Anatomy and Physiology: Tissues
5. Blood – Blood is considered a connective tissue which is composed of blood cells that are surrounded by a fluid matrix called blood plasma. It is also termed as vascular tissue where the fibers it contains are soluble protein molecules that become visible only when the blood clots.
Muscle tissues produce movement in the body by their ability to shorten and contract.
Types of Muscle Tissues
- Skeletal Muscle Tissue
Skeletal muscle tissues are muscles that can be consciously or voluntarily controlled. These tissues are attached to the skeleton which is packaged by connective tissue sheets into the skeletal muscles. When the muscles contract, they pull the bones or skin resulting to the gross body movements or changes in the facial expression. Skeletal muscle cells are elongated. The elongated shape of these muscles provides a long axis for contraction and they are often called muscle fibers. Obvious striations in the muscle cells are noted and they are long, cylindrical and multinucleated.
- Cardiac Muscle Tissue
Cardiac muscle tissues are found only in the heart. Unlike the skeletal muscle, cardiac cells are short and unicleated. However, cardiac muscles have striations also like the skeletal muscles. Presence of cardiac muscles allows the heart to pump blood through the vessels and be distributed to the different parts of the body. These muscle tissues function under involuntary control. Hence, a person cannot consciously control them.
- Smooth Muscle Tissue
Another term for smooth muscle tissue is visceral muscle. As the name implies these muscles are smooth, thus, no striations are visible. They are spindle-shaped and have a single nucleus. It is found in the walls of the hollow organs such as the stomach, the bladder, uterus and the blood vessels. Compare to the two muscle types, smooth muscles contract more slowly.
Nervous tissues are also called the NEURONS in the body. Neurons are very important in the body as they are responsible for conducting and receiving impulses from a certain part of the body to the other. The distinct characteristics of neurons are their ability to function on IRRITABILITY and CONDUCTIVITY. Unlike the other tissues, their cytoplasm is drawn out into long processes, thus making their structure unique. The cytoplasm of the neurons can be drawn out as much as 3 feet long or more.