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Stratified Squamous Epithelium
- structure -
- multiple layers of cells that are cuboidal in bassal layer and progressively flatten toward the surface. In moist, surface cells retain a nucleus and cytoplasm. In keratinized, surface cells are dead
- location -
- Moist - mouth,throat, larynx, esophagus, anus, vagina, inferior urethra, and cornea
- karatinized -
- functions : protection against abrashion, caustic chemicals, water loss, infection
Stratified Cuboidal Epithelium
- Structure - multiple layers of cube shaped cells
- location - sweat, glands, salivary gland ducts
- function - secretion and absorbtion
stratified columnar epithelium
- structure: multiple layers of cells with thin walls resting on layers of more cuboidal cells. Cells ciliated in the larynx.
- Locations- mammary gland duct,larynx, portion of male urethra
- Function - protection and secretion
Pseudostratified columnar epithilium
- Structure: all cells are attached to to basement membrane but not all cells reach free surfaces. Appears stratified because nuclei are at various levels. Almost always ciliated and associated with goblet cells
- Locations - lining of nasal cavity, nasal sinuses,pharynx, trachea, and bronchi of lungs
- Functions -
- Synthesize and secrete mucus onto free surface
- move mucus that contains foriegn particles over the free surface and from passages
- structure : stratified; cells change shape depending upon amount of distention of the organ
- Location - lining of urinary bladder ureters and superior urethrea
- Functions : accomidates fluctuations in the volume of fluid in an organ or tube; protection against the caustic effects of urine
- found on lateral and basal surfaces of cells
- Functions -
- form permeablility layer
- blind cells together
- provide mechanism for intercellular communiction
- Types -
- tight junctions
- gap junction
- Desmosomes: disk-shaped regions of cell membrane; often found in areas that are subjected to stress.
- Contain especially adhesive glycoproteins.
- Intermediate protein filaments extend into cytoplasm of cells.
- Striated squamous epithelium of the skin.
- Hemidesmosomes: half of a desmosome; attach epithelial cells to basement membrane.
- Tight Junctions: hold cells together, form permeability barrier.
- Gap Junctions: protein channels aid intercellular communication.
- Allows ions and small molecules to pass through.
- Coordinate function of cardiac and smooth muscle.
- May help coordinate movement of cilia in ciliated types of epithelium
- Epithelium with supporting network of C.T.
- Two types of glands formed by infolding of epithelium:
- Endocrine: no open contact with exterior; no ducts; produce hormones
- Exocrine: open contact maintained with exterior; ducts
- Abundant; found in every organ
- Consists of cells separated by extracellular matrix
- Many diverse types
- Performs variety of important functions
Functions of Connective Tissue
- Enclose organs as a capsule and separate organs into layers
- Connect tissues to one another (i.e. tendons and ligaments)
- Support and movement (i.e. bones)
- Storage (i.e. fat)
- Cushion and insulate (i.e. fat)
- Transport (i.e. blood)
- Protect (i.e. cells of the immune system)
Cells of Connective Tissue
- Specialized cells produce the extracellular matrix
- Descriptive word stems
- Blasts: create the matrix, example osteoblast
- Cytes: maintain the matrix, example chondrocyte
- Clasts: break the matrix down for remodeling, example osteoclasts
Cells of Connective Tissue
- Adipose or fat cells (adipocytes). Common in some tissues (dermis of skin); rare in some (cartilage)
- Mast cells. Common beneath membranes; along small blood vessels. Mediate allergic reactions and play an important protective role in wound healing and defend against pathogens.
- White blood cells (leukocytes). Respond to injury or infection
- Macrophages. Phagocytize or provide protection
- Fixed: stay in position in connective tissue
- Wandering: move by amoeboid movement through the connective tissue
- Platelets. Fragments of hematopoietic cells involved in clotting.
- Protein fibers of the matrix
- Collagen. Most common protein in body; strong, flexible, inelastic
- Reticular. Fill spaces between tissues and organs. Fine collagenous, form branching networks
- Elastic. Returns to its original shape after distension or compression. Contains molecules of protein elastin that resemble coiled springs.
Other Matrix Molecules
- Most common molecules are called the ground substance and include:
- Hyaluronic acid: polysaccharide. Good lubricant. Vitreous humor of eye.
- Proteoglycans: protein and polysaccharide. Protein part attaches to hyaluronic acid. Trap large amounts of water.
- Adhesive molecules: hold proteoglycan aggregates together. Chondronectin in cartilage, osteonectin in bone, fibronectin in fibrous connective tissue.