Term
| List and describe the function of the 2 primary layers of the skin. |
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Definition
Epidermis
- provides protection, when initially entered, begins healing process – scab – - scar tissue – provides seal but is not as strong as original
- the most superficial layer that contains cells, but not blood vessels
- hyperpigmentation may occur with repeated injury ex: hot spots, chronic dermatitis, etc
- surface film – made of sweat, sebum, various cells/chemicals
Dermis
- the middle layer that is composed of blood and lymph vessels, nerve fibers, and the accessory organs of skin such as glands and hair follicles |
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Term
| What is keratinazation and why is it an important process? |
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Definition
The normal foundation of keratin (a tough, waterproof protein) inside epithelial cells of the skin. As the epithelial cells mature, they fill with granules filled with keratin
Enables millions of dead cells to rub off or exfoliate daily at no expense to the health of the animal. An entirely new epidermis forms in humans every 7 to 8 wks |
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Term
| Identify the 6 layers of the epidermis, described in your textbook, from the deepest to the most superficial and list the function of each layer. |
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Definition
Stratum germinativum (aka stratum basale or basal layer) - the base layer – a single layer of mostly columnar cells capable of mitotic cell division. It is from this layer that all cells of superficial layers come from, incl keratinocytes and melanocytes. Only the cells in the deepest stratum of the epithelium undergo mitosis. As a result of this regenerative activity, cells transfer or migrate from the basal layer through the other layers until they are shed from the skin surface
Stratum spinosum - “the spiny layer” – formed by 8 – 10 layers of irregularly shaped cells with very prominent intercellular bridges or desosomes. When viewed under a microscope, these appear to pull adjoining points of the plasma membrane together for a spiny or prickly appearance
Stratum granulosum - – “the granular layer” 2 – 5 layers of dying, somewhat flattened cells that are filled w/ darkly staining granules and multi-layered bodies of glycophospholipids. In this layer of skin the nuclei are disappearing and the keratinocytes also form small bodies of glycophospholipids, which are part sugar and part phospholipids which are built up in multiple layers. Although there are some important biochemical activity at this stage, cells are starting to deteriorate. When this occurs high levels of lysosomal enzymes are present in the cytoplasm. Nuclei in process of breaking down. This level more represented in thick skinned patients rather than thin as not many cells at this stage are present in thin skinned patients.
Stratum lucidum - “the clear layer” – a few layers of squamous cells filled with a keratin precursor gives this layer a translucent quality. Keratinocytes in this layer are usually very flat, closely packed, and clear, typically nuclei are absent and cell outlines indistinct. These dying cells are filled with elodin which will eventually be transformed into keratin. Absent in thin skin but apparent in thick skin such as the soles of the feet and the skin of the hands.
Stratum corneum - composed of dead keratinocytes, continuously being shed and replaced. Held together by various phosplipids and form tough waterproof layer, fxns as barrier to water loss, trauma and many other things. If glycophosolipid layer is wasked away to prolonged exposure to water, water is absorbed and skin becomes puffy and wrinkled. Also hyperkeratosis |
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Term
| How is the dermis different from the epidermis? |
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Definition
| Unlike the epidermis, which is primarily cellular, the dermis is highly fibrous. Composed of dense irregular connective tissue that contains collagen, elastic and reticular fibers. Hair follicle, nerve endings, glands, smooth muscle, blood vessels and lymphatic channels are all found in the dermis |
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Term
| List and describe the functions of the skin. |
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Definition
- prevents desiccation
- reduces the threat of injury
- forms a critical barrier between the delicate inner workings of the body and the harsh elements of the external world
- body temp
- excretes water, salt, organic wastes
- sensory organ via touch and pressure
- engaged in the synthesis of vit D and in the storage of nutrients |
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Term
| What causes pigmentation of the skin? |
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Definition
- Caused by the presence or absence of melanin granules in the armlike extensions of the melanocytes.
- Grossly, no pigmentation is apparent if the granules are concentrated around the nucleus in the cell body of the melanocyte.
- As the granules move into the cellular “arms” and into the surrounding tissue, pigmentation becomes grossly apparent.
- The more granules in the arms of the melanocyte and surrounding tissue, the darker the pigmentation.
- The dispersion of the granules is controlled by the release of melanocyte-stimulating-hormone (MSH), which in turn is controlled by the intermediate lobe of the hypophysis.
- The melanosomes are transported to the tips of the cellular projections, where they are released into the intracellular space and ultimately absorbed by keratinocytes.
- The keratinocytes arrange the melanin on the side of the cell that has the greatest amt of sun exposure. In this way, the pigment acts to protect the keratinocytes from exposure to damaging UV rays |
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Term
| the 3 types of skin glands |
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Definition
sebaceous glands
sweat glands (eccrine and apocrine)
tail glands |
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Term
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Definition
– generally found all over body, except in certain specialized regions, such as paw pads and the planum nasale
– located in dermis and may be simple or complex alveolar structures
– most have a single duct that empties into a hair follicle but some have ducts that empty directly onto the surface of the skin (mucocutaneous jxns of the lips, labia vulvae, penis, prepuce, anus, eyelid, and in the ear canal
– the ones assoc w/ hair follicles are found in the triangle formed by the surface of the skin, the hair follicle and the arrector pilli muscle
– the alveoli are lined with epithelial cells that manufacture and store an oily, lipid substance composed primarily of glycerides and free fatty acids. Eventually the cells become so full that they rupture and release their contents, together w/ cellular debris, into the center of the alveolus. This white, semiliquid mixture is called sebu, (in sheep, the seb glands produce a substance called lanolin)
– because the epithelial cell is lost in the process of secretion, the s. gland is classified as a holocrine structure
– arrector pilli contracts, compresses gland, forces sebum from the alveolus through the duct into the hair follicle
– coats base of hair. Surrounding coat, important for trapping moisture to prevent excessive drying, keeps skin and hair soft, pliant, somewhat waterproof
– also possesses some anti-bacterial and antifungal properties, which reduce the skin’s level of infxn
– sensitive to changes in sex hormones – esp puberty in humans |
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Term
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Definition
- aka sudoriferous glands and are found over the entire body of most domestic species, incl pigs, horses, cattle, dogs, and sheep
- numerous in most species but only the horse produces a profuse sweat, which sometimes works itself into a white froth.
2 types of sweat glands – eccrine and apocrine
Eccrine sweat glands
- excretory portion of the eccrine gland consists of a simple, coiled tube located in the dermis or hypodermis, connected to the surface of the skin by a long duct
- in dogs, eccrine sweat glands are found only in the deep layers of fat and in the connective tissue of footpads
Apocrine sweat glands
- like eccrine, have a coiled, excretory portion buried in the dermis or hypodermis w/ a single excretory duct
- unlike eccrine glands, they empty into hair follicles rather than onto the surface of the skin
- in dogs, apocrine glands are located in the external hair canal
- interestingly, dogs w/ long hair have more sebaceous and apocrine glands in their external ear canal than do dogs with short hair. Dogs w/ more hair in their ear canals have an increased incidence of developing otitis externa |
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Term
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Definition
- most felids and canids have an oval region at the dorsal base of their tails called the tail gland
- thought to assist w/ the recognition and id of indiv animals and may be grossly recognizable by the presence of coarse, oily hairs
- apocrine and sebaceous glands are esp lg here
- like seb glands, appocrine glands are sesntive to changes in sex hormone levels – partic active during puberty and estrus |
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| an increase in scaling of the skin; sebum production may or not be increased |
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Definition
| pertaining to a drug or agent applied to the skin to control seborrhea or seborrheic dermatitis |
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Definition
| an agent that promotes loosening or separation of the horny layer of the epidermis – an antiseborrheic |
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| an agent that causes contraction after application to tissue |
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| – inhibit the growth of bacteria |
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| – substances that destroy tissue at the application site. They are used to destry excessive granulation tissue (proud flesh), superficial tumors (warts) or horn buds |
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Term
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| An agent that induces local inflammation to relieve inflammation in underlying or adjacent tissues |
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Term
| Formula to determine the amt of solute needed to make a desired amt of soln |
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Definition
| Grams of solute to q.s. to desired volume = % x desired volume/100 |
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Term
| The ways concentrations may be expressed |
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Definition
Parts
w/v = weight per volume for liquids
v/v = volume per volume for liquids
w/w = weight per weight for solids |
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Term
| When the amt of solute and the volume of soln are known, the % soln is calculated with the following formula.: |
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Definition
| % soln = grams of solute x 100 /vol of soln |
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Term
| To solve problems involving a change in concentration of a soln, use the following formula: |
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Definition
| Volume one x concentration one = volume two x concentration two |
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