Chapter 4

Human Anatomy & Physiology - Chapter 4

• Body membranes cover body surfaces, line body cavities, and form protective sheets around organs. They are classified by tissue types.

Epithelial Membranes

• Epithelial membranes are simple organs, also called covering and lining membranes.
• They consist of an epithelial tissue layer and a connective tissue layer.
• Cutaneous membrane is skin, the outermost protective boundary.
  • Consists of two layers:
    • Epidermis: keratinized stratified squamous epithelium
    • Dermis: mostly dense (fibrous) connective tissue
• Mucous membranes (mucosae) are moist membranes.
  • Some mucosae secrete protective, lubricating mucus.
  • Line body cavities opening to the exterior.
  • Adapted for absorption or secretion.
  • Consist of two layers:
    • Epithelium type depends on site
    • Loose connective tissue (lamina propria)
• Serous membranes (serosae) line closed ventral body cavities.
  • Occur in pairs, separated by serous fluid.
  • Consist of two layers:
    • Simple squamous epithelium
    • Areolar connective tissue
  • Specific serous membranes include:
    • Peritoneum: covers organs in the abdominal cavity
    • Pleurae: surround the lungs
    • Pericardia: surround the heart

Connective Tissue Membranes

• Synovial membranes are composed of loose areolar connective tissue only (no epithelial tissue).
• They line fibrous capsules surrounding joints, bursae, and tendon sheaths.
• They secrete a lubricating fluid to cushion organs during movement.

Integumentary System

• Consists of skin and skin appendages:
  • Sweat glands
  • Oil glands
  • Hair
  • Nails

Functions of the Integumentary System

• Insulates and cushions deeper body organs
• Protects the body from:
  • Mechanical damage (bumps, cuts)
  • Chemical damage (acids, bases)
  • Thermal damage (heat, cold)
  • Ultraviolet (UV) radiation
  • Microbes
  • Water loss
• Regulates heat loss through nervous system control.
• Acts as a mini-excretory system, aiding in the loss of urea, salts, and water.
• Synthesizes vitamin D.
• Secretion of a protective acid mantle.

Structure of the Skin

• Two main tissue types:
  • Epidermis: outer layer, composed of stratified squamous epithelium.
    • Most cells are keratinocytes that produce keratin (a fibrous protein).
    • Keratinization makes the epidermis tough.
    • Desmosomes connect keratinocytes together.
    • Avascular.
    • Five layers (strata)
      • Stratum basale, Stratum spinosum, Stratum granulosum, Stratum lucidum, Stratum corneum
      • Stratum basale is deepest layer; cells actively divide, pushing daughter cells upwards.
      • Stratum corneum is outermost layer; shingle-like dead cells filled with keratin.
  • Dermis: connective tissue under the epidermis
    • Two regions: papillary layer (upper) and reticular layer (lower)
      • Papillary layer: areolar connective tissue; contains capillary loops and touch receptors. Finger prints!
      • Reticular layer: dense irregular connective tissue, blood vessels, sweat & oil glands, deep pressure receptors.
  • Subcutaneous tissue (hypodermis) anchors skin to underlying organs and serves as a shock absorber.

Skin Color

• Three pigments contribute to skin color:
  • Melanin (yellow, reddish brown, or black) produced by melanocytes mostly in stratum basale of the epidermis.
  • Carotene (orange-yellow) found in vegetables.
  • Hemoglobin (red) from blood cells in dermal capillaries; oxygen content influences red coloring.

Homeostatic Imbalances of Skin

• Infections and allergies
  • Athlete's foot
  • Boils
  • Cold sores
  • Contact dermatitis
  • Impetigo
  • Psoriasis
• Burns
  • First-degree: epidermis damaged
  • Second-degree: epidermis and superficial dermis damaged
  • Third-degree: full-thickness burn, destroys epidermis and dermis, burned area painless, requires skin grafts.
  • Fourth-degree: extends into deeper tissues like bone, muscle, etc; dry leathery appearance, surgical intervention required, often amputation.
  • Rule of Nines for burn estimation.
• Skin cancer (most common cancer type)
  • Main types:
    • Basal cell carcinoma: least malignant, most common
    • Squamous cell carcinoma: believed to be induced by UV exposure.
    • Malignant melanoma: most deadly, cancer of melanocytes; ABCDE rule to detect.

Developmental Aspects of Skin and Body Membranes

• Lanugo: downy hair covering the fetus.
• Vernix caseosa: oily covering present at birth; often disappears within a few weeks.
• Milia: small white spots present at birth; usually disappears by the third week.
• Acne is more common during adolescence.
• Aging skin is affected by skin cancer, thinning, loss of elasticity and graying or balding.