Animal Cell Types and Tissues

• Anatomy


  The study of the biological form of an organism
• Physiology


  The study of the biological functions an organism performs
• We will take a comparative study approach to understanding each animal system. The comparative study of animals reveals that form and function are closely correlated
• 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 organisms
  • All life functions are confined within the boundaries of a single cell
  • Protoplasm is the living part of the cells, that contains organelles (i.e., nucleus) and the cell's cytoplasm
• Cellular grade of organization


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


  • Aggregation of similar cells into definite patterns or layers, thus becoming a tissue (there are 4 major tissue types we will discuss later)
• Tissue-organ grade of organization


  • An Individual Organ is formed from a variety of tissue
• Organ System grade of organization


  • Organs work together to perform some function
  • Systems are associated with basic body functions
• Animal Cell/Tissue Types


  • Epithelial Tissue
  • Connective Tissue
  • Muscle Tissue
  • Nervous Tissue
• 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 or free surface


  • Exposed to air or fluid
  • Structures on free surfaces: microvilli, cilia, flagella
• Basal surface


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


  • Tight junctions
  • Desmosomes
  • Gap junctions
• Tight junction

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


  • Fasten cells together into strong sheets, much like rivets
  • Reinforced by intermediate filaments of keratin
• Gap junction


  • 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 epithelium


  Made up of a single layer of cells
• Stratified epithelium


  Made up of many layers of cells
• Pseudostratified epithelium


  Made up of a single layer of cells but appears stratified
• Simple squamous epithelium


  • Composed of flattened cells
  • Form a continuous delicate lining of blood capillaries, lungs, and other surfaces
  • Permits the passive diffusion of gases and tissue fluids into and out of cavities
• CO2 + H2O → Carbonic acid → H+ + Bicarbonate ion (HCO3)


  1. At active tissues

  2. At the lungs

  3. Carbonic anhydrase (Binds to hemoglobin)

  4. Exits red blood in exchange with Cl-
• Stratified squamous epithelium


  • Consists of 2 to many layers of cells
  • Adapted to withstand mild mechanical abrasion
  • Basal layers of cells undergo continuous mitotic divisions
  • Lines the oral cavity, esophagus, anal canal, vagina of mammals, skin
• Simple cuboidal epithelium

  • Short, boxlike cells
  • Usually lines small ducts and tubules
• Simple columnar epithelium


  • May have active secretory and absorptive functions
  • Like cuboidal epithelium but cells are taller, active secretory and absorptive functions
  • Found on highly absorptive surfaces such as intestinal tract and female reproductive tract
  • In some organs, cells may be ciliated
• Stratified columnar epithelium


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


  • Consists of a single layer of cells varying in height and the position of their nuclei
  • In many vertebrates, forms a mucous membrane that lines portions of the respiratory tract
• Exocrine & Endocrine Epithelia - absorb or secrete chemicals
• Types of epithelia based on how products are released


  • Exocrine – secrete substance into ducts into epithelial surface
  • Endocrine – directly into bloodstream
  • Mix of both exocrine and endocrine (e.g., pancreas)
• Mesothelium


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


  Lining of blood and lymph vessels