Lec 4: Tissues

• Tissues


  A "fabric" or group of cells with similar structure and function.

  
• 4 tissue types (CMEN)

  connective (support),

  muscle (movement),

  epithelial(covering),

  nervous(control)

  
• Histology


  Study of tissues
• Biopsy


  Study of live tissues
• Autopsy


  Study of dead tissues
• Epithelial Tissues and Glands


  Sheet of cells that cover all free body surfaces (inside or out), forming an interface or boundary between two environments.

  
• 5 functions of epithelial tissue (FAPSS)

  Filtration,

  Absorption

  Protection,

  Secretion,

  Sensory Reception
• Filtration


  Closely fitted cells can from a "strainer" with small holes
• Absorption


  Intake of molecules and substances
• Secretion


  Release of molecules and substances (glands)
• Sensory Reception


  The detection of a stimulus through nervous tissue working with epithelial
• 6 Special Characteristics of epithelial tissue (SPARCS)

  Specialized contacts,

  Polarity,

  Avascular but innervated,

  Regeneration,

  Cellularity,

  Supported by connective tissue

  
• specialized contacts


  Epithelial tissue hastight junctions(adjacent cells tied together to prevent substances leaking through) anddesmosomes(keeps cells from pulling apart)

  
• Polarity


  1 Free surface (Apical) and 1 Bound surface (Basal)

  
• Apical Surface


  Free Surface (ex: On top of the skin)

  Includes Microvilli & Cilia

  
• Basal Surface


  Bound Surface (ex: Below the skin)

  Includes Basal Lamina & Basement Membrane

  
• Avascular


  without blood vessels (blood vessels are in the connective tissue and brings the epithelial oxygen)

  
• Innervated


  has a nerve supply

  
• Epithelial tissue Regeneration


  Highly mitotic- almost in a constant state of repair

  
• Cellularity


  Cells are physically touching each other, closely associated with one another

  
• Microvilli


  fingerlike extensions of epithelial cells lining some parts of digestive tract or kidney.

  Increased surface area for absorption and secretion.

  
• Cilia


  "Hair-like" they can move substances along the surface of a sheet of epithelial cells.

  Propels mucus

  
• Lateral Cell Junctions


  Desmosomes

  Tight Junctions

  Gap Junctions

  
• Desmosomes


  Anchoring junctions (linking proteins) between cells that prevent cells subjected tp mechanical stress (such as skin) from being pulled apart.

  Confers strength

  
• Tight Junctions


  Rivets that securely fuse adjacent plasma membranes together into leak proof sheets;

  Seals extracellular space

  
• Gap Junctions


  Allows substances to leak between cells

  
• Basal Lamina


  Noncellular, adhesive sheet of glycoproteins secreted by epithelial cells toward the neighboring connective tissues layer (connects epithelial and connective tissues),

  Combines with fibers from CT layer to form basement membrane

  
• Basal Lamina 2 Functions

  Selective filter,

  Scaffold to which epithelial cells can migrate or grow upon
• Basement Membrane


  Located just deep to basal lamina+

  Reinforces epithelial sheet and defines epithelial boundary

  
• Classification of Epithelium


  1st: Number of cell layers

  2nd: Shape of cell

  3rd: Followed by epithelium

  
• Simple


  One layer

  
• Stratified


  More than one layer

  
• Pseudostratified


  Looks like more than one layer but isn't

  It is one layer

  
• Squamous


  Flat, plate or scale like

  Nucleus: Flat & disc like

  
• Cuboidal


  Cube shaped or box like

  Nucleus: Large & Round; Spherical

  
• Columnar


  Tall and Column Shaped

  Nucleus: Oval and elongated, located in basal 1/3

  
• Glands


  One or more epithelial cells organized to make and secrete (export) a particular product (often an aqueous fluid that contains proteins)

  
• Secretory Pathway


  RER->Golgi->Vesicles->Exocytosis

  
• What type of epithelial tissue is found in the endocrine glands?

  Glandular Epithelium
• Two major gland types

  Endocrine Glands and Exocrine glands