1. Muscle Tissue: Muscle tissue is contractile in nature and functions to move the skeletal system and body viscera.
|Skeletal||Striated, voluntary||Skeletal muscles of the body|
|Smooth||Non-striated, involuntary||Walls of digestive tract and blood vessels, uterus, urinary bladder|
2. Nervous Tissue: Nervous tissue is composed of cells (neurons) that respond to external and internal stimuli and have the capability to transmit a message (impulse) from one area of the body to another. This tissue thus induces a response of distant muscles or glands, as well as regulating body processes such as respiration, circulation, and digestion.
3. Epithelial Tissue: Epithelial tissue covers the external surfaces of the body and lines the internal tubes and cavities. It also forms the glands of the body. Characteristics of epithelial tissue (epithelium) are that it
- has compactly aggregated cells;
- has limited intercellular spaces and substance;
- is avascular (no blood vessels);
- lies on a connective tissue layer—the basal lamina;
- has cells that form sheets and are polarized;
- is derived from all three germ layers.
Microvilli—fingerlike projections of plasma membranes.
Cilia—motile organelles extending into the luman consisting of specifically arranged microtubules.
Flagella—similar to cilia. Primary examples are human spermatozoa.
Stereocilia—are actually very elongated Microvilli.
4. Connective Tissue: Connective tissue is the packing and supporting material of the body tissues and organs. It develops from mesoderm (mesenchyme). All connective tissues consist of three distinct components: ground substance, cells and fibers.
- Ground substance. Ground substance is located between the cells and fibers, both of which are embedded in it. It forms an amorphous intercellar material. In the fresh state, it appears as a transparent and homogenous gel. It acts as a route for the passage of nutrients and wastes to and from the cells within or adjacent to the connective tissue.
- Fibers. The fiber components of connective tissue add support and strength. Three types of fibers are present: collagenous, elastic and reticular.