Endocrine glands: pituitary, thyroid and parathyroid
Endocrine glands pour hormones straight into the blood. The pituitary is the master gland; the thyroid controls metabolism; the parathyroid controls calcium.
Endocrine vs exocrine glands
The pancreas is both: its duct carries digestive juice, and its islets release hormones into blood. It is a mixed (heterocrine) gland.
Where the pituitary sits
The pituitary gland is a pea-sized gland at the base of the brain. A short stalk joins it to the hypothalamus. It has an anterior lobe and a posterior lobe. It is called the master gland because many of its hormones control other glands. The hypothalamus, in turn, controls the pituitary.
Hormones of the pituitary gland
| Lobe | Hormone | What it does |
|---|---|---|
| Anterior | Growth hormone (GH, somatotropin) | Growth of bones and muscles |
| Anterior | Thyroid stimulating hormone (TSH) | Makes the thyroid release its hormones |
| Anterior | Adrenocorticotropic hormone (ACTH) | Makes the adrenal cortex release its hormones |
| Anterior | Gonadotropins: FSH and LH | Control the testes and ovaries; FSH helps ova and sperms form; LH causes ovulation |
| Anterior | Prolactin | Milk production after childbirth |
| Posterior | Vasopressin (antidiuretic hormone, ADH) | Kidneys take back water, so less urine is made |
| Posterior | Oxytocin | Contraction of the uterus at childbirth; release of milk |
Thyroid and parathyroid glands
| Gland | Where | Hormone | Job |
|---|---|---|---|
| Thyroid | Neck: two lobes on either side of the windpipe (trachea), joined by a narrow bridge (isthmus) | Thyroxine (T₄) and triiodothyronine (T₃), which contain iodine | Controls the basal metabolic rate (BMR), the energy used at rest; growth; body heat; brain development |
| Parathyroid | Four small glands on the back of the thyroid | Parathormone | Raises calcium in the blood; keeps bones and teeth healthy; needed for muscles and nerves |
How to draw the positions of the endocrine glands
- Draw a simple outline of the human body.
- Head: a small dot under the brain. Label pituitary, with hypothalamus just above it.
- Neck: a butterfly shape. Label thyroid. Draw four dots behind it. Label parathyroid.
- Chest, above the heart: a two-lobed shape. Label thymus.
- Abdomen, below the stomach: a leaf-shaped gland. Label pancreas (islets of Langerhans).
- On top of each kidney: a small cap. Label adrenal gland.
- Lower abdomen: label ovaries (female); outside the body in the scrotum, label testes (male).
The thyroid needs iodine to make thyroxine, so use iodised salt at home. Milk, curd, ragi and green leaves give the calcium that parathormone keeps in balance.
2 marks: “Why is the pituitary called the master gland?” Its hormones (TSH, ACTH, FSH, LH) control other endocrine glands such as the thyroid, adrenal cortex and gonads.
2 marks: “Name the hormones of the posterior pituitary and give their functions.” Vasopressin (ADH): water reabsorption in the kidneys. Oxytocin: contraction of the uterus at childbirth and release of milk.
4 marks: “List the hormones of the anterior pituitary and their functions.” GH: growth; TSH: thyroid; ACTH: adrenal cortex; FSH and LH: gonads and ovulation; prolactin: milk production.
Anterior pituitary: 'Go Tell All Friends Love Pets' (GH, TSH, ACTH, FSH, LH, Prolactin). Posterior: Vasopressin and Oxytocin.