Question

Renin is produced by:
A. Liver
B. Spleen
C. Juxtaglomerular cells
D. Stomach

Answer 1

Hint: Juxtaglomerular cells are one type of specialised cells present in the nephron of the kidney and maintain body homeostasis. Renin is a type of hormone usually secreted by the kidney.

Complete answer:
Liver usually secrets or produces bile whose main function is the excretion of toxic drugs from the body.
Spleen is the part of our lymphatic system which helps in removal of waste, by making our immune system strong.
Renin is produced by juxtaglomerular cells of the kidney. It is an important part of the renin-angiotensin-aldosterone system of the body. Volume of blood plasma, interstitial fluid means extracellular fluid is mediated by this renin-angiotensin axis. It also mediates vasoconstriction of arteries. Thus, arterial blood pressure is regulated. Renin is a hormone but also acts as an enzyme. Angiotensinogen is hydrolysed to angiotensin I by its activity. Cleavage of angiotensinogen is activated by renin, then it is converted into angiotensin II by angiotensin converting enzyme (ACE). Blood vessels constriction, increased ADH and aldosterone secretion, stimulation of hypothalamus for activation of thirst reflex as well as increased blood pressure etc. are results of activation of this axis. Perfusion pressure of the kidney can be restored by the activity of renin. The stretch receptor of vascular walls gets activated and renal perfusion pressure is altered via renin released from juxtaglomerular cells. Macula densa also sends signals for renin release from JG cells. Sodium level alteration in distal tubules of nephrons can be sensed by macula densa after which it gets activated. Stimulation of the sympathetic nervous system leads to renin secretion. Baroreceptors play a major role in renin release. JG cells are present in the kidney.
Stomach is the core for digestion and mainly produces digestive enzymes by aiding acid secretion and gastrointestinal motility.
 So, options a, b and d are incorrect. As their primary functions are related mainly to detoxification, immune system and digestion. But juxtaglomerular are the cells of kidneys which produce renin.

So, option C is correct.

Note:
The Juxtaglomerular complex is composed of macula densa and juxtaglomerular cells. Water and sodium level alteration activates the complex to maintain homeostasis.