Body Membranes Quiz

Body Membranes

• Thin sheet-like structures consisting of an epithelia overlying a connective tissue (exception)
• Types:
  • Serous membranes: found lining body cavities that do not open up directly to the outside
    • Consist of two layers: parietal and visceral layers
    • Produce lubricating watery fluid between the two layers
    • Examples: peritoneum, pleura, pericardium
  • Mucous membranes: found lining cavities that directly open up to the outside of the body
    • "Moist" membranes bathed by fluid
    • Some contain goblet cells (mucus secreting cells)
    • Examples: digestive, respiratory, and urogenital tracts
  • Synovial membranes: form the inner lining of joint cavities (connective tissue only)
  • Cutaneous membranes: an organ of the integumentary system - skin

Integumentary System

• Composed of skin and other various accessory organs
• Accessory organs include:
  • Sweat glands
  • Oil glands
  • Hair
  • Finger nails
  • Toe nails
• Characteristics of skin:
  • Surface area: 1.2 to 2.2 square meters (varies)
  • Makes up about 7% of overall body weight
  • Thickness: 1.5 - 4.0 mm
• Primary skin functions:
  • Protection against invading pathogens
  • Water loss
  • Ultraviolet radiation
  • Helps to regulate body temperature
  • Houses receptors for general cutaneous sensations
  • Excretes some wastes

Skin Layers

• Epidermis: outermost layer
  • Composed primarily of a stratified squamous epithelium
  • Avascular and limited sensory innervation
  • Divided into 4 (thin skin) or 5 (thick skin) layers depending on location
  • Sublayers:
    • Stratum basale: deepest single cell layer
      • In contact with basement membrane
      • Cuboidal in shape
      • Also called the germinating layer
      • Keratinocytes give rise to all other layers
      • Produce fibrous protein keratin and glycolipids
    • Stratum corneum: outermost layer
      • Approximately 20-30 layers of dead anucleated keratinized cells
      • Makes up to 75% of the thickness of skin
      • Sheds off regularly
• Dermis: connective tissue layer
  • Found below the epidermis
  • Semi-fluid matrix with embedded protein fibers
  • Contains many of the connective tissue proper cells
  • Sublayers:
    • Papillary dermis: outermost superficial layer
      • Consists of areolar CT and small blood vessels
      • Outer surface forms projections called dermal papillae
    • Reticular dermis: accounts for 80% of the dermis thickness
      • Contains collagen fibers in bundles and networks
      • Blood vessel networks found at bottom border
• Sweat glands:
  • Tiny tube-like exocrine glands
  • Lined with epithelial cells that produce and release sweat
  • Found everywhere but nipples and external genitalia
  • Approximately 3 million sweat glands per person
  • Types:
    • Eccrine sweat glands: most numerous
      • Activated in times of elevated body temperature
      • Most open up directly onto skin surface
    • Apocrine sweat glands:
      • Approx. 2000 become active at puberty
      • Produce sweat when a person is emotionally upset
• Sebaceous glands: "Oil glands"
  • Groups of specialized epithelial cells associated with hair follicles
  • Release a fatty oil-like substance called sebum
  • Found throughout the body except on palms and soles
  • Overactive and inflamed sebaceous glands cause acne
• Hair follicles:
  • Present on all skin surfaces except palms, lips, nipples, and parts of external reproductive organs
  • Tube-like depressions of the epidermis and into dermis
  • Contain the hair root which grows from dividing cells
  • Hair color is genetically determined by the amount of melanin produced
• Arrector pili muscle:
  • Bundles of smooth muscle fibers
  • Attached to the follicle on one end and the dense irregular CT framework of the papillary layer on the other
  • When contracted, causes the hair strand to stand up and the surface of the skin above it to bulge upward (goosebumps)
• Sensory receptors:
  • Respond to changes in the surrounding environment
  • Most are limited to the dermis layer
  • Types:
    • Touch: Merkel's disk, Meissner's corpuscles
    • Pressure: Pacinian corpuscle
    • Heat: Ruffini's endings, pain nerve ending (extreme)
    • Cold: Krause end bulbs, pain nerve endings (extreme)
    • Pain: free nerve endings

Subcutaneous Layer

• Consists of a loose fibrous connective tissue and adipose
• Collagen and elastic fibers are continuous with dermis
• Adipose thickness varies from one body region to another
• Eyelids lack adipose
• Contain major blood vessels supplying skin

Common Skin Disorders

• Acne: inflammatory disease of sebaceous glands
  • Bacteria thrive on sebaceous gland secretions
  • Most prevalent at puberty
• Athlete's foot: fungus infection
  • Often present on the soles and between the toes of the feet
• Decubitus ulcers: tissue damage and ulcerations
  • Result of deficiency of blood due to prolonged pressure
  • Most frequently seen in bedridden patients
• Impetigo: highly contagious bacterial skin infection
  • Most commonly found in children
  • Characterized by pus-filled sacs that rupture and become crusted over
• Moles: pigmented tumors found in skin
  • Vary in color from yellow to brown to black
  • Average about 20 per person
  • Grow slowly, remain stable, and then slowly diminish in size
• Warts: result of a viral invasion of the skin
  • Cause epithelial cells to proliferate
  • Most regress spontaneously
  • Genital warts can be spread through sexual contact
• Burns: tissue damage due to thermal, electrical, radioactive, or chemical agents
  • Types:
    • Partial thickness burns: first and second degree burns
      • Heal in two to three days with little scarring
    • Full thickness burns: third degree burns
      • Entire thickness of skin is destroyed
      • Surface is leathery and may be tan, brown, or black
      • No pain in immediate area
      • Regeneration of tissue is slow with much scarring
  • Major concerns in cases of severe burns:
    • Body fluid loss
    • Heat loss
    • Bacterial infection