Muscles build muscle tissue.
The type of tissue that builds our muscles is the skeletal striated muscle tissue (below photo) – they connect with the skeletal system – a passive movement system. The muscles maintain our figure in a vertical position, they are generators of a lot of energy. We try our best to train our figure so that our muscles are visible. Let’s see how they are built and how they work.
The basic muscle unit is the sarcomere. The sarcomeres arranged successively form myofibrils, and these myoblasts – muscle cells, in other words, muscle fibers. Myoblasts can be 1-5 cm long or even longer. It is a large cell containing even several thousand nuclei. One of the main functions of skeletal muscle is motor skills, or moving around. This is possible due to the shrinking of proteins. When contracting, the muscle burns energy drawn from ATP while doing mechanical work. However, the structure of the entire muscle does not consist of filaments alone. Each group is organized into higher-level units.
Clusters of filaments form myofibril. A certain amount of myofibrils is then collected in so-called myofibril bundles. Then a certain amount of harvested bunches is collected in the upper class – muscle fiber. These, building a bunch of muscle fibers, create skeletal muscle. Miofibrils occupy about 80% of the muscle fiber volume. Muscle fibers can be divided into two types
– type I, aerobic (red) for example at riders
– type IIA, aerobic-anaerobic
– type IIX, anaerobic (white), e.g. for bodybuilders
Type I fibers are slow twitch fibers (ST), while type II fibers are fast twitch (FT). ST are slow to contract and are more durable than FT fibers whose contractions are fast and strong.
Type I fibers contain large amounts of myoglobin – an oxygen storage protein in the muscles.
Type II fibers contain smaller amounts of myoglobin due to the source of energy being drawn
IIA – glycolytic-oxygen
IIB – glycolytic
The right training mainly develops a certain type of muscle fiber.
In the area free from fine filaments (area H) there is also the M line (in the next picture visible).
Miofibrils are made of sarcomeres. Each sarcomer is the area between the two Z lines that builds the alpha-actinin. Dark and bright bands seen in the photo above are thin proteins (7nm x 1 um) built mainly from actin and thick (15nm x 1.5um), mainly made of myosin. The thin filaments are attached to the Z-line with one end, and the other penetrate between the thick filaments. Thick filaments are anchored on the M.
Myofibrils and myofibril bunches are separated from each other by sarcoplasm, in which there is myoglobin, glycogen grains, mitochondria, Golgi system, numerous cell nuclei and smooth endoplasmic reticulum together with tubules T.
The endoplasmic reticulum is responsible for the accumulation of calcium ions necessary for the contraction of the sarcomeres in the so-called Marginal tanks that are located at each end of the given sarcomeres (at each Z line). Tubular bumps to the muscle fiber are T channels. They get into each sarcomer, between the IA bands between the two marginal tanks. The T channel in combination with the marginal cisterns creates the so-called muscle triad visible in the picture below. Kanalik T participates in muscle contraction, by opening calcium channels from marginal tanks. By means of these channels, the substance is also exchanged between myofibrils and the external environment.
Muscle fibers are covered with a basal lamina and a thin membrane called sarcolemma.
Adjacent cells, separates the mesh of collagen and reticulin fibrils.
Individual fragments of the muscle, connects the solid tissue
A single muscle fiber surrounds a single muscle fiber that carries hair vessels and individual nerve fibers. The bundles of muscle fibers are surrounded by the internal bone, which arises from the outgoing intramuscular septum. In the omelet there are larger blood vessels and bunches of nerve fibers. The skeletal muscle is surrounded by a thick, strong outer bone (also found in the gums).
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