How muscles work

Definition:
Muscle (from Latin musculus, diminutive of mus "mouse") is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells.
These help in locomotion and movement of an organism i.e are specialized for movement.

 Types:
1-Cardiac muscles(heart muscles)
2-Skeletal muscles
3-Smooth muscles

Muscles

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Muscles are predominantly powered by the oxidation of fats and carbohydrates, but anaerobic chemical reactions are also used, particularly by fast twitch fibers and lactic acid is formed anaerobically. These chemical reactions produce adenosine triphosphate (ATP) molecules which are used to power the movement of the myosin heads. 

Organisms with muscles:
Muscles are present only in kingdom animalia specially in higher organisms which can perform quick moves and locomotion.

Embryology:

All muscles derive from paraxial mesoderm. The paraxial mesoderm is divided along the embryo's length into somites, corresponding to the segmentation of the body (most obviously seen in the vertebral column. Each somite has 3 divisions, sclerotome (which forms vertebrae), dermatome (which forms skin), and myotome (which forms muscle). The myotome is divided into two sections, the epimere and hypomere, which form epaxial and hypaxial muscles, respectively.Fpaxial muscles in humans are only the erector spinae and small intervertebral muscles, and are innervated by the dorsal rami of the spinal nerves. All other muscles, including limb muscles, are hypaxial muscles, formed from the hypomere, and inervated by the ventral rami of the spinal nerves.
During development, myoblasts (muscle progenitor cells) either remain in the somite to form muscles associated with the vertebral column or migrate out into the body to form all other muscles. Myoblast migration is preceded by the formation of connective tissue frameworks, usually formed from the somatic lateral plate mesoderm. Myoblasts follow chemical signals to the appropriate locations, where they fuse into elongate skeletal muscle cells.

Efficiency:

Definition:The efficiency is defined as the ratio of mechanical work output to the total metabolic cost, as can be calculated from oxygen consumption.

The efficiency of human muscle has been measured (in the context of rowing and cycling) at 18% to 26%.
This is low efficiency and is the result of about 40% efficiency of generating ATP from food energy, losses in converting energy from ATP into mechanical work inside the muscle, and mechanical losses inside the body.  For an overal efficiency of 20 percent, one watt of mechanical power is equivalent to 4.3 kcal per hour. For example, a manufacturer of rowing equipment shows burned calories as four times the actual mechanical work, plus 300 kcal per hour, which amounts to about 20 percent efficiency at 250 watts of mechanical output. The mechanical energy output of a cyclic contraction can depend upon many factors, including activation timing, muscle strain trajectory, and rates of force rise & decay. These can be synthesized experimentally using work loop analysis.

Density of muscle tissue compared to adipose tissue

The density of mammalian skeletal muscle tissue is about 1.06 kg/liter.
This can be contrasted with the density of adipose tissue (fat), which is 0.9196 kg/liter.
Muscle tissue is approximately 15% denser than fat tissue.

Resting energy expenditure of muscle

At rest:
Skeletal muscle consumes 54.4 kJ/kg (13.0 kcal/kg) per day.
This is larger than adipose tissue (fat) at 18.8 kJ/kg (4.5 kcal/kg), and bone at 9.6 kJ/kg (2.3 kcal/kg).

Muscle evolution

Evolutionarily, specialized forms of skeletal and cardiac muscles predated the divergence of the vertebrate/arthropod evolutionary line. This indicates that these types of muscle developed in a common ancestor sometime before 700 million years ago (mya). Vertebrate smooth muscle was found to have evolved independently from the skeletal and cardiac muscles.

Human muscles:

Muscles

Muscles