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Questions and Answers
What is the main function of epithelial tissue?
What type of epithelium is responsible for secreting substances like sweat, hormones, and mucus?
What is the function of the basal lamina in epithelial tissue?
What is a characteristic of epithelial tissue?
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What is the term for the specialized structures that hold epithelial cells together?
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What is the orientation of cells within covering epithelial tissues?
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What is the characteristic of pseudostratified epithelium?
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What is the shape of squamous cells?
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What is the characteristic of the endothelium?
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What is the characteristic of cuboidal cells?
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What determines the shape of cells in a multi-layered epithelium?
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How are covering epithelia classified?
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What is the characteristic shape of cuboidal cells?
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What is the location of the nucleus in columnar cells?
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What type of epithelium is seen in the micrograph of a sweat gland duct?
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What is the function of microvilli in cells?
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What is the characteristic of the apical domain of columnar cells?
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What is the classification of covering epithelia based on?
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What is the primary function of cilia in the epithelium?
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Where are goblet cells typically found?
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What is the characteristic shape of goblet cells?
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What is the main component of cilia?
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What is the primary function of keratinocytes?
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Where are Pseudostratified epithelium with stereocilia found?
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Which layer of the epidermis is responsible for providing a protective barrier?
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What is the characteristic shape of melanocytes?
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In which layer of the epidermis do keratinocytes start to accumulate keratin?
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Which layer of the epidermis is found only in the thick skin of the palms, soles, and digits?
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What is the function of keratinocytes in the epidermis?
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Where are new keratinocytes formed in the epidermis?
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Study Notes
Epithelial Tissue
- Epithelial tissue, also known as epithelium, forms the covering of the body and lines its organs and surfaces.
- It consists of tightly packed cells arranged in continuous sheets, either as a single layer or multiple layers.
Characteristics of Epithelial Tissue
- Epithelial cells are held together by specialized structures called cell junctions.
- Epithelial tissue is avascular, lacking its own blood vessels, but receives nutrients and oxygen through diffusion from underlying connective tissue.
- Epithelial cells have distinct orientations (polarity) within covering epithelial tissues.
Types of Epithelial Tissue
- Two main types of epithelia are distinguished:
- Covering or lining epithelium
- Glandular epithelium
Covering Epithelial Tissue
- Covering epithelial tissue has two distinct surfaces: a free surface exposed to the external environment or internal cavities, and a basal surface firmly attached to a basal lamina (basement membrane).
- Cells have distinct orientations (polarity) within covering epithelial tissues.
- Apical domain faces the external environment or body cavities, while the basal surface connects to the basement membrane.
Classification of Covering Epithelium
- Classification is based on several descriptive criteria:
- The number of cell layers
- The shape of the cell
- The specialization of the plasma membrane at the apical domain
- The presence of specific cell types
Classification by Cell Shape
- Squamous cells: cells are flattened, wider than they are tall, with the nucleus bulging into the lumen
- Cuboidal cells: appear in section as high as they are wide, with a quadrangular appearance
- Columnar cells: appear in section, taller than they are wide
Classification by Specialization of the Plasma Membrane
- Microvilli: non-motile microscopic finger-like projections that extend from the surface of some cells
- Cilia: microscopic, hair-like projections that extend from the surface of many cells, composed of microtubules, and are motile structures that beat in a coordinated rhythm to move fluid or mucus over cell surfaces
- Stereocilia: specialized microvilli found in some cells
Classification by Presence of Specific Cell Types
- Goblet cells: unicellular intraepithelial mucin-secreting glands scattered within simple epithelia
- Keratinocytes: major cell type in the epidermis (outermost layer of skin), undergo progressive changes in their shape and function, contributing to the formation of distinct layers within the epidermis
- Melanocytes: producing cells are melanin- (pigmentary cells) located in the bottom layer of the skin's epidermis, characterized by a dendritic shape
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Description
Test your knowledge of epithelial tissue, a fundamental type of tissue that covers the body and lines its organs and surfaces. Learn about the structure and functions of epithelial cells, including cell junctions and gland formation.
