In the kidney, a tubular structure called the nephron filters blood to form urine. At the beginning of the nephron, the glomerulus is a network of capillaries that performs the first step of filtering blood. The glomerulus is surrounded by Bowman’s capsule. The blood is filtered through the capillaries of the glomerulus into the Bowman’s capsule. The Bowman’s capsule empties the filtrate into a tubule that is also part of the nephron.
mouseover for arrows Virtual microscopy
The juxtaglomerular cells (JG cells, or granular cells) are cells in the kidney that synthesize, store, and secrete the enzyme renin. They are specialized smooth muscle cells in the wall of the afferent arteriole that delivers blood to the glomerulus. The macula densa is an area of closely packed specialized cells lining the wall of the distal tubule at the point of return of the nephron. (adapted from wikipedia)