous and fenestrated capillaries?

Answer 25

sinusoidal capillaries is more about nutrient exchange of plasma and blood rather than gas exchange

Question 26

what are the 3 ways you can get out of the lumen of a continuous capillary?

Answer 26

1) diffusion through membrane (lipid-soluble)
2) movement through intercellular clefts (water-soluble)
3) transport via vesicles

Question 27

what are the 4 ways you can get out of the lumen of a fenestrated and a sinusoidal capillary?

Answer 27

1) diffusion through membrane (lipid-soluble)
2) movement through intercellular clefts (water-soluble)
3) movement through fenestrations (water-soluble)
4) transport via vesicles

Question 28

what are the 4 functions of the lymph vascular system?

Answer 28

1) drains excess tissue fluid & plasma proteins from tissues and returns them to the blood
2) filters foreign material from the lymph
3) ‘screens’ lymph for foreign antigens & responds by releasing antibodies & activated immune cells
4) absorbs fat from intestine and transports to blood