Skin Accessories and Appendages Pages 119-124 Skin Accessories and Appendages

Appendages of the Skin Glands Hair/hair follicles Nails © 2015 Pearson Education, Inc. Appendages of the Skin Glands all exocrine glands (meaning they release secretions via ducts) Sebaceous glands Sweat glands Hair/hair follicles Nails

• 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)

Sebaceous (oil) glands © 2015 Pearson Education, Inc. Sebaceous (oil) glands Produce sebum (oil) which: Lubricates skin/ slows water loss Prevents brittle hair Kills bacteria Most empty into hair follicles; others directly onto skin surface Highly active at puberty

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×)

Sweat glands Two types: Eccrine glands Apocrine glands © 2015 Pearson Education, Inc. Sweat glands Two types: Eccrine glands Produce sweat through pores all over skin surface Sweat has salts, Vit. C, excretory wastes (uric acid) Apocrine glands Ducts empty into hair follicles Activated at puberty; found in armpit and genital areas Sweat that also contains fatty acids and proteins (milky or yellowish color) Bacteria like this stuff – they create body odor when they use it

Function of sweat dissipate excess heat (homeostatic) Excretion © 2015 Pearson Education, Inc. Function of sweat dissipate excess heat (homeostatic) Excretion Inhibits bacterial growth (acidic environment) Make us feel really yucky 

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×)

hair Produced by hair follicle Root is enclosed in the follicle © 2015 Pearson Education, Inc. hair Produced by hair follicle Outer tissue= connective Inner= epithelial Root is enclosed in the follicle Shaft (dead part) projects from surface of scalp or skin Consists of hard keratinized epithelial cells Melanocytes provide pigment for hair color Hair grows from hair bulb in stratum basale

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)

Appendages of the Skin Arrector pili muscle Smooth muscle tissue © 2015 Pearson Education, Inc. Appendages of the Skin Arrector pili muscle Smooth muscle tissue Pulls hairs upright when person is cold or frightened (gives us goosebumps) You could consider this a vestigial structure- it has lost all of its function/use for humans

Figure 4.8a Structure of a hair and hair follicle. shaft Arrector pili Sebaceous gland Hair root Hair bulb in follicle (a)

© 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×)

Figure 4.9 Scanning electron micrograph showing a hair shaft emerging from a follicle at the skin surface.

Nails Heavily keratinized = very hard Functions: © 2015 Pearson Education, Inc. Nails Heavily keratinized = very hard Stratum basale is responsible for growth Lack of pigment makes them colorless Functions: Protection Tools Scratch an itch!

Appendages of the Skin Nail structures Free edge © 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