5.2 Accessory Structures of the Skin

4 min read•august 28, 2024

Your skin isn't just a simple covering—it's got some cool extras! Accessory structures like hair, nails, and glands do more than you might think. They protect you from UV rays, help you feel touch, and even regulate your body temperature.

These structures grow from your skin and have specific jobs. Hair and nails are made of keratin, while glands produce important substances like sweat and oil. Together, they keep your skin healthy and functioning properly.

Accessory Structures of the Skin

Hair and Nails

Top images from around the web for Hair and Nails

  • Unit 11: The Integumentary System – Douglas College Human Anatomy & Physiology I (2nd ed.) View original

    Is this image relevant?

  • Accessory Structures of the Skin | Boundless Anatomy and Physiology View original

    Is this image relevant?

  • Unit 11: The Integumentary System – Douglas College Human Anatomy & Physiology I (2nd ed.) View original

    Is this image relevant?

1 of 3

Top images from around the web for Hair and Nails

  • Unit 11: The Integumentary System – Douglas College Human Anatomy & Physiology I (2nd ed.) View original

    Is this image relevant?

  • Accessory Structures of the Skin | Boundless Anatomy and Physiology View original

    Is this image relevant?

  • Unit 11: The Integumentary System – Douglas College Human Anatomy & Physiology I (2nd ed.) View original

    Is this image relevant?

1 of 3
  • The accessory structures of the skin include hair, nails, and various glands derived from the epidermis but located mainly in the dermis
  • Hair and nails are keratinized structures that grow out of the epidermis and serve protective (shielding from UV radiation) and sensory functions (detecting touch and vibration)

Glands

  • Sebaceous glands, sudoriferous (sweat) glands, and ceruminous glands are the main glandular structures associated with the skin, each with specific functions and secretions
    • Sebaceous glands secrete sebum to lubricate and waterproof the skin and hair
    • Sudoriferous glands regulate body temperature through sweat production
    • Ceruminous glands produce earwax to protect the ear canal

Hair Follicle Structure and Growth

Hair Follicle Anatomy

  • Hair follicles are tubular invaginations of the epidermis that extend into the dermis, with the base of the follicle forming the hair bulb
    • The hair bulb contains the germinal matrix, responsible for hair growth and regeneration through cell division and keratinization
  • Hair follicles are associated with arrector pili muscles, which can cause the hair to stand erect in response to stimuli such as cold or emotional stress (goosebumps)

Hair Growth Cycle

  • The growth cycle of hair consists of three phases: anagen (active growth), catagen (transitional phase), and telogen (resting phase)
    • Anagen phase is the longest, lasting several years, during which the hair actively grows
    • Catagen phase is a short transitional period, lasting a few weeks, during which the follicle shrinks and the hair stops growing
    • Telogen phase is the resting period, lasting a few months, after which the old hair is shed and a new anagen phase begins
  • The length of each phase varies depending on the body location and individual factors (genetics, age, hormones)

Nail Composition and Growth

Nail Structure

  • Nails are composed of tightly packed, keratinized epithelial cells and consist of a nail plate, nail bed, and nail root
    • The nail plate is the visible, hard portion of the nail that grows out from the nail root and over the nail bed
    • The nail bed is the skin beneath the nail plate, containing blood vessels and nerves that provide nutrients and sensation to the nail
  • The cuticle is a fold of skin at the base of the nail that protects the nail root from infection and damage

Nail Growth

  • Nail growth occurs at the nail root, where epithelial cells divide and keratinize, pushing the nail plate forward
    • The rate of nail growth is slower than hair growth, averaging about 3 mm per month for fingernails and 1 mm per month for toenails
  • Factors affecting nail growth include age, nutrition, health status, and environmental conditions (temperature, humidity)

Sebaceous, Sudoriferous, and Ceruminous Glands: Functions vs Secretions

Sebaceous Glands

  • Sebaceous glands are holocrine glands that secrete sebum, an oily substance that lubricates and waterproofs the skin and hair
    • Sebum is composed of lipids, such as triglycerides, wax esters, and squalene, which help maintain the skin's barrier function and prevent moisture loss
    • Sebaceous glands are most abundant on the face, scalp, and upper body, and their activity is regulated by hormones, particularly androgens (testosterone)
  • Overproduction of sebum can contribute to acne development

Sudoriferous (Sweat) Glands

  • Sudoriferous (sweat) glands are of two types: eccrine and apocrine glands, both of which secrete sweat onto the skin's surface
    • Eccrine glands are more numerous and are found throughout the body, producing a clear, odorless secretion that helps regulate body temperature through evaporative cooling
    • Apocrine glands are larger and are primarily found in the axillary (armpits) and genital regions, producing a thicker, milky secretion that can acquire an odor when metabolized by bacteria on the skin
  • Sweat also contains electrolytes (sodium, potassium, chloride) and helps maintain fluid and electrolyte balance

Ceruminous Glands

  • Ceruminous glands are modified apocrine glands found in the external ear canal that secrete cerumen (earwax)
    • Cerumen is a sticky, waxy substance that helps protect the ear canal from dust, debris, and microorganisms, as well as lubricating and waterproofing the skin of the ear canal
    • Cerumen also has antimicrobial properties, helping to prevent infections in the ear canal
  • Excessive earwax buildup can lead to impaction and hearing difficulties
© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.
Back
Glossary
Glossary
Next guide