Question

The diagrams given below are cross sections of blood vessels:

(i) Identify the blood vessels A, B and C.
(ii) Name the parts labelled 1 to 3.
(iii) Name the type of blood that flows through A.
(iv) Mention one structural difference between A and B.
(v) In which of the above vessels does exchange of gases actually take place?

Answer 1

(i) A – Artery, B – Vein, C – Blood capillary

(ii) 
1 – External layer of connective tissue
2 – Lumen
3 – Middle layer of smooth muscles and elastic fibres

(iii) A (Artery)- Oxygenated blood, B (Vein)- Deoxygenated blood

(iv) An artery has thick muscular walls and a narrow lumen. It does not have any valve. A vein on the other hand has thin muscular walls and a wider lumen. It has valves to prevent backflow of blood.

(v) At the capillary level the actual exchange of gases takes place.