4 tissue types and epithelium
TRANSCRIPT
The Tissue Level of Organization
Four main types of tissueEpithelial tissue
Four Tissue Types• Epithelial (epithelium)• Connective• Muscle• Nervous
Function of Epithelial tissue• Covers body surfaces• Lines body cavities and ducts• Forms glands
Functions of Connective Tissue • Protects and supports body and organs• Binds organs together• Storage of energy reserve
Function of Muscular Tissue• Generate force for movement• Body temperature maintenance
Functions of Nervous Tissue• Initiates nerve impulses• Body coordination
Epithelium• Two types of epithelium– Covering and lining– Glandular
Covering and lining epithelium• Characterized by– cell arrangement – cell shape
Epithelial cell arrangements• Simple– One layer of cells
• Stratified– Two or more layers of cells
• Pseudostratified– One layer of cells; appears to have multiple layers
Epithelial cell shapes• Squamous– Flat, thin, arranged like floor tiles.• Shape allows for rapid transport
• Cuboidal– Shaped like cubes (or hexagons)• Secretion and absorption
Epithelial cell shapes• Columnar– Tall and cylindrical
• Protect underlying layers of tissue• May also have cilia, may also secrete and absorb materials
• Transitional– Shape can change (from columnar to flat)
• Allows body parts to stretch or expand or move
Simple squamous epithelium
Simple cuboidal epithelium
Simple columnar epithelium
Pseudostratified columnar epithelium
Transitional epithelium
Stratified squamous epithelium
Stratified cuboidal epithelium• Rare• Found in ducts of some glands (mammary,
sweat, salivary, pancreas)
Stratified columnar epithelium• Rare• Found only in male urethra and lactiferous
ducts
Epithelial structure• Little or no space between cells• Cells meet at “junctions”.• Avascular
Epithelial structure• Held in place by underlying connective tissue• Nutrients supplied by underlying tissue
Glandular epithelium• Has cells that are specialized to produce and
secrete substances into ducts or into body fluids• gland = 1 or more cuboidal or columnar cell• secretion• salivary glands, sweat glands, endocrine glands
Exocrine and Endocrine gland• Endocrine – ductless – secrete products
directly into blood.– Pituitary, thyroid, adrenal glands
• Exocrine – secretions sent into ducts at skin surface or organ.
Types of ducts
Exocrine glands classified by function• Holocrine– Cell dies as it secretes; replaced by new cell
• Merocrine– Cell secretes via exocytosis Golgi produced secretory
vesicles• Apocrine– Part of cell pinches off and becomes secretion. Cell repair
itself and repeats