Histology of Epithelial Tissue

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Questions and Answers

What is one characteristic of epithelial cells regarding their arrangement?

They are arranged in a single layer only.

They are extensively vascularized.

They form long muscular fibers.

They exhibit polarity. (correct)

Which of the following is a function of simple epithelium?

Production of keratin.

Absorption of nutrients only.

Protection from friction.

Transport as a regulatory barrier. (correct)

In which location can you commonly find cuboidal cells?

Surface of the skin.

Kidneys, ducts, and glands. (correct)

Lining of blood vessels.

Lining of the lungs.

What type of stratified squamous epithelium lacks nuclei and contains keratin intermediate filaments?

Orthokeratinized stratified squamous epithelium. Signup and view all the answers

Which epithelial tissue is specifically designed for absorption and secretion?

Columnar epithelium. Signup and view all the answers

What is the primary function of stratified squamous epithelium?

Protection against abrasion. Signup and view all the answers

What defines the shape of squamous cells?

Flat, resembling an egg shape. Signup and view all the answers

Which of the following statements about epithelial tissue is true?

Epithelial tissue is avascular and generally innervated. Signup and view all the answers

What is the primary function of microvilli in epithelial cells?

Increases surface area Signup and view all the answers

Which junction prevents diffusion of lipids and proteins in the paracellular space?

Zonula occludens Signup and view all the answers

What type of epithelial junction is responsible for allowing communication between two epithelial cells?

Gap junction Signup and view all the answers

Where is the basement membrane located in relation to epithelial cells?

Between epithelial cells and connective tissue Signup and view all the answers

Which type of epithelial tissue is characterized by multiple layers of squamous cells?

Stratified squamous epithelium Signup and view all the answers

What structural components are microvilli and stereocilia made of?

Actin microfilaments Signup and view all the answers

What is the role of hemidesmosomes in epithelial cells?

Attach epithelial cells to the basement membrane Signup and view all the answers

Which of the following statements about epithelial cells is true?

All epithelial cells contain keratin intermediate filaments Signup and view all the answers

Study Notes

Histological Organization

Four levels: Cells, Tissues, Organs, Organ Systems

Epithelial Cells Characteristics

Exhibit polarity with apical, lateral, and basal domains
Lack extracellular matrix (ECM) between them

Locations of Epithelium

External body surfaces (skin)
Lining of internal body cavities
Glands

Epithelial Tissue Properties

Avascular (no blood supply)
Innervated (has nerve supply)

Cytoskeleton Composition

Microtubules: made of tubulin
Microfilaments: made of actin
Intermediate filaments: made of keratins

Simple vs. Stratified Epithelium

Simple: one cell thick, functions in transport, regulatory barrier
Stratified: multiple cell layers, provides protection against friction and abrasion

Cell Types in Epithelium

Squamous Cells: Flat shape; functions in filtration and diffusion; located in kidneys, lungs, blood vessels.
Cuboidal Cells: Cube shape, circular nuclei; functions in absorption and secretion; found in kidneys, ducts, and glands.
Columnar Cells: Column shape, oval nuclei; functions in absorption and secretion; located in stomach, small intestine, large intestine.

Types of Stratified Squamous Epithelium

Orthokeratinized: Lacks nuclei, full of keratin; found close to the environment.
Parakeratinized: Some nucleated cells and some keratinized; moderately keratinized.
Nonkeratinized: All cells nucleated; has keratin intermediate filaments but minimally keratinized.

General Function and Location of Stratified Squamous Epithelium

Function: Protects against abrasion/desiccation, provides nonspecific defenses.
Location: Oral cavity, esophagus, epidermis of skin, vagina.

Keratinization Process

Cells progress through layers of epidermis, transforming from mitotic to keratin-filled.
Non-differentiated, mitotic cells near connective tissue; terminally differentiated, keratin-filled near environment.

Epithelial Domains

Apical Domain: Faces lumen/environment; contains microvilli, cilia, and stereocilia.
Lateral Domain: Areas where cells touch; contains various types of junctions.
Basal Domain: Contacts the basement membrane, a specialized connective tissue.

Epithelial Surface Structures

Microvilli: Increase surface area; made of actin microfilaments.
Cilia: Motile structures for moving substances; made of microtubules.
Stereocilia: Found in the inner ear and male reproductive tract; made of actin microfilaments.

Junctions in Lateral Domain

Zonula: Belt-like structure surrounding cells.
Macula: Spot-like adhesion.
Fascia: Covers larger areas than macula, not continuous.

Types of Junctions

Zonula Occludens (Tight Junctions): Prevents diffusion between cells, maintains cell polarization.
Zonula Adherens (Adhesion Junctions): Adheres adjacent epithelial cells.
Macula Adherens (Desmosomes): Anchors cells together, connects to keratin filaments.
Gap Junctions: Allow ionic communication between cells.
Hemidesmosomes: Attach epithelial cells to the basement membrane.

Basement Membrane

Located between epithelial cells and underlying connective tissue.
Composed of extracellular matrix with collagen type IV.
Functions include supporting epithelial cells, facilitating transition to connective tissue, and contributing to cell polarity.

Microscopy Observation

Stratified squamous epithelium identified if observing six layers with flattened uppermost cells.

Keratin Intermediate Filaments

All epithelial cells, including nonkeratinized types, contain keratin intermediate filaments as part of their cytoskeleton.

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Description

This quiz explores the histological organization and characteristics of epithelial cells. It covers various types, properties, and locations of epithelium, as well as the composition of the cytoskeleton. Test your knowledge on the fundamental aspects of epithelial tissue!