Membrane Types: Mucous, Serous, Cutaneous, Synovial

• There are four membrane types: mucous, serous, cutaneous, and synovial.
• Membranes consist of two or more tissue types, with epithelial tissues being just one component of a more complex membrane.
• Membranes line a free surface and typically include epithelial tissue at the surface plus underlying connective tissue(s).
• Each membrane produces one or more products like mucus, serous fluid, synovial fluid, or sweat/oil.

Mucous Membranes

• Line body structures that open to the external environment, such as the digestive, respiratory, reproductive, and urinary tracts.
• Structure includes an epithelial tissue and a layer of areolar connective tissue called the lamina propria.
• Produce mucus, a slippery and viscous fluid.
• Examples:
  • Lining of oral cavity, esophagus, vulva: stratified squamous epithelium (without keratin) + lamina propria of areolar CT
  • Lining of urinary bladder and ureters: transitional epithelium + lamina propria
  • Lining of stomach and intestines: simple columnar epithelium + lamina propria
  • Lining of nasal cavity and trachea: pseudostratified ciliated columnar epithelium (PCCE) + lamina propria
• Goblet cells are unicellular exocrine glands found in the PCCE of the trachea that secrete mucus.

Serous Membranes

• Line body cavities that do not open externally, like portions of the thoracic and abdominopelvic cavities.
• Examples: pleura, pericardium, and peritoneum.
• Structure consists of a thin epithelium (simple squamous epithelial tissue called mesothelium) and areolar connective tissue.
• Produce serous fluid, a watery secretion.

Cutaneous Membrane (Skin)

• Located externally
• Structure includes the epidermis (epithelial tissue) and dermis (connective tissue).
• Functions include secretion by exocrine glands.

Synovial Membranes

• Found in freely movable joints like the knee, hip, and elbow.
• Produce synovial fluid, a viscous fluid that nourishes articular cartilage and lubricates joints.
• Synovial fluid is often compared to egg white in consistency.
• Structure is unique, lacking a true epithelial tissue and consisting of a unique connective tissue structure lining synovial joint cavities.