Text В Hypophysis (the Pituitary)

We know the hypophysis to be a small oval body weighing about 0,5 g; it is located in the cranial cavity and is connected with the hypothalamus. The gland consists of an anterior lobe, an intermediate part and a posterior lobe; the borders between them can be seen only under the microscope. Experimental and clinical observations strongly suggest anterior lobe to be necessary for proper growth to adult stature, for normal development and function of the reproductive system and for control the ac-livities of other endocrine glands. The posterior lobe remains connected to the brain by means of the pituitary stalk, through which nerve impulses travel from the hypothalamus. The anterior lobe, so far as is known, receives no nerve fibres of any kind, and its control must then depend on the presence of substances in the blood. In spite of all this, there appears to be a way whereby the brain can exercise a fairly direct control over the anterior lobe. The blood vessels leading to the hypothalamus break up into capillaries; having passed through these capillaries, the blood is gathered into small veins; these veins pass downward so that they open into another set of capillaries in the anterior lobe. This is called the hypotha-lamic-hypophyseal portal system. Excision of the anterior hypophysis neither alters the lipid content of the liver nor inhibits the accumulation of large amounts of lipids in the liver.

The hypothalamus has been found to secrete special substances which regulate the secretion of the hypophysical hormones. The activities of the other endocrine glands are thus subject to neurohumoral regulation through the hypophysis.

Disfunction of the anterior lobe of the hypophysis is accompanied by changes throughout the organism. For example, excessive secretion of the growth hormone in childhood results in gigantism. Such people may grow to a height of 2,5-2,6 m. Excessive secretion of this hormone in adults results not only in excessive growth of the bones of the face, fingers and toes, but in enlarged nose, tongue and certain other organs. This disease is called ac-romegaly. Insufficient secretion of the growth hormone in childhood is accompanied by retarded growth (dwarfism). It is a relatively rare condition iissociated with either early atrophy or absence of the anterior lobe.

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Text В The Excretory Function of the Kidney	\|	Text A The Nervous System. Brain and Nerves

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