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Questions and Answers

What is the primary role of the apical domain in epithelial cells?

  • To anchor cells to the underlying matrix
  • To provide structural support to neighboring cells
  • To mediate transport of ions, molecules, and water (correct)
  • To facilitate sensory reception

Which of the following are specialized forms of covering epithelium?

  • Germinal epithelium (correct)
  • Ciliated epithelium
  • Transitional epithelium
  • Squamous epithelium

Which structure is primarily associated with increasing the surface area for absorption in epithelial cells?

  • Microvilli (correct)
  • Flagella
  • Stereocilia
  • Cilia

What is the clinical significance of membrane specialization in epithelial cells?

<p>They correlate to various structural abnormalities related to disorders (B)</p> Signup and view all the answers

In what type of epithelial cells would you expect to find a significant presence of aquaporins?

<p>Absorptive epithelial cells (D)</p> Signup and view all the answers

Which of the following specialized epithelial structures is NOT typically found in the apical domain?

<p>Desmosomes (A)</p> Signup and view all the answers

What is the main function of the glycocalyx associated with microvilli?

<p>To assist in cell recognition and protection (C)</p> Signup and view all the answers

What is the primary function of integrins in hemidesmosomes?

<p>To connect the basal membrane to the basal lamina (C)</p> Signup and view all the answers

Which component is NOT part of the basal lamina?

<p>Keratin tonofilaments (C)</p> Signup and view all the answers

Which feature distinguishes exocrine glands from endocrine glands?

<p>Exocrine glands have ducts that transport secretions (C)</p> Signup and view all the answers

What characterizes metaplasia in epithelial cells?

<p>Transformation into another cell type with loss of function (A)</p> Signup and view all the answers

What happens if malignant cells cross the basal lamina?

<p>The tumor classification is upgraded, indicating a worse outcome (C)</p> Signup and view all the answers

What primarily enables stereocilia to maintain their rigidity?

<p>Core of actin filaments (D)</p> Signup and view all the answers

What is the primary organization of the axoneme in a cilium?

<p>9 + 2 arrangement (A)</p> Signup and view all the answers

Which feature is NOT associated with the basolateral domain of epithelial cells?

<p>Cilia (B)</p> Signup and view all the answers

What condition results from defects in ciliary dynein, impacting ciliary movement?

<p>Kartagener's syndrome (C)</p> Signup and view all the answers

What is one of the critical functions of hemidesmosomes in epithelial cells?

<p>Anchoring the basal membrane (C)</p> Signup and view all the answers

Which of the following is true regarding cilia and their movement?

<p>Cilia exhibit rhythmic bending movements (C)</p> Signup and view all the answers

What characteristic distinguishes stereocilia from typical cilia?

<p>They are long microvilli. (D)</p> Signup and view all the answers

What role do the finger-like enfoldings of the basal plasma membrane serve?

<p>To increase surface area for transport (B)</p> Signup and view all the answers

In the respiratory system, cilia primarily function to:

<p>Assist in the movement of mucus (A)</p> Signup and view all the answers

Which ion channels or pumps are particularly abundant in the basolateral domain of epithelia?

<p>Na+, K+-ATPase pumps (B)</p> Signup and view all the answers

Flashcards

Germinal Epithelium

Epithelial cells that differentiate into sperm (males) or ovum (females). Found in seminiferous tubules of testes and ovaries.

Sensory Epithelium

Epithelial cells with sensory nerve supply, acting as sensory receptors. Include taste buds, ear hair cells, and retina.

Epithelial Cell Polarity

Structural changes in cell membranes to specialize in specific functions, directed towards a particular surface.

Apical Domain

Region of the epithelial cell facing the lumen, involved in transport of substances.

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Microvilli

Small, finger-like projections on apical surface, increasing surface area for absorption.

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Striated border

Microvilli, observed on the intestinal absorptive cells.

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Brush Border

Microvilli found in kidney proximal tubule cells.

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Hemidesmosome

A specialized cell junction that anchors epithelial cells to the basal lamina. It contains integrins, which bind to laminin and type IV collagen.

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Basal Lamina

A thin, extracellular layer that separates epithelial cells from the underlying connective tissue. Composed of laminin and type IV collagen.

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Metaplasia

A change in the type of epithelial cells, often in response to stress or injury. This change can lead to loss of function.

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Carcinoma

A type of cancer that arises from epithelial cells.

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Glandular Epithelium

Epithelium found in glands, responsible for secretion. Classified based on duct presence, number of cells, branching, and secretion mode.

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Stereocilia

Long, non-motile microvilli found only in the epididymis, increasing surface area. They are more rigid due to their actin filament core.

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Cilia

Long, motile apical cell processes with rhythmic bending movement. Their core contains a 9+2 arrangement of microtubules (two central single microtubules and nine outer doublets). Dynein, an ATPase protein, provides energy for movement.

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Kartagener's Syndrome

Hereditary condition caused by defects in ciliary dynein, leading to impaired ciliary movement. This results in susceptibility to lung infections and male infertility.

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Basolateral Domain

Region of the epithelial cell that faces the basement membrane. It includes the lateral plasma membrane and the basal plasma membrane, each with specific junctions, receptors, and ion channels.

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Plasma Membrane Infolding

Finger-like extensions of the basal plasma membrane, increasing surface area and partitioning the mitochondria-rich cytoplasm. Usually found in cells involved in ion transport.

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Study Notes

Other Forms of Epithelium & Epithelial Cell Polarity

  • Epithelial cells adapt structurally to specific functions
  • Cell membrane specializations are correlated to their function
  • Clinical disorders can be related to structural abnormalities in cell membranes

Specialized Forms of Covering Epithelium

  • Special types of epithelium perform specialized functions
  • Germinal epithelium differentiates into sperm (males) or ovum (females)
    • Found in seminiferous tubules (testes) and ovaries
  • Sensory epithelium contains sensory nerves
    • Functions as sensory receptors
    • Examples: taste buds, ear hair cells, retinal cells

Epithelial Cell Polarity

  • Most epithelial cells exhibit structural changes in cell membranes
  • This represents adaptation to specific functions
  • Cell membranes have polarity, directed towards a surface

Apical Domain

  • Refers to the part of the epithelial cell facing the lumen
  • Functions in ion, molecule, and water transport
  • Rich in ion channels, carrier proteins, ATPase, glycoproteins, hydrolytic enzymes, and aquaporins
  • Contains microvilli with associated glycocalyx, and potentially stereocilia, cilia, and flagella

a. Microvilli

  • Finger-like cytoplasmic projections on cell surface
  • Increase surface area for absorption
  • Contain microfilaments for rigidity
  • Examples: striated border of intestinal cells and brush border of kidney proximal tubule cells.

b. Stereocilia

  • Long, non-motile microvilli
  • Found in the epididymis
  • Increase surface area

c. Cilia

  • Long, motile apical processes with rhythmic bending
  • Composed of microtubules (9+2 arrangement)
  • Contain dynein for energy
  • Found in ciliated epithelia (respiratory system, oviduct)

Clinical Hint: Kartagener's Syndrome

  • Hereditary defect in ciliary dynein
  • Results in infertility and susceptibility to lung infections

II. Basolateral Domain

  • Divided into lateral and basal plasma membranes
  • Contains specialized features like receptors, ion channels, and constitutive secretion pathways
  • Includes junctional specializations

a. Basal Enfolding

  • Basal surface of some epithelia contains numerous infoldings
  • Increases surface area, and partitions mitochondria-rich cytoplasm
  • Important for ion transport

b. Hemidesmosomes

  • Structurally similar to half-desmosomes
  • Connect basal cell membrane to the basal lamina
  • Keratin tonofilaments are attached to plaques within the cell
  • Extracellular moieties of transmembrane linker proteins bind to laminin and type IV collagen in the lamina

c. Basal Lamina

  • Lies between epithelium and underlying connective tissue
  • Composed of adhesive glycoproteins, like laminin and collagen type IV
  • Important for cell attachment and tissue integrity

Clinical Hint: Metaplasia

  • Transformation of one type of epithelium into another
  • Loss of function is possible

Glandular Epithelium

  • Found in glands
  • Classified by number of cells, duct presence/absence, duct branching, mode and type of secretion
  • Endocrine glands secrete hormones directly into the blood
  • Exocrine glands secrete into a cavity or onto a surface, have ducts

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Description

Explore the specialized forms of epithelium and the concepts of epithelial cell polarity in this quiz. Understand how structural adaptations enable epithelial cells to perform specific functions, and learn about the significance of the apical domain in epithelial cells. This quiz examines the connection between cell membrane structures and clinical disorders.

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