Question

In the event of a lacerated femoral artery, the rapid loss in blood volume causes a precipitous decline in blood pressure. Describe in detail—from the local/cellular level all the way up to the systemic level—each of the steps both the heart and the kidneys will take to counter this loss in pressure and the downstream effects of each of these steps. Furthermore, many smaller local blood vessels will also be ruptured by the laceration. Describe in detail how these vessels, and the blood flowing into them, will act to limit blood loss.

Answer 1

Injury to the femoral artery will result in heavy loss of blood from the body. This will cause a drop in blood volume and blood pressure. As the BP and blood volume decreases the baroreceptors in the arteries gets activated. They sense the drop in BP and signals the medulla oblongata. The cardiac centre present in the medulla gets activated and increase the myocardial contraction. This results in increased stroke volume, heart rate and increased cardiac output. This causes increase in blood volume. The sympathetic nervous system is also stimulated that cause vasoconstriction and decreased venous reserve.
Low blood volume and BP also cause decreased perfusion of the kidneys. The kidneys in turn secretes renin which acts on liver to release angiotensinogen. The angiotensinogen is converted to angiotensin l and then angiotensin ll which results in vasoconstriction. Angiotensin ll acts on the adrenal cortex and posterior pituitary to release aldosterone and ADH. Both aldosterone and ADH acts on renal tubules to increase water and sodium reabsorption. This causes increase in blood volume and blood pressure.
The local response to injury are blood vessel vasoconstriction and activation of coagulation cascade to limit blood loss.
This is how body acts to restore homeostasis and minimize blood loss.