Transport in Man Ex

1(i) Outline the pathway taken when blood flows through the double circulatory system.
(ii) Suggest the advantages of a double circulatory system. [6]

2 Describe the mechanism of blood clotting when tissue cells are damaged. [7]

3 (a) Explain what is meant by “double circulation”. [2]

(b) Explain how structure is related to function in the following parts of the circulatory system:
(i) arteries.
(ii) veins,
(iii) capillaries [8]

4 (i) Outline the pathway taken when blood flows through the double circulatory system.
(ii) Suggest the advantages of a double circulatory system. [6]

ANSWERS

1(i) • Blood is pumped by the left ventricle to all parts of body via the aorta and returns via the superior and inferior vena cava into the right atrium;
• This circuit is known as systemic circulation [1/2]
• Blood then is pumped into the right ventricle and then pumped out to the lungs via the pulmonary arteries, then returns to the heart via the pulmonary veins;
• This is known as pulmonary circulation [1/2]
• Blood from the lungs enters the left atrium which pumps the blood into the left ventricle and the cycle repeats itself;

(ii) • Blood pressure maintained (Higher pressure in systemic circulation to supply oxygen to tissues at a faster rate & lower
pressure in pulmonary circulation to enable slower flow through lungs to allow more time for blood to pick up oxygen;
• Oxygenated blood kept separate from deoxygenated blood;

2 Mechanism of blood clotting:
When blood vessels are damaged, the damaged tissues and platelets release an enzyme: Thromboplastin;
Thromoplastin reults in the conversion of prothrombin (contained in the plasma) into thrombin;
In the presence of calcium ions;
Thrombin is an enzyme that converts soluble fibrinogen into insoluble fibrin;
The fibers trap blood cells and platelets;
Forming the blood clot which seals up the damaged area;
Prevents excessive blood loss and entry of pathogens;

3(a) -Double circulation is one where the blood passes through the heart twice ; in one complete circuit of the body ;

(b) - Arteries transport blood away from the heart ;
- It has thick muscular walls to withstand high blood pressure ;
- It has elastic walls to allow for stretching and recoiling to push the blood forward ;
- Veins transport blood towards the heart ;
- Veins have valves to prevent backflow of blood / ensure one way direction of the blood ;
- Capillaries are sites of exchange of substances ;
- Walls of the capillaries are only one cell thick (endothelium) to allow for faster diffusion rate due to decreased diffusion distance ;
- Walls of the capillaries are partially permeable to allow only certain substances such as water, glucose to diffuse through while larger proteins and red blood cells do not;

4 (i) • Blood is pumped by the left ventricle to all parts of body via the aorta and returns via the superior and inferior vena cava into the right atrium;
• This circuit is known as systemic circulation [1/2]
• Blood then is pumped into the right ventricle and then pumped out to the lungs via the pulmonary arteries, then returns to the heart via the pulmonary veins;
• This is known as pulmonary circulation [1/2]
• Blood from the lungs enters the left atrium which pumps the blood into the left ventricle and the cycle repeats itself;

(ii) • Blood pressure maintained (Higher pressure in systemic circulation to supply oxygen to tissues at a faster rate & lower
pressure in pulmonary circulation to enable slower flow through lungs to allow more time for blood to pick up oxygen;
• Oxygenated blood kept separate from deoxygenated blood;