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120 Cards in this Set
- Front
- Back
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What is the largest organ of the body?
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Integument
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What layers make up the integument?
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Epidermis (Epithelium)
Dermis (CT) Hypodermis (Adipose)- not really considered to be part of the skin |
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What are the two types of skin?
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Epidermis
Dermis |
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What type of epithelium makes up the Epidermis?
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Stratified Squamous Keratinized Epithelium
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What is the most numerous type of cell in the Epidermis?
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Keratinocytes
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What are keratinocytes?
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Keratin-producing cells that form the layers in the stratified epithelium.
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What are the five layers of keratinocytes in the epidermis? (outside to inside)
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1) Stratum Corneum
2) Stratum Lucidum 3) Stratum Granulosum 4) Stratum Spinosum 5) Stratum Basale (Germinativum) |
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Stratum Basale (Germinativum)
Structure? |
A single layer of cuboidal to columnar cells next to the dermis.
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What layer of the epidermis undergoes mitosis?
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Stratum Basale
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These cells have many desmosomes for attachment to withstand the friction and pressure that are constantly being put on the skin.
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Stratum Spinosum
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Stratum Spinosum
Structure? |
These cells are polygonal in the lower layers, but become flattened toward the surface. They have many desmosomes for attachment to withstand the friction and pressure that are constantly being put on the skin.
Tonofilaments fill the cytoplasm. |
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Tonofilaments fill the cytoplasm of what layer of the epidermis?
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Stratum Spinosum
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What cell layer of the epidermis are sometimes referred to as "prickle cells" and why?
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Stratum Spinsoum
During histological processing, the cells of this layer shrink while the desmosomes remain attached. This gives the appearance of spiny projections on the cells. |
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Stratum Granulosum
Structure? |
This layer is three to five cells thick in thick skin and one to two cells thick in thin skin. The cells in this layer are more flattened than the cells in the Stratum Spinosum.
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What is contained in the Stratum Granulosum?
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Keratohyalin Granules
Carbohydrates |
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Keratohyalin Granules
Where? Function? Staining? |
Stratum Granulosum
During keratinization, form a matrix which cements the keratin filaments together. Very basophilic. |
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Why does the Stratum Granulousm contain carbohydrates?
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The carbohydrates are linked to proteins and lipids. These are deposited into the intercellular space to act as a barrier to water loss and to act as an adhesive for cells of the Stratum Corneum.
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Which layer of epidermis represents the lowest portion of keratinization?
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Stratum Lucidum
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Which layer of the epidermis is not usually visible in thin skin?
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Stratum Lucidum
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Stratum Lucidum
Structure? |
The cells are very flat and contain no nucleus or organelles.
The cell membrane is thickened. Mixture of filaments and matrix = immature keratin. |
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The mixture of filaments and matrix in the Stratum Lucidum represents what?
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Immature Keratin
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What does the Stratum Lucidum look like under the light microscope?
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Sometimes not visible in thin skin.
Layer can be clear or translucent. |
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This epidermal layer is composed of many layers of dead cells filled with mature keratin.
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Stratum Corneum
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Dead cells of the Stratum Corneum are continuously exfoliated from the surface and replaced how?
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Through successive waves of mitosis and differentiation, by cells from the deeper layers.
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What are the functions of keratinocytes?
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1) To provide protection against physical and chemical trauma.
2) To prevent water loss from the body. 3) To produce Vitamin D. |
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The _____ provides a barrier against an invasion by microorganisms.
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Stratified Squamous Keratinized Epithelium.
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How is Vitamin D produced and why is it needed?
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The action of UV radiation on the keratinocytes forms Vitamin D which is needed for the proper absorption of calcium from the intestine.
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Psoriasis
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The cell turnover rate is increased three to four days. There is also an increase in the number of cels undergoing mitosis in the stratum basale. The epidermis becomes thickened. The keratinocytes do not differentiate completely and there is a decrease in keratohyalin synthesis.
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What is the normal turnover rate for the cells of the epidermis? How long does it take them to move through the cornified layer.
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Normally the turnover rate for the cells of the epidermis is from 26 to 42 days. It takes about 14 days for the cells to move through the cornified layer.
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Melanocytes
Produce? Located where? |
Produce melanin.
They are found between or beneath the keratinocytes of the Stratum Spinosum. Make up about 10% of the cells here. |
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What do melanocytes look like in an H & E?
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Appear as clear cells having a small, dark-staining nucleus and a clear cytoplasm.
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How do keratinocytes get melanin?
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In the Stratum Spinsoum, the melanocytes have dendritic processes that extend between cells and inject melanin into the keratinocytes.
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What is the function of melanin?
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to protect the cells undergoing mitosis from UV light
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What is the effect of UV light?
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Darkens preexisting melanin and stimulates its synthesis by melanocytes.
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What determines skin color?
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Depends on the activity of the melanocytes. The more active the melanocytes are, the darker the skin becomes. Repeated exposure to UV light causes an increase in the size and functional activity of melanocytes.
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Albinism
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Lack the enzyme tyrosinase.
This is needed in one step of melanin production. |
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Nevi
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Mole
A mole is a benign tumor of melanocytes. |
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Malignant Melanoma
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Melanomas are malignant tumors of melanocytes.
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Langerhans cells
What are they? Where are they found? |
Antigen-presenting cells.
Found in the epidermis. |
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Langerhans cells are derived from ____?
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Melanocytes
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These are difficult to distinguish from keratinocytes in an H & E stain.
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Langerhans cells
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What does UV radiation do to Langerhans cells?
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UV radiation interferes with the antigen-presenting capability of Langerhans cells.
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These cells are scattered in the thick skin of palms and soles.
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Merkel cells
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Merkel cells
Structure? Suggested Function? |
Free nerve endings form an expansion that covers the basal surface, suggesting that these cells function as mechanoreceptors.
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What is the structure of the dermal-epidermal attachment?
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The junction of the epidermis and dermis is irregular.
Projections of the dermis, the dermal papillae, extend into the epidermis. The epidermis dips into the dermis as the epidermal ridges. |
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What reinforces the dermal-epidermal attachment?
Where would this be most prominent? |
Dermal papillae and Epidermal Ridges.
More prominent in areas that take more stress, like the palms of the hands. |
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What are the layers of the Dermis? (outside to inside)
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1) Papillary Layer
2) Reticular Layer |
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Papillary Layer
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This is a loose areolar CT layer that includes the dermal papillae. It is rich in capillaries that nourish the epidermis.
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Reticular Layer
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Thicker than the papillary layer.
Composed of dense irregular CT. Has collagenous, elastic and reticular fibers that weave through it. |
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As a rule, the ______ is altered in conjunction with epidermal diseases and disorders that affect the superficial capillaries and venules, such as psoriasis.
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Papillary dermis
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This layer of the dermis is a less common site of pathogenic change.
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Reticular layer
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When the Reticular Layer of the dermis is diseased, it is usually a manifestation of ____, such as ____.
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Systemic disease
Scleroderma |
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What is the function of the extensive blood supply of the dermis?
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Temperature Regulation
Cutaneous Inflammation |
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What nerve receptors can be found in the dermis?
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Pacinian Corpuscles
Meissner's Corpuscles Free Nerve Endings |
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Pacinian Corpuscles
What? Where? Structure? |
Encapsulated receptors that sense pressure in the deep dermis and hypodermis.
Widely distributed throughout body. Unipolar cell body is located in the dorsal root ganglia. |
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Meissner's Corpuscles
What? Where? |
Encapsulated touch receptors.
Located in the dermal papillae. The neuron cell bodies of these receptors are found in the dorsal root ganglia. |
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Free Nerve Endings
what? where? |
Unencapsulated nerve endings that sense temperature and pain.
Found in the epidermis and papillary layer of the dermis. Their neuron cell bodies are found in the dorsal root ganglia. |
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Thermoreceptors
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Sense heat and cold.
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Nociceptors
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Sense pain
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What causes the aging of skin?
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Damage by UV light causes most of the visible signs of aging such as pigmentation changes and wrinkles.
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What happens to skin as it ages?
1) Elastic fibers? 2) Collagen fibers? 3) Blood vessels? 4) Hair and glands? 5) Stratum Basale? |
1) Elastic fibers become coarser, denser, and less resilient.
2) Collagen fibers decrease in number, organization, and density. 3) Blood vessels in the dermis become thick-walled yet leakier. 4) General loss of hair, sweat ducts and sebaceous glands. 5) The Stratum Basale becomes disorganized due to the breakdown in the normal process of cellular proliferation and organization. |
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Hypodermis
Where? What? Function? |
Layer of loose CT below the dermis (also called subcutaneous CT and superficial fascia).
Allows the skin to slide over the underlying tissues. |
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What are the derivatives of skin?
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Hair
Nails Sebaceous glands Eccrine sweat glands Apocrine sweat glands |
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What are hairs?
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Dead epithelial fibers made up of fused, keratinized cells
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Where does a hair grow from?
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Grow out of a hair follicle which is an invagination of the epidermis into the dermis. The expanded end of the follicle in the hypodermis is the hair bulb and houses the root of the hiar. There is a dermal papilla that projects into the bulb and has an extensive capillary network.
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Hair grows as a result of what?
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The mitotic division of cells in the germinal matrix, a cluster of epithelial cells that caps the dermal papilla.
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What are the divisions of a hair shaft?
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Internal root sheath- does not extend above the level of the sebaceous glands.
External root sheath- an extension of the cells of the epidermis |
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What are the parts of a hair shaft?
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Outer cuticle
Middle cortex Inner medulla |
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Where does hair color come from?
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Derived from eumelanin and pheomelanin produced by melanocytes in the hair bulb
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What is the smooth muscle associated with the hair follicle called?
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Arrector Pili muscle
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Where does the Arrector Pili muscle arise from?
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Arises in the CT of the dermis and inserts into the hair follicle.
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Arrector Pili Muscles are innervated by what part of the NS?
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Sympathetic NS
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What is the proximal part of the nail plate called?
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Nail Root
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What covers the Nail Root?
What is this made of? What is it called? |
Proximal Nail Fold
Stratum Corneum Eponychium (cuticle) |
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The nail plate corresponds to the ____?
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Stratum Corneum
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Hair grows as a result of what?
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The mitotic division of cells in the germinal matrix, a cluster of epithelial cells that caps the dermal papilla.
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What are the divisions of a hair shaft?
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Internal root sheath- does not extend above the level of the sebaceous glands.
External root sheath- an extension of the cells of the epidermis |
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What are the parts of a hair shaft?
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Outer cuticle
Middle cortex Inner medulla |
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Where does hair color come from?
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Derived from eumelanin and pheomelanin produced by melanocytes in the hair bulb
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What is the smooth muscle associated with the hair follicle called?
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Arrector Pili muscle
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Where does the Arrector Pili muscle arise from?
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Arises in the CT of the dermis and inserts into the hair follicle.
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What part of the NS innervates the Arrector Pili Muscle?
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Sympathetic NS
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What is the proximal part of the nail plate called?
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Nail Root
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What covers the Nail Root?
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Proximal Nail Fold
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What epidermal layer makes up the Nail Fold and what is its proper name?
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Stratum Corneum
Eponychium (cuticle) |
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The nail plate corresponds to the ___?
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Stratum Corneum
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How is the keratin of the nails different from that of the skin?
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Keratin in the nails is harder because it contains sulfur.
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What is the visible part of the nail plate called?
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Nail Body
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The nail plate rests on what?
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Nail Bed
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The pale, crescent-shaped area at the proximal part of the nail plate is the ___?
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lunula
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What is the lunula a result of?
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Result of a thickened nail bed in the area and immaturity of the keratin.
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There is a high rate of mitosis in what area of the nail?
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Lunula
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What is the region of increased mitotic activity in the lunula called?
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Nail Matrix
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What does the Nail Matrix give rise to?
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Nail Plate and Nail Bed
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What does a Sebaceous Gland produce?
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lipid substance called sebum
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Where are Sebaceous Glands located?
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Located in the angle between the hair follicle and the arrector pili muscles and have a short duct that opens into the hair follicle.
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Where in the body would Sebaceous Glands occur independent of hair shafts?
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Margins of the lips, glans penis, labia minora and areola of the breast.
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What type of secretions do Sebaceous Glands have?
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Holocrine
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What helps Sebaceous Glands to discharge their secretion?
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Contraction of the Arrector Pili Muscles
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Secretion of the sebaceous glands is almost ______ and is stimulated by ______.
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Continuous
Androgens |
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Eccrine Sweat Glands
Structure? Location? |
Simple, coiled tubular glands
Found throughout most of the body, but are concentrated in the palms, soles, and forhead. |
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Eccrine sweat glands ducts open ___?
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Directly onto a skin surface
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What type of secretion is produced by Eccrine Sweat Glands and what is its function?
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Watery secretion.
Maintenance of body temperature. |
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Eccrine sweat glands are under the control of ____ fibers in which the NT is ___?
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Sympathetic fibers
ACh |
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Where are Apocrine Sweat Glands found?
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Only in the axilla, anal and areolar regions.
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Where do Apocrine Sweat Glands ducts open?
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Their ducts usually open into a hair follicle.
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What type of secretion do APocrine Sweat Glands have?
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Thick and Oily.
Odorless until it undergoes bacterial degradation. |
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Do Apocrine Sweat Glands function in temperature regulation?
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No
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When do Apocrine Sweat Glands begin to function and why?
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Begin to function at puberty.
Under control of sex hormones. |
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Eleidin
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A transformation product of keratohyalin contained in the Stratum Lucidum.
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These skin cells are derived from the neural crest.
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Melanocytes
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These are star shaped cells found in a pale halo.
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Langerhans' cells
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This transduce responds to vibration and pressure.
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Pacinian's Corpuscles
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If looking at a hair shaft in cross section, what are the parts of the hair from outside in?
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Connective Tissue Sheath
Glassy Membrane External Root Sheath Internal Root Sheath Cuticle Cortex Medulla |
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What are the three stages of Hair Growth?
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1) Catagen
2) Telogen 3) Anagen |
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Catagen
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Cells in the cycling segment die, and the shaft loses its mooring. Meanwhile the basement membrane pulls the dermal papilla up to the bulge.
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Telogen
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The follicle rests. Hair may fall out now or in the next phase.
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Anagen
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On instructions from the dermal papilla, the lower part of the follicle rebuilds and begins producing hair again.
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These glands have large lumens compared to Eccrine Sweat Glands.
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Apocrine Glands
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Why does the cytoplasm of Merocrine and Eccrine Sweat Glands appear acidophilic?
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Contains actin
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