being Duchenne MD. In DMD the gene that codes for the protein dystrophin is mutated so little or none of this protein is present allowing for easy tearing of the sarcolemma during muscle contraction.
Connective Tissue Components of Skeletal Muscle
Connective tissue surrounds and protects muscle tissue. The subcutaneous layer or hypodermis separates muscle from skin. The hypodermis provides a pathway for nerves, blood vessels, and lymphatics to enter and exit muscle. As previously mentioned, the hypodermis stores most of the body’s triglycerides, and serves as an insulating layer that reduces heat loss and protects muscle from physical trauma. Fascia is a dense sheet or broad band of irregular CT (dense irregular) that lines the body wall and limbs and supports and surrounds muscles and other organs of the body. Fascia holds muscles with similar function together. Fascia also allows free movement of muscles, carries nerves, blood vessels, and lymphatic vessels and fills spaces between muscles.
Fascia is generally divided into two layers:
a) Superficial Fascia: separates muscle tissue from the skin; also called the subcutaneous layer as it lies deep to the cutaneous membrane (skin) composed of areolar and adipose connective tissues b) Deep Fascia: lines individual muscles and muscle groups; lies deep to the superficial fascia composed of dense irregular connective tissue
Three layers of CT extend from the deep fascia to protect and strengthen skeletal muscle:
Epimysium : the outer most layer encircling the entire muscle composed of dense irregular CT.
Perimysium : surrounds groups of 10 to 100 or more muscle fibres separating them into bundles called Fascicles. It also is composed of dense irregular CT. **Fascicles are generally large enough to be seen by the naked eye and give cut meat it’s “grained” appearance. Tearing meat tears along the fascicles. Endomysium : Penetrates the interior of each fascicle and separate individual muscle fibres from one another. It is composed of a thin sheath of areolar CT.
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