skin

Skin and Membranes

Classification of Body Membranes

  • Two Major Types: Epithelial membranes and Connective tissue membranes.

  • Epithelial Membranes: Composed of epithelial tissue over connective tissue. Types include:

    • Cutaneous Membrane: Skin.

    • Serous Membranes: Line closed cavities, secrete lubricating fluid (parietal covers cavity walls, visceral covers organs).

    • Mucous Membranes: Line open body surfaces, secrete mucus.

  • Connective Tissue Membranes: Do not contain epithelial components; example includes synovial membranes that secrete synovial fluid.

Structure of Skin

  • Epidermis: Outermost layer, stratified squamous epithelium; contains melanocytes (produce melanin).

  • Dermis: Deeper layer, contains connective tissue, blood vessels, nerves; has dermal papillae for support.

  • Layers: Dermal-epidermal junction provides support; differences between thick and thin skin (hairs vs. no hairs).

Accessory Organs of Skin

  • Hair Follicle: Structure for hair growth.

  • Sebaceous Glands: Secrete sebum; regulated by hormones; linked to acne.

  • Sweat Glands: Eccrine (temperature regulation) and Apocrine (associated with odor).

  • Nails: Formed from epidermal cells; provide protective covering.

Functions of the Skin

  1. Protection: Against microbes, UV rays, and physical damage.

  2. Temperature Regulation: Heat loss via sweating and blood flow adjustment.

  3. Sensation: Detects environmental changes (pressure, temperature).

  4. Excretion: Releases waste products through sweat.

  5. Vitamin D Synthesis: Triggered by UV light exposure.

Skin Disorders

  • Major categories include:

    • Infections: Impetigo, Tinea, Warts, Scabies.

    • Inflammatory Disorders: Psoriasis, Eczema, Allergies.

Skin Cancer Types

  • Basal Cell Carcinoma: Most common; rarely metastasizes.

  • Squamous Cell Carcinoma: Slow growing; can metastasize.

  • Melanoma: Most serious; characterized by asymmetry, irregular borders, uneven colors, and changing moles.