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Appendages of the Skin
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© 2015 Pearson Education, Inc.
Appendages of the Skin Cutaneous glands are all exocrine glands Sebaceous glands Sweat glands Hair Hair follicles Nails © 2015 Pearson Education, Inc.
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• Sebaceous (oil) gland • Hair follicle • Hair root
Figure 4.3 Skin structure. Hair shaft Dermal papillae Epidermis Papillary layer Pore Appendages of skin • Eccrine sweat gland • Arrector pili muscle Dermis Reticular layer • Sebaceous (oil) gland • Hair follicle • Hair root Hypodermis (subcutaneous tissue) Cutaneous vascular plexus Nervous structures • Sensory nerve fiber Adipose tissue • Lamellar corpuscle • Hair follicle receptor (root hair plexus)
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© 2015 Pearson Education, Inc.
Appendages of the Skin Sebaceous (oil) glands Produce sebum (oil) Lubricant for skin Prevents brittle hair Kills bacteria Most have ducts that empty into hair follicles; others open directly onto skin surface Glands are activated at puberty © 2015 Pearson Education, Inc.
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Figure 4.7a Cutaneous glands.
Sweat pore Eccrine gland Sebaceous gland Sebaceous gland duct Dermal connective tissue Hair in hair follicle Secretory cells (a) Photomicrograph of a sectioned sebaceous gland (100×)
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© 2015 Pearson Education, Inc.
Appendages of the Skin Sweat (sudoriferous) glands Produce sweat Widely distributed in skin © 2015 Pearson Education, Inc.
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© 2015 Pearson Education, Inc.
Appendages of the Skin Two types of sudoriferous glands Eccrine glands Open via duct to pore on skin surface Produce sweat © 2015 Pearson Education, Inc.
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© 2015 Pearson Education, Inc.
Appendages of the Skin Sweat: Composition Mostly water Salts and vitamin C Some metabolic waste Fatty acids and proteins (apocrine only) Function Helps dissipate excess heat Excretes waste products Acidic nature inhibits bacteria growth Odor is from associated bacteria © 2015 Pearson Education, Inc.
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Figure 4.7b Cutaneous glands.
Sweat pore Eccrine gland Sebaceous gland Dermal connective tissue Eccrine gland duct Secretory cells (b) Photomicrograph of a sectioned eccrine gland (205×)
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© 2015 Pearson Education, Inc.
Appendages of the Skin Two types of sudoriferous glands Apocrine glands Ducts empty into hair follicles Begin to function at puberty Release sweat that also contains fatty acids and proteins (milky or yellowish color) © 2015 Pearson Education, Inc.
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© 2015 Pearson Education, Inc.
Appendages of the Skin Hair Produced by hair follicle Root is enclosed in the follicle Shaft projects from the surface of the scalp or skin Consists of hard keratinized epithelial cells Melanocytes provide pigment for hair color Hair grows in the matrix of the hair bulb in stratum basale © 2015 Pearson Education, Inc.
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Figure 4.8c Structure of a hair and hair follicle.
Fibrous sheath Hair follicle Epithelial sheath Hair matrix (growth zone) in hair bulb Melanocyte Hair papilla containing blood vessels Subcutaneous adipose tissue (c)
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© 2015 Pearson Education, Inc.
Appendages of the Skin Hair anatomy Central medulla Cortex surrounds medulla Cuticle on outside of cortex Most heavily keratinized region of the hair © 2015 Pearson Education, Inc.
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Figure 4.8b Structure of a hair and hair follicle.
Cuticle Cortex Medulla (b) Hair
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© 2015 Pearson Education, Inc.
Appendages of the Skin Associated hair structures Hair follicle Dermal and epidermal sheath surround hair root Arrector pili muscle Smooth muscle Pulls hairs upright when person is cold or frightened Sebaceous gland Sudoriferous gland © 2015 Pearson Education, Inc.
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Figure 4.8a Structure of a hair and hair follicle.
shaft Arrector pili Sebaceous gland Hair root Hair bulb in follicle (a)
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© 2015 Pearson Education, Inc.
Appendages of the Skin Notice how the scale-like cells of the cuticle overlap one another in this hair shaft image (660×) © 2015 Pearson Education, Inc.
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Figure 4.9 Scanning electron micrograph showing a hair shaft emerging from a follicle at the skin surface.
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© 2015 Pearson Education, Inc.
Appendages of the Skin Nails Scale-like modifications of the epidermis Heavily keratinized Stratum basale extends beneath the nail bed Responsible for growth Lack of pigment makes them colorless © 2015 Pearson Education, Inc.
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© 2015 Pearson Education, Inc.
Appendages of the Skin Nail structures Free edge Body is the visible attached portion Nail folds are skin folds that overlap the edges of the nail Growth occurs from nail matrix Root of nail is embedded in skin Cuticle is the proximal nail fold that projects onto the nail body © 2015 Pearson Education, Inc.
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Figure 4.10 Structure of a nail.
Lunule Lateral nail fold (a) Free edge of nail Body of nail Cuticle Root of nail Proximal nail fold Nail matrix (b) Nail bed Bone of fingertip
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