Epithelial Tissue: Characteristics and Classification
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Questions and Answers

Which characteristic is LEAST useful when classifying epithelial tissue?

  • Cell shape
  • Cell arrangement
  • Function of the tissue (correct)
  • Number of cell layers

A tissue sample shows multiple layers of cells with the most superficial layer being flattened and scale-like. Which type of epithelium is this?

  • Stratified cuboidal
  • Simple squamous
  • Transitional
  • Stratified squamous (correct)

In which location would you expect to find pseudostratified columnar epithelium?

  • Lining of blood vessels
  • Lining of the stomach
  • Lining of the trachea (correct)
  • Epidermis of the skin

Which type of epithelium is specialized to stretch and is found in the lining of the urinary bladder?

<p>Transitional (D)</p> Signup and view all the answers

Which of the following is a critical distinction between endocrine and exocrine glands?

<p>Endocrine glands lack ducts and secrete directly into the bloodstream or surrounding tissues, while exocrine glands secrete through ducts onto epithelial surfaces. (C)</p> Signup and view all the answers

A gland releases its secretion by rupturing the entire cell. Which type of secretion is this?

<p>Holocrine (D)</p> Signup and view all the answers

Which of the following properties is shared by ALL types of epithelium?

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

What is the PRIMARY function of the basal lamina found underlying epithelial tissues?

<p>To serve as a selective filter and provide structural support to the epithelium. (B)</p> Signup and view all the answers

Which type of cancer originates from glandular epithelial cells?

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

What is the role of intercellular junctions (junctional complexes) in epithelial tissue?

<p>To provide structural support that prevents separation of cells, and control paracellular passage (A)</p> Signup and view all the answers

Which characteristic primarily distinguishes pseudostratified columnar epithelium from stratified columnar epithelium?

<p>All cells reach the basement membrane. (B)</p> Signup and view all the answers

How does the transitional epithelium of the urinary bladder accommodate volume changes?

<p>By flattening its cells and decreasing the number of apparent cell layers. (B)</p> Signup and view all the answers

Which of the following best describes the functional distinction between microvilli and stereocilia found on epithelial cells?

<p>Microvilli increase surface area for absorption; stereocilia have specialized sensory functions. (C)</p> Signup and view all the answers

What is the primary difference in secretion mechanism between merocrine and holocrine glands?

<p>Merocrine glands release secretory products through exocytosis, while holocrine glands accumulate secretion until the cell ruptures. (A)</p> Signup and view all the answers

How do mucous glands differ structurally from serous glands in the epithelium?

<p>Mucous glands have wider lumens and flattened nuclei, while serous glands have narrower lumens and round nuclei. (A)</p> Signup and view all the answers

Which modification to epithelial cells is most directly related to facilitated diffusion?

<p>Expression of specific transmembrane proteins. (C)</p> Signup and view all the answers

What is the functional significance of myoepithelial cells found in association with certain exocrine glands?

<p>They contract to help expel secretions from the gland. (A)</p> Signup and view all the answers

How does the distribution of simple squamous epithelium contribute to its function in the alveoli of the lungs?

<p>Its single layer facilitates rapid gas exchange between the air and blood. (A)</p> Signup and view all the answers

What is a key structural adaptation of goblet cells that supports their function of mucus secretion?

<p>Extensive Golgi apparatus and rough endoplasmic reticulum. (A)</p> Signup and view all the answers

What is the major role of epithelial cell junctions in maintaining tissue integrity and function?

<p>Providing a selective barrier controlling paracellular transport. (C)</p> Signup and view all the answers

Flashcards

Epithelial Tissue

Avascular tissue that covers body surfaces and lines cavities.

Cell Characteristics

Epithelial cells are arranged in sheets with distinct surface domains: apical, lateral, and basal.

Types of Epithelium

Classified by cell arrangement (simple or stratified) and shape (squamous, cuboidal, columnar).

Simple Squamous Epithelium

One cell layer thick, found in areas of exchange like blood vessels and lungs.

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Cuboidal Epithelium

Cells where width, height, and depth are about the same, found in glands and kidney tubules.

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Columnar Epithelium

Cells that are taller than they are wide, found in intestines and uterus.

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Pseudostratified Epithelium

Appears stratified but is actually simple; all cells rest on the basal lamina.

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Transitional Epithelium

Stratified tissue that can stretch, found in bladder and ureters.

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Exocrine Glands

Glands that secrete substances through ducts to the surface (e.g., sweat, saliva).

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Endocrine Glands

Glands that secrete hormones directly into the bloodstream for regulation.

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Epithelial Characteristics

General and specific features that define epithelial tissue types.

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Glandular Epithelium

Epithelial cells grouped to form glands performing specific functions.

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Mucous Glands

Glands that secrete mucus, typically producing viscous fluid.

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Serous Glands

Glands that secrete a watery fluid, often enzymes.

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Exocrine Secretion Modes

Different processes through which exocrine glands release substances.

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Merocrine Secretion

Glandular secretion where cells remain intact, releasing product via exocytosis.

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Apocrine Secretion

Glandular secretion involves part of the cell breaking off with the secretion.

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Holocrine Secretion

Glandular secretion where the entire cell disintegrates to release the secretion.

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Comparative Functions of Epithelium

How different epithelial types have specialized functions based on morphology.

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Study Notes

Epithelial Tissue

  • Characteristics: Epithelial tissues are arranged in sheets, possessing intercellular junctions. They have distinct apical (free), lateral, and basal surfaces, with properties determined by membrane proteins. They rest on a non-cellular basal lamina, a protein-polysaccharide layer.

  • Avascular: Lacking blood vessels.

  • Locations: Cover body surfaces, line internal cavities (closed), form glands and ducts, and make up sensory receptors.

  • Functions: Transport (via cilia moving mucus), sensory reception (neuroepithelia like taste buds), lubrication (mucus or serous fluid), excretion (filtering blood, producing urine/sweat), and reproduction (in ovaries/testes).

Epithelial Classification

  • Based on cell arrangement: Simple (single layer) or stratified (multiple layers).

  • Based on cell shape: Squamous (width > height), cuboidal (width, height, depth similar), columnar (height > width), low columnar (height slightly exceeds width), pseudostratified (appears stratified but all cells rest on the basal membrane)

Specific Epithelial Types

  • Simple Squamous: One layer, flat cells. Found lining blood vessels, Bowman's capsule, respiratory spaces. Function: exchange, barrier.

  • Simple Cuboidal: One layer, cube-shaped cells. Located in thyroid follicle walls, kidney tubules, ovary surface, small gland ducts. Function: secretion, absorption.

  • Simple Columnar: One layer, tall, column shaped. Lines the intestines, uterus, gall bladder. Function: absorption, secretion, barrier.

  • Stratified Squamous: Multiple layers, squamous cells on surface; functions as a barrier. Keratinized (skin) or non-keratinized (lining of oral cavity/vagina).

  • Pseudostratified Columnar: Appears layered but all cells rest on the basement membrane. Found in the respiratory tract (ciliated), epididymis, and ductus deferens

  • Transitional Epithelium: Stratified epithelium that can stretch (distension). Located in the urinary bladder, parts of the urethra, and ureters (renal calyces).

Glands

  • Definition: Masses of epithelial cells adapted for secretion.

  • Types:

    • Exocrine: Secrete substances onto epithelial surfaces via ducts. Unicellular (goblet cells) or multicellular.
    • Endocrine: Secrete hormones into the bloodstream.

Exocrine Gland Structure & Secretion

  • Multicellular exocrine glands are categorized by: duct type (simple or compound), shape of the secretory unit (acinar/alveolar or tubular), and secretion mode.

  • Modes of secretion:

    • Merocrine: Most common, products released by exocytosis (e.g., salivary glands).
    • Apocrine: Portions of the gland's cells are lost with the secreted product (e.g., some sweat glands).
    • Holocrine: Entire cells rupture and release the product (e.g., sebaceous glands).

Epithelial Regeneration and Pathology

  • Regeneration: Epithelia (like epidermis and intestines) have high renewal rates.

  • Carcinoma: Cancer of epithelial origin.

  • Adenocarcinoma: Cancer of glandular epithelium.

  • Sarcomas: Cancers of mesenchymal origin.

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Description

Explore epithelial tissue: its arrangement in sheets with specialized surfaces, avascular nature, and locations covering body surfaces and forming glands. Learn about its diverse functions, including transport, sensory reception, lubrication, excretion, and reproduction. Understand classification based on cell arrangement and shape.

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