Epithelium Tissue Structure and Function
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Questions and Answers

What is the main characteristic of epithelium?

  • It is composed of scattered polyhedral cells and a lot of extracellular matrix.
  • It is composed of scattered polyhedral cells and very little extracellular matrix.
  • It is composed of closely aggregated polyhedral cells and a lot of extracellular matrix.
  • It is composed of closely aggregated polyhedral cells and very little extracellular matrix. (correct)

    • What is the function of basement membrane?

  • To separate epithelium from underlying connective tissue (correct)
  • To provide nutrition to epithelial cells
  • To facilitate sensory reception
  • To protect epithelial cells from infection

    • What is the characteristic of avascular epithelium?

  • It has a rich blood supply
  • It has no blood vessels (correct)
  • It has a variable blood supply
  • It has a limited blood supply

    • What is the function of glands?

    <p>To secrete substances</p> Signup and view all the answers

    What type of epithelium lines the inner surface of body cavities?

    <p>Covering epithelium</p> Signup and view all the answers

    What is the main function of simple cuboidal epithelium?

    <p>Covering and secretion</p> Signup and view all the answers

    What is the characteristic of simple squamous epithelium?

    <p>It has a single layer of flattened cells</p> Signup and view all the answers

    What is the function of endothelium?

    <p>Transport of materials</p> Signup and view all the answers

    What is the characteristic feature of pseudostratified ciliated columnar epithelium?

    <p>Presence of four types of cells</p> Signup and view all the answers

    What is the function of simple squamous epithelium in the human body?

    <p>To protect underlying tissues</p> Signup and view all the answers

    Where is simple squamous epithelium commonly found?

    <p>In the lining of body cavities</p> Signup and view all the answers

    Where is stratified squamous epithelium found?

    <p>Skin and mucosa</p> Signup and view all the answers

    What is the function of transitional epithelium?

    <p>Stretching and accommodating varying amounts of urine</p> Signup and view all the answers

    What is the shape of nucleus in simple cuboidal epithelium?

    <p>Spherical</p> Signup and view all the answers

    What is the function of goblet cells in pseudostratified ciliated columnar epithelium?

    <p>Producing mucus</p> Signup and view all the answers

    What is unique about transitional epithelium?

    <p>It is flexible and can change shape</p> Signup and view all the answers

    What type of epithelium is found in the conjunctiva?

    <p>Stratified columnar epithelium</p> Signup and view all the answers

    What is the function of microvilli?

    <p>To increase the surface area of the cell</p> Signup and view all the answers

    What is the structure of a cilium?

    <p>Microtubules, 9×2+2, dynein, and cell membrane</p> Signup and view all the answers

    Where are stereocilia found?

    <p>Sensory cells of the ear</p> Signup and view all the answers

    What type of epithelium is found in the urinary bladder?

    <p>Transitional epithelium</p> Signup and view all the answers

    What is the function of cilia?

    <p>Produce a forward-moving wave</p> Signup and view all the answers

    Where are microvilli found?

    <p>Intestinal epithelial cells and proximal renal tubule</p> Signup and view all the answers

    What is the function of intercellular junctions?

    <p>Hold adjacent cells together</p> Signup and view all the answers

    What is the thickness of the lamina lucida?

    <p>10-50 nm</p> Signup and view all the answers

    What is the primary function of tight junctions?

    <p>To seal the space between cells</p> Signup and view all the answers

    What is the main function of reticular lamina?

    <p>Support and connection</p> Signup and view all the answers

    What is the function of plasma membrane infolding in epithelial cells?

    <p>Increase the basal surface area</p> Signup and view all the answers

    What is the characteristic feature of the structure of desmosomes?

    <p>A plate or spot-shaped structure with a 20-30 nm gap</p> Signup and view all the answers

    What is the function of hemidesmosomes?

    <p>Bind epithelial cells to the subjacent basal lamina</p> Signup and view all the answers

    What is the function of gap junctions?

    <p>To provide a pathway for communication between cells</p> Signup and view all the answers

    What is the characteristic of exocrine glands?

    <p>Maintain contact with the surface and discharge secretion through a duct system</p> Signup and view all the answers

    What is the composition of the basal lamina?

    <p>A layer of amorphous ground substance produced by epithelial cells</p> Signup and view all the answers

    What is the characteristic of endocrine glands?

    <p>Release secretion directly into blood stream</p> Signup and view all the answers

    What is the characteristic feature of the structure of intermediate junctions?

    <p>A plaque of electron-dense materials with microfilaments</p> Signup and view all the answers

    What is the role of the basement membrane?

    <p>To separate epithelial cells from underlying connective tissue</p> Signup and view all the answers

    Where are plasma membrane infoldings mainly found?

    <p>Proximal and distal renal tubule</p> Signup and view all the answers

    What is the composition of reticular lamina?

    <p>Reticular fibers and ground substance</p> Signup and view all the answers

    What is the characteristic feature of the structure of tight junctions?

    <p>Point-like fused structures arranged in 2-4 thread-like structures</p> Signup and view all the answers

    What is the term used to describe the complex of four types of junctional structures?

    <p>Junctional complex</p> Signup and view all the answers

    Study Notes

    Epithelium Characteristics

    • Composed of closely aggregated polyhedral cells with little extracellular matrix
    • Cells cover body surfaces, line body cavities, and constitute glands
    • General features:
      • Contain more cells and less extracellular ground substance
      • Polarity: free surface faces air or other substances, basal surface faces underlying CT, and lateral surface faces adjacent cells
      • Avascularity, but innervation: no blood vessels, but rich in nerve terminals
      • Functions: protection, secretion, absorption, excretion, and sensory reception

    Classification of Epithelium

    • Covering epithelium: covers body surface or lines inner surface of body cavities, tubes, and sacs
    • Glandular epithelium: main function is secretion
    • Sensory epithelium: has special sensory function

    Covering Epithelium Classification

    • Simple epithelium:
      • Simple squamous epithelium: one layer of flattened cells, found in mesothelium, endothelium, alveoli, and parietal layers of renal capsule
      • Simple cuboidal epithelium: one layer of cells with same height and width, found in renal tubule, thyroid, and some ducts of many glands
      • Simple columnar epithelium: one layer of columnar cells, found in respiratory tract, digestive tract, and glands
      • Pseudostratified ciliated columnar epithelium: one layer of columnar cells with cilia, found in respiratory tract
    • Stratified epithelium:
      • Stratified squamous epithelium: multiple layers of cells, found in skin, mouth, pharynx, esophagus, urethra, and vagina
      • Stratified cuboidal epithelium: multiple layers of cells, found in sweat glands and developing ovarian follicles
      • Stratified columnar epithelium: multiple layers of cells, found in conjunctiva

    Epithelial Specializations

    • Specialization of free surface:
      • Microvilli: increase cell surface area, found in intestinal epithelium and proximal renal tubule
      • Cilia: move substances or particles stuck to the epithelium, found in respiratory tract
      • Stereocilia: increase cell surface area, found in epididymis, ductus deferens, and sensory cells of the ear
    • Specialization of lateral surface:
      • Intercellular junctions:
        • Tight junction (zonula occludens): seal the space between cells
        • Intermediate junction (zonula adherens): adhere and keep cell shape
        • Gap junction (communicating junction): provide a pathway between cells
        • Desmosome (macula adherens): firmly connect cells
    • Specialization of basal surface:
      • Basement membrane: a sheet of amorphous material between epithelial cells and underlying CT
      • Plasma membrane infolding: increase basal surface area and facilitate passage of water and ions, found in proximal and distal renal tubule
      • Hemidesmosomes: bind epithelial cells to the subjacent basal lamina

    Glandular Epithelium and Gland

    • Glandular epithelium: specialized for secretion
    • Gland: organs composed mainly of glandular epithelium
    • Classification of glands:
      • Exocrine gland: maintain contact with the surface, discharge secretion through a duct system
      • Endocrine gland: do not maintain contact with the surface, release secretion directly into blood stream
    • Formation of glands from covering epithelia: epithelial cells proliferate and penetrate connective tissue

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    Description

    Learn about the characteristics and functions of epithelial tissue, including its structure, junctions, and polarity. Understand the role of epithelium in covering body surfaces, lining cavities, and forming glands.

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