The human endocrine system is made up of glands. A gland releases chemicals called hormones directly into the bloodstream. The blood carries each hormone around the body to a target organ, where the hormone produces its effect.
Hormones are not as quick as nerves. A nerve impulse reaches its target almost at once, but a hormone has to be carried in the blood. So compared with the nervous system the effects of hormones are slower, but they act for longer.
The pituitary gland, in the brain, is the master gland. It releases several hormones into the blood in response to conditions in the body. These hormones act on other glands and stimulate them to release their own hormones, which bring about the final effects.
You need to know where the glands are. The pituitary gland is in the brain and the thyroid gland is in the neck. The adrenal glands sit above the kidneys and the pancreas lies below the stomach. A woman has two ovaries in her lower abdomen, and a man has testes.
