Circulatory system

Question 1

how are molecules transported in single-celled organisms

Answer 1

through diffusion

Question 2

why cant diffusion work for large organisms

Answer 2

• too great of distance
• high energy requirements so the delivery of reactents must be quick

Question 3

mass transport

Answer 3

bulk movement of gases or liquids in one direction via vessels and tubes

Question 4

advantages of mass transport

Answer 4

• bring substances quickly
• maintains diffusion gradients between sites
• ensures effective cell activity

Question 5

Ateries

Answer 5

• carries blood away from heart
• high pressure to tissues

Question 6

arterioles

Answer 6

• transports blood into capillaries

Question 7

veins

Answer 7

• transports blood to the heart
• low pressure

Question 8

venules

Answer 8

• narrow blood vessels which transports blood from the capillaries to the veins

Question 9

what are the three layers of the arteries

Answer 9

tunica intima
tunica media
tunica externa

Question 10

tunica intinma

Answer 10

• endothelium is one cell thick and lines the lumen of blood vessels
• smooth-> reduce friction
• highly folded, so it can expand under high pressure

Question 11

tunica media

Answer 11

• contains smooth muscle and elastic tissue
• thick in arteries
• layer of muscle to withstand high pressure and so it can constrict and narrow the lumen for reduced blood flow
• elastic tissue to help maintin b.p which streches and recoils to even out any fluctuations in presure

Question 12

what does contraction of muscle in tunica media cause

Answer 12

constriction of the lumen which is useful to divert blood away from certain locations

Question 13

tunica externa

Answer 13

• contains collagen to help protect the blood vessel to prevent over stretching

Question 14

lumen of artery

Answer 14

narrow to help maintain blood pressure

Question 15

what helps arteries accomodate increased volume of blood

Answer 15

a pulse

Question 16

smooth muscle and elastic layer in veins

Answer 16

• much thinner as it doesnt need to withstand high pressure

Question 17

lumen in vein

Answer 17

wider, to help ensure blood returns to heart at the right speed
- reduces friction between blood and the endothelium of the vein

Question 18

rate of blood flow in veins

Answer 18

slower but the volume of blood per unit is equal to arteries

Question 19

why do veins have valves

Answer 19

to prevent backflow of blood

Question 20

why dont veins have a pulse

Answer 20

due to increased distance from the heart

Question 21

what do capillaries from

Answer 21

capillary beds which are important exchange surfaces

Question 22

why do a large numbers of capillaries branch between cells

Answer 22

so substances can diffuse between the blood and calls quickly as there is a short distance

Question 23

lumen in capillaries

Answer 23

narrow as red blood cells need to pass through in single file, so blood travels slowly and provides time for diffusion to occur

Question 24

what is the wall of the capillary made of

Answer 24

endothelial cells

Question 25

capillary wall

Answer 25

one cell thick to reduce the diffusion distance
- contains pores so blood plasma can leak out as tissue fluid