Term
| what are usually termed "partial thickness" burns? |
|
Definition
|
|
Term
| why are melanin granules strategically placed over the nuclei? |
|
Definition
| to protect the cell from ultravioltet radiation (compared to an umbrella) |
|
|
Term
| what determines the difference in complexion between individuals? |
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Definition
| the rate at which melanin breaks down |
|
|
Term
| describe features of the epidermis |
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Definition
| stratified squamous, keratinized epithelium; has 5 identifiable layers in thick skin |
|
|
Term
| describe features of the dermis |
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Definition
| connective tissue; has 2 identifiable layers |
|
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Term
| is the hypodermis considered a layer of skin? |
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Definition
|
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Term
| what are the 5 layers of epidermis from most deep to most superficial? |
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Definition
1. Stratum germinativum
2. Stratum spinosum
3. Stratum granulosum
4. Stratum lucidum
5. Stratum corneum |
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Term
| the epidermis is ______ in origin. |
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Definition
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Term
| describe the stratum germinativum |
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Definition
| also called stratum basale - single layer of cuboidal or columnar cells which rest on a basal lamina. These basal cells are attached to the basal lamina by hemidesmosomes. Adjacent cells are attached by desmosomes. As name germinativum implies, this is a layer of cell mitoses |
|
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Term
| what is the stratum spinosum made up of? |
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Definition
| It is made up of polygonal cells that have spiny projections that form “intercellular bridges”. These bridges were once believed to represent sites of cytoplasmic continuity between cells. They are now known to be locations of desmosomes that contribute to the cohesiveness of the epidermis. Mitoses seen in this layer as well. |
|
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Term
| what is the malphigian layer? |
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Definition
| the stratum germinativum and stratum spinosum are frequently referred to as this |
|
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Term
| what is the stratum granulosum characterized by? |
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Definition
| This layer is characterized by basophilic granules, keratohyaline granules, which are not membrane bound. There are also membrane bound granules called membrane-coating granules. These granules contain glycosaminoglycans and phospholipids that are extruded out into the extracellular space to form a barrier to micro-organisms, foreign substances and most importantly water. |
|
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Term
| where is the stratum lucidum most prominent? |
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Definition
| It is most prominent in thick skin. In thin skin, this layer is often not identifiable. It is a translucent layer of normally very acidophilic cells that are devoid of nuclei and organelles. |
|
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Term
| what is the stratum corneum and what are other names for it? |
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Definition
- flattened keratin-
filled cells devoid of any organelles including the nucleus. They are called horny cells or squams. |
|
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Term
| describe 1st degree cutaneous burns |
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Definition
| damage to superficial epidermis; cells of stratum germinativum remain viable and regenerate epidermis |
|
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Term
| describe 2nd degree burns |
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Definition
Epidermis completely destroyed
Remnants of sweat glands and hair follicles in the dermis are able to regenerate the epidermis |
|
|
Term
| describe 3rd degree cutaneous burns |
|
Definition
Full-thickness burn
Destroys epidermis and dermis
Skin grafts are typically necessary
Loss of body fluids can cause hypovolemia and shock
With 15% of body area in adults
With 10% of body area in children |
|
|
Term
| what is the origin of the keratinocytes in the epidermis? |
|
Definition
|
|
Term
| what is the origin of melanocytes? |
|
Definition
|
|
Term
| what are langerhans cells? |
|
Definition
| dendritic, antigen presenting cells |
|
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Term
|
Definition
| specialized keratinocyte that is involved in touch |
|
|
Term
|
Definition
| They are the predominent cell type in the epidermis. They go through a very specialized differentiation to give rise to the protective dead cell layer, the stratum corneum. |
|
|
Term
| what is basal cell carcinoma? |
|
Definition
(70% of skin cancers)
They only arise in regions of skin containing sebaceous glands.
They typically occur after the age of 40 in fair skinned individuals and are usually found on the eyelids and bridge of nose.
Histologically basal cell carcinoma cells form discrete nests or islands of cells that resemble normal basal cells.
Basal cell carcinoma seldom metastasize. |
|
|
Term
| what is squamous cell carcinoma? |
|
Definition
| (20% of skin cancers). Fair-skinned blonds with outdoor occupations are particularly prone to this form of cancer. Histologically, there is a complete replacement of normal epithelium with pleomorphic cells. In later stages, the cells penetrate the dermis. The prognosis depends more on location, size and depth of penetration than on the degree of anaplasia. Relatively few squamous cell carcinomas (2-5%) metastasize to regional lymph nodes. |
|
|
Term
| what are langerhans cells? |
|
Definition
These dendritic cells are mainly found in the stratum spinosum.
They are NOT attached to adjacent keratinocytes by desmosomes.
They are similar to dendritic cells seen in lymphoid tissues.
They are responsible for engulfing invading micro-organisms in the epidermis and presenting antigens to lymphoid cells. |
|
|
Term
| where can langerhans cells migrate to? |
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Definition
| Langerhans cells can migrate out of the epidermis, enter lymphatics in the underlying dermis and travel to local lymph nodes |
|
|
Term
| what role do langerhans cells play in HIV positive individuals? |
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Definition
| There is now ample evidence that in AIDS patients and HIV positive individuals, Langerhans cell cytoplasm can contain HIV-1 in their cytoplasm. Some evidence suggest that these cells can actually serve as a reservoir for the virus. |
|
|
Term
| can langerhans cells be distinguished easily in H&E stained tissue? |
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Definition
|
|
Term
| what must one use to visualize langerhans cells? |
|
Definition
| gold impregnation techniques |
|
|
Term
| describe melanocytes and their origin |
|
Definition
neural crest origin - specialized cells located in stratum germinativum. Melanocytes can replicate slowly throughout life, thereby maintaining epidermal-melanin units (one melanocyte associates with a fixed number of keratinocytes). Epidermal-melanin units vary regionally. Epidermal-melanin units are not determined by race or gender.
Melanocytes are NOT connected to surrounding keratinocytes by desmosomes, but can be attached to the basal lamina by hemidesmosomes. Melanocytes contain large amount of the enzyme, tyrosinase. Tyrosinase is responsible for conversion of tyrosine through a series of steps to melanin |
|
|
Term
| what is cytocrine secretion? |
|
Definition
| melanin granules are injected into keratinocytes by a process |
|
|
Term
| do melanocytes need special stains to be seen? |
|
Definition
|
|
Term
| lysosomal degradation of melanin granules is slower in _____-skinned races. |
|
Definition
|
|
Term
| where do melanin granules take position? |
|
Definition
| above the nuclei of keratinocytes in the strata germinativum and spinosum; the rolw of the granules is to protect the dividing cells from UV |
|
|
Term
| what is a malignant melanoma? |
|
Definition
2% of skin cancers
Because of their neural crest origin (i.e. highly migratory cells), they are very metastatic.
Melanoma appears as nests of pigmented melanocytes that penetrate the epidermis. The cells also invade the dermis where they have access to blood vessels and lymphatics. |
|
|
Term
|
Definition
They are primarily found in thick skin where touch is acute.
They appear to be mechano-receptive cells as suggested by their association with nerve endings.
These specialized keratinocytes contain 80nm neurosecretory granules.
They cannot be distinguished from keratinocytes in H and E preparations. |
|
|
Term
| what are the 2 layers of the dermis? |
|
Definition
|
|
Term
| describe the papillary layer of the dermis |
|
Definition
| loose CT containing fibroblasts, mast cells and macrophages as well as some leukocytes - major part of the dermal papillae or pegs |
|
|
Term
| describe the reticular layers of the dermis |
|
Definition
| dense irregular CT - composed of collagen fibers (type I) and fewer cells than the papillary layer |
|
|
Term
| describe the papillary layer of the dermis |
|
Definition
| loose CT containing fibroblasts, mast cells and macrophages as well as some leukocytes - major part of the dermal papillae or pegs |
|
|
Term
| describe the reticular layer of the dermis |
|
Definition
| dense irregular CT - composed of collagen fibers (type I) and fewer cells than the papillary layer |
|
|
Term
| the distinction made between thick skin and thin skin is dependent on? |
|
Definition
| thickness of the epidermis |
|
|
Term
| where is thick (glabrous) skin found? |
|
Definition
| found in areas exposed to greater wear and abrasion; the palms of the hands and the soles of the feet; Thick skin has all five epidermal layers with a prominent stratum lucidum and a thick stratum corneum |
|
|
Term
| does thick skin have sebaceous glands? |
|
Definition
|
|
Term
| describe thin (hairy) skin |
|
Definition
found covering all the rest of the body
It typically has no distinct stratum lucidum and a quite thin stratum corneum |
|
|
Term
| where is the hypodermis located? |
|
Definition
lies deep to the dermis, but not considered part of the skin.
It is also called superficial fascia or subcutaneous CT.
loose CT with varying numbers of fat cells.
The fat cells vary in size according to the degree of obesity of the individual. |
|
|
Term
| what are the appendages of the skin? |
|
Definition
| hair follicles, sweat glands, sebaceous glands, mammary glands, nails |
|
|
Term
|
Definition
invaginations of epidermis which during periods of growth have bulbous terminal dilations -the hair bulb.
The bulb rests upon a dermal papilla that contains the capillaries that nourish the hair follicle.
The cells of the hair bulb are like those of the stratum germinativum. |
|
|
Term
| what are the two types of sweat glands? |
|
Definition
|
|
Term
| how do sweat glands develop? |
|
Definition
| as invaginations of epidermis into the underlying connective tissue |
|
|
Term
| what are eccrine sweat glands? |
|
Definition
| simple, coiled tubular glands - secrete a non-viscous fluid. Evaporation of the fluid cools skin. Eccrine sweat glands are also excretory. Sweat contains catabolites; have lightly staining, simple cuboidal secretory acini (arrows) and darker staining, stratified cuboidal ducts (arrowheads) |
|
|
Term
| what are myoepithelial cells? |
|
Definition
| specialized cells that squeeze the secretions from the sweat acini. |
|
|
Term
| what type of cells compose eccrine sweat glands? |
|
Definition
| epithelial, not smooth muscle; they are acidophillic because they contain actin filaments |
|
|
Term
| are eccrine sweat glands smooth muscle cells? |
|
Definition
|
|
Term
| are eccrine sweat glands acidophilic or basophilic? |
|
Definition
| acidophilic since they contain actin filaments |
|
|
Term
| where are apocrine sweat glands located? |
|
Definition
| in the axillary, areolar and anal regions |
|
|
Term
| the mammary gland is believed to be a highly modified _____ sweat gland. |
|
Definition
|
|
Term
| describe apocrine sweat glands |
|
Definition
| The ducts open into hair follicles and secrete a viscous, odorless fluid. The secretion attains a distinctive odor by the action of bacteria that reside on the skin |
|
|
Term
| sebaceous glands develop in association with _____ _____. |
|
Definition
|
|
Term
| where are sebaceous glands typically found? |
|
Definition
| the skin of the lips, the glans penis, and the clitoris where they are not associated with hair follicles |
|
|
Term
| what do sebaceous glands secrete? |
|
Definition
| sebum by holocrine secretion |
|
|
Term
| during what stage in life are sebaceous glands most active? |
|
Definition
| puberty when they respond to hormones; when clogged they are an ideal site for bacterial growth |
|
|
Term
| the cells at the base of the sebaceous gland are what type of cell? |
|
Definition
|
|
Term
| as the cells in sebaceous glands fill with sebum, their nuclei become ______ and eventually are lost. |
|
Definition
|
|
Term
| what are nails composed of? |
|
Definition
| keratinized epithelial cells |
|
|
Term
| what do nail plates provide a quick assessment of? |
|
Definition
| oxygenation of blood (blue indicates poor oxygenation (cyanosis)) |
|
|
Term
| describe the layers of the nail |
|
Definition
1. nail root - germinal region
2. underlying the nail plate is the nail bed which consists of stratum germinativum and stratum spinosum only (the malpighian layer)
3. the epithelium of the nail bed arises from the nail matrix. The matrix extends deep to the root.
4. nail grows from proximal end and slides over the nail bed. The bed does not contribute to the nail plate. |
|
|
Term
| what are free nerve endings in the epidermis? |
|
Definition
Unmyelinated axons that penetrate the basal lamina of the epidermis to enter the stratum germinativum and spinosum.
Ramify among the epithelial cells.
Involved in temperature and pain perception.
May also function in crude touch as evidenced by the fact that they are the only type of receptor found in the cornea. |
|
|
Term
| where are meissner's corpuscles most abundant? |
|
Definition
| in thick skin as well as in the skin of the lips and nipples |
|
|
Term
| what are meissner's corpuscles involved with? |
|
Definition
| discriminative touch, ability to discriminate two points |
|
|
Term
| in what region of thick skin are meissner's corpuscles found? |
|
Definition
|
|
Term
| where are pacinian corpuscles normally found? |
|
Definition
| in the dermis and often in the hypodermis of both thick and thin skin |
|
|
Term
| where are pacinian corpuscles especially abundant in the body? |
|
Definition
| the skin of the fingertips |
|
|
Term
| what is a pacinian corpuscle? |
|
Definition
| The corpuscle is traditionally described as a pressure sensor, but its rapid adaptation has lead some to believe the pacinian corpuscle signals a vibratory sense, i.e. it responds to a tuning fork placed against the skin. |
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