Unit 9: Transport in Humans

Question 1

Describe the circulatory system

Answer 1

• A system of blood vessels with a pump and valves to
  ensure one-way flow of blood
• Transports useful things like oxygen from lungs / digested food from small intestines to cells; hormones, antibodies, and blood proteins
• Removes waste chemicals like carbon dioxide from cells to lungs / other wastes from cells to kidneys

Question 2

Describe the single circulation of a fish

Answer 2

Blood flows through the heart once during a complete circuit of the body.
Blood from the organs flow into the heart from the veins. This blood has little oxygen => deoxygenated blood. The heart pumps blood into an artery that takes it to the gills of a dish to be oxygenated. The blood flows on from the gills in arteries to the body organs.

Question 3

Describe the double circulation of a mammal

Answer 3

Blood flows through the heart twice during a complete circuit around the body.
A low pressure flow to the lungs; high pressure flow to the body tissues
- The right side of the heart pumps deoxygenated blood to the lungs, back to the heart again. Pressure is not very high => little resistance to flow in lungs. Blood absorbs oxygen => loses carbon dioxide. Oxygenated blood returns to the heart in a vein.
- The left side of the heart pumps oxygenated blood to the rest of the body, and back to the heart again. Pressure is high => big resistance to flow to rest of body. Gas exchange occurs as blood flows through capillaries in organs. Oxygen leaves the blood, carbon dioxide enters.

Question 4

What are the advantages of a double circulation?

Answer 4

• Delivers greater blood flow rate to tissues around the body => heart pumps the oxygenated blood returned to it from the lungs. This is useful because when blood passes through the lungs its pressure is reduced.
• Ensure that we are giving our tissues and muscles blood full of oxygen, instead of a mixture of oxygenated and deoxygenated blood => much more efficient!