The Human Endocrine Glands

What are the functions of the major endocrine glands?

The human endocrine system regulates a wide variety of activities. The major glands of the endocrine system include the pituitary gland, the hypothalamus, the adrenal glands, the pancreas, the thyroid gland, the parathyroid glands, and the reproductive glands.

Pituitary Gland The pituitary gland is a bean-size structure that dangles on a slender stalk of tissue at the base of the brain. As you can see in Figure 34–4, the gland is divided into two parts: the anterior pituitary and the posterior pituitary. The pituitary gland secretes hormones that directly regulate many body functions or control the actions of other endocrine glands.

Proper function of the pituitary gland is essential. For example, if the gland produces too much growth hormone (GH) during childhood, the body grows too quickly, resulting in a condition called gigantism. Too little GH during childhood causes pituitary dwarfism, which can be treated with GH produced by genetically engineered bacteria.

Hypothalamus The hypothalamus, which is attached to the posterior pituitary, is the link between the central nervous system and the endocrine system. The hypothalamus controls the secretions of the pituitary gland. The activities of the hypothalamus are influenced by the levels of hormones and other substances in the blood and by sensory information collected by other parts of the central nervous system.

The hypothalamus contains the cell bodies of neurosecretory cells whose axons extend into the posterior pituitary. Antidiuretic hormone, which stimulates the kidney to absorb water, and oxytocin, which stimulates contractions during childbirth, are made in the cell bodies of the hypothalamus and stored in the axons entering the posterior pituitary. When the cell bodies are stimulated, axons in the posterior pituitary release these hormones into the blood.

FIGURE 34–4 Pituitary Gland The pituitary gland is located below the hypothalamus in the brain. Some of the hormones released by the pituitary control other glands, while others affect other types of tissues.

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