Exchange- Mass transport in Animals

Question 1

Why is the transport system in mammals called a double circulatory system?

Answer 1

the heart pumps twice, the blood goes through the heart twice – generates enough pressure
to supply all body cells

Question 2

Why is the transport system in mammals called a closed circulatory system?

Answer 2

blood is transported in blood vessels – helps to maintain pressure and redirect blood flow

Question 3

Layout of Circulatory System?

Answer 3

 heart pumps blood which is carried in arteries which flow into arterioles which flow into capillaries which then are carried in venules then veins back to the heart
 Artery to Arterioles to Capillaries to Venules to Veins
 Artery/Arterioles carry blood away from the heart
(arterioles are small arteries)
 Capillaries are the site of exchange (nutrients out, waste in)
 Veins/Venules return blood back to the heart
(venules are small veins)

Question 4

Heart?

Answer 4

 job is to pump blood around the body (delivers nutrients to cells and remove waste)
 made of 4 muscular chambers (2 atria, 2 ventricles)
 atria pumps blood to ventricles, ventricles pump blood out of heart (R to lungs, L to body)
 ventricles thicker then atria (has to pump blood further)
 left ventricle has a thicker muscular wall then right ventricle, therefore has stronger contractions, so can
generate higher pressure and pump the blood further around the body

Question 5

Blood vessels of the heart?

Answer 5

 artery takes blood away from the heart, vein returns blood to the heart
 Vena Cava supplies R atrium (with deoxygenated blood from body)
 Pulmonary Vein supplies L atrium (with oxygenated blood from lungs)
 R ventricle supplies Pulmonary Artery (deoxygenated blood to lungs)
 L ventricle supplies Aorta (oxygenated blood to body)

Question 6

Job of valves in heart?

Answer 6

 Ensure one way flow of blood, no backflow
 (blood flows from atria to ventricles to arteries)
 2 sets of valves: Atrio-ventricular Valve & Semi-lunar Valve
 AV valve = between atria and ventricles
 SL valve = between ventricles and arteries

Question 7

When are AV valves open or closed?

Answer 7

Open = pressure in atria greater then pressure in ventricles,
Closed = pressure in ventricles greater then pressure in atria

Question 8

When are SL valves open or closed?

Answer 8

Open = pressure in ventricles greater then pressure in arteries, Closed = pressure
in arteries greater then pressure in ventricles

Question 9

Cardiac cycle

Diastole

Answer 9

atria relaxed, ventricles relaxed, AV valve open, SL valve closed

Question 10

Atrial Systole

Answer 10

atria contracts and pushes all the remaining blood into the ventricles so it becomes full

Question 11

Ventricular Systole

Answer 11

the ventricles contract from the base upwards, pushing the blood up thru the arteries, when the ventricles start to contract the AV valve closes then the SL valve opens and blood leaves the heart

Question 12

Formula for Cardiac Output?

Answer 12

 CO = Stroke Volume x Heart Rate
 stroke volume = volume of blood pumped out of the heart in one beat
 heart rate = number of beats per minuted
 Cardiac Output = volume of blood pumped out of the heart in one minute

Question 13

Role of Arteries/Arterioles?

Answer 13

 generally carry oxygenated blood away from the heart
 Coronary Artery - heart muscle
Hepatic Artery to liver
Renal Artery to kidneys
 exception = Pulmonary Artery carries deoxygenated blood to lung

Question 14

Role of Veins/Venules?

Answer 14

 generally carry deoxygenated blood back to the heart
 Coronary Vein -heart muscle
Hepatic Vein from liver
Renal Vein from kidneys
 exception 1 = Pulmonary Vein carries oxygenated blood back to the heart

Question 15

Function of Arteries/Arterioles?

Answer 15

carry blood away from the heart so should be able to withstand high blood pressures & maintain high blood pressures

Question 16

Structure of Arteries/Arterioles?

Answer 16

 narrow lumen = maintains pressure
 lining made of squamous epithelial cells = smooth lining to reduce friction
 thick wall = withstand pressure
 elastic tissue stretches and recoils to withstand pressure

Question 17

Function of Veins/Venules?

Answer 17

return blood back to the heart, the blood is under low pressure

Question 18

Structure of Veins/Venules?

Answer 18

wide lumen = ease of blood flow
 lining made of squamous epithelial cells = smooth lining to reduce friction
 thin wall = vein can be squashed by skeletal muscle pushing blood back to the heart
 valves in lumen = prevents backflow of blood

Question 19

Function of Capillaries?

Answer 19

site of exchange
 3 locations,
 takes in O2 and removes CO2
 deliver nutrients and remove waste

Question 20

Adaptation of Capillaries?

Answer 20

 many small capillaries = large surface area
 thin wall, one cell thick = short diffusion distance
 pores between cells = allows fluid to move in and out
 narrow lumen = increase diffusion time and decrease diffusion distance

Question 21

How does exchange occur between Capillaries & All Cells?

Answer 21

 by mass flow
 fluid moves out of the blood in the capillaries carrying the nutrients
 fluid moves back into blood in the capillaries carrying the waste
 (fluid in the blood called plasma, fluid surrounding cells called tissue fluid, fluid in lymph system called
lymph)

Question 22

How is tissue fluid formed and returned to circulatory system?

Answer 22

 at the start of the capillary (arterial end) there is a build up hydrostatic pressure
 this pushes fluid out of the capillary via the pores
 the fluid carries the nutrients with it
 the fluid surrounds the cells, this is called tissue fluid
 at the finish of the capillary (venous end) the fluid moves back in by osmosis
 the capillary has low water potential due to the presence of proteins (too large to move out of capillaries)
 any excess tissue fluid is picked up by the lymph system and deposited in the vena cava

Question 23

Why does high blood pressure cause accumulation of tissue fluid?

Answer 23

increases hydrostatic pressure, so more tissue fluid is formed – not as much can be returned to the
circulatory system

Question 24

Why does diet low in protein cause accumulation of tissue fluid?

Answer 24

the water potential in the capillary is not as low as normal, so not as much fluid can move back into the
capillary by osmosis

Question 25

Job of Red Blood Cells?

Answer 25

 found in humans/mammals (animals)
 carries haemoglobin
 haemoglobin carries oxygen

Question 26

Structure of Haemoglobin?

Answer 26

 protein
 quaternary structure made of 4 polypeptide chains
 each chain carries a haem group
 each haem group carries Fe2+
 each Fe2+ carries an O2
 therefore, each haemoglobin carries 4 lots of O2

Question 27

Job of Haemoglobin?

Answer 27

load oxygen in the lungs and deliver it to the respiring tissues

Question 28

What is Affinity?

Answer 28

the level of attraction haemoglobin has to oxygen

high affinity = strong attraction, low affinity = weak attraction

Question 29

Role of haemoglobin in oxygen transport?

Answer 29

 haemoglobin has High Affinity in the lungs – due to high partial pressure of oxygen and low partial
pressure of carbon dioxide, so haemoglobin loads/associates oxygen in the lungs and becomes saturated
 the haemoglobin is transported in the blood in the red blood cell
 at the respiring tissues, haemoglobin has Low Affinity – due to low partial pressure of oxygen and high
partial pressure of carbon dioxide, so oxygen is unloaded/dissociated/delivered and haemoglobin becomes
unsaturated

Question 30

Relationship between O2 Partial Pressure & Affinity/Saturation of Haemoglobin?

Answer 30

 positive correlation
 as O2 partial pressure increases, affinity/saturation of haemoglobin increases
 the correlation is not linear but is curved (produces a s-shaped curve called Oxygen Dissociation Curve)
 middle portion of ODC has a steep gradient so when respiring tissues change from resting to active and
partial pressure of O2 falls, there is a large drop in affinity, so more O2 would be delivered to the respiring
tissues

Question 31

Relationship between CO2 Partial Pressure & Affinity/Saturation of Haemoglobin?

Answer 31

 negative correlation
 as CO2 partial pressure increases, affinity/saturation of haemoglobin decreases
 this occurs at the site of respiring tissues = the carbon dioxide lowers the pH of the blood, makes the
haemoglobin change shape, so oxygen is released, lowering affinity. this shifts the ODC to the right,
called the bohr effect. more oxygen delivered to respiring cells