Nephrons are the functional units of the kidney. Each nephron consists of a capsular region called the glomerular capsule or Bowman's_capsule that surrounds a tuft of capillaries, which are termed the glomerulus, and a series of tubules that including the:
loop_of_Henle (nephron loop), and
A nephron's capsular portion is located in the upper region of the kidney, which is known as the cortex (cortical_region). The nephron's elongated tubular section is located primarily in the lower area of the kidney, which is called the medulla (medullary_region). Hence, the difference in the appearance of the two regions.
Special cells associated with the nephron help regulate blood pressure and the rate of filtration of blood through the glomerular capsule's capillaries.
One group of cells is called the macula_densa (MD). The MD cells are chemoreceptors that are associated with the distal convoluted tubule (DCT).
The other cells are called granular (juxtaglomerular) cells. The granular cells are mechanoreceptors that are associated with the arteriole walls.
The MD and granular cells create the juxtaglomerular_apparatus (JGA), which assists in blood pressure regulation.