Glands of the skin

Chemical Acne Many chemical compounds induce skin lesions that are similar to acne. Oils, tar, creosote, and several cosmetic products induce chemical acne. These compounds induce keratinization of the sebaceous glands of the skin, obstruction of the glands, and formation of acne. Chloracne is a specific skin lesion that is induced by chemical compounds that are structurally similar to 2,5,7,8-tet-rachloro dibenzo-p-dioxin (TCDD). Chloracne is slow to heal and difficult to... 

The cuticle of the glands of the skin is partly enlarged by stretching, partly by subsequent development. Its principal purpose is unquestionably to prevent a too rapid exudation or loss of the secretions. In the case of all the persistent glands of the Lahiatce, Pelargonia, Compositce, etc., all of which possess a strong cuticle, a continuous volatilisation of... 

S-100 protein (38) is a 20-kDa calcium-binding protein composed of two subunits, S-lOOa and S-IOOP, which are differentially expressed by individual human tissues. For example, S-100(a,a) is found in myocardial and skeletal muscle cells S-100(a,P) is found in glial cells, melanocytes, chondrocytes, and adnexal glands of the skin and S-100(P,P) is found in Schwann cells and Fangerhans cells of the skin (39). There are currently monoclonal antibodies... 

Seborrhea is another long-term side effect of eating the oily fish. Wax esters are released through the sebaceous gland of the skin, blocking the... 

Fig. 3. Immunohistochemical expression of (a) hK7 by the epithelium of eccrine glands of the skin (monoclonal antibody, clone 73.2), (b) hK13 by the epithelium of the bronchus (monoclonal antibody, clone IIC1), (c) hK5 by the ductal epithelium of the parotid gland (polyclonal antibody), (d) hK7 by the esophageal glands (monoclonal antibody, clone 73.2), (e) hK13 by the gastric mucosa (monoclonal antibody, clone 2-17), (f) hK6 by the large intestine mucosa (polyclonal antibody), (g) hK10 in an islet of Langerhans in the pancreas (monoclonal antibody, clone 5D3), (h) hKll by the epithelium of the urinary tubuli (monoclonal antibody), (i) hKll by a papillary renal cell carcinoma (monoclonal antibody).

Additionally, Propionibacterium acnes, which thrives in the pilosebaceous glands of the skin, secretes enzymes that cause local skin irritation and inflammation, and is generally accepted to play a role in the dermatologic condition, acne (178). The role of other microbiota in the development of acne, however, is still under investigation. 

In dogs and cats, selamectin is rapidly absorbed from the skin into the bloodstream, where it kills heart-worm microfilaria. Selamectin is excreted into the intestinal tract where it kills intestinal parasites. Finally, selamectin is selectively distributed from the bloodstream into the sebaceous glands of the skin, forming reservoirs that provide persistent efficacy against fleas, ear mites, and sarcoptic mites. Active concentrations of selamectin are found in the plasma for at least 30 days. It is excreted mostly in the feces and a small unmetabolized amount in the urine. 

Antiseborrheic. An agent that relieves seborrhea i.e., an oil-secreting gland of the skin). 

Waxes are water-insoluble and not as easily hydrolyzed as fats and oils consequently, they often occur in nature as protective coatings on feathers, fur, skin, leaves, and fruits. Sebum, a secretion of the sebaceous glands of the skin, contains many different waxes. It keeps the skin soft and prevents dehydration. Waxes are used commercially to make cosmetics, candles, ointments, and protective polishes. 

Sheep and fur animals are protected primarily by their wool or hair. The fiber stmcture of the skin is very fine and has less strength than calfskin or other nonfur mammals. The sheepskin has a high concentration of hair foUicles and sebaceous glands. When taimed the fur skin has an open stmcture, is soft, and lacks strength relative to many other leathers. 

Three hormones regulate turnover of calcium in the body (22). 1,25-Dihydroxycholecalciferol is a steroid derivative made by the combined action of the skin, Hver, and kidneys, or furnished by dietary factors with vitamin D activity. The apparent action of this compound is to promote the transcription of genes for proteins that faciUtate transport of calcium and phosphate ions through the plasma membrane. Parathormone (PTH) is a polypeptide hormone secreted by the parathyroid gland, in response to a fall in extracellular Ca(Il). It acts on bones and kidneys in concert with 1,25-dihydroxycholecalciferol to stimulate resorption of bone and reabsorption of calcium from the glomerular filtrate. Calcitonin, the third hormone, is a polypeptide secreted by the thyroid gland in response to a rise in blood Ca(Il) concentration. Its production leads to an increase in bone deposition, increased loss of calcium and phosphate in the urine, and inhibition of the synthesis of 1,25-dihydroxycholecalciferol. 

Sweating, the other powerful heat loss mechanism actively regulated by the thermoregulatory center, is most developed in humans. With about 2,6 million sweat glands distributed over the skin and neurally controlled, sweat secretion can vary from 0 to 1 I7(h m ). The other, lesser, passive evaporative process of the skin is from the diffusion of water. The primary resistance to this flow is the stratum corneum or outermost 15 pm of the skin. The diffusion resistance of the skin is high in comparison to that of clothing and the boundary layer resistance and as a result makes water loss by diffusion fairly stable at about 500 grams/day. 

Anthropologic features of humans, their physical activities, ventilation capacities, and the state of their circulation all affect exposure to chemical compounds. Some of the physiological determinants of exposure will be dealt with below. Exercise typically increases cardiac output, facilitates circulation, increases the minute volume of ventilation, is associated with vasodilation of the skin circulation, and increases perspiration and secretory activity of the sweat glands. All of these changes tend to facilitate the absorption of chemicals through multiple routes. 

As you can judge from Table A, transition metal cations are frequently found in enzymes. The Zn2+ ion alone is known to be a component of at least 70 different enzymes. One of these, referred to as "alcohol dehydrogenase," is concentrated in the liver, where it acts to break down alcohols. Another zinc-containing enzyme is involved in the normal functioning of oil glands in the skin, which accounts for the use of Zn2+ compounds in the treatment of acne. 

Decreased activity of the thyroid gland results in hypothyroidism and, in severe cases, myxoedema. It is often of immunological origin and the manifestations are low metabolic rate, slow speech, lethargy, bradycardia, increased sensitivity to cold, and mental impairment. Myxoedema includes a characteristic thickening of the skin. Therapy of thyroid tumours is another cause of hypothyroidism. Thyroid deficiency... 

The pilosebaceous unit of the skin consists of a hair follicle and the surrounding sebaceous glands. An initial acne lesion called a comedo forms when there is a blockage in the pilosebaceous unit.8... 

Net chemical penetration of the skin is simply the sum of the accumulations by each of the mentioned routes and by other routes, for instance eccrine glands, where these contribute. The latter tiny glands are ubiquitously distributed over the body but are generally discounted in importance due to the limited fractional area they occupy and their unfavorable physiological states, either empty or profusely sweating. 

---