7.5 + 7.6

Question 1

1. Diastole(relaxation of heart)

Answer 1

• blood enters atria from pulmonary vein (from lungs) and vena cava (from body)
• as atria fills, pressure rises
• when pressure exceeds that in ventricles, the atrioventricular valves open allowing blood to pass into the ventricles
• the passage of blood is aided by gravity
• muscular walls of atria and ventricles are relaxed
• relaxation of ventricles walls causes them to recoil and reduces pressure within ventricle so pressure is lower than in aorta and pulmonary artery
• semi-lunar valves in aorta and pulmonary artery close

Question 2

2. Contraction of atria(atrial systole)

Answer 2

• contraction of atrial walls, along with recoil of ventricle walls forces the remaining blood into ventricles from atria
• muscle of ventricle walls remain relaxed

Question 3

3. Contraction of ventricles(ventricular systole)

Answer 3

• walls contract simultaneously after ventricles fill with blood
• ventricles increase blood pressure, forcing shut the atrioventricular valves and preventing backflow of blood into atria
• the shut valves increase ventricle pressure
• once pressure exceeds aorta and pulmonary artery, blood is forced from ventricles into them(creates high pressure to pump blood round body)

Question 4

control of blood flow

Answer 4

when pressure difference favours the backflow of blood (wrong direction), valves are designed to shut

Question 5

atrioventricular valve

Answer 5

between left atrium and ventricle(bicuspid valve)
between right atrium and ventricle(tricuspid valve)

Question 6

semi-lunar valves

Answer 6

in aorta and pulmonary artery
close when elastic walls of vessels recoil, increasing pressure within them and ventricle walls relax reducing pressure within ventricles

Question 7

pocket valves

Answer 7

when veins are squeezed, blood flows towards heart rather than away

Question 8

design of valves

Answer 8

made up of flaps of tough, but flexible, fibrous tissue which are cusp shaped

when pressure is greater on convex side of cusps, they move apart to let blood pass between cusps

when pressure is greater on concave side, blood collects within the cusps, this pushes them together to form a tight fit to prevent passage of blood

Question 9

cardiac output

Answer 9

volume of blood pumped by one ventricle of the heart in one minute

heart rate x stroke volume

Question 10

arteries

Answer 10

carry blood away from heart and into arterioles

Question 11

arterioles

Answer 11

smaller arteries that control blood flow from arteries to capillaries

Question 12

capillaries

Answer 12

tiny vessels that link arterioles to veins

Question 13

veins

Answer 13

carry blood from carpillaries back to heart

Question 14

5 basic structures in blood vessles

Answer 14

1. tough fibrous outer layer that resists pressure changes
2. muscle layer that can contract and control flow of blood
3. elastic layer that helps to maintain blood pressure by stretching
4. thinner inner lining(endothelium) that is smooth to reduce friction and thin to allow diffusion
5. lumen is central cavity which blood flows

Question 15

artery structure

Answer 15

• muscle layer is thick compared to veins (constricts and dilates to control volume of blood passing through)
• elastic layer is thick (maintains high pressure)
• overall thickness of wall is great which resists vessel bursting under pressure
• no valves as blood doesn’t flow backward

Question 16

arteriole structure

Answer 16

• muscle layer thicker than arteries which restricts flow of blood so controls movement into capillaries
• elastic layer is thinner than arteries because blood pressure is lower

Question 17

Vein structure

Answer 17

• muscle layer thin because veins carry blood away from tissues so cannot control flow of blood
• elastic layer is thin because pressure is low so vessels won’t burst
• wall thickness is small as it allows them to be flattened easily aiding the flow of blood within them
• valves at intervals throughout so blood doesn’t flow backwards because pressure is low

Question 18

Capillary structure

Answer 18

• walls consist mostly of lining so they’re very thin so diffusion is short
• numerous and highly branched providing large SA
• lumen is narrow so that red blood cells are squeezed flat against side of capillary, bringing them closer to cells reducing diffusion distance
• spaces between lining cells that allow white blood cells to escape in order to deal with infections within tissues

Question 19

tissue fluid

Answer 19

watery liquid containing glucose, amino acids, fatty acids, ions in solution and oxygen

supplies those substances to tissues and receives Co2 and other waste materials

Question 20

hydrostatic pressure

Answer 20

caused by pumping of heart
at arterial end of capillaries
causes tissue fluid to move out of blood plasma

Question 21

Forces that push tissue fluid out of capillaries at arterial end

Answer 21

• hydrostatic pressure of tissue fluid outside capillaries, which resists outward movement of liquid
• lower water potential of blood due to plasma proteins that causes water to move back into blood within carpillaries

Question 22

ultrafiltration

Answer 22

The pressure that forces small molecules out of capillaries, leaving all cells and proteins in the blood because they are too large to cross membranes

Question 23

Return of tissue fluid

Answer 23

• loss of tissue fluid from carpillaries reduces hydrostatic pressure inside them
• by time blood reaches venous end of capillary network the hydrostatic pressure is lower than tissue fluid outside it
• tissue fluid is forced back into capillaries down pressure gradient
• plasma has lost water and still contains proteins(lower wpt than tissue fluid)
• water leaves tissue by osmosis down wpt gradient
• remainder of tissue fluid is carried back via lymphatic system

Question 24

lymphatic system movement

Answer 24

gradually merge into larger vessels that form network through body
they drain contents back into bloodstream via two ducts that join veins close to heart

Question 25

what contents of lymphatic system is moved by

Answer 25

• hydrostatic pressure of tissue fluid that as left capillaries
• contraction of body muscles that squeeze lymph vessels