520 VERTEBRATE LIFE AND ORGANIZATION 



hormones is known as Cushing's syndrome. All three types of corti- 

 coids are produced in excess, and salt, water and carbohydrate metab- 

 olism is deranged. Females with this disease develop a pattern ol body 

 hair like the male, and have an enlarged clitoris. Fat is deposited in 

 the trunk, but not the legs, muscles are weak and tend to waste away, 

 bones are weakened and fracture easily, and the excess ot glucocorti- 

 coids produces a metabolic condition very similar to diabetes mellitus. 

 This can be cured by surgical removal of the adrenal. A different dis- 

 ease, called adrenogenital syndrome, results from the hyperactivity of 

 the adrenal cortex from birth. This disease is characterized by in- 

 creased production of adrenal androgens, which leads to precocious 

 sexual maturity in males and to masculinization of females. 



We can summarize the major roles of the several adrenal hormones 

 as follows: they regulate the concentration of sodium, potassium and 

 water in the body fluids and tissues, they participate in the control of 

 carbohydrate metabolism, accelerating the conversion of proteins to 

 carbohydrates, and they supplement the actions of the sex hormones. 



253. The Pituitary Gland 



The pituitary gland, or hypophysis cerebri, is an unpaired endo- 

 crine gland which lies in a small depression on the floor of the skull, 

 just below the hypothalamus of the brain, to which it is attached by a 

 narrow stalk. Its only known function is the secretion of hormones. The 

 pituitary has a double origin: a dorsal outgrowth (Rathke's pouch) from 

 the roof of the mouth grows up and surrounds a ventral evagination 

 (the infundibulum) from the hypothalamus (Fig. 30.6). Both parts are 

 of ectodermal origin. Rathke's pouch soon loses its connection to the 

 mouth, but the connection to the brain, the infundibular stalk, remains. 

 The hypophysis has three lobes: anterior and intermediate lobes de- 

 rived from Rathke's pouch and a posterior lobe from the infundibulum. 

 The pituitary, like the adrenal, is a double gland whose parts have 

 quite different functions. The anterior lobe has no nerve fibers and is 

 stimulated to release its hormones by hormonal factors reaching it 

 through its blood vessels. The anterior lobe receives a double blood 

 supply, arterial and portal. Some branches of the internal carotid artery 

 pass directly to the pituitary; others serve a capillary bed around the 

 infundibular stalk and the median eminence of the hypothalamus (Fig. 

 30.7). Portal veins from these capillaries then pass down the infundib- 

 ular stalk and empty into the capillaries surrounding the secretory cells 

 of the anterior lobe. The posterior lobe has a separate blood supply, 

 via the inferior hypophysial arteries. There is thus a direct route for 

 substances to pass from the hypothalamus to the anterior lobe by way 

 of these portal vessels. Axons are known to release active neurohumors 

 (e.g., acetylcholine or sympathin) at their tips and this portal system 

 provides a means by which substances released by the tips of axons end- 

 ing in the median eminence may be carried to the anterior lobe and in- 

 fluence its secretory rate. 



The anterior lobe is composed of irregular cords and masses of 



