epithelial tissue

• What are the four basic tissue types?

  Epithelial, connective, muscle, nervous
• What is the main function of epithelial tissue?

  Lining surfaces and glandular secretion
• What type of cells make up epithelial tissue?

  Aggregated polyhedral cells
• How does epithelial tissue relate to body surfaces?

  It lines all external and internal surfaces
• What characterizes the extracellular matrix of epithelial tissue?

  It is made up of thin material
• What are the general characteristics of epithelial tissue?

  Variable shape, size, and polarity
• What are the three shapes of epithelial cells?

  Columnar, cuboidal, squamous
• What does cell polarity in epithelial tissue refer to?

  Basal and apical poles of cells
• Where do all epithelial tissues lie?

  In the basement membrane
• What is a key feature of epithelial tissues regarding blood vessels?

  They are avascular, lacking blood vessels
• What is one function of epithelial tissue related to protection?

  Protects against abrasion and injury
• How does epithelial tissue facilitate absorption?

  Through cilia-mediated transport in the trachea
• What role does epithelial tissue play in secretion?

  Secretes mucus, hormones, and proteins
• How does epithelial tissue contribute to gas exchange?

  Through alveoli in the lungs
• What is the function of lubrication in epithelial tissue?

  Facilitates movement between surfaces
• What is the role of the basement membrane in epithelial tissue?

  Provides structural support and filtration
• What are the two parts of the basement membrane?

  Basal lamina and reticular lamina
• What is the composition of the basal lamina?

  Type IV collagen and laminin
• What does the reticular lamina contain?

  Type III collagen and anchoring fibrils
• How can the basal and reticular lamina be viewed?

  Using Transmission Electron Microscopy (TEM)
• What are junctional complexes in epithelial tissue?

  Connections for cell-to-cell adhesion
• What are occluding or tight junctions also known as?

  Zonula occludens
• What is the function of tight junctions?

  Seals adjacent cells and controls passage
• What are adherent junctions also known as?

  Zonula adherens
• What is the role of adherent junctions?

  Links cytoskeletons and stabilizes tight junctions
• What do desmosomes provide between adjacent cells?

  Strong intermediate filament coupling
• What is the function of hemidesmosomes?

  Anchors cytoskeleton to the basal lamina
• What do gap or communicating junctions allow?

  Direct transfer of small molecules and ions
• What is a connexon?

  A pair of protein subunits in gap junctions
• What is the diameter of a gap formed by connexons?

  1.5 nanometers
• What is the function of microvilli in epithelial cells?

  Increase apical surface for absorption
• What are stereocilia?

  Long microvilli with mechanosensory function
• What is the primary function of cilia?

  Propel material along epithelial surfaces
• What is the axoneme structure in cilia?

  A 9+2 assembly of microtubules
• How are epithelial cells classified based on shape?

  Squamous, cuboidal, columnar
• What is simple epithelium?

  One layer of closely packed cells
• What is pseudostratified epithelium?

  Appears to have multiple layers due to nuclei
• What characterizes stratified epithelium?

  Two or more layers of cells
• What is transitional epithelium?

  Found in urinary bladder and ureters
• What happens to transitional epithelium when the bladder is full?

  Cells become flat as it stretches