Animal Cell Types and Tissues Part 1

• Anatomy


  Study of biological form
• Physiology


  Study of biological functions
• Levels of Organization in Organismal Complexity

  • Protoplasmic grade of organization
  • Cellular grade of organization
  • Cell-tissue grade of organization
  • Tissue-organ grade of organization
  • Organ system grade of organization
• Protoplasmic grade of organization

  • Unicellular
  • All life functions are confined within the boundaries of a single cell
  • Protoplasm is the living part of the cell that contains organelles
• Protoplasmic grade of organization

  • Paramecium
• Cellular grade of organization

  • Aggregation of cells that are functionally differentiated
  • A division of labor is evident (somatic vs reproductive cells)
• Cellular grade of organization

  • Algae, sponges
• Cell-tissue grade of organization

  • Aggregation of similar cells into definite patterns or layers, thus becoming a tissue
• Cell-tissue grade of organization

  • Hydra (cnidarians)
• Tissue-organ grade of organization


  • An Individual Organ is formed from a variety of tissue
• Tissue-organ grade of organization

  • Planaria
• Organ system grade of organization


  • Organs work together to perform some function
  • Systems are associated with basic body functions
• Organ system grade of organization

  • Complete digestive system – comprised of organs such as the oral cavity, liver, stomach, pancreas, intestines
• Epithelial Tissue


  • Covers the outside of the body and lines organs and cavities within the body
  • Compact; occurs in sheets of tightly packed cells
  • Little intercellular substance
  • Polarized (Apical and Basal surface or lamina)
  • Cells are closely joined
  • Avascular (no blood vessels)
  • Innervated (supplied by nerves)
  • Regenerate very quickly
• Polarity


  • Apical or free surface
  • Basal surface
• Apical or free surface

  • Exposed to air or fluid
  • Structures on free surfaces: microvilli, cilia, flagella
  • Great for absorption
  • Great for propelling substances
• Basal surface


  • Where the cells at the base of the barrier are attached
  • Also called basal lamina and Basement membrane
• Types of intercellular links

  • Tight junctions
  • Desmosomes
  • Gap Junction
• Tight junctions


  • Membranes of adjacent cells are fused, forming continuous belts around cells
  • Prevent leakage of extracellular fluid across a layer of epithelial cells
• Desmosomes


  • Fasten cells together into strong sheets, much like rivets
  • Reinforced by intermediate filaments of keratin
  • Hyper-adhesive state allows resistance to mechanical stress
• Gap Junctions


  • Provide cytoplasmic porous channels between adjacent cells
  • Salt ions, sugar, amino acids, and other small molecules can pass through channels
• Types of Epithelial cells according to shape

  • Cuboidal
  • Squamous
  • Columnar
• Types of Epithelial cells according to layering


  • Simple epithelium
  • Stratified epithelium
  • Pseudostratified epithelium
• Simple Squamous


  • Composed of flattened cells
  • Form a continuous lining of blood capiliaries , lungs and other surfaces
  • Permits the passive diffusion of gases (small) and tissue fluids into and out of cavities
• Stratified Squamous


  • Consist of 2 to many layer cells
  • Adapted to withstand mild mechanical abrasion
  • Basal layer of cells undergo continuous mitotic cell division
  • Lines the oral cavity, esophagus, anal canal, vagina of mammals, skin
• Simple Cuboidal


  • Short box-like cells
  • Usually lines small ducts and tubules
  • May have active secretory and absorptive functions
  • May involve in balance of water and salt
  • Collective duct in kidney
• Simple columnar


  • Like cuboidal epithelium but taller
  • Active secretory and absorptive functions (bigger molecules)
  • Found on highly absorptive surfaces such as intestinal tract and female reproductive tract
  • In some organs cell are ciliated
• Stratified columnar


  • Consists of at least two layers of cell
  • Found along some areas of anorectal regions and salivary duct
  • Specialized in secretion and absorption to regulate salt levels
• Pseudostratified


  • Single layer of cells, varying in height
  • Can be ciliated
  • Secrete mucous
  • Forms mucous membranes that lines respiratory tract in most vertebrates
• Types of epithelial tissue

  • Exocrine
  • Endocrine
• Exocrine


  Secrete substances into ducts into epithelial tissues (apical), non hormones
• Endocrine


  Secrete directly into bloodstreams, hormones
• Mesothelium


  • Squamous cells lining cavities such as peritoneal (cavity containing the abdomen and the pelvic area) and pleural cavity (chest cavity containing the lungs) and lining of visceral organs
• Endothelium


  • Lining of blood and lymph vessels
• Transitional epithelium


  • Made up of several layers of cells that become flattened when stretched
• Transitional epithelium


  • Urinary bladder
• Glandular epithelium


  Epithelial tissue involved in the production and release of different secretory products