Endocrine system

Activity - Endocrine system

Explore the male and female endocrine systems by finding where the thyroid gland, adrenal cortex and the pancreas sit in the body.

Hormones

Hormones are chemical substances secreted by endocrine glands directly into the blood. Hormones are classified as proteins. Hormones are aimed at the ‘receptors’ of target organs. These receptors are located on the outer surface of the cells of those organs. Hormone secretion is controlled by three mechanisms: negative feedback, biorhythms and the central nervous system.

Glands

Glands are located throughout the body.

The pituitary gland is the master gland and is located at the base of the brain. It is divided into two parts - the anterior and the posterior pituitary. Each part secretes specific hormones that affect the action of other glands in the body.

The hypothalamus lies above the pituitary. It produces releasing and inhibiting hormones that either stop or start the production of other hormones in the body.

The pineal gland is located near the hypothalamus and houses our biologic clock. It produces melatonin which modulates sleep patterns.

The thyroid gland lies in the neck near the ‘Adams Apple’. It produces a hormone called thyroxine that regulates growth and general metabolism.

The thymus gland lies behind the sternum and between the lungs and gets smaller after puberty. It produces the hormone, thymosin , which plays a part in the body’s immune system.

The parathyroids lie within the thyroid capsule. They produce a hormone called parathyroid hormone that regulates, along with one of the hormones of the thyroid gland, the level of phosphorus and calcium in the blood. Calcium is important for many functions of the body, such as muscle contraction and conduction of nerve impulses.

The pancreas produces insulin and glucagon, which help regulate blood glucose levels. Insulin acts to lower blood sugar level and glucagon acts to raise blood sugar level.

The adrenal glands lie on top of the kidneys and secrete adrenaline hormone that helps the body grow and adapt to stress.

The ovaries in the female secrete oestrogen and progesterone. The rise and fall of these hormones determine the menstrual cycle and are important in causing the release of the ovum (egg) and in the maintenance of pregnancy. They are also responsible for the development of secondary sex characteristics.

The testes in the male produce testosterone, which causes the production of sperm. Testosterone is also responsible for the development of secondary sex characteristics.

Activity - Adrenal gland

Explore the cross section of the adrenal gland. Then have a look at where the thyroid gland sits in the body.

Summary of glands and their hormones