Term | Definition |
Simple squamous | Lines blood vessels and air sacs of lungs. Permits exchange of nutrients, wastes and gases. |
Simple cuboidal | Lines kidney tubules and glands. Secretes and reabsorbs water and small molecules. |
Simple columnar | Lines most digestive organs. Absorbs nutrients, produces mucus. |
Stratified squamous | Outer layer of skin, mouth, vagina. Protects against abrasion, drying out and infection. |
Stratified cuboidal | Lines ducts of sweat glands. Secretes water and ions. |
Stratified columnar | Lines epididymus, mammary glands, & larynx. Secretes mucus. |
Tissues | Groups of cells that are similar in structure that perform common functions. |
Glands | Epithelial tissues that are specialized to synthesize and secrete a product. |
Endocrine glands | Secrete hormones into the bloodstream. Ex) thyroid gland that secretes hormones to regulate growth and metabolism |
Exocrine glands | Secrete their products into a hollow organ or duct. Ex) glands that secrete saliva in your mouth, sweat glands in your skin |
Tight junctions | Seal the plasma membranes of adjacent cells so tightly together that nothing can pass between the cells. Important in epithelial layers that must control the movement of substances into or out of the body. |
Adhesion junctions | "spot desmosomes" are looser in structure. The protein filaments of adhesion junctions allow for some movement between cells so that the tissues can stretch and bend. Located in epithelium of your skin. |
Gap junctions | Represent connecting channels made of proteins that permit the movement of ions or water between two adjacent cells. Commonly found in the epithelial cells in the liver, heart and some muscle tissues. |
Connective tissue | Stores fat and produces the cells of blood. Most of the structure consists of nonliving extracellular material. |
Collagen fibers | Made of protein, confer strength and slightly flexible. |
Elastic fibers | Made primarily of the protein elastin which can stretch without breaking. |
Reticular fibers | Interconnect with each other. Serve as an internal structural framework for some of the "soft" organs such as the liver, spleen and lymph nodes. |
Fibroblasts | Cells responsible for producing and secreting the proteins that compose of the collagen, elastic and reticular fibers. |
Loose connective tissue | Also called "areolar connective tissue" is the most common type. It surrounds many internal organs, muscles and blood vessels. Contains a few collagen fibers and elastic fibers, giving great flexibility but not much strength. |
Dense connective tissue | Found in tendons, ligaments, and lower layers of skin. |