TISSUES
TISSUE TYPES
Four major tissue types
• Epithelial tissue
• Connective tissue
• Muscle tissue
• Nervous tissue
EPITHELIAL TISSUE
• Sheets of cells covering body surfaces or lining
body cavities
• Form boundaries between different
environments
– e.g., Epidermis of skin separates inside and outside
of body
– e.g., Epithelium lining urinary bladder separates
underlying cells from urine
EPITHELIAL TISSUE
• Many diverse functions
– Protection
– Absorption
– Filtration
– Excretion
– Secretion
– Sensory reception
EPITHELIAL TISSUE
• Classification According
to shape:
- Squamous cells:
Flattened like fish scales
- Cuboidal cells: Cubeshaped
- Columnar cells: Columnshaped
EPITHELIAL TISSUE
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Classification according to cell arrangement:
Simple : one layer
Stratified: more than one layer
Simple epithelial
Simple squamous: usually forms membranes
Simple cuboidal: commonly in glands and their
ducts
- Simple columnar: lines the entire digestive tract
- Pseudostratified columnar: mainly functions in
absorption and secretion
EPITHELIAL TISSUE
• Stratified epithelial
- Stratified squamous:
most common stratified epithelial
Is found in sites that receive a good deal of
abuse or friction such as the esophagus, mouth
and outer skin
- Stratified Cuboidal and Columnar:
Found mainly in the ducts of large glands
CONNECTIVE TISSUE
• Found everywhere in the body
– Most widely distributed primary tissue
• Four main classes
– Loose connective tissue (Provides a matrix of
support and cushing) eg. Adipose tissue
– Cartilage
– Bone tissue
– Blood
CONNECTIVE TISSUE
• Major functions
– Binding and support
– Protection
– Insulation
– Transportation
• Which of these functions are accomplished by
bone and cartilage? Fat? Blood?
NERVOUS TISSUE
• Main component of the nervous system
– Brain, spinal cord, and nerves
– Regulates and controls body functions
• Two main cell types
– Neurons
• Generate and conduct
nerve impulses
– Supporting cells
• Non-conducting cells
that support, insulate,
and protect neurons
MUSCLE TISSUE
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Highly cellular
Well vascularized
Responsible for most types of body movement
Possess myofilaments
– Actin and myosin
• Three types
– Skeletal muscle
– Cardiac muscle
– Smooth muscle
TISSUE REPAIR
• Injured cells release growth factors
– Stimulate cells to divide and migrate
• Two major tissue repair means:
– Regeneration
• Replacement of destroyed tissue with same type of tissue
– Fibrosis
• Replacement with fibrous connective tissue (scar tissue)
• Type of repair dependent upon
– Type of tissue damaged
– Severity of injury
TISSUE REPAIR
• The regenerative capacity of different tissues
varies widely
– Some tissues regenerate extremely well
• e.g., Epithelial, bone, blood-forming tissue
– Some tissues have a moderate regenerative capacity
• e.g., Smooth muscle, dense regular connective tissue
– Some tissues have a weak regenerative capacity
• e.g., Skeletal muscle, cartilage
– Some tissues have a virtually no functional
regenerative capacity
• e.g., Cardiac muscle, nervous tissue
TISSUE REPAIR
• In non-regenerative tissue and severe wounds,
damaged tissue is replaced by fibrosis
• Resulting scar tissue is strong, but lacks
flexibility, elasticity, and function of normal
tissue