3.4.1.3: Blood vessels

Question 1

name the 3 types of blood vessels

Answer 1

arteries, capillaries, veins

Question 2

Describe and explain the difference between the wall thickness and lumen diameter between an artery and a vein

Answer 2

an artery has a smaller lumen diameter and a much thicker wall than a vein because the arteries are under much higher blood pressure than veins. In a vein, blood pressure is much lower and the blood moves more slowly, hence, it has a larger lumen diameter and a thinner wall

Question 3

How does the total cross sectional area change as blood vessels become smaller and increase in number

Answer 3

total cross sectional area increases as blood vessels become smaller and increase in number

Question 4

Describe the rate of flow in smaller and larger blood vessels

Answer 4

rate of flow is smaller in smaller blood vessels, higher in larger blood vessels

Question 5

describe the blood pressure starting from the aorta and as blood flows further away from the heart

Answer 5

highest in the aorta, and decreasing in fluctuation as blood flows further away from the heart

Question 6

describe the structure of arteries

Answer 6

collagen fibres, thick layer of smooth muscle and elastic tissue, endothelium, lumen

Question 7

describe the structure of capillaries

Answer 7

basement membrane (collagen), endothelium cell, lumen

Question 8

describe the structure of veins

Answer 8

collagen and connective tissue, thin layer of smooth muscle and elastic tissue, endothelium, semilunar valve, lumen

Question 9

do arteries have valves?

Answer 9

no

Question 10

do capillaries have valves?

Answer 10

no

Question 11

do veins have valves?

Answer 11

yes, semilunar valves to prevent backflow of blood caused by low blood pressure

Question 12

what is the importance of the thick elastic tissue layer in the walls of arteries

Answer 12

allows walls to expand with each pulse of blood and then return to original shape - elastic recoil, this evens out blood flow and maintains a high blood pressure

Question 13

what is the importance of the thick smooth muscle layer in the walls of arteries

Answer 13

can contract/relax under nervous stimulation, therefore altering blood pressure

Question 14

what is the importance of the lumen in arteries having a narrow diameter

Answer 14

high resistance to blood flow which maintains pressure

Question 15

describe the structure of the walls in capillaries

Answer 15

wall has fenestrations (small pores) making it permeable so small molecules can filter out, wall is made from single, squamous layer of endothelial cells which reduces the diffusion pathway

Question 16

what is the importance of the lumen in capillaries being narrow
and why is low blood pressure significant?

Answer 16

causes increase in total cross sectional area, so more surface is in contact with blood, causing greater friction between blood and capillary wall, resulting in loss of blood pressure
low blood pressure means a reduced flow allowing more time for diffusion of substances into/out of capillary

Question 17

describe the thin elastic tissue layer in the walls of veins

Answer 17

thin elastic tissue layer as there is no need to expand with each pulse of blood therefore no need for elastic recoil

Question 18

describe the thin smooth muscle layer in the walls of veins

Answer 18

less muscle to contract so will not narrow lumen to resist blood flow

Question 19

what is the importance of the lumen in veins being wide

Answer 19

less resistance to blood flow, which helps blood return to heart

Question 20

How is high blood pressure maintained in arteries

Answer 20

during systole, elastic fibres can expand to withstand high pressure and during diastole elastic fibres recoil to maintain the pressure

Question 21

What is venous return

Answer 21

blood being returned to the heart via Vena Cava

Question 22

describe the process of venous return

Answer 22

1. skeletal muscles contract, squeezing the vein, volume decreases, increases blood pressure, valve in front opens and valve behind closes and so blood is forced through the front valve
2. suction effect pulling blood back to heart due to atrial diastole, and so due to lower pressure in thoracic cavity during inhalation

Question 23

How are capillaries adapted to provide a large surface area for exchange

Answer 23

dense network of capillaries

Question 24

How are capillaries adapted to provide a short diffusion pathway

Answer 24

single squamous layer of endothelial cells, narrow lumen causes RBCs to pass in single file and RBCs are in contact with the capillary wall

Question 25

what feature of capillaries allow oxygen and carbon dioxide to easily diffuse

Answer 25

their walls are permeable to gas

Question 26

what feature of capillaries allow molecules and plasma to pass out of blood for tissue fluid formation

Answer 26

fenestrations between endothelial cells

Question 27

explain why there is a greater proportion of smooth muscle in an arteriole and how this helps to redistribute blood around the body

Answer 27

the muscle can contract and partially shut of blood flow to particular organs, e.g. during exercise, blood flow to the stomach and intestines is reduces, allowing greater blood flow to the muscles being exercised