Body Membranes Quiz

Body Membranes

• Thin sheet-like structures consisting of an epithelium overlying a connective tissue (except for one exception)
• Serous membranes: found lining body cavities that do not open directly to the outside
  • Types: Peritoneum (abdominopelvic cavity), Pleura (pleural cavities), Pericardium (pericardial cavity)
• Mucous membranes: found lining cavities that directly open 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)

Integumentary System

• Composed of skin and other various accessory organs
• Accessory organs include sweat glands, oil glands, hair, finger nails, and toe nails
• Characteristics of skin:
  • Surface area: 1.2 to 2.2 square meters (varies)
  • Weight: about 7% of overall body weight
  • Thickness: 1.5 to 4.0 mm
• Primary skin functions:
  • Protection against invading pathogens
  • Water loss regulation
  • Ultraviolet radiation protection
  • Regulation of body temperature
  • Houses receptors for general cutaneous sensations

Skin Layers

• Epidermis:
  • Outermost layer, composed primarily of stratified squamous epithelium
  • Avascular and limited sensory innervation
  • Divided into 4 (thin skin) or 5 (thick skin) layers depending on location
• Dermis:
  • Connective tissue layer found below the epidermis
  • Semi-fluid matrix with embedded protein fibers
  • Contains many of the connective tissue proper cells (fibroblasts, macrophages)
• Sublayers of dermis:
  • Papillary dermis: outermost superficial layer consisting of areolar CT and small blood vessels
  • Reticular dermis: accounts for 80% of dermis thickness, contains collagen fibers in bundles and networks

Sweat Glands

• Tiny tube-like exocrine glands with coiled ends lined with epithelial cells that produce and release sweat
• Types:
  • Eccrine sweat glands: most numerous, activated in times of elevated body temperature
  • Apocrine sweat glands: approximately 2000, become active at puberty, produce sweat in response to emotional stimuli

Hair Follicles

• Present on all skin surfaces except palms, lips, nipples, and parts of external reproductive organs
• Tube-like depressions of the epidermis and dermis containing the hair root
• Hair color is genetically determined by the amount of melanin produced by melanocytes

Sensory Receptors

• Respond to changes in the surrounding environment
• Most are limited to the dermis layer
• Types:
  • Touch: Merkel's disks, Meissner's corpuscles
  • Pressure: Pacinian corpuscle
  • Heat: Ruffini's endings, pain nerve endings (extreme)
  • Cold: Krause end bulbs, pain nerve endings (extreme)
  • Pain: Free nerve endings

Subcutaneous Layer (Hypodermis)

• Consists of a loose fibrous connective tissue and adipose tissue
• Collagen and elastic fibers are continuous with dermis
• Adipose tissue thickness varies from one body region to another

Common Skin Disorders

• Acne: inflammatory disease of sebaceous glands
• Athlete's foot: fungal infection often present on the soles and between the toes of the feet
• Decubitus ulcers: tissue damage and ulcerations due to deficiency of blood flow
• Impetigo: highly contagious bacterial skin infection
• Moles: pigmented tumors found in skin
• Warts: result of viral invasion of the skin
• Burns: tissue damage due to thermal, electrical, radioactive, or chemical agents