1. THE ANATOMY OF THE SKIN


A detail lecture on the anatomy of skin, including all the layers of epidermis and dermis, nails and hairs; the blood supply, nerves and pigmentary cells, sweat and sebaceous glands are all discussed….


SKIN DISEASES by M.E.DOUGLASS, M.D

In order to correctly understand the nature of the morbid changes that go on in the skin, and to comprehend correctly how and where these changes begin, it is necessary to have an accurate knowledge of the healthy skin in its different parts.

The healthy skin is, of course, the standard of comparison for all changes in the skin, and without the clearest perception of what the standard is the student can, of course, only fall into error from the inability to distinguish between what is normal and what is abnormal

The skin consists of an epithelium resting upon a connective tissue basis. The epithelium, which is composed of many layers of cells, is called epidermis, the connective tissue basis is called cutis vera, dermis, or corium. The surface of the dermis is thrown up into a number of elevations-papilla-which differ in size, form, complexity and arrangement in different regions of the body. Some are small, more or less conical elevations, simple papillae. In others, a broader primary elevation is divided at its summit into a number of secondary elevations; these are compound papilla. In many regions of the skin, as, for example, in the palms of the hands, the papillae are arranged in ridges separated by shallow furrows. The surface of the skin, that is, the contour of the epidermis, does not follow the papillary contour of the dermis; the papillae accordingly appear to plunge into and be covered up by the more even epidermis, the surface of which, however, is marked by the ridges and furrows spoken of above as well as by bolder creases and folds.

The surface of the dermis is not developed into a distinct and separable basement membrane, as is so often the case in a mucous membrane; but in the most superficial portions of the dermis the connective tissue shows little or no fibrillation and consists of a homogeneous matrix, in which are imbedded connective tissue corpuscles and extremely fine elastic fibres. This superficial portion of the dermis, which is especially well developed in the papillae, serves accordingly the purposes of a basement membrane, and sharply defines the distance from the overlying epidermis. At a very little distance from the epidermis, fibrillation makes its appearance, the bundles of fibrillae interlacing in a network which very closely set in the outer, more superficial layers, becomes more and more open in the inner, deeper parts, The connective tissue of the dermis thus passes insensibly into the subcutaneous connective tissue, in which thick interwoven bundles of fibrillae, bearing in transverse section a certain resemblance to sections of tendon bundles, form a tough open network, the larger spaces of which are frequently occupied by masses of fat cells of the subcutaneous adipose tissue. Elastic fibres are very abundant in the dermis proper, being very fine immediately beneath the epidermis and becoming coarser in the deeper parts; they are present also, though to a less extent, in the subcutaneous connective tissue. The skin, as a whole, is a very elastic structure.

Blood vessels are very abundant, forming close-set capillary outworks and looks immediately under the epidermis, especially in the papillae, and more open networks elsewhere; but no blood vessel passes into the epidermis. Lymphatic vessels and lymphatic capillaries are abundant in the dermis, being connected here as in other regions of the body with smaller “Lymph spaces.”

The consideration of the nerves of the skin will be deferred until we come to deal with the skin as an organ of sense; for though some of the cutaneous nerve fibres are efferent fibres distributed to the blood vessels, and probably to the sweat glands and other structures not directly connected with the sense of touch, by far the greater number are afferent fibres beginning in the distinct tactile organs, or otherwise serving as sensory structures.

Melford Eugene Douglass
M.E.Douglass, MD, was a Lecturer of Dermatology in the Southern Homeopathic Medical College of Baltimore. He was the author of - Skin Diseases: Their Description, Etiology, Diagnosis and Treatment; Repertory of Tongue Symptoms; Characteristics of the Homoeopathic Materia Medica.