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What is a tissue?
A collection of cells with similar structure that’s function is to carry out specialized activities.
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4 basic categories of tissues in human body
- EPITHELIAL TISSUE
- CONNECTIVE TISSUE
- MUSCLE TISSUE
- NERVOUS TISSUE
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EPITHELIAL TISSUE
- lines body cavities and ducts
- No blood supply (avascular)
- Anchored in place by a basement membrane
- Functions are to protect, absorp, diffuse, secrete, and lubricate.
- Forms secretory portions of most glands
- In the outer surface of skin, lining of GI tract, respiratory tract, and lining of blood vessels
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Types of Epithelial tissue
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- one layer of deep, square (box- or cube- like) cells
- found: surface of ovaries, ducts of some glands
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- 1 layer of flat, scale-like cells; have central nuclei;
- adapted for diffusion and filtration
- found: inside lungs, blood vessels, capillaries; lens of eye; eardrum
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- one layer of long, tall cells (like a fence); nuclei of neighboring cells are usually found at same height along bottom of cells;
- May have extensions of the membrane called microvilli (brush border);
- May have goblet cells which produce mucus;
- May have cilia on outside of membrane to propel particles (and mucus) along surface of the cells
- found: lining the digestive tract – with microvilli from stomach to anus; Ciliated columnar epithelium is found in portions of the upper respiratory tract, and the uterus
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STRATIFIED COLUMNAR
EPITHELIUM--SALIVARY GLAND DUCTS
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- Notice how the bottom layer
- (Red Line), looks cuboidal in nature
- but the because the top layer is columnar,
- and it is the top layer which determines the classification, this is called stratified columnar.
- Green line - Top layer
- Red Line - Bottom layer
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Pseudostratified columnar
- cells appear to be stratified but are not;
- nuclei are at different levels and some cells do not reach the surface.
- found: Eustachian tubes (internal auditory tubes) and in the upper respiratory tract; nonciliated found in male urethra
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Connective Tissue
- supports, protects and binds other tissues together
- has few cells that are widely separated by large amounts of material between the cells
- e.g. adipose tissue, cartilage, bone, blood
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Connective Tissue Cell types
- 1. Fibroblast
- 2. Macrophage
- 3. Mast cells
- 4. Blood cells
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1. Fibroblast
large star shaped cell whose function is to produce intercellular matrix; this matrix is largely the protein collagen
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2. Macrophage
a phagocyte attached to fibroblasts
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3. Mast cells
found near blood vessels for the inflammatory response
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RBC's and WBC's and platelets
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Loose - connective tissue
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found beneath the skin; has white collagen and yellow elastic fibers; flexible
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- this type of connective tissue has very little intercellular matrix. Each cell contains a large drop of fat that pushes the cytoplasm (and nucleus) into a thin band around the outer edge of the cell.
- This fat is stored as a food source, as insulation, and as a cushion
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Dense - connective tissue
- Tendons - connect muscle to bone
- Ligaments - connect bones to bone
- connective tissue which is closely packed with high amounts of collagen and elastic fibers in matrix; tough; periosteum, fascia
- Cartilage
- Hyaline cartilage
- - “gristle” - gives shape (to nose, larynx, trachea, bronchi), connects (ribs) and is found on ends on bones in joints; (most cartilage is this type)
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contains fibers; Found in vertebral discs
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has elastic fibers; found in ear (pinna), epiglottis
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MUSCLE TISSUE
- consists of elongated cells that are capable of contracting
- produces the movement of body parts
- e.g. skeletal muscle, cardiac, smooth muscle
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Striated - makes up skeletal muscles; (voluntary muscles)cells have striations or stripes and many nuclei;
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makes up the walls of hollow organs, as in respiratory, digestive reproductive tracts and blood vessels; involuntary muscles
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in heart only; resembles striated muscle tissue but also has branches; Involuntary muscle
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NERVOUS TISSUE
- consists of neurons and associated support cells
- they’re capable of conducting electrical impulses between body sites
- e.g. brain, spinal cord, and nerves
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- makes up the brain, spinal cord and nerves;
- initiates and sends nerve impulses;
- directs and coordinates all body’s activities
- Neuron - principal cell of nervous system
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