3 2 4 



HISTOLOGY. 



SEBACEOUS GLANDS. 



The sebaceous glands are simple, branched or unbranched alveolar 

 structures situated in the superficial layer of the corium and usually appen- 

 ded to the sheath of a hair (Fig. 370). In connection with the lanugo, 

 a large gland may be associated with a very small hair (Fig. 377), and in 

 exceptional cases as at the margin of the lip or on the labia minora, they 

 occur independently of hairs. They vary in size from 0.2 to 2.2 mm., the 

 largest being found in the skin of the nose where the ducts are macro- 

 scopic. None are found in the t palms or soles where hairs also are absent. 



The short duct is a prolongation of the outer sheath of the hair and is 

 formed of stratified epithelium, the number of layers of which decreases 

 toward the alveoli. The alveoli consist of small cuboidal basal cells, and 



Epidermis, j J , 



Corium. 



Cell with shrunken 

 nucleus. 



Cell with well devel- 

 oped drops of se- 

 cretion. 



Cell with develop- 



- ing drops of secre- 

 tion. 



- Cubical cell. 



FIG. 377. A, FROM A VERTICAL SECTION THROUGH THE ALA NASI OF A CHILD. X 40. C, Stratum 

 corneum ; M, stratum germinativum ; t, sebaceous gland consisting of four sacks, a, duct of the same ; 

 w, lanugo hair, about to be shed, h, sheath of the same, at the base of which a new hair, x, is form- 

 ing. 



B, FROM A VERTICAL SECTION OF THE SKIN OF THE ALA NASI OF AN INFANT. X 240. Sack of a 

 sebaceous gland containing gland cells in various stages of secretion. 



of large rounded inner cells in all stages of fatty metamorphosis. As the 

 cell becomes full of vacuoles the nucleus degenerates, and the cell is cast 

 off with its contained secretion. This in life is a semi-fluid material com- 

 posed of fat and broken down cells. 



Glandidae praeputiales are sebaceous glands without hairs which are 

 sometimes, but not always, found on the glans and praeputium penis. 

 The designation "Tyson's glands" is not justified since Tyson described 

 the epithelial pockets i to i cm. long which regularly occur near the fren- 

 ulum praeputii. Praeputial glands and crypts are not found in the em- 

 byro. The praeputium is united to the outer surface of the glans by an 

 epithelial mass, which often persists after birth and is broken up by the 

 formation of concentric epithelial pearls. Glands and crypts aje absent 

 from the praeputium and glans clitoridis. 



