Which of the following statements are correct regarding skeletal muscle?

A. Muscle bundles are held together by 200 collagenous connective tissue layer called fascicle.

B. Sarcoplasmic reticulum of muscle fibre is a store house of calcium ions.

C. Striated appearance of skeletal muscle fibre is due to distribution pattern of actin and myosin proteins.

D. M line is considered as functional unit of contraction called sarcomere.

Choose the most appropriate answer from the options given below:

B and C are correct. A and D are incorrect. 

A. Muscle bundles are held together by collagenous connective tissue layer called fascia, not fascicle. 

B. Sarcoplasmic reticulum is a specialized type of endoplasmic reticulum found in muscle fibres. It plays a vital role in
regulating muscle contraction and relaxation by serving as a storehouse for calcium ions and releasing them when muscle fibres are stimulated. 

C. The striated appearance of skeletal muscle fibres is due to the ordered arrangement of actin and myosin filaments within sarcomeres. This organised structure is critical for efficient muscle contraction and it accounts for the characteristic appearance of skeletal muscle fibres under the light microscope. 

D. Sarcomere is considered the functional unit of contraction in a myofibril. It includes one A band and two halves of

Iband. The M line holds myosin filaments together at the center of the A band. By itself, M line does not constitute
sarcomere.