Sebaceous gland

“ The skin also contains little sacs, or follicles, in which the hairs originate. In its deeper portions are found two kinds of glands; sebaceous glands for the secretion of sebaceous or fatty matter to lubricate the skin, and the perspiratory or sweat glands, the latter of which will receive a more definite description shortly.
The Cuticle, or Epidermis.—At the upper portion of the true skin, new cells are being constantly formed, which become old in a short time and are pressed outward by the formation beneath them of other new cells. ”

“ It is an organized texture containing blood vessels, glands and nerves. It is composed of several layers; the outside, called the epidermis, is not supplied with blood vessels, and is produced by the under layers.
The glands of the skin are first, those which secrete the perspiration. This is poured out to keep the temperature of the body even, also to rid the circulation of many injurious substances. Then there are glands which secrete an oily matter which aids in preserving the softness and pliability of the skin. These glands are called sebaceous glands. ”

“ The skin, in which disturbances so readily occur at the time of the menarche, requires careful attention, all the more because it is precisely at this age that young girls have the greatest need of their personal charms. The skin of the face, which is often disfigured by comedones and acne, must be carefully guarded against the accumulation of sebum in the sebaceous glands by sedulous washing with warm water and a good soap. ”

“ For not only does the moisture of the skin favor its accumulation, but so also does the oily substance continually poured out by the small bottle-shaped glands—sebaceous glands, as they are called—which are found in the skin in great numbers, with their mouths opening on its surface. ”

“ As, however, the sebaceous glands on the face and elsewhere are the vestiges of former hairs and survive from a period when the whole body was hairy, they also tend to experience in an abortive manner this same impulse. ”

“ The sebaceous glands are branching tubes ending in follicles or sacs and opening into the hair follicles, lined by a very vascular fibrous network representing the dermis, and an internal layer of cells representing the mucous layer of the cuticle. The oily secretion gives gloss to the hair and prevents its becoming dry and brittle, and keeps the skin soft and supple, protecting it at once against undue exhalation of water and undue absorption when immersed in that medium. ”

“ The skin consists of two layers, the derma, or true skin, and the epidermis, or cuticle. It is the principal seat of the sense of touch, and on the surface of the upper layer are the sensitive papillae, which receive and respond to impressions; and within, or imbedded beneath it, are organs with special functions, viz., the sweat glands, hair follicles and sebaceous glands. Its value as a means of depuration is incalculable, as by it, vast quantities of the aqueous and gaseous refuse matter is conveyed from the body. ”

“ The liquid sweat, which in the ordinary state of the body is only given off in sufficient amount to prevent the skin from becoming over-dry, is secreted by the sudoriferous glands, whose ducts terminate in large numbers on the surface at every part. There is in the third place an oily material, formed for a similar purpose by the sebaceous glands, which are widely distributed, but fewer in number than the last. ”

“ It is highly probable that the causes of these modifications of the epidermis in diverse groups of animals could be traced to the habits and modes of life of each, but I make no attempt here to do this. It is also matter for inquiry, upon which no agreement has apparently been reached, how it came to pass that man has virtually lost his hairy coat, and in regard to the palms and soles of animals, what may be the reason that so few have any hair on them, and why man has no sebaceous glands, but has very numerous sweat-glands in these regions. ”

“ These glands on the face and forehead frequently appear, on the faces of the young, as small black points, which are incorrectly called "worms." It is true, that occasionally living animalcules are found in this thickened sebaceous matter, but they can only be detected by the aid of the microscope. This sebaceous matter acts not only to keep the skin flexible, and furnish for the hair an oily dressing, but it especially serves to protect the skin and hair, from the acridity arising from the perspiration. ”

“ The sebum frequently accumulates in the sebaceous ducts, giving rise to the minute black points often noticed on the face, back and chest in young adults, to which the term comedones is applied. A form of this disorder, of larger size and white appearance, is termed milium. These affections may to a large extent be prevented by strict attention to ablution and brisk friction of the skin, which will also often remove them when they begin to appear. The retained secretion may be squeezed out or evacuated by incision and the skin treated with some simple sulphur application. ”

“ Now, the skin of the head is additionally protected by an oily solution—the sebaceous secretion—which forbids entirely the absorption of any watery hair-dye. So, protected with nature’s waterproof cape and oiled epidermis, it is impossible for an aqueous solution to enter the body and destroy life. ”

“ The black appearance is really due the accumulation of dirt which gets under the edges of the skin of the enlarged sweat glands and cannot be removed in the ordinary way by washing, because the abnormal, hardened secretion of the gland itself becomes stained. ”

“ Excreting glands take from an organ or from a part substances which have outlived their usefulness and are to be cast out of the body, while the secreting glands form from the blood substances that did not exist in it before, but which are of use to the body, as the ptyalin of the saliva. A strict line cannot, however, be drawn between the two kinds of glands, most glands partaking more or less of both functions, though the sebaceous and sweat glands are probably purely excreting glands and the salivary glands are almost purely secreting. ”

“ Keratosis follicularis (Darier's disease, ichthyosis follicularis, ichthyosis sebacea cornea, psorospermosis) is a rare disease characterized by pin-head to pea-sized pointed, rounded, or irregularly-shaped grayish, brownish, red or even black, horny papules or elevations, arising from the sebaceous or hair-follicles. They are, for the most part, discrete, with a tendency here and there to form solid aggregations or areas. ”

“ On the scalp, however, the hair at birth is otten more deeply pigmented than that which succeeds it The sebaceous and sweat glands, like the hair follicles, are ingrowths of the stratum mucosum of the epidermis into the corium. ”

“ It is obvious that, the blacker the pigment, the less light and heat will be transmitted to excite these glands into activity. In the second place, there is a continual transudation of sweat from the minute vessels of the surface of the body through the epidermis at every point. The thicker or the more oily the scarf-skin, the less will the amount of this transudation be. If it be both thick and oily, as in many dark races, the quantity transuded will be reduced to a minimum; if it be thin and not oily, as in the fairest members of the white race, transudation will be copious. ”

“ The glands enclose no cavity, and there is no duct, so that whatever poisonous fluid their cells secrete is probably set free by the rupture of the cells and discharged into the grooves, along which it passes to the point of the spine, somewhat after the fashion of a hypodermic syringe. The origin of the gland-cells from an in-pushing of the epidermis is indicated by the continuity of the two structures near the point of the spine. Both in structure and in their relation to poison-glands each of the spines of the {177}dorsal fin is almost precisely similar to the opercular spine. ”

“ There is at first redness, usually of the bridge of the nose and it rapidly spreads to the cheeks, eyes, ears, etc. It is red, shiny hot, drawing, but with a distinct margin at its edges, showing how much skin is inflamed. It may take the form of vesicles. The eyelids may be so swollen as to close, the face and scalp greatly swollen with watery swelling of the eyelids, lips, eyes, ears, etc. The glands under the jaw may become enlarged. The general or constitutional symptoms may be severe. ”

“ A perforated spur, with a special secreting gland in connexion with it, is found attached to each hind-leg of the males of the existing species of Monotremata.
Scent-glands, &c.—Besides the universally distributed sweat-glands connected with the hair-system, most mammals have special glands in modified portions of the skin, often involuted to form a shallow recess or a deep sac with a narrow opening, situated in various parts of the surface of the body, and secreting odorous substances, by the aid of which individuals recognize one another. ”

“ The glands are the seat of congestion, and produce a modified secretion in excess, which dries into crusts instead of preserving its normal oleaginous consistency. As these glands open into the follicles of the eyelashes, their walls are implicated and shedding of the lashes is a common result. It may be assumed that this affection is often associated with the proliferation of microbes in the glands and gland ducts, while in other forms the presence of acari is the controlling factor. ”

“ The eyelids are developed as ectodermal folds, which blend with one another about the third month and separate again before birth in Man (fig. 7, κ) . The lachrymal sac and duct are formed from solid ectodermal thickenings which later become canalized.
It will thus be seen that the optic nerve and retina are formed from the brain ectoderm; the lens, anterior epithelium of the cornea, skin of the eyelids, conjunctiva and lachrymal apparatus from the superficial ectoderm; while the sclerotic, choroid, vitreous and aqueous humours as well as the iris and cornea are derived from the mesoderm. ”

“ The inner side is lined with a mucous membrane that is exceedingly sensitive, and thus aids in protecting the eye from any irritating substance. The looseness of the skin favors swelling from inflammation or the effusion of blood, as in a "black eye." The eyelashes serve as a kind of sieve to exclude the dust, and, with the lids, to shield against a blinding light. Just within the lashes are oil glands, which lubricate the edges of the lids, and prevent them from adhering to each other. ”

“ When we consider the functions of the skin, with its myriads of minute glands, innumerable little tubes, employed in removing the worn-out, useless matter from the system, we cannot fail to appreciate the utility of frequent bathing with soap and water. Unless these excretions are removed, the glands become obstructed, their functions are arrested, and unpleasant odors arise. Many persons think because they daily bathe the face, neck, and hands, dress the hair becomingly and remove the dirt from their clothing that the height of cleanliness has been reached. ”

“ The lining membrane of the nostrils is covered with papules similar in character to those on the skin, which form ulcers, and may lead to the destruction of the cartilaginous and bony textures of the nose. The diseased action extends into the throat, mouth and eyes, while the whole face becomes swollen and erysipelatous, and the lymphatic glands under the jaws inflame and suppurate. ”

“ In spring, as the days grow longer and the nights shorter, the increasing amount of light received day by day through the eyes stimulates the pituitary gland to produce the gonadotropic hormone which directly or indirectly, stimulates molt and, probably by enzyme action, the melanoblasts are caused to be present in cells of the hair follicle and the melanoblasts provide granules of melanin pigment which are incorporated in cells of the growing hair. These granules of pigment give the hair its color. ”

“ Now when even in our temperate climate the cutaneous glands play a not unimportant part in the morbid processes of Venereal disease, how much146 more must this be the case in Asia and Egypt, where the activity of the skin generally and that of the cutaneous glands in particular is even under normal conditions far more conspicuously energetic, as may be seen from the constant oily state of the skin, more particularly in Negroes. ”

“ Describe the symptoms of acne rosacea.
The disease may be slight or well-marked. Redness, capillary dilatation, and acne lesions seated on the nose and cheeks, and sometimes on chin and forehead also, constitute in most cases the entire symptomatology.
A mild variety consists in simple redness or hyperæmia, involving the nose chiefly and often exclusively, and is to be looked upon as a passive congestion; this is not uncommon in young adults and is often associated with an oily seborrhœa of the same parts. ”

“ It is common upon the scalp. The skin is covered with irregularly diffused, greasy, grayish or brownish scales and crusts, in some cases moderate in quantity, in others so great that large irregular masses are formed, pasting the hair to the scalp. If removed, the scales and crusts rapidly re-form. The skin beneath is found slate-colored, hyperæmic or mildly inflammatory, and exceptionally it has in places an eczematous aspect (eczema seborrhoicum) . Extraneous matter, such as dust and dirt, collects upon the parts, and the whole mass may become more or less offensive. ”