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Epidermis
Contains 4 distinct types of cells?
- Is a keratinized stratified squamous epithelium that contains four distinct types of cells:
- keratinocytesMelanocytesTactile Epithelial CellsDendrictic Cells
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Keratinocytes
The most abundant epidermal cell, produce keratin, a tough fibrous protein that gives the epidermis its protective properties
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Thick Skin vs. Thin Skin
- Thick: covers the palms and soles, the epidermis consists of five layers
- Thin: covers the rest of the body, only four strata ("bed sheet") are present
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Stratum Basale
the deepest epidermal layer, is firmly attached to the underlying dermis along a wavy boderline
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Tactile Epithelial Cells
- AKA Merkel Cells
- are distributed sparsely among the keratinocytes
- each hemisphere-shaped tactile epithelial cell is intimately associated with a disclike sensory nerve ending and functions as a receptor for touch
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Melanocytes
- makes up about 10%-25% of the cells in the stratum basale
- spider shaped
- makes the dark skin pigment melanin
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How much skin does a person shed in a lifetime?
about 40 lbs
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The dermis has two regions:
- Papillary dermis
- Recticular Dermis
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Papillary dermis
the superficial 20% of the dermis, is areolar connective tissue containing very thin collagen and elastic fibers
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Reticular Dermis
accounts for about 80% of the thickness of the dermis, is dense irregular connective tissue
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Three pigments contribute to skin color:
- melanin
- carotene
- hemoglobin
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Hematoma
the general term for a clotted mass of escaped blood anywhere in the body
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Skin Appendages
- include nails, hair and hair follicles, sebaceous (oil) glands, and sweat glands
- derive from the epithelial cells of the epidermis, they all extend into the dermis
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Nail
is a scalelike modification of the epidermis that corresponds to the hoof or claw of other mamals
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Hair
is a flexible strand made of dead cells filled with hard keratin
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