Fundamentals of Anatomy & Physiology 11th Edition by Frederic H. Martini 12

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Introduction to the Integumentary System

  1. Components:

    • Consists of the cutaneous membrane (skin) which includes:

      • Epidermis

      • Dermis

      • Accessory structures

    • Beneath the dermis is the subcutaneous layer (hypodermis).

  2. Functions of the Integument:

    • Protection

    • Excretion

    • Temperature maintenance

    • Vitamin D3 synthesis

    • Nutrient storage

    • Sensory detection

    • Coordination of immune response

Characteristics of the Epidermis

  1. Skin Types:

    • Thin Skin: Covers most of the body, composed of four layers of keratinocytes.

    • Thick Skin: Found on heavily abraded surfaces, contains five layers of keratinocytes.

  2. Epidermal Functions:

    • Provides physical protection.

    • Prevents fluid loss and keeps microorganisms out.

  3. Cell Regeneration:

    • New cells are produced in the stratum basale layer and migrate superficially.

    • As cells age, they progress through stratum spinosum, granulosum, lucidum (if thick skin), and corneum before shedding.

  4. Interlayer Bonding:

    • Epidermis and dermis are bonded by epidermal ridges and dermal papillae.

  5. Cell Types in Epidermis:

    • Dendritic (Langerhans) cells: Part of immune response.

    • Tactile (Merkel) cells: Sensory receptors for touch.

  6. Epidermal Growth Factor (EGF):

    • Promotes growth, division, repair of the epidermis, and gland synthesis.

Structure of the Dermis

  1. Layers of the Dermis:

    • Papillary Layer:

      • Contains blood vessels, lymphatic vessels, sensory nerves.

    • Reticular Layer:

      • Contains collagen and elastic fibers, provides strength and elasticity.

  2. Skin Distension:

    • Extensive stretch can cause stretch marks.

  3. Tension Lines:

    • Collagen and elastic fiber arrangement shows cleavage lines important for incisions.

  4. Vascular Supply:

    • Arteries form the cutaneous plexus, aiding skin nutrient supply.

    • Subpapillary plexus lies at the base of the papillary layer.

  5. Sensory Detection:

    • Dermis includes receptors for light touch and pressure.

Subcutaneous Layer (Hypodermis)

  1. Function:

    • Stabilizes skin position against underlying tissues.

Skin Color Factors

  1. Influence on Color:

    • Color determined by epidermal pigmentation and dermal blood supply.

    • Melanin (produced by melanocytes) protects from UV radiation.

    • Carotene is another pigment impacting color.

  2. Conditions Affecting Color:

    • Cyanosis: From poor dermal blood supply.

    • Vitiligo: Nonpigmented patches on skin.

Vitamin D3 Synthesis

  1. UV Radiation Role:

    • Epidermal cells convert steroid to vitamin D3 upon sunlight exposure.

    • Vitamin D3 deficiency can lead to Rickets.

Hair Structure and Function

  1. Hair Characteristics:

    • Composed of keratinized dead cells.

    • Hair originates from hair follicles; includes root, shaft, papilla, bulb, root hair plexus.

    • Hair grows in cycles (2-5 years).

  2. Hair Types:

    • Types include vellus (fine) and terminal (thicker) hairs.

    • Club hairs are those that have ceased growing.

  3. Arrector Pili Muscle:

    • Can erect single hairs; contributes to goosebumps.

Glands in the Skin

  1. Sebaceous Glands:

    • Discharge sebum into hair follicles, contributing to skin moisture.

  2. Sweat Glands:

    • Eccrine glands produce sensible perspiration (watery secretion).

    • Apocrine glands produce odorous secretion.

    • Mammary glands and ceruminous glands (ear wax) are modified apocrine glands.

Nails

  1. Nail Structure:

    • Composed of keratinized epidermal cells, nail body covers nail bed.

    • Production occurs at nail root, protected by cuticle (eponychium).

Skin Repair Mechanism

  1. Repair Phases:

    • Involves bleeding/inflammation, migration with granulation tissue, proliferation, and scarring.

    • Keloids form as raised fibrous scar tissue.

Aging Effects on Skin

  1. Aging Changes:

    • Thinning of integument, reduced blood flow, slower repair processes.

Review Questions

  • Questions covering facts and terms regarding the integumentary system, its structure, functions, and repair processes.