Vascular System

Question 1

what is blood composed of?

Answer 1

45% cells - RBC, WBC, P
55% plasma

Question 2

what are the characteristics of the arteries (3)

Answer 2

• thick, muscular wall because the blood is at such high pressure
• small lumen (4mm)
• blood is oxygenated, coming away from the heart to the body

Question 3

what is the function of the arteries?

Answer 3

to distribute oxygen-rich blood to the body cells/organs

Question 4

at any given time, only around ___ to ___% of the body’s blood is in the arteries

Answer 4

at any given time, only around 10 to 15% of the body’s blood is in the arteries

Question 5

what are the characteristics of the arterioles (4)

Answer 5

• vessel wall is thicker than veins but thinner than arteries
• small lumen, size averaging at around 30 micrometres
• blood pressure is slightly decreased from the arteries, but still high
• blood is oxygenated

Question 6

what is the function of the arterioles?

Answer 6

to maintain mean arterial pressure, regulating blood flow

Question 7

what are the characteristics of capillaries? (4)

Answer 7

• vessel wall is one-cell thick
• lumen is narrow (5-10 micrometres)
• blood pressure is low
• blood is oxygenated and deoxygenated

Question 8

what is the function of the capillaries?

Answer 8

gaseous exchange

Question 9

what are the characteristics of the venules? (5)

Answer 9

• vessel wall is thin, thinner than arterioles
• lumen is larger than that of capillaries but smaller than that of veins
• blood pressure is relatively low (very little pressure remains by the time the blood leaves the capillaries)
• blood is deoxygenated
• have valves in the lower extremities

Question 10

what is the function of the venules? (2)

Answer 10

• receive blood from the capillaries
• play a role in the exchange of oxygen and nutrients for water products

Question 11

what are the characteristics of the veins? (5)

Answer 11

• vessel wall is relatively thin
• large lumen
• low blood pressure
• blood is deoxygenated, travelling from the body cells to the heart
• have valves

Question 12

what is the function of veins?

Answer 12

receive oxygen-poor blood and return it to the heart

Question 13

define vascular shunting

Answer 13

the process of redistributing blood to the areas that need it most via vasodilation and vasoconstriction

Question 14

what is the percentage of blood flow, towards the organs and muscles alike, during rest?

Answer 14

to the organs, 80% of blood flow is directed there (the brain, kidneys, liver, skin etc) to carry out normal body functions such as digestion

to the muscles, around 20% of blood flow is directed there

Question 15

what is the percentage of blood flow, towards the organs and muscles alike, during exercise?

Answer 15

to the organs, around 20% of blood flow is directed there, and they are now classes as non-essential organs

to the working muscles, around 80% of blood flow is directed there

Question 16

define pre-capillary sphincters

Answer 16

rings of muscle at the junction between the arterioles and capillaries

Question 17

what is the role of pre-capillary sphincters

Answer 17

they can effectively “open” or “close” the capillaries leading to the muscles or the organs

Question 18

vasomotor control centre

Answer 18

controls mechanisms, allowing for the redistribution of blood

Question 19

explain the vascular shunt mechanism (5)

Answer 19

• chemoreceptors detect chemical changes in the blood, such as an increase in carbonic acid and lactic acid
• baroreceptors detect changes in systolic blood pressure
• these receptors then send this information to the vasomotor control centre (VCC) in the medulla oblongata
• this in turn acts on the SNS, using the sympathetic nervous system to speed up vasodilation and cause vasoconstriction to occur towards the NEO
• this can only happen because the arterioles have a middle layer of muscle which is connected to the VCC and becomes stimulated via the accelerator nerve