Epithelial Tissues Four types of tissue.Epithelial Tissues slide show video.Epithelial Tissues.

Epithelial tissues are widespread throughout the body. They form the covering of all body surfaces, line body cavities, and hollow organs, and are the major tissue in glands. They perform a variety of functions that include protection, secretion, absorption, excretion, filtration, diffusion, and sensory reception. Groups of cells closely associated that have a
similar structure and perform a related function
Epithelial = covering
Connective = support
Muscle = movement
Nervous = control
Exocrine Glands
Secrete substance onto body surface or into body cavity
Have ducts
E.G., salivary, mammary, pancreas, liver
Secrete product into bloodstream
Either stored in secretory cells or in follicle surrounded by secretory cells
Hormones travel to target organ to increase response
No ducts
Skeletal muscle makes up most of the body's muscle and does not contract without nervous stimulation. It is under voluntary control and lacks anatomic cellular connections between fibers. The fibers (cells) are multinucleate and appear striated due to the arrangement of actin and myosin protein filaments. The heart is made of specialized muscle tissue with some similarities to both smooth and skeletal muscles. It is involuntary and mononucleate as is smooth muscle. It is striated like skeletal muscle which means that it has microscopically visible myofilaments arranged in parallel with the sarcomere structure. Cardiac muscle fibers branch and have a single nucleus per cell. Another difference in cardiac muscle is the presence of intercalated discs that are specialized connections between one cardiac muscle cell and another. These tight connections allow for almost completely free movement of ions so that action potentials can freely pass from one cell to another.
Smooth muscle is found in the walls of blood vessels, tubular organs such as the stomach and uterus. It has the ability to stretch and maintain tension for long periods of time. It is not under voluntary control and each cell exists as a discreet independent unit that is innervated by a single nerve ending. The myofilaments are loosely organized and attached to dense bodies.

Histology 194 channel.

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