534 



CHORDATE ANATOMY 



Pituitary Gland. The human pituitary gland is a flattened oval body, 

 its longest diameter averaging lo to 12 mm., located at the base of the 

 brain near the optic chiasma, where it is attached by a stalk to the lower 

 end of the infundibulum. Lodged in a cavity, the sella turcica, in the 

 sphenoid bone, the pituitary is as safe from injury as possible. (Fig. 296) 



Like the suprarenals, the pituitary is formed of two elements of diverse 

 origin and function. The chief parts are a larger anterior glandular 

 lobe, and a smaller posterior nervous lobe partly surrounded by the 

 anterior lobe. Between the two major lobes are two smaller glandular 

 masses, the pars intermedia and the pars tuberalis. Blood is richly 

 supplied from the adjacent arterial circle, while numerous veins drain the 



CORPORA QUADRIGEMIN/^ 

 PINEAL ORGAN ! 



POST commissure; | 



THIRD "'^"'■^"'^' "^ -' 



MAS. INTERMEDIA,^, 

 CHORlOIDurT '{ 

 CORPUS ' ' 



CALLOSUM 



FORNIX 



MEDULLA 



OPTIC CHIASMA'^ 

 INFUNDIBULUM 



MAMMILLARY BODY 

 SPHENOID BONE 



^^POSTERIORIlobE of PITUITARY 

 ^^ INTERIOR J 



Fig. 2g6. — A median section of the human brain-stem, showing the relations of the 

 pituitary gland. (After Sobotta.) 



blood into the venous circle and the basilar plexus of veins. Nerves are 

 supplied from the carotid plexus and the infundibulum. In the pars 

 intermedia some colloid-filled foUicles resembUng those of the thyroid occur 

 among the cell cords. The cells of the posterior lobe are chiefly neuroglia 

 cells with numerous connective-tissue fibers. 



One of the important functions of the anterior lobe is the stimulation 

 of growth. Enlarged pituitary in early life is accompanied by excessive 

 growth of bone. Deficient secretion, on the other hand, produces a certain 

 type of dwarf, the ateliotic dwarf or "midget." 



After the growth of the long bones has ceased, as in the normal adult, 

 it is of course impossible to stimulate further growth in height. But 



