Animal Cell Types and Tissues Part 1

• Protoplasmic grade - unicellular organisms where all life functions are confined within the boundaries of a single cell (paramecium)
• Protoplasm - living part of the cells, that contains organelles (i.e., nucleus) and the cell’s cytoplasm
• Cellular grade - aggregation of cells that are functionally differentiated

  and has a division of labor is evident (somatic vs reproductive cells)
• Cell-tissue grade - aggregation of similar cells into definite patterns or layers, thus becoming a tissue and can be seen in cnidarians

  
• Tissue-organ grade - An Individual Organ is formed from a variety of tissue
• In the tissue-organ grade of flatworms, The eye spots of a flatworm is an organ made up of primarily nervous tissue, but also includes connective tissue and epithelial tissue, mostly surrounding the eyes.
• Organ system grade - organs work together to perform some function and that systems are associated with basic body functions
• Epithelial Tissue - covers the outside of the body and lines organs

  and cavities within the body, compact; occurs in sheets of tightly packed cells and has little intercellular substance
• Apical surface - is 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
• What are the 3 main types of intercellular links?

  Tight junctions, Desmosomes, Gap junctions
• Tight junction - prevent leakage of extracellular fluid across a layer of

  epithelial cells and where membranes of adjacent cells are fused, forming continuous belts around cells
• Desmosomes - fasten cells together into strong sheets and are reinforced by intermediate filaments of keratin, hyper-adhesive state allows resistance to mechanical stress
• Gap Junctions (Connexins, channels between cells) - provide cytoplasmic porous channels between adjacent cells wherein salt ions, sugar, amino acids, and other small molecules can pass through channels
• Pseudostratified epithelium - Made up of a single layer of cells but appears stratified

  
• Simple squamous epithelium - composed of flattened cells that form a continuous delicate lining of blood capillaries, lungs, and other surfaces

  
• What specific type of tissue permits the passive diffusion of gases and tissue fluids into and out of cavities?

  Simple squamous epithelium
• Stratified squamous epithelium - consists of 2 to many layers of cells and is adapted to withstand mild mechanical abrasion wherein 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 that usually lines small ducts and tubules which may have active secretory and absorptive functions

  
• Simple columnar epithelium - cells are taller and have active secretory and absorptive functions that are found on highly absorptive surfaces such as intestinal tract and female reproductive tract wherein cells can be ciliated in some organs

  
• Stratified columnar epithelium - consists of at least two layers of cells

  found along some areas of the anorectal region and salivary duct which 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 and in many vertebrates, these form a mucous membrane that lines portions of the respiratory tract.
• Exocrine epithelia - secrete substance into ducts into epithelial surface
• Endocrine epithelia - secretions directly into bloodstream
• What organ has both endocrine and exocrine secretions?

  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