Regulation of body functions; glands

Glands are of three kinds: exocrine (salivary, sweat, tear, milk glands) – secretion leaves through a duct into an organ cavity or onto the skin; endocrine (thyroid, pituitary, adrenal) – no duct, hormones enter the blood; mixed (pancreas, sex glands, liver) – do both jobs. The thyroid gland, at the front of the neck near the larynx, is the largest endocrine gland and makes the hormone thyroxine, which contains iodine. Thyroxine speeds up metabolism and raises nervous excitability. If the hormone is too little or too much, a child’s growth and development and an adult’s general state are disturbed; in regions with too little iodine the gland can enlarge, causing goitre. To prevent it, iodised table salt is used; only a doctor identifies and treats such conditions.