Mass transport in humans A1

Question 1

Why is a double circulatory system required?

Answer 1

1. right side of heart pumps deoxygenated blood to the lungs for gas exchange (pulmonary circulation system)
2. blood then returns to left side of heart so oxygenated blood can be pumped at high pressure around body (systemic circulatory system)

Question 2

Describe how the heart muscle and the heart
valves maintain a one-way flow of blood from
the left atrium to the aorta. (9)

Answer 2

1. Atrium has higher pressure than ventricle
   (due to filling / contraction);
2. Atrioventricular valve opens;
3. Ventricle has higher pressure than atrium
   (due to filling / contraction);
4. Atrioventricular valve closes;
5. Ventricle has higher pressure than aorta;
6. Semilunar/aortic valve opens
7. Higher pressure in aorta than ventricle (as
   heart relaxes);
8. Semilunar/aortic valve closes
9. (Muscle / atrial / ventricular) contraction
   causes increase in pressure;

Question 3

Describe the structure of an artery and a vein.
Explain how the features you have described
help these blood vessels to carry out their
functions. (9)

Answer 3

1. Thick wall of artery;
2. Allowing it to withstand (higher) pressure;
   OR
3. Thin wall of vein;
4. Does not need to withstand pressure;
5. Both have endothelium/epithelium;
6. Consisting of squamous/flat cells;
7. Reduces friction with blood / allows smooth
   flow of blood;
8. Muscle which may contract and alter vessel
   diameter / divert blood;
9. Elastin smooths out pressure / stretches and
   recoils;
10. Valves in veins;
11. Prevent backflow of blood;

Question 4

4/ Arteries and arterioles take blood away
from the heart. Explain how the structures of
the walls of arteries and arterioles are related
to their functions. (8)

Answer 4

Elastic tissue
1. Elastic tissue stretches under
pressure/when heart beats;
2. Recoils/springs back;
3. Evens out pressure/flow;
Muscle
4. Muscle contracts;
5. Reduces diameter of
lumen/vasoconstriction/constricts vessel;
6. Changes flow/pressure;
Epithelium
7. Epithelium smooth;
8. Reduces friction/blood clots/less
resistance;

Question 5

Describe how the movement of the diaphragm
leads to air movement into the lungs

Answer 5

1. Diaphragm contracts and flattens.
   2.Volume of lungs increases.
2. Pressure inside the lungs is lower than
   atmospheric pressure.
3. Air moves into the lungs.

Question 6

Describe and explain how the lungs are adapted
to allow rapid exchange of oxygen between air in
the alveoli and blood in the capillaries around
them.

Answer 6

1. Many alveoli/ alveoli walls folded provide a
   large surface area;
2. Many capillaries provide a large surface area;
3. (So) fast diffusion; allow only once in question
4. Alveoli or capillary walls/ epithelium/ lining are
   thin/ short distance between alveoli and blood;
   accept: one cell thick for ‘thin’
5. Flattened/ squamous epithelium; accept:
   endothelial
6. (So) short diffusion distance/ pathway;
7. (So) fast diffusion;
8. Ventilation / circulation; Accept: descriptions
9. Maintains a diffusion / concentration gradient;
10. (So) fast diffusion;

Question 7

The thickness of the aorta wall changes all
the time during each cardiac cycle.
Explain why. (5)

Answer 7

1. (Aorta wall) stretches;
2. Because ventricle/heart contracts / systole
   / pressure increases;
3. (Aorta wall) recoils;
4. Because ventricle relaxes / heart relaxes
   /diastole / pressure falls;
5. Maintain smooth flow / pressure;

Question 8

Describe how tissue fluid is formed and how it
is returned to the circulatory system. (6)

Answer 8

Formation
1. High blood / hydrostatic pressure / pressure
filtration;
2. Forces water / fluid out;
3. Large proteins remain in capillary;
Return (in neck lymph node)
4. Low water potential in capillary / blood;
5. Due to (plasma) proteins;
6. Water enters capillary / blood;
7. (By) osmosis;
8. Correct reference to lymphatic fluid;

Question 9

State the main blood vessels and what they do.

Answer 9

1. Pulmonary artery - carries deoxygenated blood away from the heart, towards the lungs
2. Pulmonary vein - carries oxygenated blood away from the lungs, towards the heart
3. Coronary arteries - supply the heart with oxygenated blood
4. Aorta - carries oxygenated blood out of the heart and to the rest of the body
5. Vena cava - carries deoxygenated blood into heart
6. Renal artery - supplies the kidneys with oxygenated blood
7. Renal vein - carries deoxygenated blood away from the kidneys, towards the heart

Question 10

What supplies the heart itself with blood?

Answer 10

Coronary arteries

Question 11

State the hearts structure and functions.

Answer 11

1. consists of an upper chamber (atrium) and lower chamber (ventricle)
2. wall of heart is made up of cardiac muscle fibres
3. deoxygenated blood returns from the body in vena cava (vein) and enters right atrium
4. the blood the passes via an atrio-ventricular valve into right ventricle and out, via semi-lunar valve into pulmonary artery
5. the blood passes through lungs and returns to left atrium via pulmonary vein
6. the blood passes through a second atrio-ventricular valve into left ventricle and then through the semi-lunar valve into aorta
7. then travels to body tissues

Question 12

Why is the left side of the heart structured different for its role than the right side?

Answer 12

1. thicker muscle fibres for a greater contraction force
2. ventricle thicker as requires more pressure (pumping around the whole body)

Question 13

What is pressure and how does it change in the chambers?

Answer 13

1. pressure is the amount of force acting on a surface
2. changes pressure in chambers as a result of both changes in volume of blood in chamber (high pressure) and contractions of heart muscles (increases pressure)

Question 14

What is the name for…
- when the heart muscle is contracted
-when the heart muscle is relaxed

Answer 14

1. systole
2. diastole

Question 15

Explain pressure change in the chambers (7)

Answer 15

1. blood enters atrium - blood volume increases pressure in atrium so its greater than the pressure in ventricle, atrioventricular valve opens
2. atrium muscles contract - further increasing pressure, remaining blood forced into ventricle
3. blood enters ventricle - increased pressure in ventricle, pressure in ventricular higher than atrium so atrioventricular valve closes
4. ventricle muscles contract - increases pressure until greater than aorta/pulmonary artery, semi-lunar valve opens
5. blood enters aorta/pulmonary artery - blood pumper to body or lungs (left or right)
6. ventricle muscles relax - pressure in ventricles less than aorta so semi-lunar valve closes
7. blood enters atrium - increases pressure in atrium (cycle starts again)

Question 16

How do valves work and why?

Answer 16

1. ensure that blood flows in one direction through the heart
2. only open in one direction due to pressure differences on either side of valve - due to tendons that anchor the valve (called heart strings)

Question 17

Name the two valves in the heart and how they work.

Answer 17

1. atrioventricular valves - these open when pressure in atrium is higher than pressure in ventricles. They close when pressure in ventricles is higher than pressure in atrium
2. Semi-lunar valve - open when pressure in ventricles is higher than in aorta and close when pressure in ventricles is lower than aorta

Question 18

Explain and give the equation for cardiac output.

Answer 18

1. volume of blood pumped out of left ventricle per minute
2. CO = stroke volume (volume expelled per heart beat) x heart rate per minute

Question 19

Explain a bit about the causes and effects of coronary heart disease.

Answer 19

1. any interference with the coronary arteries which supply blood to the heart muscle itself
2. blockage - cells passed the blockage won’t be able to get any oxygen/glucose as blood can’t get in so will die/heart attack
3. can also cause physical damage due to build up of pressure

Question 20

Describe atherosclerosis (process of atheroma forming) (5)

Answer 20

1. lumen of artery narrowed due to build up of fatty deposits and cholesterol underneath endothelium of artery (deposit called atheroma)
2. muscle fibres and calcium salts accumulate forming plaque. Plaque grows and bulges into lumen of artery
3. reduced blood flow to heart muscle beyond the point - deprived of oxygen during exercise
4. cells have to respire anaerobically to produce lactic acid, causes pain (angina)
5. if completely blocked, muscle cells have no oxygen and die - heart attack (myocardial infarction)

Question 21

What is thrombosis?

Answer 21

1. the plaque may rupture and build and trigger blood clotting over damaged area
2. clot builds up rapidly, causing further blockage of artery
3. known as thrombus
4. the clot may travel up bloodstream causing clot somewhere else (stroke)

Question 22

What is an aneurysm?

Answer 22

1. artery becomes blocked
2. leading to build up of blood pressure in front of blockage
3. pressure can weaken wall + it starts to bulge outwards (aneurysm)
4. this may rupture and cause internal bleeding

Question 23

What are the risk factors of coronary heart disease?

Answer 23

1. causes - high cholesterol, high lipid diet, lack of exercise, smoking, stress
2. effects - high blood pressure, increase blood toxins, increase cholesterol in blood
3. leads to - damage to epithelium wall, increase in lipid uptake

Question 24

Describe how the movement of the diaphragm leads to air movement into the lungs.

Answer 24

1. diaphragm contracts and flattens
2. volume of lungs increases
3. pressure inside lungs is lower than atmospheric pressure
4. air moves into lungs

Question 25

Name 5 properties that any respiratory surface should have.

Answer 25

1. large surface area
2. permeable
3. thin
4. moist
5. efficient transport system (maintains a concentration gradient)

Question 26

Describe what happens during inhalation.

Answer 26

1. external intercostal muscles contract (internal relax) expanding ribcage
2. diaphragm contracts and moves down
3. lung volume increases
4. pressure in lungs less than outside
5. air moves into lungs

Question 27

Describe what happens during exhalation.

Answer 27

1. external intercostals relax (internal contract)
2. diaphragm relaxes and moves up
3. lung volume decreases
4. pressure in lungs greater than outside
5. air moves out of the lungs

Question 28

Explain the antagonistic muscles in the lungs/ribs.

Answer 28

1. as the internal intercostals contract, external intercostals relax
2. and vise-versa

Question 29

Explain the diffusion of gases during respiration.

Answer 29

1. deoxygenated blood from pulmonary artery has low concentration of oxygen and high concentration of CO2 compared with air inside alveoli
2. as blood reached capillaries surrounding alveoli, oxygen diffused into blood through epithelial membrane (squamous) moving from high to low O2 concentration
3. at same time CO2 moves from blood to alveoli as the concentration of CO2 in blood of pulmonary artery is greater than inhaled air in alveoli
4. both gases move in opposite directions from high to low concentrations via diffusion. The blood is then circulated away from alveoli to move newly oxygenated blood away from lungs back to heart to be pumped around body
5. this maintains a concentration gradient at alveolar epithelium, so ensure gases diffuse efficiently in either direction and do not reach equilibrium.

Question 30

How does Fick’s law link to the diffusion of gases?

Answer 30

1. diffusion = (SA x conc gradient) / diffusion distance
2. SA = capillaries and alveoli folds
3. concentration gradient = circulation of blood, breathing and ventilation of lungs
4. diffusion distance = alveoli, epithelium capillaries (1 cell thick)

Question 31

How do you calculate the pulmonary ventilation (amount of air exchanged in one breathing cycle)?

Answer 31

pulmonary vent = ventilation rate (n. of breaths) x tidal volume (volume of air exchanged in one breath)

Question 32

Why do we have residual air in our lungs when breathing out to max capacity?

Answer 32

to stop deflation

Question 33

What risk factors cause the following lung diseases?
- tuberculosis
- fibrosis
- asthma
- emphysema

Answer 33

1. infection
2. occupation (exposure to irritants) and genetic pre-disposition
3. smoking, air pollution, occupation, genetic pre-disposition
4. smoking, occupation

Question 34

Define mass transport

Answer 34

1. all substances move in the same direction
2. at the same speed
3. due to a pressure difference

Question 35

Relate the need for a transport system and the need for a pump to circulate the transport medium to…
- the SA to volume ratio of an organism
- the activity level of an organism

Answer 35

1. the lower SA to volume ratio of an organism and the more active it is
2. the greater need for a specialist transport system with a pump

Question 36

What is the function of the liver?
- name the 3 veins/artery that are associated with it

Answer 36

1. one function is to process absorbed food molecules eg glucose and amino acids and adjust their concentration in the blood
2. Hepatic artery - takes blood from the aorta to liver (provides oxygen)
3. Hepatic vein - takes blood from liver to vena cava
4. Hepatic portal vein - takes blood from intestines to the liver, contains absorbed food molecules

Question 37

What are the structures and functions of the following…
- arteries
- veins
- arterioles
- endothelial layer

Answer 37

1. Arteries - transport blood away from heart (usually high pressure), therefore thick, elastic protein fibre wall to stretch and recoil. Smooth muscle layer to smooth out blood flow. Muscle contractions constrict vessel and reduce volume of blood passing through
2. Veins - transport blood to the heart (usually at low pressure) muscle and elastic layer very thin , have valves to prevent backflow of blood and keep it moving in one direction. Use skeletal muscles contracting to push up blood.
3. Arterioles - arteries branch into narrower blood vessels called arterioles which transport blood into capillaries - more friction to reduce blood pressure, thinner elastic layer but thicker muscle layer (need to contract to constrict vessel and reduces flow into organ). Vessel can also relax to allow more blood flow into organ.
4. endothelial layer - one cell thick, gives smooth layer which reduced friction and gives smooth flow (on side of artery).

Question 38

Name the function of the kidney and the two blood vessels associated with it.

Answer 38

1. excretion of nitrogenous waste and osmoregulation (maintaining correct w.p in blood)
2. renal artery + vein - take blood to and from the kidney

Question 39

How is a capillary structures for its function?

Answer 39

1. very thin - increase rate of diffusion
2. numerous and branched - increases SA for diffusion
3. narrow diameter - ensures RBC (red blood cell) is in contact with wall
4. wall spaces - gaps between endothelial cells which allows rapid formation of tissue fluid and WBC (white blood cells) to pass through tissue spaces

Question 40

Explain the role of the lymphatic system (5)

Answer 40

1. more liquid leaves capillary than re-enters
2. due to net force pushing liquid out the capillary being greater
3. the liquid can’t stay in tissue space or swelling (oedema) occurs
4. the fluid drains into open-ended tubes known as lymphatic vessels
5. these eventually empty back into bloodstream in veins in the neck region