What is the gross and microscopic structure of striated muscle?

Question

What is the gross and microscopic structure of striated muscle?

Answer

Striated muscle tissue can be identified by its unique banding or ‘striations’ which can be observed under microscope. The visible ‘striations’ contained within the muscle tissue are a functional sub unit unique to skeletal muscle known as sarcomeres, which are not present within the smooth muscle variation. Striated or ‘skeletal’ muscles are voluntary in their ability to contract, unlike smooth or cardiac muscle which act involuntarily (although cardiac muscle is a form of striated muscle itself). Sarcomeres are the basic unit of skeletal muscle, which are composed of muscle fibres (myocytes). Myocytes are composed of ‘myofibrils’ which are themselves made up of repeating sections of sarcomeres. Under microscopic observation it is these structures that can be visualised as both light and dark bands. It is the structure of these bands which under voluntary innovation via motor neuron neurotransmitter release, are able to slide past each other when a muscle contracts or relaxes allowing a range of movement. Under microscope striated muscle can be differentiated from its smooth counterpart, through the existence of a high number of mitochondria (due to the high energy demand of skeletal muscle) and multinucleated cells (eukaryotic cells which contain more than one nucleus per cell).

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