Week 6 - Hair Structure and Follicle Function

Hair structure

• Hair originates from the hair bulb, a swelling at the base of the hair in the dermis
• The hair bulb surrounds the hair papilla, composed of connective tissue
• The hair bulb is the only region containing living epithelial cells
• The hair root extends from the bulb to the skin surface
• The hair shaft is the portion of hair beyond the skin surface
• The hair matrix is a structure at the base of the hair bulb where epithelial cells divide
• New cells are produced, gradually pushed toward the surface
• The medulla is a remnant of the matrix containing flexible, soft keratin
• The cortex contains flattened cells closer to the outer hair surface and is relatively hard
• The cuticle is a single cell layer around the cortex

Hair Follicle and Function

• The hair follicle is an oblique tube that surrounds the hair root
• The hair follicle extends into the dermis and sometimes the subcutaneous layer
• The outer connective tissue root sheath originates in the dermis
• The inner epithelial tissue root sheath originates from the epidermis
• Arrector pili are thin ribbons of smooth muscle that extend from the hair follicle to dermal papillae
• Arrector pili elevate hair with contraction, causing "goosebumps"
• Hair functions in protection, heat retention, sensory reception, and visual identification
• Hair on the head protects from sunburn and injury
• Hair in the respiratory system and ears traps particles and debris
• Root hair plexuses detect light touch

Nail Structure

• The nail body is pinkish because it overlays the vascular dermis
• The free edge of the nail is white because it lacks an underlying vascular supply

Exocrine Glands of the Skin

• Apocrine sweat glands produce viscous, cloudy secretions containing proteins and lipids
• Apocrine sweat glands discharge secretions into hair follicles
• Apocrine sweat glands are located in the axillae, around the nipples, and in the pubic and anal regions
• Apocrine sweat glands produce odor when acted on by bacteria
• Apocrine sweat glands start producing secretions during puberty
• Sebaceous glands are holocrine glands that produce oily secretion, sebum
• Sebaceous glands are located in the dermis and discharge into the hair follicle
• Sebaceous gland secretions lubricate the skin and hair, and have bactericidal properties
• Sebaceous gland secretions are stimulated by hormones, especially male sex hormones
• Sebaceous glands become active during puberty
• Ceruminous glands are modified apocrine sweat glands located only in the external ear canal
• Ceruminous glands produce secretions of waterproof earwax, cerumen, which traps foreign material and lubricates the acoustic meatus and eardrum
• Mammary glands are modified apocrine sweat glands of the breast that function only in pregnant and lactating females
• Mammary glands produce breast milk

Acne

• Acne is caused by plugged sebaceous ducts
• Acne typically begins during puberty due to increased activity of gland secretions blocking pores
• Acne treatments include benzoyl peroxide, salicylic acid, antibiotics, vitamin A-like compounds, and systemic retinoids
• Acne may lead to scarring if untreated

Explore the fascinating details of hair structure and the function of hair follicles. This quiz covers the anatomy of hair, including the hair bulb, root, shaft, and the associated components like the medulla and cortex. Test your knowledge on how these elements work together to support hair growth and health.