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What is a tissue?
Groups of cells with a common structure and function– Structure is suited to its function
Epithelial tissue
Covers outside of body and lines organs and cavities inside the body– Functions as a protective barrier
• Protects against injury• Protects against invasion by bacteria, etc.
Epithelial Tissue
Classified by number of cell layers and shape of cells
Remember: form reflects function!
Epithelial Tissue
By Layers:– Simple epithelium
• Single layer of cells
– Stratified epithelium• Multiple layers of cells
– Pseudostratified epithelium• Single layer of cells that appears to be multi-
layered
Connective Tissue
Functions to bind and support other tissues– Few cells scattered in a matrix of various
substances
Main types of connective tissue
Loose connective tissue
Adipose tissue
Fibrous connective tissue
Cartilage
Bone
blood
Loose connective tissue
Most commonHas all 3 fiber types (collagenous, elastic, reticular)Binds epithelia to underlying tissues, holds organs in placeFibroblasts and macrophages scattered in the meshAlso called “areolar” connective tissue
Fibrous connective tissue
Large numbers of collagen fibers– Arranged in parallel bundles– Strong– Found in tendons (join muscle to bone)
and ligaments (join bone to bone)
Cartilage
Collagen fibers embedded in a rubbery matrix of chondroitin sulfate– Strong, yet flexible– In human ears, nose, rings of trachea
• Flexible support
– Chondrocytes secrete chondroitin and collagen
Bone
Mineralized connective tissue--hard
Osteoblasts = bone-forming cells
May be compact or spongy (cancellous)
Repeating units are called osteons (Haversian systems)
Blood
Matrix = plasma– Made of salt, water, dissolved proteins
Types of cells:– Erythrocytes = RBC’s– Leukocytes = WBC’s– platelets
Nervous Tissue
Functional unit = neuron– Transmit nerve impulses
Structure:– Cell body, dendrites, axons
• Dendrites transmit impulses from tips toward the neuron cell body
• Axons transmit impulses toward another neuron or a muscle cell
Muscle Tissue
Fibers are capable of contraction
Made of proteins, actin and myosin
3 types– Skeletal– Cardiac– smooth
Skeletal Muscle tissue
Attached to bones by tendons
Responsible for voluntary movement
Striated appearance
Smooth Muscle
Lacks striations
Spindle-shaped
Responsible for involuntary movements
Lines digestive tract, bladder, arteries