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Tissue
A group of cells that usually have a common function and are similar in structure.
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Four Major Families of Tissues
- 1. Epithelial Tissue
- 2. Connective Tissue
- 3. Muscle Tissue
- 4. Nervous Tissue
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Epithelial Tissue
- Covers body surfaces; lines hollow organs, body cavities, and ducts; forms glands
- Allows body to interact with internal and external environments
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Connective Tissue
Protects and supports the body and its organs; binds organs together; stores energy reserves as fat; provides immunity
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Muscle Tissue
- Provides movement and generation of force
- Generates heat that warms the body
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Nervous Tissue
Initiates and transmits nerve impulses (signals) that help control and coordinate body activities.
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All tissues develop from what?
Three (embryonic) primary germ layers.
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Primary germ layers
Ectoderm, Endoderm, and Mesoderm
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Three main functions of Epithelial Tissue or Epithelium
- 1. Selective Barriers
- 2. Secretory surfaces (to release products)
- 3. Protective Surfaces
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Two Major types of epithelium
- 1. Covering and lining epithelium
- 2. Glandular epithelium
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Covering and lining Epithelium
- Outer covering of skin and some internal organs or vessels, ducts and cavities.
- Interior of respiratory, digestive, urinary, and reproductive systems.
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Glandular Epithelium
Secreting portion of glands (Ex: Thyroid, adrenal, sweat glands)
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Simple epithelium
- Single layer of cells
- functions in diffusion, osmosis, filtration, secretion, absorption
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Stratified epithelium
- Several layers of cells
- protect underlying tissues in locations where there is considerable wear and tear
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Pseudostratified epithelium
single layer that appears stratified (because nuclei lay @ different layers)
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Transitional epithelium
cells that undergo changes in shape and therefore is located in areas subject to stretching (urinary bladder)
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Squamous cells
- Flattened
- Thin like floor tiles (rapid passage of substances)
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Cuboidal cells
- cube-shaped
- microvilli @ their apical surface and function in sercretion or absorption
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Columnar cells
- tall and cylindrical or rectangular
- Protect underlying cells
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Transitional cells
able to undergo changes in shape caused by distentsion
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Endocrine glands
- ductless (thyroid, adrenal)
- secrete horomones which diffuse through the extracellular fluid into the blood
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exocrine glands
- Secrete substances into ducts or onto the surface of the body
- structually classified into unicellular and multicellular glands
- Sweat/salivary
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Unicellular glands
- Goblet cell
- secrete their products into body tubes such as the respiratory tract (secrete mucus directly on apical surface)
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