MUSCLES

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In muscle tissue, it is the internal structures, protein, giving it the ability to actively shorten. This is what is called the: CONTRACTILITY. The surface is covered with muscles conjunctiva blade much stronger, called: FASCIA or MUSCULAR DUCT. It is the connective tissue between the muscle fibers and bundles found and the NERVE FIBER HAIR.

A) SMOOTH MUSCLE: Consists of tapering cells, the nucleus and central and elongated. It forms the muscular layer of vessels and hollow organs (stomach, intestines peristalsis =). Its contraction is slow, involuntary, rhythmic and autonomous under the influence of the autonomic nervous system.

B) MUSCLE RIDGED: Made of clear disks juxtaposed with dark disks visible under a microscope at low power. It consists of long fibers, containing many nuclei located at the periphery. Its contraction is fast, depends on the will, does not match any rate, is dependent on the cerebro-spinal nervous system.

C) HEART MUSCLE: Has properties of both smooth muscle and striated muscle. The cell nucleus is central, the fibers are striated and are interconnected networks. Heart contractions are rapid, involuntary, rhythmic and autonomous under the influence of the autonomic nervous system.

The body has approximately 640 skeletal muscles, including the following as a guide, some of the best known:

1 = Frontal * 16 = sterno mastoid * 17 = trapezoid * 18 = deltoid * 19 = the pectoralis major * 20 = large Serrated * 21 = Grand Oblique * 22 = right big * 23 = Biceps * 24 = Anterior brachial * 25 = long Supinator

1 = Epi-cranial aponeurosis * 5 = Trapèze * 7 = Deltoid * 11 = Triceps * 18 = Anterior cubital * 27 = Grand Dorsal * 30 = Grand Oblique * 32 = gluteus Maximus

2 = Orbicularis palpebrarum * 13 = Orbicularis oris * 15 = Sterno-cléido-mastoïdien * 20 = Scalènes * 22 = intercostals * 23 = small Pectoral * 24 = Grand Dentelé * 25 = small Oblique * 26 = Rectus abdomen * 27 = Transverse * 28 = Coraco-Brachial

The muscle weight relative to body is between 40 and 50% for men and between 30 and 40% in women.

The longest muscle is the "Grand Couturier" 50 centimeters in the photo below is one that forms a "V" in the center of the image:

The Petite muscle is the "stapedius" 0.5 cm and is located in the ear (caliper):

Muscles, which are the "flesh" of man and animals, representing nearly half the weight of the body. All our movements depends on the striated muscles that are attached to the skeleton and obey our will. A striated muscle is capable of only one type of activity to contract by pulling on the bones to which it is attached, thanks to TENDONS:

The muscles are divided in pairs, two elements are antagonistic, ie they operate OPPOSITION. If there is a muscle to lift the leg, there is the other for fall.

The first can be in one direction and the second in the other direction, but when one contracts, the other is automatically released, which allows the first to do its job:

But this is a simplification of reality. Because in most cases, the muscles work in teams of twenty, thirty or even more, allowing us to walk, jump or sit throw a ball! While the muscles of a body region trigger a movement, others have a compensatory action that helps keep us in balance.

Muscles are made of bundles of FIBRE. Each fiber consists itself of filamentous cells: myofibrils, which contain many nuclei, which can grow up to 30cm long. These myofibrils are formed by assembling smaller filaments, which correspond to two types of protein: ACTIN and extremely small MYOSIN: 80000 Myosin molecules juxtaposed would achieve only a millimeter wide! :

The overlap of these two proteins give the whole a striated appearance, visible under the microscope.

The MUSCULAR CONTRACTION is triggered by a chemical mechanism involving movement of actin filaments compared to Myosin. Here is the process of muscle contraction:

The head of Myosin then releases control its phosphate and its "neck" connecting the folds by pulling the actin:

The head of the myosin in turn releases ADP, which replaces a new ATP molecule charged with energy and tightens its link:

The same process is repeated hundreds of times per second, in thousands of actin-myosin associations of each myofibril.

The energy expended during muscle contraction appears to be 75% the form of heat. The mechanical efficiency is therefore only 25%. For a muscle can contract, it takes energy it provides, the state of rest mainly in the form of fatty acids, and in labor, in the form of glucose, stored glycogen in both muscles in the liver.

CONTRACTURE: State in which the actin and myosin are combined. Myofibrils can no longer relax;

HYPERTROPHY: abnormal increase in the size of a muscle, without structural change, such as body-builders for example. This increases the volume without changing the structure of the muscle;

ATROPHY: Default nutrition muscle tissue resulting in decreased volume and the structure of the muscle is not altered;

PARASITES: Being alive who takes food from another living being, called the host;

MYOGELOSES: Development of "agar plates" when muscle area is too long hypertonic. They are in the form of size, ranging from a pinhead to a walnut, round or elongated

MYOPATHY: severe muscle atrophy progressive evolution, leading to paralysis;

DISUSE ATROPHY: Progressive atrophy of certain skeletal muscles, usually those members. Muscle atrophy is secondary to degeneration of the corresponding nerve cells located in the spinal cord.