Ch 20Chemical Coordination and Integration — Class 11 Biology, concept-first.

Every multicellular organism needs a way to make its distant organs and tissues work together as a single coordinated whole, rather than as a loose collection of independently functioning parts.

The hypothalamus is a small but functionally very important region forming the floor and part of the lateral wall of the third ventricle, at the base of the forebrain.

The pituitary gland (also called the hypophysis) is a small, pea-sized endocrine gland lying in a bony depression at the base of the skull called the sella turcica, connected to the overlying hypothal…

The pineal gland is a small, cone-shaped (hence its name, from the Latin for 'pine cone') endocrine structure attached by a short stalk to the roof of the diencephalon, deep within the brain, close to…

The thyroid gland is the largest of the endocrine glands in the human body, a soft, highly vascular, bilobed structure lying in the front of the neck, its two lobes situated one on either side of the…

The parathyroid glands are four very small, pea-sized (or smaller) endocrine glands, typically two embedded in the posterior surface of each of the thyroid gland's two lobes — an upper and a lower par…

The adrenal glands are a pair of small, roughly triangular or pyramid-shaped endocrine glands, one situated capping the upper pole of each kidney (hence their alternative name, the suprarenal glands).…

The pancreas is an elongated gland lying behind the stomach, in close association with the duodenum, and is unusual among the body's glands in being heterocrine — that is, in possessing both an exocri…

The gonads — the paired testes in the male and the paired ovaries in the female — are unusual among the organs of the body in serving two quite distinct roles simultaneously.

Having surveyed the individual endocrine glands and their hormones, it is important to understand how a hormone, once it has been carried by the blood to a target cell, actually produces its physiolog…

Beyond understanding how a single hormone molecule acts on a single target cell, it is equally important to understand how the endocrine system as a whole manages to keep the level of each circulating…

Every endocrine gland described earlier in this chapter secretes its hormone within a fairly narrow, appropriate physiological range under normal conditions, held there chiefly by the feedback mechani…

This chapter has covered the human endocrine system as the body's second, chemical coordination system, working alongside the faster nervous system through hormones — chemical messengers secreted dire…