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39 Cards in this Set

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  • Back
Homeostatic Functions of Skin (6) and additional functions (2)
1 Regulation of body temperature
2 Regulation of body fluid volume
3 Protection from U.V. radiation
4 Protection from minor traumas
5 Protection against disease organisms
6 Excretion of water, fats

Additional functions:
Sensory reception
Vitamin D synthesis
Epidermis consists of 5 layers containing 4 cell types
Layers:
1)stratum basale
2)stratum spinosum
3)stratum granulosum
4)stratum lucidum
5)stratum corneum

Cell types:
1) Keratinocytes
2) Melanocytes
3) Langerhans Cells
4) Merkel Cells
Keratinocytes
-predominant epithelial cell type
-deeper part of epidermis consists of proliferating cells which are continually being pushed toward the surface. as they get farther from their source of nutrients, they become filled with keratin, which is family of fibrous, insoluble proteins;
Soft (skin)
Hard (hair & nails)
Stratum Basale
a single layer; cells
contact basement membrane via hemidesmosomes and attach to their neighbors by desmosomes
contains mitotically active stem cells
polyribosomes in these cells synthesize tonofilaments in the first stage of keratin formation
Stratum Spinosum
Tonofilaments aggregate to form bundles (tonofibrils)
Stratum granulosum - contains 2 types of granules
-Keratohyaline granules contain filaggrin which promotes formation of tonofibrils
-Lamellar granules contain stacks of lipid bilayers. discharge their glycolipid contents (ceramides) into what becomes known as the lipid envelope, which contributes to the Epidermal Water Barrier
Stratum Lucidum
-most visible in thick skin
-is subdivision of stratum corneum
-dying squamous cells that lack nuclei
-filaggrin has combined with the tonofibrils to form a dense matrix
stratum cornuem
-Dead cells (squames)
-cells contain mostly keratin
-Tonofibrils surrounded
by keratohyalin matrix
-the keratins, filaggrin, and a protein called Loricrin contribute to the formation of a Cell Envelope just beneath the plasma membrane that also contributes to the EPIDERMAL WATER BARRIER
Differences between thick and thin skin
Thick skin has all 5 layers, is hairless, and found only on the palms of hand and soles of feet
Thin skin has no stratum lucidum visible by LM and on most parts of body has hairs
melanocytes - taken up in which layers, desmosomal and hemidesmosomal attachments
-involved in process of pigmentation
-taken up by cells of s. basale, s. spinosum
-melanin accumulates in these cells in these 2 layers to protect their nuclei from ultraviolet rays
-melanin granules formed in specialized vesicular organelles (melanosomes)
-No desmosomal attachment to neighbors, but has hemidesmosomes at basal lamina
what rxn allow easy viewing of melanocytes
DOPA reaction, which exploits the process of melanin formation so that you can see the cells
how does melanin function, relation to skin color and suntans and albinism and Vitiligo
scatters UV rays to prevent injury to the deeper epidermal layers.
in upper layers, melanin fuses with lysosomes and is degraded
-skin color is due to the rate of melanin degradation, not to differing number of melanocytes
-in lighter skinned ppl, it is degraded quicker and is more concentrated in the deep layers of the epidermis
-suntans result from increased melanin production as well as darkening of previously formed melanin granules
-Albinism results when there is no tyrosinase activity or its defective (tyrosine forms melanin)
-Vitiligo – loss of
melanocytes
langerhans cells - found where, initiates what kinds of rxns, derived from and express what glycoprotein, part of what system
-in upper stratum spinosum
-initiate cutaneous hypersensitivity reactions (allergic contact dermatitis)
-sensitizes you to specific antigens b/c they are antigen presenting cells that stimulate T lymphocytes.
-Derived from the bone marrow and exress the CD1 antigen binding surface glycoprotein

Belong to Mononuclear Phagocyte System
Merkel Cells - found where, enable what reception and have what types of granules
-on basement membrane in the stratum basale
-contain neurosecretory granules
-enable touch and pressure reception
-sensory nerves connected to them
Dermis consists of 2 layers
Papillary layer and reticular layer
Papillary Layer - what type of CT, where is it, contains what (2), fingerprints? what does papillae do and how is it formed
-loose, vascular, connective tissue
-just below epidermis
-contains many blood vessels and sweat glands
-extends up into epidermis and forms Papillae — increases surfaces area to increase number of hemidesmosomes connecting dermis to epidermis
-dermal ridges give rise to fingerprints
Reticular Layer - what type of CT, what 2 types of collagen present, what are langer's lines, surgery precautions
-dense, irregular, avascular connective tissue
-Type I and Type III collagen bundles form a network that contains glands and hair follicles
-Langer’s lines—lines of tension within the skin
-in surgery, want to cut parallel to Langer’s lines of cleavage to leave the smallest scar possible; if don’t cut parallel to lines, skin ‘puckers’ and forms a large scar
Functions of Dermis (4)
1) Functions of Dermis
a) Supports epidermis and binds it to hypodermis
b) Capillary networks of dermis nourish epidermis and regulate body temp
c) Common site of inflammatory and immune responses d) Contains sensory receptors (3 types) and nerves that supply the skin
sensory receptors of dermis (3)
1) Mechanoreceptors—stimulated by pressure/vibration
i) Free nerve endings - pain, temp, light touch
ii) Merkel endings - touch
iii) Pacinian corpuscles- afferent axon in center, vibration, deep pressure
iv) Krause endbulbls
v) Meissner’s corpuscles-light touch
vi) Ruffini corpuscles - stretch

2)Thermoreceptors are stimulated by heat or cold
3)Nociceptors convey pain
Hypodermis - lies where, consists of what, contains what
-lies below the dermis
-loose connective tissue, possible with fat cells
-it is the superficial fascia of gross anatomy
-contains largest vessels that supply the skin
Sweat glands consist of two portions
a secretory portion and a duct protion
2 types of sweat glands found on body
1) Eccrine glands
2) Apocrine Glands
Eccrine Glands - produce what, epithelium, 2 types of cells found here and their secretions, main secretion, glands' association with hair follicles
-light cells produce watery fluid while dark cells contain granules and produce glycoproteins
-duct portion has stratified cuboidal structure
-main secretion is hypotonic sweat is released by Merocrine Secretion (exocytosis) (thus regulate body temp and also deal with excretory organs)
-these simple coiled glands are not associated with hair follicles
Apocrine Glands - duct opens up into what, present where, lumen size, epithelia of secretory and duct portion, mechanism
-duct opens up into hair follicle
-probably contain pheromones
-present in the axillary and circumanal regions, labia majora and areolae of breasts.
-secretory portion has large lumen
-secretory portion has pseudostratified structure
-duct portion has stratified cuboidal portion
-mechanism is MEROCRINE, not apocrine
Pilosebaceous apparatus - consists of
hair follicle, its associated sebaceous gland, and arrector pili muscle
Sebaceous Glands - production, mitosis, sebum (function)
-produce lipid
-the mitotically active cells at the base divide and the daughter cells are pushed up through the layers, eventually die and the cells burst and the lipid content is secreted (holocrine secretion)
-Sebum acts as moisturizer, preventing chapping of skin, and is released into hair follicle
Arrector pili muscle - consists of, function
-Consists of band of smooth muscle arising from the papillary layer and attaching at angle to hair follicle
-pulls up on bottom of hair follicle and down on epidermis -->goose bumps (mechanism to conserve heat-traps air in hair)
-sebum released as well
Hair Follicles - two sheaths found here, growth of hair, 3 concentric layers formed during growth of hair
-External and Internal Root Sheath
-External root sheath surround a Germinal Matrix, whose cells proliferate and keratinize to form a hair:
-Growth of hair occurs as a matrix of cells proliferate and push older cells towar the surface. As they ascend, they become keratinized and form 3 concentric layers:
a) Central Medulla - soft keratin
b) Coretx of hard keratin - melanin pigment
c) Cuticle - outermost layer consisting of scale-like cells (hard keratin)
Internal root sheath
-formed by the matrix and is a form of soft keratin
- disappears at level of sebaceous gland ducts
- deep to the internal root sheath is the cortex of the hair follicle
- a central medulla is composed of soft keratin
Hair Growth is not continuous, but occurs in 3 cycles
-Anagen: growth phase (80-90% of hairs are in this stage at all times)
-Catagen: rest, growth stops
-Telogen: quiescent, follicle atrophy, hair loss

*in scalp, 80-90% of hairs are in the anagen phase at any one time
Hair Color
results when the cells of the matrix and cortex take up pigment released by melanocytes. Gray hair results from decrease in tyrosinase activity in the melanocytes
4 parts of the nail
1) nail plate: visible, analogous to stratum corneum
- growth occurs from the nail matrix to produce hard keratin which develops into the nail plate

2) Nail matrix - site of hard keratin formation and nail growth

3)Cuticle (eponychium): protective growth that slides over the proximal portion of the nail

4) Lunula: thick layer of partially keratinized cells
- is white area distal to the cuticle
After a surgical Incision or Accidental Cut, within 24-48 hours epidermal continuity is re-established if the cut surfaces are brought in close proximity to each other through these 4 steps:
1) Epidermis Thickens due to cellular proliferation at its cut edge.
2) Epithelial cell clusters migrate and grow along the cut margins of the wound until they meet to become continuous again.
3) As proliferation continues, fibroblasts produce collagen
4) Collagen is laid down and a scar forms by 2nd week. Full epidermal thickness is reached in 5 days. Scar formation.

*skin appendages (hair, glands) that have been lost will not reappear.
Burns - 1st Degree Burn
-causes the capillaries and venules of the papillary layer to dilate, making the skin red, ex: mild sunburn
Burns - 2nd Degree Burn
-characterized by blistering b/c of plasma leakage.
-accumulating plasma causes epidermis to peel off
- skin breaks to expose a raw area
- epidermis can be renewed and burn is healed because follicles and glands remain in tact
Burns - 3rd Degree Burn
-occurs when both the skin and subcutaneous tissues are damaged. Damage to subcutaneous tissues
with destruction of hair follicles and glands; epidermal renewal only at edges b/c hair follicules and glands are destroyed
– grafts needed b.c its a slow process and burn may never heal will unless a graft is applied (graft - healthy tissue or organ removed from one site and transplanted to another)
Free Split Grafts
-a thin layer of skin consisting of epidermis and upper part of dermis is shaved off in one area of the body and placed on the damaged surface.
-graft is nourished by the tissue fluid until a new blood supply is established.
Free Full Thickness Grafts
-give better cosmetic effects.
-epidermis and the entire dermis are removed from the donor site, which then must be covered wit ha split graft
Artificial Skin
-newest technology
-after removal of damaged skin from 3rd degree burn, remaining tissue is covered with a mixture of collagen and other ECM molecules to encourage dermal renewal.
-This layer is covered w/ a thin layer of silicon
-Once dermal layer has begin to regenerate, the silicon layer is removed and ulta-thin skin grafts from the patient are placed on the area.
-If patient does not have much healthy skin left, EPIDERMAL CELLS FROM THE PATIENT CAN BE CULTURED and seeded on the artificial skin; culturing provides a continuous source of the patient's own skin