The diagram below represents a certain category of blood vessels showing the role of a special structure in their walls :
(i) Name the kind of blood vessels shown.
(ii) What is the structure shown inside the blood vessels?
(iii) What is the role of these structures?
(iv) Are these structures present in any other kind of blood vessel? If so, name it.
(v) Towards which side of the figure (Top or Bottom) is the heart located?
(ii) Pocket valves.
(iii) These structures maintain the flow of blood in one direction only by preventing its back¬flow.
(iv) Yes. These are present in lymph vessels.
(v) The heart is located towards the top side of the figure.