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Booktopia has Harry's Cosmeticology 7th Edition by J.B. Wilkinson. download a discounted Hardcover of Harry's Cosmeticology 7th Edition online from Australia's. At last, the version of this classic book has been published. This book, unlike others in the market, is about cometicology, i.e., it includes a very thorough . Wilknson J. B.; Moore, R. J.; Ship, Arthur G. M.D.. Plastic and Reconstructive Surgery: February - Volume 73 - Issue 2 - ppg Book Reviews: PDF Only.
People with personal planets aspecting Jupiter especially conjunct or Jupiter in the 1st house, 7th house, 10th house are usually are or seen as really awesome and are liked because of it.
Hi Sri, thank you for commenting. Before Neptune was discovered, Jupiter was considered the ruling planet of Pisces and thus he is still considered as the co-ruler of this mystical house. Because synastry is all about the connection between two people, and venus is the planet of love, I will break it down in its own post right here.
Despite falling out, this couple always seem to get back together because there is a connection that extends beyond the natural realm; it enters into the spiritual and the intuitive. You are likely to identify with each other emotionally, and to feel an instant affinity with each other, especially if Venus is within a couple of degrees of the first house cusp. Part of the reason this happens, is that the venus in the 8th house person feels very exposed with thier emotions and empathy, therfore hiding a relationship or the feelings within it is made to protect them from exposure- which is precieved as dangerous.
Random Astrology Observations Part 1 In synastry, Venus-Saturn harsh aspects can cause dislike of each other clothing style. So if I said Venus does one thing, the other person could do it as well. Venus in your Partners 12th house The Venus person will be highly complimentative with the house person which will help increase their overall self-confidence.
Posts about synastry written by fugitiveumbrellas. On a good day though 8th house person gets rewarding push towards spiritual growth which you like supporting. Soulful connection.
The physical attraction and sexual chemistry is likely to last a lifetime if this aspect shows up in synastry. Venus in the 11th: Someone who is friendly and loves to go out with you and your friends. Venus in Pisces 11th house opposing Uranus from the 6th and Pluto in the 5th. Now, there is always a bit of warning with ANY synastry aspect. See more ideas about Astrology, Relationship astrology and Astrology compatibility.
Venus in the 4 th House. The moon person has a psychological influence to the the Mars person to reproduce. Venus is a pretty easy-going personal planet so you might be the romantic ideal who brings out house person's sexuality on a good day. For example, if the composite Sun is effectively brought to the fifth house of person A, they will always feel the relationship is of a lighthearted and creative nature. You put a clear approach to synastry! Synastry and marriage aspects If you want to know which astrology aspects are interesting to look at, you can think about the aspects of personal planets made with saturn, and saturn is certain houses.
Venus in House Eight. The 12th house wants to dissolve. I think that 5th house connections can show what attracted two people in the first place. The Moon person may seem too clingy to the Venus person and the Moon person often feels that the Venus person is insensitive.
They need someone who is caring, sentimental and understanding. With your example, the house person is most affected in 5th house matters in their life and the planet person is affected by having a way to express themselves in that area of your life.
In all of these cases Vesta adds the extra dimension of a sacred and inviolable understanding. Energy, Survival and Conflict. Moon to Moon Synastry. Goals and objectives of both individuals may be similar and compatible. Venus to harmonise in the House of Shared Resources. On a bad day, there are problems to be worked out and they could get intense.
Venus In 8th House: Positive Traits. Rahu Venus in 12 th house or Venus rahu conjunction 12th house: Luxury prone will harm you in later part of life because you will finish you savings in enjoy before age The twelfth house rules the subconscious mind, dreams, intuition, instinct, and secrets. There is some potential for the twelfth house person to over idealize, or to have unrealistic expectations of the Sun person, and to become disappointed as a result.
A cabin in the woods, on boat, by the bonfire or the grill, or on a plane or bridge. Their energy Planet and house overlays in synastry are like permanent transits. Venus brings love to the 5th house person, the planet person finds someone to love.
Explore Kelly Well's board "Venus in 12th", followed by people on Pinterest. The house person can help the ascendant person to become more self Venus overlays in synastry. Moon conjunct Mars is a great synastry aspect for a loving sexual pleasure that both party will enjoy. Which are love, romance, respect and harmony affection for each other.
Pluto synastry. Psyche in Astrology. Second, look for someone who has planets in the same houses that you do. Venus in the 12th: Someone gentle and not overbearing. Mars in 8th House This combination produces dynamic business, scientific or occult relationships. With disharmonious aspects it can indicate the relationship possibly causing a deep wound to your psyche, a teaching lesson, it depends on communication. Obviously not always a good thing, but how is this in terms of synastry with combined aspects?
Synastry Series: Moon Overlays. Venus in the ninth often brings profitable, harmonious relationships with in-laws. The desire to connect with others can be thwarted by a fear of being hurt and taken advantage of. Moon-Mars aspects can be rather difficult to deal with.
Cancer - Capricorn axis is telling us a story about growing up. They are a typical indication of the idealization of the partner: a male with his Midheaven on his partner's Venus or Moon is likely to idealize her and to admire her as a goddess in all circumstances. Jupiter in the eighth house can indicate having a large quantity of sex with a partner think quantity over quality but can be good for having joint finances and sharing.
The 8th House describes the kind of lover you are along with your Mars and Venus and other chart stuff! Jewel Mayberry Truth in Aspect Astrology has a really informative YouTube series on Synastry and Composite aspects and overlays and I highly recommend watching her videos. Semi-sextile, doubtful. Your partner may feel like they are a secret in your life. It represents our subconscious, our blind spot, our vulnerability, and What it is like to have the Moon of one partner captured by the fourth house of another in synastry.
You might enjoy being around the 1st house person because in their presence you feel more vital and sexually desirable than you normally would. Active 8th house types people with the Sun, Moon or a plethora of planets in the 8th are super-strong extremophiles. If you want to marry, or to pair off for life, but are not sure what you want, do these things before you look at the Moon, Venus, or Mars: First, look at your sun by sign and house placement.
Synastry: Planet Overlays in Houses. If no other planets are in the 12th, the overlay may not even be noticed by the 12th House person. This is a very optimal placement to have in Synastry. For example, you may not be a needy person, but you find yourself being very needy or vulnerable around the house person.
In practicing synastry I've found the short answer is "no. A person with the Sun in the 12th house has a deep receptivity to the sensitive and watery world of collective dreams, longings, and yearnings. The Midheaven and Venus In Synastry I wanted to take a moment to talk about Venus and the MC and the influence these two have in your friendships and romantic relationships. Often with this synastry, the house person either really gravitates towards the Sun person, or absolutely abhors them.
According to the United Nations, the number of people worldwide aged 60 years or older will increase from 1 in 10 currently to 1 in 5 by By , the ratio of people aged 65 years or older to those aged 15—64 years will double in developed nations and triple in developing nations. This demographic shift compels us to confront the changes associated with aging and the various antiaging therapies [ 2 ].
Theories of Aging 2.
Modern Perspective Aging is complex phenomena generally defined by gerontologists as a process that results in an age-related increase of death rate or failure rate. Biologists define aging as the sum total of all changes that occur in a living organism with the passage of time and lead to a decreasing ability to survive stress, functional impairment and death [ 3 ].
The most common theories include Mutation Accumulation and Antagonistic Pleiotropy theory, the two theories posit that aging is due to pleiotropic genes with beneficial early-life effects but deleterious late-life effects antagonistic pleiotropy or mutations with purely deleterious late-life effects mutation accumulation [ 4 ].
Reliability theory consists of a body of ideas, mathematical models and methods directed to predict, estimate, understand and optimize the life span distribution of systems and their components [ 5 ]. Programmatic Theory states that aging is a preordained process due to an inherent genetic program, played out at a rate characteristic of each species, this theory takes in consideration aging genes, cellular senescence, telomere shortening, failure of apoptosis and longevity genes [ 6 ].
Stochastic Theory, which states that random cumulative environmental damage to genes and proteins produces aging and homeostatic failure, takes in consideration oxidative stress free radical damage , amino acid racemization and nonenzymatic glycolysation [ 7 ].
Other theories, such as Random Chemical Damage and Information Transfer theories [ 8 ] are based around the idea of genetic damage and impaired information transfer. Double-Agent theory is a new, unifying synthesis which argues that there is a tradeoffs between oxidative stress as a critical redo signal that marshals genetic defenses against physiological stress and oxidative stress as a cause of aging [ 9 ].
Ayurveda divides human life into—childhood up to the age 16 years ; youth and middle age [from 16 to 60 years charaka or 70 years sushruta and exhibits progressively the traits of growth vivardhamana, 16—20 years of age , youth youvana, 20—30 years , maturity sampoornata, 30—40 years , deterioration parihani, 40 years onwards which gradually sets in up to 60 years]; old age, wherein after 60—70 years the body elements, sense organs, strength, and so forth.
While describing aging, Ayurveda takes in consideration Prana life energy that performs respiration, oxygenation and circulation. It governs two other subtle essence ojas and tejas. Ojas the essence of the seven dhatus or bodily tissues is responsible for the auto-immune system and mental intelligence, it is necessary for longevity.
Displaced ojas creates the kapha-related disorders and decreased ojas creates vata-related reactions. Tejas the essence of a very subtle fire or energy governs metabolism through the enzyme system. Agni central fire or energy source in the body promotes digestion, absorption and assimilation of food. Tejas is necessary for the nourishing and transformation of each dhatu.
Aggravated tejas, burns away ojas reducing immunity and overstimulating pranic activity. Aggravated prana produces degenerative disorders in the dhatus. Lack of tejas results in over production of unhealthy tissue and obstructs the flow of pranic energy.
Just as it is essential to maintain balance amongst the tridosha—vata, pitta, kapha principles of motion, metabolism, structure, respectively, the dhatus and the three malas bodily wastes ; it is also important for longevity that prana, ojas and tejas remain in balance.
The tridosha play a very important role in the maintenance of cellular health and longevity. Kapha maintains longevity on the cellular level. Pitta governs digestion and nutrition.
Vata, which is closely related to pranic life energy, governs all life functions. Proper diet, exercise and lifestyle can create a balance among these three subtle essences, ensuring long life [ 12 ].
Skin Aging Skin aging is a complex process determined by the genetic endowment of the individual and the environmental factors [ 13 ]. The most obvious signs of aging skin are atrophy, laxity, wrinkling, sagging, dryness, a multiplicity of pigmented other blemishes and sparse gray hair [ 14 ].
Symptoms of chronological aging include dry and thin skin, fine wrinkles, abnormal blood vessels, age spots, benign and malignant skin tumors due to the deterioration of the skins immune system. Intrinsic skin aging is determined primarily by genetic factors and hormonal status. Photo aging is a separate process and largely involves damage to the collagen and the elastin fibers in the skin.
The deleterious effects of solar radiation on dermal connective tissue leads to visible manifestations of photo aging termed as premature aging. The UVB rays directly interact with the DNA of the cutaneous cells where as the deleterious effects of UVA are principally due to the formation of free radical oxygen, which result in an alteration in the nuclear and also mitochondrial DNA and also an activation of enzymes, metalloprotenase, capable of damaging the extra cellular matrix [ 15 , 16 ].
In Ayurveda, Charaka has described twak skin in six layers, he has named the first two as udakadara bahyatwak and astrikdhara and has not named the remaining four layers. Sushruta has described the same in seven layers viz. Avabhasini, the outermost layer, reflects the complexion and the quality of the Rasa Dhatu nutrient fluid, the first of the seven tissues of the body.
It also acts as a mirror as it indicates whether the physiology as a whole is balanced or imbalanced, and whether there is inner health or disorder; it also reflects the aura of the individual. Mamsadhara is the innermost layer is the platform for the skin's stability and firmness. When this layer is in balance, the skin looks young and supple.
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A skin product that has a vayasthapana antiaging effect nourishes this layer to help retard the aging process. Vata skin which is dry, thin, fine pored, delicate and cool to touch tends to develop wrinkles earlier than the other skin types. Pitta skin which is fair, soft, warm and medium thickness is photosensitive and has least tolerance to sun and is most likely to accumulate sun damage over the years.
Kapha skin which is thick, oily, soft and cool to touch tends to develop wrinkles much later in life than Vata or Pitta type but because of its thickness and oiliness, is more prone to accumulate ama toxins under the skin [ 17 , 18 ].
Wrinkles Wrinkles are result of dermal-hypodermal junction and shrinking of the superficial muscles, which have their points of insertion at the dermi. With reduction in muscle mass, skin thickness, diminished elasticity of dermal collagen and elastin and drying of the stratum corneum, the resulting behavioral change observed in the skin is loss of mechanical strength and viscoelasticity.
Development of fine wrinkles begins to take place at the age of 30s, reaching a peak in 40s but tending to rather decrease from the 60s and over, deep wrinkles are considered to be increasing in the 50s.
Wrinkles are formed and promoted by both internal and external factors. Internal factors include aging, changes in the endocrine system and nerve system and hereditary factors. External factors include exposure to UV rays and the oxidation or drying associated with UV exposure [ 19 ]. Antiaging Approaches The human skin loses its antioxidation ability with age, by exposure to the surrounding environment for a considerable period of time, and the skin undergoes emaciation as a result of the formation of peroxylipids.
Wrinkles are considered to appear as an outcome of this emaciation. Hence use of products, which enhance antioxidation, should be taken into consideration. Even brief exposure to UV radiation increases the activity of enzymes that break down the proteins collagen and elastin that provide structural support for the skin, thus pretreatment of skin with creams containing actives that can reduce the activation of these enzymes is recommended.
Use of sunscreens, which minimize the harmful effects of solar radiation is also advisable [ 20 — 22 ]. Antiaging Therapies 6. Retinoids are used in topical treatment of photo-aged skin, as it appears to increase the rate of cell division and improves wrinkling, coarseness, hyper pigmentation and roughness associated with over exposure to the sun.
It repairs photoaged skin by inhibiting collagenase and improving dermal vasculature, while also stimulating new collagen deposition, it promotes the down growth of rate ridges, restoring the undulating dermo-epidermal interphase and improves the skin's water barrier properties [ 23 ].
Hyaluronic acid helps to keep the surface of the skin hydrated, supple and less prone to wrinkling; when used in cosmeceutical products it forms an undetectable transparent film. Restylane hyaluronic acid , an injectable gel that acts as a filler to remove the wrinkle is used which binds to the water and provides volume to fill in larger folds of skin [ 24 ].
AHAs, BHAs can cause increased skin thickness, improvement in skin elasticity and increased collagen content and glycosaminoglycans. AHAs ascorbic acid, citric acid, gluconic acid, glycolic acid, lactic acid, malic acid, mandelic acid and tartaric acid and the BHAs salicylic acid and pyruvic acid are used in cosmetic products [ 25 ].
Vitamin C can accelerate wound healing; it is a potent antioxidant that protects fatty tissues from oxidation damage and play an integral role in elastin and collagen synthesis. It is capable of controlling inflammatory responses associated with UV exposure. Vitamin E has significant moisturizing properties, anti-inflammatory effects and may provide protection from UV damages.
It acts as an antioxidant and inhibits the formation of lipid peroxides and thus prevents skin aging. It is known to improve decreased function of the sebaceous gland and ameliorate excessive pigmentation in the skin [ 26 ].
Other topical antioxidants include leaf wax of Eucalyptus and Prunus, the seeds of black rice, leaves of barley, sesame seeds, rosemary green tea, turmeric, beta-carotene, coral extracts, aloe, and so forth.
Natural antioxidants include flavonoids anthocyanins; red grapes, blueberries, strawberries, red cabbage , quercetin onions, apple skins, berries, broccoli , catechins green tea, cacao , isoflavones soybeans , carotenoids carrots, sweet peppers, oranges , lycopene tomatoes , oligomeric proanthocyanidins or procyanidins grape seed extract.
EFAs are building blocks of cellular membranes which allow efficient transportation of nutrients from the extracellular space into the intracellular environment where metabolism takes place. Rosehip seed oil Rosa Mosqueta which is high in EFAs smoothes wrinkles by hydrating the skin and slows new signs of aging.
Estrogen topical application shows improvement in skin elasticity and firmness, increase in skin moisture and collagen synthesis and decrease in wrinkle depth. Lipoic acid is a potent scavenger with anti-inflammatory properties, it has beneficial effects on photo-aged skin [ 27 , 28 ]. Sunscreens are of two types: chemical sunblocks, such as PABA, PABA esters, benzophenones, salicylates and anthranilates contain molecules that mainly absorb the UVB radiation, while physical sunblocks, such as titanium dioxide, magnesium silicate, zinc oxide, red petrolatum and kaolin place a coating on the skin that reflects the light.
UVA exposure can produce elastic tissue damage, actinic skin damage and contribute to the formation of skin cancer. The only sunscreen agents that can completely block both the UVB and UVA wavelengths are physical or opaque sunblocks [ 29 ]. Chemical peeling is a safe and efficient treatment for moderate facial skin aging; in this treatment, chemicals remove layers of skin which results in smoother texture less evident fine wrinkles and evident lightening of hyperpigmentations.
Commonly used peeling agent is glycolic acid and pyruvic acid [ 30 ]. Noninvasive methods for assessing moisturizers. In: Waggoner WC, ed.
Clinical Safety and Efficacy Testing of Cosmetics. New York: Marcel Dekker, — Substantiating preformance claims. Cosmet Toilet ; 99 3 : 79—81, Trade correspondence. Judicial and Administrative Record — TC, in Ref. Definition of Cosmetics 17 United States v. An Article. Line Away, F. Sudden Change, F. Magic Secret, F. MD McNamara SH.
Performance claims for skin care cosmetics or how far may you go in claiming to provide eternal youthfulness. Food Drug Law J ; — The AHA phenomenon. Longevity ; Sept. AHA-type products proliferate in Cosmet Dermatol ; 6 12 , 24— Dry Skin and Moisturizers: Chemistry and Function. Cosmet Toilet ; — Alpha hydroxy acids are more than moisturizers. J Geriatr Dermatol 3 suppl. A : 33A—37A.
Actions of alpha hydroxy acids on skin compartments. Smith WP. Hydroxy acids and skin aging. Cosmet Toilet ; 41— Epidermal and dermal effects of topical lactic acid. Kurtzweil P. Alpha hydroxy acids for skin care. Alpha hydroxy acids in cosmetics.
Brody HJ. Chemical Peeling and Resurfacing 2nd ed. Louis: Mosby-Year Book, Inc. Draelos ZD. In: Advances in Dermatology. Yingling GL and Onel S. Cosmetic Regulation Revisited. Cosmet Dermatol ; 10 7 —39 Effects of Alpha Hydroxy Acids on Skin.
February 22, Reed RE. Vogue ; October Why Cosmeceuticals? Cosmet Toilet ; 8 — Piacquadio D. Cosmetic therapeutic vs. Privat Y. A new definition of cosmetology. Cosmetic Dermatology. London: Martin Dunitz, Ltd. Morganti P-F. The cosmetic patch. A new frontier in cosmetic dermatology. Elias University of California at San Francisco School of Medicine, San Francisco, California A general review of the microscopic structure of the epidermis and those epidermal derivatives that are distributed widely over the skin and, therefore, may be of interest in considerations of mechanisms of percutaneous absorption, will be presented here.
Both light and electron microscopic information will be discussed in order to give an integrated brief summary of the basic morphological picture.
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The epithelial component of the skin, the epidermis, is classified histologically as a stratified squamous keratinizing epithelium. It is thickest on the palms and soles Fig. It lies on the connective tissue component of the skin, the dermis, in which are located the blood vessels and lymphatic vessels. Capillary loops in the dermis come to lie in close apposition to the underside of the epidermis.
The epidermis, in common with other epithelia, is avascular. The living cells of the epidermis receive their nutrients by diffusion of substances from the underlying dermal capillaries through the basement membrane and then into the epithelium.
Metabolic products of the cells enter the circulation by diffusion in the opposite direction. As in the case of other epithelia, the epidermis lies on a basement membrane basal lamina.
This extracellular membrane, interposed between the basal cells of the epidermis and the connective tissue of the dermis, serves the important function of attaching the two tissues to each other.
The point of contact of the epidermis with this structure is the basal cell membrane of the basal cells. Along this surface the basal cells show many hemidesmosomes, which increase the adherence of the basal cells and therefore of the entire epidermis to the basement membrane and therefore to the dermis. In some locations, such as the renal glomerulus, the basal lamina has been shown to also play a role as a diffusion barrier to certain molecules.
The plane of contact between the epidermis and dermis is not straight but is an undulating surface, more so in some locations than others. Upward projections of connective tissue, the dermal papillae, alternate with complementary downgrowths of the epider- This chapter is reproduced with permission from Bronaugh RL, Maibach HI, eds. New York: Marcel Dekker, Inc. The spiral channel through the extremely thick stratum corneum sc carries the secretion of a sweat gland to the surface.
The stratum granulosum sg stands out clearly because its cells are filled with keratohyalin granules that stain intensely with hematoxylin. Hematoxylin and eosin. This serves to increase the surface area of contact between the two and presumably, therefore, the attachment. Within the epidermis are found four different cell types with different functions and embryologic origins: keratinocytes, melanocytes, Langerhans cells, and Merkel cells.
These will be considered in turn. The keratinocytes are derived from the embryonic surface ectoderm and differentiate into the stratified epithelium. Dead cells are constantly sloughed from the upper surface of the epidermis and are replaced by new cells being generated from the deep layers. It is generally considered that the basal layer is the major source of cell renewal in the epidermis. Lavker and Sun distinguish two types of basal cells, a stem cell type and a type that helps anchor the epidermis to the dermis, and an actively dividing suprabasal cell population.
The basal cells have desmosomes connecting them to surrounding cells and, as mentioned earlier, hemidesmosomes along the basal lamina surface. They have tonofilaments coursing through the cytoplasm and coming into close apposition to the desmosomes. These protein filaments are of the intermediate filament class and are made up principally of keratin.
Basal cells have the usual cell organelles and free ribosomes, the site of synthesis of intracytoplasmic proteins. As a result of the proliferation of cells from the deeper layers the cells move upward through the epidermis toward the surface. The strata spinosum, granulosum, and corneum are considerably thinner than in Figure 1. Microscopic Structure of the Epidermis 21 which allowed microscopists to define various layers.
The cells from the basal layer enter the stratum spinosum, a layer whose thickness varies according to the total thickness of the epidermis. The layer derives its name from the fact that, with light microscopic methods, the surface of the cell is studded with many spiny projections. These meet similar projections from adjacent cells and the structure was called an intercellular bridge by early light microscopists Fig. The number of tonofilaments increases in the spinous cells prickle cells and they aggregate into coarse bundles—the tonofibrils—which were recognizable to light microscopists using special stains.
Electron microscopy reveals the formation within the spinous cells of a specific secretory granule. These small, membrane-bound granules form from the Golgi apparatus and are the membrane-coating granules MCG; lamellar bodies; Odland bodies. They contain lipids of varying types which have become increasingly characterized chemically Grayson and Elias, ; Wertz and Downing, As the cells of the stratum spinosum migrate into the next layer there appear in their cytoplasm large numbers of granules that stain intensely with hematoxylin.
These are the keratohyalin granules and their presence characterizes the stratum granulosum. Electron microscopy shows that the granules are not membrane bound but are free in the cytoplasm. Histidine-rich proteins Murozuka et al.
The tonofilaments come to lie in close relationship to the keratohyalin granules. The membrane-coating granules are mainly in the upper part of the granular cell.
When observed by either light or electron microscopy there is an abrupt transformation of the granular cell to the cornified cell with a loss of cell organelles. In thick epidermis, the first cornified cells stain more intensely with eosin and this layer has been called the stratum lucidum. The interior of the cornified cell consists of the keratin filaments, which appear pale in the usual electron microscopic preparations, and interposed between them a dark osmiophilic material.
The interfilamentous matrix material has been shown to have derivations from the keratohyalin granule and is thought to serve the function of aggregation of the keratin filaments in the cornified cell Murozuka et al. When the cells move up into the stratum granulosum, keratohyalin granules k appear in their cytoplasm. Thus, the intercellular space in the cornified layer is filled with lipid material which is generally thought to be the principal water permeability barrier of the epidermis Grayson and Elias, ; Wertz and Downing, The stratum corneum has been compared to a brick wall, with the bricks representing the cornified cells, surrounded completely by mortar, representing the MCG material Elias, The cornified cell is further strengthened by the addition of protein to the inner surface of the cell membrane.
Two proteins that have been identified in this process are involucrin Banks-Schlegel and Green, ; Simon and Green, and keratolinin Zettergren et al. A transglutaminase cross-linking of the soluble proteins results in their fusion to the inner cell membrane to form the tough outer cell envelope of the cornified cell.
Desmosomes between the cells persist in the cornified layer. It can be seen that formation of an outer structure stratum corneum which can resist abrasion from the outside world and serve as a water barrier for a land-dwelling animal has proven incompatible with the properties of living cells. The living epidermal cells, therefore, die by an extremely specialized differentiative process that results in their non-living remains having the properties that made life on land a successful venture for vertebrates.
Distributed among the keratinocytes of the basal layer are cells of a different embryologic origin and function, the melanocytes.
In the embryo, cells of the neural crest migrate from their site of origin to the various parts of the skin and take up a position in the basal layer of the epidermis. They differentiate into melanocytes and extend long cytoplasmic processes between the keratinocytes in the deep layers of the epidermis.
Because they contain the enzyme tyrosinase they are able to convert tyrosine to dihydroxyphenylalanine dopa and the latter to dopaquinone with the subsequent formation of the pigmented polymer melanin.
The tyrosinase is synthesized in the rough endoplasmic reticulum and transferred to the Golgi body. From the latter organelle, vesicles with an internal periodic structure are formed which contain the tyrosinase. These are the melanosomes, the melanin-synthesizing apparatus of the cell.
Melanin is formed within the melanosome, and as it accumulates the internal structure of the melanosome becomes obscured. Seen with the light microscope the pigmented melanosome appears as the small brown melanin granule.
Within the keratinocyte varying numbers of melanosomes are often contained within a single membrane-bound vesicle. The classic method of demonstrating melanocytes is the dopa test. Sections of skin are placed in a solution of dopa and only the melanocytes turn a dark brown color Fig. Within the epidermis is another population of cells which were first demonstrated by Langerhans in By placing skin in a solution of gold chloride he showed that a number of cells in the epidermis, particularly in the stratum spinosum, turned black.
The cytoplasmic extensions of the cell give them a dendritic appearance. For many decades the nature of this cell type was unknown, including whether it was a living, dead, or dying cell. Electron microscopy showed that it was a viable cell in appearance, lacked desmosomes, and possessed a very unusual cytoplasmic structure—the Birbeck granule. Microscopic Structure of the Epidermis 23 FIGURE 4 A thick section of the epidermis was made with the plane of section running parallel to the surface of the skin and including the deep layers of the epidermis.
Dopa reaction shows whole melanocytes on surface view, illustrating their branching, dendritic nature. With the development of methods for identifying cell membrane receptors and markers in immune system cells it was shown that Langerhans cells originate in the bone marrow.
They are now thought to be derived from circulating blood monocytes, with which they share common marker characteristics. The monocytes migrate into the epidermis and differentiate into Langerhans cells. Considerable evidence shows that these dendritic cells capture cutaneous antigens and present them to lymphocytes in the initiation of an immune response.
Their population in the epidermis is apparently constantly replenished by the bloodborne monocytes.Obviously not always a good thing, but how is this in terms of synastry with combined aspects? Mercury trine Venus in synastry can mean the Mercury person finds it easy and comfortable to open up to the Venus person.
Having Saturn in a partners fifth house can be challenging.
New York: Chemical Publishing Co. Sunscreen, suntan and anti-sunburn products. Maibach, M. Botulinum toxin type A, when injected in hyperactive corrugator superciliaries or procerus muscles of the face that controls frowning, it produces a transient localized muscle weakness resulting in temporary improvement in frown lines.
Louis: Mosby-Yearbook, Inc.
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