L2.2: Hallmarks of Epithelium

• Hallmarks of epthelium

  • formation of continuous sheets
  • apical surface
  • basement membrane
  • avascular
• Formation of Continuous Sheets

  ○ Epithelial cells fit closely together and neighboring cells are bound together at many points by specialized cell junctions.

  ○ Cellularity

  ■ Cells are close together.

  ■ Magkadikit-dikit

  ■ Reason: cell junctions
• Apical Surface – Free Surface (Unattached)

  ○ Exposed to the body’s exterior or to the cavity of an internal organ.

  ○ Either slick and smooth or with cell surface modification (microvilli or cilia).
• Basement Membrane – Anchored Surface (Basal)

  ○ Structureless material secreted by both epithelial and connective tissue cells.

  ○ Glue that holds the epithelium in place.

  ○ “The resting membrane”
• “Basal and Surface parts of a tissue are unique to Epithelial Tissues; Polarity”
• Avascular

  ○ No blood supply and dependent on the diffusion from capillaries (connective tissues from the dermis) for food and oxygen through diffusion.

  ○ Explains why some parts of our skin don’t bleed.

  ■ “Hanggang epidermis lang yung cut and hindi umabot sa dermis which contains the

  blood vessels.”

  ○ Epidermis: epithelium (avascular) :: Dermis:

  connective (vascular).