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Lecture 11:
What makes Tissue and Organs?
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Tissue are a group of the same cell type that have a
similar function.
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Skeletal muscle
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Organ: two or more different tissue types grouped
together that perform a specific function. – Heart
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Organ system: groups of organs that work together to
form a specific task.
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Circulatory system
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All of the organ system combined make an organism
Tissues: Groups of Cells with a Common Function
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Four primary tissues
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Epithelial tissues
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Connective tissues
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Muscle tissues
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Nervous tissue
Epithelial Tissues
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Two basic purposes
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1. 2.
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Line body cavities and cover surfaces
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Glandular epithelia
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Epithelial cells adapted to form glands
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– Exocrine glands
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Secrete products into hollow organs or ducts
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– Endocrine glands
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Secrete products (hormones) into the blood for
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distribution throughout the body
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Epithelial Tissues: Classification According to Shape
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Three types, based on shape –
Squamous
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– Flattened cells
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– Line vessels, part of lungs, body surface –
Cuboidal
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– Cube shaped
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– Form lining of tubules, glandular tissue –
Columnar
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– Column shaped
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Line respiratory, digestive, reproductive tracts
Epithelial Tissues: Further Classification Based on Number
of Layers
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Number of layers
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Simple/single-layered
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– Adapted for diffusion across cell barriers
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Line glands, and respiratory, digestive, reproductive
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systems
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Stratified/multiple-layered
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Provide protection, as in the skin surface
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The Basement Membrane Provides Structural Support
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Basement membrane
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– Non-cellular layer directly beneath epithelial tissue
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– Composed of proteins secreted by epithelial cells and
connective tissue
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– Provides structural support to overlying cells
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– Attaches epithelial layer to underlying tissues
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Tight junctions
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Seal plasma membranes tightly together – Digestive tract
lining, bladder lining
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movement between cells
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Allow tissues to stretch and bend
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Skin
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Gap junctions
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– Protein channels enable movement of materials
between cells
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– Liver, heart
