Final answer:
Juxtaglomerular cells are part of the juxtaglomerular apparatus in the kidneys, secreting renin which plays a key role in blood pressure regulation and maintaining the glomerular filtration rate.
Step-by-step explanation:
The juxtaglomerular cells are specialized cells located in the kidney which play a crucial role in regulating blood pressure and filtration rate of the kidneys. These cells secrete the enzyme renin in response to a decrease in blood pressure or when stimulated by the sympathetic nervous system. Renin catalyzes the conversion of angiotensinogen into angiotensin I, which is further converted into angiotensin II by angiotensin-converting enzyme (ACE). Angiotensin II functions to increase blood pressure and stimulates aldosterone release, resulting in sodium and water retention, thus further increasing blood pressure. The juxtaglomerular apparatus, which includes the juxtaglomerular cells, is found at the point where the afferent and efferent arterioles meet with the initial part of the distal convoluted tubule (DCT) and plays a pivotal role in managing renal blood flow and glomerular filtration rate (GFR).