MICROANATOMY

Detailed explanation-1: -Answer and Explanation: Actin-or myosin-containing structure is called the myofibrils. The sarcoplasm of the muscle fibers contains many threadlike structures called the myofibrils, which extend the length of the muscle fiber.

Detailed explanation-2: -A sarcomere is composed of two main protein filaments (thin actin and thick myosin filaments) which are the active structures responsible for muscular contraction.

Detailed explanation-3: -The actin to myosin filament ratio varies from 3 to 4 within each individual myofibril. The described variability of the actin filaments arrays leads to several difficulties in an explanation of the mechanism of muscular contraction.

Detailed explanation-4: -Answer and Explanation: The muscle types containing actin and myosin are (d) skeletal, smooth, and cardiac muscle. Actin and myosin, also known as the thin and thick filaments respectively, are essential for contraction of muscles. These filaments bind together to form crossbridges that enable contraction.