3.1.2 transport in animals

Question 1

arteries

Answer 1

transport blood away from the heart at high pressure to tissues
have a narrow lumen to maintain high blood pressure
pulse is present

Question 2

arterioles

Answer 2

arteries branch into narrower blood vessels which transport blood into capillaries

Question 3

veins

Answer 3

transport blood to the heart at low pressure
have a wider lumen
receive blood passed through capillary network
rate of blood flow is slower
contain valves to prevent backflow
no pulse

Question 4

venules

Answer 4

narrower blood vessels transport blood from capillaries to the veins

Question 5

the layers of blood vessel walls

Answer 5

tunica externa
tunica media
tunica intima

Question 6

structure of arteries: tunica intima

Answer 6

endothelial layer, layer of connective tissue and a layer of elastic fibres

Question 7

what does the endothelium layer do?

Answer 7

one cell thick
lines lumen of blood vessels
smooth and reduces friction for free blood flow

Question 8

structure of arteries: tunica media

Answer 8

smooth muscle cells and thick layer of elastic tissue
has a thick tunica media

Question 9

what does the layer of muscle cells do?

Answer 9

strengthens arteries to withstand high pressure
enables them to contract and narrow the lumen for reduced blood flow

Question 10

what does the elastic tissue do?

Answer 10

helps to maintain blood pressure in arteries
stretches and recoils to even out fluctuations in pressure

Question 11

structure of arteries: tunica externa

Answer 11

made up of collagen

Question 12

what does collagen do?

Answer 12

strong proteins protects blood vessels from damage by over-stretching

Question 13

structure of arterioles

Answer 13

muscular layer to contract and partially cut off blood flow to specific organs to regulate blood flow e.g. during exercise
lower proportion of elastic fibres

Question 14

structure of veins

Answer 14

tunica media - much thinner - dont have to withstand high pressure
lumen - much larger - ensure blood returns to heart at an adequate speed, reduces friction between blood and endothelial layer

Question 15

structure of venules

Answer 15

few to no elastic fibres
large lumen
low pressure - no need for muscular layer

Question 16

capillaries

Answer 16

can form networks called capillary beds which are important exchange surfaces within the circulatory system

Question 17

structure of capillaries

Answer 17

blood travels slow for diffusion to occur
branch of capillaries form so substances can diffuse across a short diffusion distance
single layer of endothelial cells - reduce diffusion distance
fenestrations - allow blood plasma to lead out and form tissue fluid
white blood cells can combat infection in

Question 18

structure of capillaries

Answer 18

blood travels slow for diffusion to occur
branch of capillaries form so substances can diffuse across a short diffusion distance
single layer of endothelial cells - reduce diffusion distance
fenestrations - allow blood plasma to lead out and form tissue fluid

Question 19

components of the blood

Answer 19

red blood cells - transport oxygen
white blood cells - role in immune system
platelets - blood clotting
blood plasma - glucose, amino acids, mineral ions etc, oxygen, albumin

Question 20

formation of tissue fluid

Answer 20

plasma leaks out of the fenestrations of capillaries as blood passes through
proteins stay in blood as they are too large to fit through the gaps

Question 21

hydrostatic pressure

Answer 21

the pressure exerted by a fluid e.g. blood pressure generated by the contraction of the heart muscle

Question 22

oncotic pressure

Answer 22

osmotic pressure exerted by plasma proteins within a blood vessel
plasma proteins lower the water potential within the blood vessel, causing water to move into the blood vessel by osmosis

Question 23

arteriole end

Answer 23

hydrostatic pressure > oncotic pressure
net movement of water, dissolved solutes, glucose and amino acids out of capillary through fenestrations
increased protein content in capillary creates a water potential gradient between capillary and tissue fluid

Question 24

venule end

Answer 24

oncotic pressure > hydrostatic pressure
net movement of water in
pressure in capillary is reduced due to increased distance from heart
water potential gradient - water moves into capillary from tissue fluid

Question 25

what happens if blood pressure is high (hypertension)?

Answer 25

pressure at arterial end is greater
pushes more fluid out of capillary and fluid begins to accumulate around tissue
called oedema

Question 26

formation of lymph

Answer 26

some tissue fluid enters lymph vessels
have closed ends and large pores to allow molecules to pass through that cannot pass through the capillary wall
liquid moves along the larger vessels by compression caused by body movement
backflow prevented by valves
lymph reenters bloodstream through veins
lipids are transported from the intestines to bloodstream by lymph system

Question 27

features of erythrocytes

Answer 27

biconcave shape - increased surface area available for diffusion
flexible - pass through narrow capillaries
no nucleus - more room for haemoglobin
last for 120 days in bloodstream
contain haemoglobin

Question 28

features of haemoglobin

Answer 28

red pigment that carries oxygen
large globular conjugated protein made up of four peptide chains, each with iron-containing haem prosthetic group
each haemoglobin can bind to 4 oxygen molecules

Question 29

haemoglobin + oxygen

Answer 29

forms oxyhaemoglobin
reversible reaction

Question 30

haemoglobin binds

Answer 30

• oxygen levels are low in capillaries - creating a steep concentration gradient between the erythrocytes and alveoli
• oxygen moves into erythrocytes and binds with haemoglobin
• as one oxygen molecule binds to the haem group, molecule changes shape, making it easier for the next oxygen to bind - positive cooperativity
• oxygen concentration stays low - to ensure the steep diffusion gradient is maintained until all haemoglobin is saturated with oxygen
• process is reversed when blood reaches the body tissues
• concentration of oxygen in cytoplasm is lower than in erythrocytes - oxygen diffuses out

Question 31

what does an oxygen dissociation curve show?

Answer 31

the affinity of haemoglobin for oxygen - small change in the partial pressure of oxygen makes a significant difference to the saturation of the haemoglobin with oxygen
= high partial pressure in lungs - red blood cells rapid load with oxygen
= low partial pressure - oxygen release rapidly from haemoglobin to diffuse into cells

Question 32

effect of carbon dioxide - the Bohr effect

Answer 32

• partial pressure of carbon dioxide rises, haemoglobin gives up oxygen more easily - Bohr effect
• in active tissue with a high partial pressure of CO2, haemoglobin gives up its oxygen more readily
• in lungs where the proportion of CO2 is low, oxygen binds to haemoglobin easily

Question 33

fetal haemoglobin

Answer 33

• oxygenated blood from the mother runs close to the deoxygenated fetal blood in placenta
• fetal haemoglobin has a higher affinity for oxygen than adult at each point along the dissociation curve so it removes oxygen from the maternal blood as they move past each other
• shifts dissociation curve to the left

Question 34

transporting carbon dioxide

Answer 34

• About 5% is carried dissolved in the plasma.
• 10-20% is combined with the amino groups in the polypeptide chains of haemoglobin to form a compound called carbaminohaemoglobin.
• 75-85% is converted into hydrogen carbonate ions (HCO3-) in the cytoplasm of the red blood cells.
• Most of the carbon dioxide that diffuses into the blood from the cells is transported to the lungs in the form of hydrogen carbonate ions.
• Carbon dioxide react slowly with water to form carbonic acid (H2CO3-). The carbonic acid then dissociates to form hydrogen ions and hydrogen carbonate ions.
• In the blood plasma this reaction happens slowly. However, in the cytoplasm of the red blood cells there are high levels of the enzyme carbonic anhydrase.