SECTION XII 



THE SKIN, MAMMARY GLANDS 

 AND DUCTLESS GLANDS 



Rewritten for the Fifth Edition 

 By ABRAM T. KERR, B.S., M.D. 



PROFESSOR OF ANATOMY IN THE CORNELL UNIVERSITY MEDICAL COLLEGE 



THE SKIN 



THE covering which envelops the whole external surface of the body is 

 known as the common integument [integumentum commune]. This con- 

 sists of the cutis or skin proper and of appendages, the hair, nails, and skin 

 glands. The cutis is composed of a superficial epithelial layer, the epidermis, 

 derived from the ectoderm, and a deep connective tissue layer developed from the 

 mesoderm and divided into a superficial part, the cerium, and a deeper part the 

 tela subcutanea (figs. 1040, 1041). The subcutaneous tela is not usually con- 

 sidered as a part of the skin in a restricted sense, but as a superficial fascia, which 

 name is often applied to it. 



Fig. 1040. — Magnified Section of the Thickened Skin of the Palm of the Hand. X 6 



Corpus papillare 



Tunica propria 



Epidermis 



Cerium 



Retinaculum - 



Fat lobule ■ 



iVV-> 



Tela Subcutanea 



< 



The skin forms an encasement for the entire body broken only in the regions where it merges 

 with the mucous membranes. It serves not only as a direct physical protection to the under- 

 lying structures, but also, through its function as an organ of touch and of general sensibility, 

 it indirectly protects the body by the action of the special end organs and peripheral termina- 

 tions of the sensory nerves which thus bring the body into relations with its surroundings. 

 Through the radiation and conduction of heat to and from the blood circulating in it, through 

 the amount of secretion of its glands and the evaporation from its surface, the skin forms the 

 principal organ for the regulation of the bodily heat. By means of the action of its sweat and 

 sebaceous glands it possesses an important secretory function. It has also a minor role as an 

 organ of respiration and absorption. 



The surface area of the skin corresponds approximately to the surfaceof the 

 body and naturally varies with the size of the individual. H has been variously 

 estimated at from 10,500 to 18,700 sq. cm. for a medium-sized adult male. 

 81 1281 



