Types of Glandular Secretions and Intercellular Junctions

Glandular Secretions

Glands are epithelial tissues and have various types of secretions.

Serous Glands

  • Produce watery substances.
  • Examples:
    • Sweat
    • Milk (for breastfeeding mothers)
    • Tears
    • Gastric juices
  • Important on serous membranes to prevent friction between organs.

Mucous Glands

  • Produce thick, sticky mucus.
  • Mucus is made of glycoproteins called mucin.
  • Mucin combines with water to form mucus.
  • Found in mucous membranes to trap pathogens.
  • Line areas vulnerable to attack:
    • Mouth
    • Reproductive tract
    • Digestive tract

Cytogenic Glands

  • 'Cyto' means cell, and 'gen' means to create.
  • Secrete entire cells, not fluids.
  • Found in:
    • Testes
    • Ovaries
  • Secrete sex cells.

Intercellular Junctions (Cell-to-Cell Junctions)

Found in epithelial tissues, cardiac tissues, and some connective tissues.
Locations where cells meet allow for a variety of functions.

Types of Intercellular Junctions

Desmosomes (Adhesion Junctions)
  • Strong, like upholstery thread.
  • Made of tough protein fibers.
  • Sew cells together tightly (strongly).
  • Prevent cells from pulling apart under mechanical stress.
Tight Junctions
  • 'Tight' means close together, not strong.
  • Located near the surface of cells.
  • Hold cells closely together, like Velcro.
  • Not very strong but form a barrier to prevent pathogens from squeezing between cells.
  • Prevent bacteria from entering the blood supply in areas like the digestive tract.
Gap Junctions
  • Open holes or channels between cells.
  • Allow cytoplasm to move from one cell to another.
  • Facilitate cell-to-cell communication.
  • Allow passage of nutrients.
  • Allow passage of electricity (e.g., in the heart).
Summary Table of Intercellular Junctions

| Junction Type | Strength | Primary Function |
| :------------ | :---------- | :------------------------------------------------ | |
| Desmosomes | Strong | Resist mechanical stress |
| Tight | Weak | Prevent passage of pathogens between cells |
| Gap | Communication | Cell-to-cell communication, passage of nutrients/electricity |