1.7 circulation in blood vessels

Question 1

artery

Answer 1

vessels that carry blood away from the heart
almost all carry oxygenated blood except for:
1. pulmonary artery
2. umbilical artery

Question 2

pulmonary artery

Answer 2

carries deoxygenated blood from the heart to the lungs

Question 3

umbilical artery

Answer 3

during pregnancy, this carries deoxygenated blood from the fetus to the placenta

Question 4

arterial system

Answer 4

system of arteries in the body

Question 5

peripheral arteries

Answer 5

arteries that are further away from the heart

Question 6

arterioles

Answer 6

smallest branches of the arterial system

Question 7

what is the structure of an artery?

Answer 7

1. external layer of tough tissue
2. middles layers of artery may contain elastic fibres and smooth muscle
3. endothelium forms a smooth lining
4. lumen (gets smaller the further away it is from the heart)

Question 8

what are the functions of elastic fibres in the walls of the arteries?

Answer 8

1. allow arteries to withstand high blood pressure by stretching to accommodate a large volume of blood without being damaged, since heartbeat increases the pressure of blood flow into arteries
2. recoil to maintain blood pressure and squeeze the blood to move along the arteries in a continuous flow
3. highly abundant in walls of major arteries

Question 9

what are the functions of muscles in the wall of arterioles?

Answer 9

1. contacts to reduce the size of lumen to increase resistance and reduce blood flow to certain areas to regulate blood flow
2. relaxes to increase the size of the lumen

Question 10

capillaries

Answer 10

tiny vessels that spread throughout the tissues of the body
- forms network that links the arteries and he venules
- carries blood with nutrients and oxygen to body cells and takes away blood with waste materials from body cells
- every cell is near a capillary

Question 11

what are the structural adaptations of capillaries?

Answer 11

1. very thin with no elastic fibres, smooth muscles or collagen.
   - can fit between individual cells and shortens distance for diffusion (it is only one cell thick)
2. very small lumen, only wide enough for 1 red blood cell to pass through
   - blood travels relatively slowly so there is more opportunity for diffusion of materials
3. there are pores/ gaps between the cells of the capillaries
   - white blood cell can change shape and pass through the gaps
   - red blood cells stay in the capillaries because they have a fixed shape

Question 12

veins

Answer 12

vessels that carry blood towards the heart
most veins carry deoxygenated blood except for:
1. pulmonary vein
2. umbilical vein
blood is carried under low pressure

Question 13

pulmonary vein

Answer 13

carries oxygenated blood from the lungs to the heart

Question 14

umbilical vein

Answer 14

during pregnancy, it carries oxygenated blood from the placenta into the fetus

Question 15

what are the 2 great veins?

Answer 15

1. superior vena cava
2. inferior vena cava

Question 16

superior vena cava

Answer 16

carries blood from upper parts of the body

Question 17

inferior vena cava

Answer 17

carries blood from the lower parts of the body

Question 18

venous system

Answer 18

the system of veins in the body
- tiny venules lead from the capillary network, combining into larger and larger vessels going to the heart
- a large volume of blood is found in the veins, they act as a blood reservoir

Question 19

what makes blood flow back to the heart/ prevents back flow of blood?

Answer 19

1. semilunar valves: half moon shaped, one-way valves found at frequent intervals in veins to prevent backflow of blood
   - developed from infoldings from the inner wall of veins
   —> when blood starts to flow backwards, the valves close
2. skeletal muscles: contract & squeeze blood in veins to flow back to the heart
   - larger veins are situated between large skeletal muscles of the body, especially arms and legs
   - muscles squeeze veins during physical activity

when valves close and muscles squeezes, the blood flows back to the heart

Question 20

what is the structure of a vein?

Answer 20

1. relatively large lumen
2. smooth inner surface
3. relatively thin layer of smooth muscles and few elastic fibres
4. outer tough layer of mainly collagen fibres

Question 21

rank the blood pressure of the circulation system in descending order & explain why

Answer 21

artery > arterioles > capillaries > venules > vein
- arteries are closest to the heart (heartbeats increase pressure)
- peripheral arteries have lower blood pressure than arteries

Question 22

rank the surface area of the circulation system in descending order & explain why

Answer 22

capillaries > venules > arterioles > veins > arteries
- capillaries have the highest SA because they are branched, other are not

Question 23

rank the velocity of the circulation system in descending order & explain why

Answer 23

arteries > arterioles > veins > venules > capillaries
- arteries are near the heart
- capillary to veins increase because all the blood from the branched blood vessels all converge into the same vein so it is very rushed