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Body Membranes and Organ Structure – Quick Notes

Organ structure and tissue integration

  • An organ is a structure composed of \ge 2 tissue types that work together to perform specific functions; tissues must operate in concert.
  • Example: the stomach contains all four tissue types: epithelium, connective tissue, muscular tissue, and nervous tissue.
    • Epithelium: Simple columnar epithelium
    • Connective tissue: Areolar and dense irregular connective tissue
    • Muscular tissue: Smooth muscle (three layers)
    • Nervous tissue: Nervous tissue
  • Roles of tissues in the stomach:
    • Epithelial glands secrete substances for chemical digestion
    • Connective tissue houses blood vessels and nerves; provides shape and support
    • Smooth muscle contracts/relaxes to mechanically mix and digest contents
    • Nervous tissue regulates contraction and glandular secretion

Tissue types in organs

  • Epithelial tissue
  • Connective tissue
  • Muscular tissue
  • Nervous tissue

Body membranes overview

  • Body membranes are formed from an epithelial layer bound to underlying connective tissue; they line cavities or cover surfaces.
  • Main types: mucous membranes (mucosa), serous membranes, cutaneous membrane; Synovial membranes are a special case formed from connective tissue.
  • Synovial membranes secrete synovial fluid to reduce friction in freely movable joints.

Mucous membranes (mucosa)

  • Line passageways and compartments that open to the external environment (e.g., digestive, respiratory, urinary, reproductive tracts)
  • Structure: epithelium + lamina propria (underlying connective tissue)
  • Function: absorptive, protective, and/or secretory

Serous membranes

  • Line body cavities that do not open to the exterior and cover external surfaces of many organs
  • Structure: simple squamous epithelium (mesothelium) + areolar connective tissue
  • Produce serous fluid (serous fluid) to reduce friction
  • Two associated layers: parietal layer (lines cavity) and visceral layer (covers organ); serous cavity lies between

Cutaneous membrane (skin)

  • Largest body membrane; covers external surface
  • Structure: keratinized stratified squamous epithelium (epidermis) + connective tissue (dermis)
  • Functions: protects internal organs; prevents water loss

Synovial membranes

  • Line spaces within certain joints (joint cavities)
  • Structure: connective tissue only
  • Function: secrete synovial fluid to reduce friction and distribute nutrients to cartilage on articular surfaces