Accessory Structures of the Skin

Accessory Structures of the Skin

• Accessory structures originate in the epidermis and include nails, hair follicles, and skin glands.
• The dermis can regenerate as long as accessory structures remain intact.

Nails

• Nails serve as protective coverings at the tips of fingers and toes.
• Key components of nails include the nail plate, nail bed, and lunula.
• The nail plate overlies the nail bed.
• The nail bed consists of specialized epithelial cells that connect with the skin's epithelium.
• The lunula is the crescent-shaped visible part of the nail root and represents the most active growth site.

Hair

• Hair is present on nearly all skin surfaces except for palms, soles, nipples, lips, and certain external reproductive areas.
• Hair follicles are tubular depressions where hair grows from a cluster of epidermal cells.
• The hair root resides in the follicle and is nourished by dermal blood vessels.
• The hair shaft extends away from the surface of the skin.
• Hair is composed of dead epithelial cells.

Hair Structure and Functions

• The hair papilla is a connective tissue projection at the base of the hair follicle.
• Hair color is genetically determined by the type and amount of pigments produced by epidermal melanocytes.

Types of Melanin

• Eumelanin is a brownish-black pigment that produces dark hair.
• Pheomelanin is a reddish-yellow pigment that results in blonde hair.

Arrector Pili Muscle

• Each hair follicle is attached to an arrector pili muscle which, when contracted, causes hair to stand on end, creating goosebumps.
• Emotional states or cold conditions can stimulate these muscles.

Sebaceous Glands

• Sebaceous glands are associated with hair follicles and consist of specialized epithelial cells; they are holocrine glands.
• These glands produce sebum, a mixture of fatty material and cellular debris.
• Sebum maintains the softness, pliability, and waterproof nature of hair and skin.
• Sebaceous glands are absent on palms and soles but open directly to the skin surface in areas like lips and genital organs.

Sweat Glands

• Sweat glands, also known as sudoriferous glands, originate as coiled tubes in the dermis or subcutaneous layer.
• Eccrine glands are the most abundant type, responding to heat and physical activity, primarily located on the forehead, neck, and back.
• Sweating serves an excretory function and consists mainly of water, with some salts and wastes like urea.
• Apocrine glands activate at puberty and may produce odor; they are concentrated in areas such as the armpits and groin.

Specialized Glands

• Ceruminous glands are located in the external ear canal and secrete ear wax.
• Mammary glands are specialized to produce milk.

Notable Functions

• Apocrine glands may release sweat in response to emotional stimuli, sexual arousal, or pain.
• The eccrine gland is crucial for thermoregulation through sweating in response to increased body temperature.

This quiz explores the accessory structures of the skin, focusing on nails, hair follicles, and their functions. Understand the anatomy and growth processes of nails and hair, as well as their significance in skin health. Test your knowledge on these vital components of the integumentary system.