The Integumentary System

Overview and Functions of the Integumentary System

  • The integumentary system consists of the skin and its accessory structures:

    • Hair

    • Nails

    • Glands

  • Functions of the integumentary system include:

    • Protecting the body against mechanical injury and disease organisms.

    • Housing sensory receptors that receive and transmit information about the external environment.

    • Preventing desiccation and drying out of tissues.

    • Assisting in maintaining a constant body temperature.

    • Excreting water and metabolic wastes.

    • Producing vitamin D.

Structural Layers of the Skin

  • The skin is divided into two main anatomical layers:

    • Epidermis: The outer layer of the skin, composed of stratified squamous epithelial tissue.

    • Dermis: The inner layer of the skin, composed of connective tissue.

  • Dynamics of the Epidermis:

    • Stratum Basale: The deepest sublayer of the epidermis where new epidermal cells are continuously produced.

    • Keratin Production: As epidermal cells migrate outward from the stratum basale toward the surface, they synthesize keratin, a tough, waterproofing protein.

    • Stratum Corneum: The outermost sublayer of the epidermis. Cells die as they move through this layer to form a protective barrier.

  • Characteristics of the Dermis:

    • Contains large amounts of collagen, a structural protein that provides strength to the skin.

    • Houses blood vessels that nourish the overlying epidermal cells.

    • Features dermal papillae, which are projections located in the upper region of the dermis that extend upward into the epidermis.

    • Capillaries extend into the dermal papillae to provide microcirculation.

    • Rich in capillaries and contains embedded accessory structures, including hair follicles and glands.

Skin Pigmentation and Clinical Conditions

  • Melanin:

    • Produced by specialized pigment cells located within the epidermis.

    • Imparts color to both skin and hair.

    • Absorbs ultraviolet (UV) radiation from sunlight, preventing radiation damage to the deeper dermis and blood vessels.

  • Albinism:

    • A clinical condition in which pigment cells are unable to produce melanin.

The Subcutaneous Layer

  • The dermis rests directly upon the subcutaneous layer.

  • The anatomical prefix sub- means "below," designating this as the deepest layer beneath the skin.

  • Composition: Consists mainly of loose connective tissue and adipose tissue.

  • Functions:

    • Cushions underlying biological structures against mechanical injury.

    • Connects the skin to underlying tissues.

    • Stores body energy in the form of fat.

Accessory Structures of the Skin

  • Hair:

    • Functions to help protect the body.

    • Shaft: The visible region of the hair extending above the skin surface.

    • Root: The hidden portion of the hair positioned below the skin surface.

    • Hair Follicle: Formed by the hair root along with its surrounding epithelial and connective tissue coverings.

  • Sebaceous Glands:

    • Produce sebum, an oily lipid substance.

    • Functions of Sebum:

    • Lubricates the surface of the skin.

    • Helps prevent fluid and water loss.

    • Inhibits the growth of bacteria on the skin surface.

  • Sweat Glands:

    • Structurally organized mostly as coiled tubes.

    • Excrete dilute salt water through surface pores onto the skin.