Ch.4- The Tissue Level of Organization

Cards (100)

  • Tissue
    a collection of specialized cells and cell products that perform a specific function; Tissues in combination form organs, such as the heart or liver
  • Histology
    study of tissues
  • Four types of tissue
    epithelial, connective, muscle, nervous
  • epithelial tissue

    covers exposed surfaces; lines internal passageways; forms glands
  • connective tissue
    Fills internal spaces;
    Supports other tissues;
    Transports materials;
    Stores energy
  • muscle tissue

    Specialized for contraction;
    Skeletal muscle, heart muscle, and walls of hollow organs
  • nervous tissue
    carries electrical signals from one part of the body to another
  • epithelial tissue

    includes epithelia and glands
  • epithelia(singular)

    Layers of cells covering internal or external surfaces
  • Glands
    structures that produce fluid secretions
  • functions of epithelial tissue

    provide physical protection; control permeability; provide sensation;produce specialized secretions
  • characteristics of epithelia
    Polarity (apical and basal surfaces)
    Cellularity (cell junctions)
    Attachment (basement membrane)
    Avascularity (avascular)
    Regeneration
  • Specialization of epithelial cells

    Move fluids over the epithelium (protection)
    Move fluids through the epithelium (permeability)
    Produce secretions (protection and messengers)
  • Polarity
    apical surface
    -microvilli increase absorption or secretion
    - cilia on a ciliated epithelium move fluids
    Basolateral surface
  • Integrity of epithelia is maintained by
    1. Intercellular connections
    2. Attachment to the basement membrane
    3. Epithelial maintenance and repair
  • intercellular connections
    support and communication
  • cell adhesion molecules (CAMs)

    transmembrane proteins
  • what act as intercellular cement?
    Proteoglycans
  • cell junctions

    form bonds with other cells or extracellular material
    1.) Gap junctions
    2.)Tight junctions
    3.)Desosomes
  • gap junctions

    -Allow rapid communication
    -Cells held together by interlocking transmembrane proteins
    - Allow small molecules and ions to pass
  • Desosomes
    CAMs and proteoglycans link opposing plasma membranes
  • spot desmosomes
    tie cells together; allow bend and twist
  • Hemidesmosomes
    attach cells to the basement membrane
  • tight junctions

    Between two plasma membranes; Adhesion belts attaches to terminal web; Prevent passage of water and solutes; Keep enzymes,acids, and wastes in the lumen of the digestive tract; Attachment to the basement membrane
  • basal lamina

    closest to the epithelium
  • reticular lamina
    deeper portion of the basement membrane, provides strength
  • Epithelial Maintenance and Repair

    Epithelial cells are replaced by continual division of stem cells; located near basement membrane
  • based on shape

    Squamous epithelia — thin and flat
    Cuboidal epithelia — square shaped
    Columnar epithelia — tall, slender rectangles
  • Based on layers
    Simple epithelium — single layer of cells
    Stratified epithelium — several layers of cells
  • Squamous epithelia

    -simple squamous epithelia
    a.) Absorption and diffusion
    -Stratified squamous epithelia
    a.) Protect against mechanical stresses
  • Cuboidal epithelia

    -Simple cuboidal epithelia
    a.) Secretion and absorption
    b.) Glands and portions of kidney tubules
    - Stratified cuboidal epithelia
    a.) Relatively rare
    b.) Ducts of sweat glands and mammary glands
  • Transitional epithelia

    Tolerate repeated cycles of stretching without damage;
    Appearance changes as stretching occurs;
    Found in urinary bladder
  • Columnar epithelia

    -Simple columnar epithelia
    a.) Absorption and secretion
    b.) Found in stomach, small intestine, large intestine
  • Pseudostratified columnar epithelia

    Typically have cilia;
    Found in nasal cavity, trachea, bronchi
  • Stratified columnar epithelia

    Relatively rare;
    Provide protection in pharynx, anus, urethra
  • Glandular epithelia

    Glands are collections of epithelial cells that produce secretions
  • endocrine glands

    release hormones into the bloodstream
  • exocrine glands

    produce exocrine secretions; discharge secretions through ducts onto epithelial surfaces
  • Methods of secretion
    merocrine, apocrine, holocrine
  • merocrine secretion

    Released by secretory vesicles (exocytosis)
    Example: merocrine sweat glands