INTRODUCTION

• Tissue

  Group of similar cells in the extra-cellular substances surrounding them
• Histology


  The microscopic study of tissue
• Epithelium


  • It is found everywhere
  • It covers the surfaces and lines the hollow organs of our body
• Epithelium


  • It attaches at the basal body
  • It is also avascular and capable of regeneration
• Simple Epithelium


  It is consist of a single cell layer, extending from the basement membrane to the free surfaces
• Stratified epithelium


  It is consist of more than one layer of cell, that only the deepest layer of the cell attaches to the basement membrane
• Pseudostratified


  • It appears to be stratified but not
  • It only has one layer of cells attached to the basement membrane
• How to name epithelium tissues

  By number of layers and shape of cells
• Squamous

  Cells that are flat or scale-like
• Cuboidal


  These are cube shaped, about as wide as they are tall
• Columnar


  Cells that are tend to be taller than they are wide
• Simple Squamous Epithelium


  • It is semi-permeable to which some substances can pass through this thin layer while others do not
  • It is a single layer that is often hexagonal that function as diffusion, filtration, and secretion
  • It can be seen in the lining of the pleural, pericardial, and peritoneal cavities
• Simple Cuboidal Epithelium


  • It is a single layer of cube-shaped cells that carry out active transport, facilitated diffusion, and function as absorption and secretion
  • It is found in kidney tubules, glands and ducts, lining of bronchioles, and the surfaces of ovaries
• Simple Columnar epithelium


  • It is a single layer of tall and narrow cells that enables to perform complex functions
  • It moves the particles, function as secretion and absorption
  • It can be found in glands and ducts, bronchioles, auditory tubes, uterus and uterine tubes, gallbladder, and bile ducts
• Pseudostratified epithelium


  • These are single layer of cells that some of them are small and thin
  • They synthesize mucus and provides protection to the body
  • It is found at the lining of the nasal canal, nasal sinuses, auditory tubes, pharynx, trachea, and bronchi
• Stratified squamous epithelium


  • These are cells that are capable of dividing and the deepest cells are cuboidal or columnar
  • It has several layers that are cuboidal in the basal layer, it can also be keratinized
  • It forms a barrier for protection and to reduce loss of water
• Transitional epithelium


  • Stratified cells that can stretch and be flattened
  • They line cavities to expand
  • They appear cuboidal when not stretched and squamous when stretched
• Free surface modifications


  These are not in contact with any other cells and can be smooth or folded
• Endothelium


  Specialized type of simple squamous epithelium
• Desmosomes


  They mechanically bind epithelial cells
• Hemidesmosomes

  Anchors cells to the basement membrane, preventing the movement of the tissue
• Adhesive material and intermediate filaments

  Mechanical linkages are consists of
• Tight junctions

  It anchors cells to each other that forms barriers
• Adhesion belts

  • It help tight junctions to anchor the epithelial cells
  • It provides additional strength
• Gap Junctions

  It is consist of group channels that allow small ions and molecules to pass from epithelial cell to the adjacent