Functions of the
• Structures that are part of the integument
• Overview of Functions
Vitamin D production
• Epidermis: Superficial layer of epithelial tissue.
• Dermis: Deep layer of connective tissue.
– Structural strength
• Subcutaneous tissue
– Not part of skin
– Loose connective tissue that connects skin to underlying structures
• Avascular; nourished by diffusion from capillaries of the papillary layer of the dermis
• Composed of cells arranged into layers or strata.
• Separated from dermis by basement membrane
• Cell types
– Keratinocytes: most cells. Produce keratin for strength
– Melanocytes: contribute to skin color. Melanin produced by these cells then transferred to keratinocytes. Same number of melanocytes in all people.
– Langerhans’ cells: part of the immune system
– Merkel’s cells: detect light, touch, and superficial pressure
• Keratinization: as cells move outward through the layers they fill with keratin, die, and serve as a layer that resists abrasion and forms permeability layer
Stratum basale (germinitivum)
– Deepest portion of epidermis and single layer.
Stratum spinosum Limited cell division.
Stratum granulosum In superficial layers nucleus and other organelles degenerate and cell dies
– Thin, clear zone. Found only in palms and soles
– Most superficial and consists of dead cells
Epidermal Layers and Keratinization
Thick and Thin Skin
• Thick skin
– Has all 5 epithelial strata
– Found in areas subject to pressure or friction
• Palms of hands, fingertips, soles of feet
– Fingerprints and footprints. Papillae of underlying dermis in parallel rows
• Thin skin
– More flexible than thick skin
– Covers rest of body
– Hair grows here
• Callus. Increase in number of layers in stratum corneum.
When this occurs over a bony prominence, a corn forms.
– Melanin: provides for protection against UV light.
Melanocytes. processes extend between keratinocytes.
• Albinism: deficiency or absence of pigment. Production determined by genetics, hormones, exposure to light
– Carotene: yellow pigment. From vegetables.
Accumulates in stratum corneum, in adipose cells of dermis, and in Subcutaneous tissue.
• Gives structural strength. C.T. with many fibers, fibroblasts, macrophages. Some adipocytes and blood vessels.
• Contains nerves, blood vessels, hair follicles, smooth muscles, glands, and lymphatic vessels.
• Sensory functions: pain, itch, tickle, temperature, touch, pressure, two-point discrimination.
Two Layers of the Dermis
• Two layers variable in thickness
– Papillary. Superficial (outer) 1/5. Areolar with lots of elastic fibers. Dermal papillae, capillary beds.
– Reticular: Deep (inner) 4/5. Dense irregular C.T. Collagen and elastic fibers. In the figure see: some adipose, hair follicles, nerves, oil glands, ducts of sweat glands, heat sensors. 5-12
Deep to skin
Consists of loose connective tissue with collagen and elastic fibers
Types of cells
– Adipose cells
– Superficial fascia
Contains about one-half of body’s adipose tissue. Functions as
– Energy source
Accessory Skin Structures: Hair
• Found everywhere on human body except palms, soles, lips, nipples, parts of external genitalia, and distal segments of fingers and toes
• Hair Growth
– Regular hair loss means hair is being replaced.
– Permanent hair loss: pattern baldness most common cause • Hair Color. Caused by varying amounts and types of melanin. Melanin can be black-brown and red
• Muscles. Arrector