Transport in Animals
Explain the need for transport systems in multicellular animals;
I. As an animal grows, cells deeper in the body will not get any oxygen or nutrients.
II. Animals that are highly metabolic will need a good supply of nutrients and oxygen to supply the energy for movement.
III. As animals get bigger, their volume increases, but the SA doesn't as much. So the surface-area-to-volume ratio of a large animal is relatively small.
IV. Larger animals don't have a large enough SA to supply all of the oxygen and nutrients that they need.
Explain the meaning of the terms;
single circulatory system
Blood flows through the heart once during each circulation of the body e.g. fish
double circulatory system
Blood flows through the heart twice during one cycle of the body e.g. mammals
Open circulatory system
The blood is not always in vessels e.g. insects
Closed circulatory system
The blood is always in vessels e.g. fish
Describe the external and internal structure of the mammalian heart;
The largest parts are the ventricles. Above those are the atria.
The coronary arteries lie over the surface of the heart carrying oxygenated blood.
At the top of the heart are the veins (blood to heart), and arteries (blood away heart).
Divided into four chambers.
The two upper chambers are atria (deoxygenated blood from body flows into right atrium from the vena cava, and oxygenated blood flows from lungs into the left atrium).
The two lower chambers are the ventricles. They are separated from each other by the septum and from the atria by the atrioventricular valves which prevent the blood from flowing the wrong way.
These are attached to tendinous cords which prevent the valves from turning inside out.
Explain the differences in the thickness of the walls of the different chambers;
· The walls of the atria are very thin. They do not need to create much pressure are they are only pushing the blood into the ventricles
· The walls of the right ventricle are thicker than the atria as only need to pump blood to the lungs. The blood vessels of the lungs are also very thin, so they would burst of the blood was under too much pressure.
· The walls of the left ventricle are two or three times thicker than the right as the blood is pumped around the entire body and so needs to be under high pressure.
Describe the cardiac cycle, with reference to the action of the valves in the heart;
1. When the heart is relaxed, blood flows into the atria from the major veins.
2. The blood flows through the atrioventricular valves into the ventricles
3. The atria contract simultaneously, pushing blood into the ventricles
4. The atrioventricular valves snap shut and prevent blood from flowing
5. When the pressure in the arteries is higher than the…