Anatomy of Muscle Cells
There are three types of muscle tissue in the human body. These muscle tissues are skeletal muscles, smooth muscles and cardiac muscles. Each of these muscle tissues has it very own anatomical makeup, which vary from muscle to muscle. The muscle cells in a muscle are referred to as muscle fibers, these fibers are skeletal muscle fibers, smooth muscle fibers and cardiac muscle fibers.
The anatomy of a skeletal muscle fiber is formed during embryonic development. Skeletal muscle fibers arise from a hundred or more small mesodermal cells called myoblasts. The mature skeletal muscle fiber has a hundred or more nuclei. Once fusion occurs the skeletal muscle fiber will lose the ability to undergo cell division. This means that the number of muscle fibers is set before birth and most of these fibers will last a lifetime.
The muscle growth that occurs after birth is a result of the enlargement of these existing muscle fibers. The mature muscle fibers have a few myoblasts, which remain as satellite cells. These myoblasts retain the capacity to join with one another or with damaged muscle fibers in order to regenerate these muscle fibers.
Anatomy & Physiology
The many nuclei of skeletal muscle fiber are located underneath the sarcolemma, which is the fiber’s plasma membrane. Thousands of invaginations of the sarcolemma, which are called T Tubules, Tunnel from the surface to the center of the muscle fiber. These T Tubules are open to the outside of the fiber and are filled with extra-cellular fluid. Muscle action potentials propagate along the sarcolemma and through the T tubules and quickly spread through the muscle fiber. This process ensures that all parts of the muscle fiber become excited by an action potential virtually simultaneously.
The sarcoplasm is located inside the sarcolemma. Sarcoplasm is the cytoplasm of a muscle fiber, it contains a good amount of glycogen, which is used for ATP synthesis. The sarcoplasm also contains myoglobin, a red colored, oxygen binding-protein, that is found only in muscle fibers. The myoglobin binds oxygen molecules, which are needed for ATP production within the mitochondria. The Mitochondria lie in rows throughout the muscle fiber, strategically close to the proteins that use ATP during contraction.
The sarcoplasm is filled with little threadlike structures. These structures are contractile elements of skeletal muscles called myofibrils. The myofibrils are about two micrometers in size and extend the length of the muscle fiber. The striations appear to make the muscle fiber look striated.
Anatomy & Physiology
The sarcoplasmic reticulum is a fluid filled system of membranous sacs. This system of sacs is similar to smooth endplasmic reticulum in non-muscle cells. In a relaxed muscle fiber the sarcoplasmic reticulum store calcium ions, the release of these calcium cells, trigger muscle contraction.
There are two types of...