876 



THE DEVELOPING ENDOCRINE GLANDS 



STOMOOAEUM 



MANDIBULAR PROCESS 



Fig. 365. The pancreatic islets and pituitary gland. (A) Origin of islet tissue from 

 developing pancreatic ducts and acini. 1 = young bud; 5 = older bud. (Modified from 

 Arey, '46, Developmental Anatomy, Philadelphia, Saunders.) (B-E) Diagrams of pi- 

 tuitary gland conditions in Petromyzon (B), Runa (C), Reptile (D), and Man(E). (Modi- 

 fied from Neal and Rand, 1939, Chordate Anatomy, Philadelphia, Blakiston.) (F) 

 Origin of Rathke's pouch material from inner layer of epidermal ectoderm in early 

 tadpole of Rana. (G-I) Developmental stages of hypophysis in human embryo. 



associated with the pancreas. In some teleost fishes, the two glands are sep- 

 arated although both are derived from the entoderm. The pancreatic islets are 

 classified as belonging to the solid, non-storage type of endocrine gland. 



2. Pituitary Gland (Hypophysis Cerebri) 



Previous to the latter part of the last century, the function of the pituitary 

 gland was presumed to be one of mucous secretion, hence the name pituitary 

 from the Latin, pituita, a nasal secretion. It was so regarded by Vesalius in 

 1543. The English anatomist, Willis, believed that the pituitary gland secreted 

 the cerebrospinal fluid. 



The pituitary gland (fig. 365E and I) is composed of three main parts as 

 follows: 



a. Anterior Lobe 



The anterior lobe (pars anterior) is composed of two subdivisions: 



( 1 ) a large anterior lobe (pars distalis), and 



(2) a smaller glandular mass (pars tuberalis). 



