1. List four principle systemic capillary beds in order of ‘priority’, briefly e
ID: 70990 • Letter: 1
Question
1. List four principle systemic capillary beds in order of ‘priority’, briefly explain the logic of this ‘prioritization’. Compare and contrast centrally mediated shunting with autoregulation. Illustrate with real life scenarios/examples of each.
2. Compare the tunica media of the aorta (large artery) with that of the radial artery (medium artery). Explain how elastic rebound of the aorta and large arteries helps maintain a smoother BP curve (and therefore a steadier flow at the level of a capillary bed).
Explanation / Answer
(i) The four principle systemic capillary beds, in order of priority, are the brain, muscle, GI tract and skin. The top priority is the brain, since it controls and co-ordinate the entire body. Without it the body would not function properly. Then are the muscles, with which body can perform actions. Third in priority is the GI Tract which will break the food and help in absorption. Lastly skin, this plays role in thermoregulation. The logic is simple, there is not enough blood for every capillary bed, hence there is priority list depending upon which the blood flows.
(ii) Centrally mediated shunting is the shunting of the blood to or away from the muscles and GI tract. This does not include brain since it must always have good blood supply. Auto regulation is mediated by sphincters, and is localized in action. Auto regulation would help in improving supply of oxygen and removal of carbon dioxide depending upon the demand. An example of centrally mediated shunting would be shunting of blood away from the GI tract and pushing towards the muscles during sprinting, or soccer match or any intense activity.
(iii) The tunica media is a smooth muscle layer which determines the diameter of the lumen by constriction and dilation. In aorta, the tunica media is less effective than the radial artery. This allows for less constriction or dilation.
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