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Questions and Answers
What are tissues?
Groups of cells that are similar in structure and in function.
What is epithelial tissue?
Sheet of cells that cover a body surface or lines a body cavity.
What are the 4 primary tissue types?
Epithelial tissue, connective tissue, muscle tissue, nerve tissue.
What are the functions of epithelial tissue?
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What are the two types of surfaces in epithelial tissue?
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Epithelial tissue is avascular.
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What is a characteristic of simple epithelial tissue?
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Which type of epithelial tissue appears stratified but is not?
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What do endocrine glands do?
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Where is simple squamous epithelium found?
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What is the function of stratified squamous epithelium?
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Study Notes
Tissues Overview
- Tissues consist of groups of cells that share similar structures and functions.
Types of Primary Tissues
- Four primary tissue types:
- Epithelial tissue
- Connective tissue
- Muscle tissue
- Nerve tissue
Epithelial Tissue
- Epithelial tissue forms sheets covering body surfaces or lining cavities.
- Functions include:
- Protection
- Absorption
- Filtration
- Excretion
- Secretion (forms both endocrine and exocrine glands)
- Sensory reception (detects temperature, pain, and vibration)
Characteristics of Epithelial Tissue
- Exhibits polarity with:
- Apical surface (upper, free side)
- Basal surface (anchored to basement membrane)
- Composed of tightly packed cells with even spacing.
- Forms continuous sheets held by tight junctions and desmosomes.
- Supported by connective tissue, is avascular (lacks blood supply), and has a high regeneration rate.
Classification of Epithelial Tissues
- Simple Epithelium: Single cell layer; ideal for absorption and filtration.
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Stratified Epithelium: Two or more layers; includes:
- Squamous: flat and thin
- Cuboidal: cube-like
- Columnar: tall and rectangular
Specialized Epithelial Tissues
- Endothelium: Innermost lining; provides a slippery surface in serous membranes.
- Mesothelium: Middle lining; found in serous membranes of the ventral body cavity and covering organs.
Unique Types of Epithelial Tissue
- Pseudostratified Columnar Epithelium: Appears stratified with nuclei at various levels; often contains goblet cells and cilia. Found in trachea and male reproductive ducts.
- Transitional Epithelium: Unique stratified squamous epithelium that allows stretching; consists of rounded cells. Found in the urinary system.
Glandular Epithelial Tissue
- Glands are specialized epithelial cells that extract materials from blood and transform them.
- Endocrine Glands: Ductless, secrete hormones directly into the bloodstream.
- Exocrine Glands: Retain ducts; secrete substances onto body surfaces or cavities (example: sweat and oil glands).
Types of Simple Epithelial Tissues
-
Simple Squamous Epithelium:
- Structure: Single layer of flattened cells.
- Function: Facilitates diffusion and filtration; secretes lubricating substances.
- Location: Air sacs of lungs, lining of heart and blood vessels.
-
Simple Cuboidal Epithelium:
- Structure: Single layer of cubelike cells.
- Function: Involved in secretion and absorption.
- Location: Kidney tubules, glands, ovary surface.
-
Simple Columnar Epithelium:
- Structure: Single layer of tall cells.
- Function: Absorption and secretion, including mucus.
- Location: Digestive tract.
Types of Stratified Epithelial Tissues
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Stratified Squamous Epithelium:
- Structure: Multiple layers with outer layers being flattened.
- Function: Provides protection against abrasion.
- Location: Esophagus, mouth, vagina.
-
Stratified Cuboidal Epithelium:
- Structure: Generally 2 layers of cubelike cells.
- Function: Offers protection.
- Location: Ducts of sweat, mammary, and salivary glands.
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