the glomerulus belongs to what system?

Question

is it the excretory or circulatory?

Answer 1

Excretory.
The glomerulus is part of the nephron in the kidney, which basically serves as a large filter for incoming blood. It filters out and reabsorbs water as well as sodium salts and numerous other ions, salts, etc. Whatever doesn't get reabsorbed into the blood constitutes urine.

Answer 2

Technicially it could be considered both. It's part of the urinary system. The Glomerulus is a filtration device for the blood and it's also involved in the formation of urine.
"A glomerulus is a capillary tuft surrounded by Bowman's capsule in nephrons of the vertebrate kidney. It receives its blood supply from an afferent arteriole of the renal circulation. Unlike most other capillary beds, the glomerulus drains into an efferent arteriole rather than a venule. The resistance of the arterioles results in high pressure in the glomerulus aiding the process of ultrafiltration where fluids and soluble materials in the blood are forced out of the capillaries and into Bowman's capsule." Judging from this definition I'd say circulatory.

Answer 3

Technically, it's renal. So that would be excretory. However, since it is renal, it would also be circulatory. To me, though, excretory and circulatory mean different things from glomerulus. I dunno. Maybe someone will give you a definitive answer. I hope so.