1. Circulation and Gas Exchange
Animal Physiology
Circulation and Gas Exchange
Mr G Davidson

2. The Heart The function of the heart is to pump blood round the body.
The blood is transported in blood vessels.
The structure of the heart is ideally suited to its function.
February 23, 2019
Mr G Davidson

3. The Heart Right atrium Left atrium Right ventricle Left ventricle
Cardiac muscle
February 23, 2019
Mr G Davidson

4. The Heart The heart consists of four chambers.
It is made of cardiac muscle.
The two upper chambers are called atria – the left atrium and the right atrium.
February 23, 2019
Mr G Davidson

5. The Heart
The two lower chambers are called ventricles – the left ventricle and the right ventricle.
The atria both receive blood back into the heart while the ventricles both pump blood out of the heart.
The heart has four valves to ensure that blood always flows in the one direction.
February 23, 2019
Mr G Davidson

6. The heart semi-lunar valve atrio-ventricular valve February 23, 2019
Mr G Davidson

7. The Heart Blood enters the heart into the atria.
When the atria contract, the blood moves down through the atrio-ventricular (AV) valves into the ventricles.
February 23, 2019
Mr G Davidson

8. The Heart
The valves prevent the blood flowing back up into the atria when the ventricles contract.
When the ventricles contract the blood moves up through the semi-lunar (SL) valves.
These valves prevent the backflow of blood into the ventricles.
February 23, 2019
Mr G Davidson

9. The Heart
All blood must pass through the heart twice in each circulation.
Blood from all parts of the body enters the heart through the main veins called the vena cava.
This blood enters the right atrium and carries deoxygenated blood.
February 23, 2019
Mr G Davidson

10. The Heart
It then passes through the right AV valve into the right ventricle.
From here it is pumped into the pulmonary arteries through the SL valve, where it will go to the lungs.
In the lungs the blood loses its carbon dioxide and gains fresh oxygen before entering the pulmonary veins.
February 23, 2019
Mr G Davidson

11. The Heart
This oxygenated blood now returns to the heart where it enters the left atrium.
When the left atrium contracts it is forced through the left AV valve into the left ventricle.
February 23, 2019
Mr G Davidson

12. The Heart
The left ventricle then pumps the blood through the SL valve into the aorta, which is the main artery, which will then distribute it throughout the body.
The wall of the left ventricle is very thick since it has to pump blood all round the body.
The wall of the right ventricle is less thick since it pumps blood only to the lungs.
February 23, 2019
Mr G Davidson

13. The Heart Pulmonary artery Aorta Vena cava Pulmonary vein
February 23, 2019
Mr G Davidson

14. The Heart
The heart wall is made of cardiac muscle and also requires its own blood supply.
The blood vessels which do this are called the coronary arteries.
February 23, 2019
Mr G Davidson

15. The Heart
Coronary artery
February 23, 2019
Mr G Davidson

16. The Heart
These spread out over the surface of the heart and deliver fresh oxygen and glucose to all the muscle cells.
Coronary veins return the blood to the vena cava.
If the coronary arteries narrow or become blocked in any way, this can result in a heart attack.
February 23, 2019
Mr G Davidson

17. Blood Vessels
There are three main types of blood vessel – arteries, veins and capillaries.
Arteries carry blood away from the heart.
Veins carry blood back to the heart.
Capillaries connect arteries to veins and this is where the exchange of essential materials takes place.
February 23, 2019
Mr G Davidson

18. Arteries Arteries have thick muscular walls.
This allows them to withstand the pressure created by the heart.
Each time the heart beats, blood is forced along the arteries, and this can be felt as your pulse.
February 23, 2019
Mr G Davidson

19. Veins Veins have thinner walls than arteries but a wider cavity.
This is because the blood is now at a much lower pressure.
Veins also contain valves all along their length to prevent the backflow of blood.
February 23, 2019
Mr G Davidson

20. Capillaries Capillaries are microscopic blood vessels.
Their walls are only one cell thick.
This allows them to exchange essential materials between the blood and the body cells.
Materials such as glucose, oxygen, carbon dioxide, etc.
February 23, 2019
Mr G Davidson

21. Circulatory System Pulmonary vein Pulmonary artery Vena cava Aorta
Hepatic artery
Hepatic vein
Mesenteric artery
Hepatic portal vein
Renal artery
Renal vein
February 23, 2019
Mr G Davidson

22. Gas Exchange Gas exchange occurs in the lungs.
When we breathe in (inhale) oxygen from the air passes from the lungs into the blood and carbon dioxide passes from the blood into the lungs.
We then breathe this air out (exhale) before inhaling fresh air.
February 23, 2019
Mr G Davidson

23. Structure of the Lungs The lungs are found in the chest cavity.
Air passes into the lungs from the trachea (windpipe) which splits into 2 bronchi, one to each lung.
Each bronchus then splits into smaller tubes called bronchioles.
These bronchioles terminate in tiny air sacs called alveoli.
February 23, 2019
Mr G Davidson

24. Lungs Trachea Rib Bronchus Bronchiole Diaphragm February 23, 2019
Next Slide
for detailed
view of this area
Diaphragm
February 23, 2019
Mr G Davidson

25. Alveoli Bronchiole Blood Capillary Alveolus February 23, 2019
Mr G Davidson

26. Gas Exchange
There are so many alveoli that they provide a huge surface area for the gases to be exchanged.
The lining of each alveolus is very thin and moist.
February 23, 2019
Mr G Davidson

27. Gas Exchange
Each alveolus is surrounded by a dense network of blood capillaries.
Blood arrives in the lungs from the body and is said to be deoxygenated.
Oxygen diffuses through the thin lining of the alveolus into the blood capillary which is only one cell thick.
This is because the concentration of oxygen in the alveolus is higher than in the blood.
February 23, 2019
Mr G Davidson

28. Gas exchange Carbon dioxide diffuses in the opposite direction.
This is because the concentration of CO2 in the blood from the body is higher than in the alveoli.
The blood now leaving the lungs is said to be oxygenated.
February 23, 2019
Mr G Davidson

29. Gas Exchange
February 23, 2019
Mr G Davidson

30. Features which make gas exchange more efficient.
Function
Lining very thin
Allows rapid diffusion
Lining moist
Allows oxygen to dissolve
Large surface area
Allows more oxygen to be absorbed
Dense network of capillaries
Allows blood to absorb oxygen
February 23, 2019
Mr G Davidson