An antagonist is defined as the muscle that strecthes when another muscle (the agonist) is contracting. When the antagonist contracts, it will stretch the agonist and move the bone in the opposite direction.

The biceps brachii is responsible for flexion of the forearm, while the triceps brachii is responsible for the extension of the forearm. As a result, we say that the triceps brachii is the antagonist of the biceps brachii.

Synergistic muscles assist agonists by properly positioning the insertion bone or stabilizing the origin bone. This cooperation by multiple muscles allows for better movement and posture. Since the temporalis assists in raising the jaw with the masseter, we say that the temporalis is the synergist of the masseter.

During muscle contraction, the H zone and I band contract, decreasing in length. The A band never changes in length. Also, while actin and myosin myofilaments slide over each other, their length does not change either.

There are three primary types of muscle tissue: skeletal, smooth, and cardiac.

Skeletal muscle and cardiac muscle are highly organized, with their contractile filaments arranged into sarcomeres. This organization results in a "striped" look on the cells, known as striations. Smooth muscle contains the same contractile filaments, but lacks the sort of highly organized structure found in the other two muscle types. As a result, smooth muscle is not striated.

Smooth muscle and cardiac muscle are generally mononucleate, meaning that each cell has only on nucleus. In contrast, skeletal muscle cells contain multiple nuclei.

The correct answer is that skeletal muscle is striated and contains multiple nuclei per cell.

The sarcolemma is the specialized cell membrane of a myocyte, or muscle cell. It performs all of the functions of a non-specialized plasmolemma, and forms T-tubules, which are important for muscle contraction.

The primary functions of muscle tissue are motion and locomotion (movement in relation to the body, and movement of the entire body). Muscle is also responsible for the shiver response, used in thermoregulation. Finally, smooth muscles move substances through the body in the process known as peristalsis.

Leverage is a function primarily accomplished by bone.

None of the answer options satisfy all of the criteria given in the question. Cardiac muscle cells have intercalated discs, but are mononucleate.

The epiphyseal plate is the site of longitudinal growth in bones. The patient likely broke the leg along the plate, which caused it to grow less than the other leg.

The first important concept to understand for this question is the process of endochondral ossification. In this process, cartilage is converted into bone during the early life of an organism. Since the question specifies that the rat has reached adulthood, it must refer to the parts of the final bone product that remain as cartilage once endochondral ossification is complete.

Spongy bone and compact bone in the diaphysis have already ossified, and the medullary cavity contains bone marrow and adipose. To find cartilage in any of these regions would indicate a developmental abnormality.

The ends of bones that are in contact with other bones are protected from frictional damage by articular cartilage. Articular cartilage is essential to maintaining healthy joint function. Deterioration of this cartilage results in arthritis, or inflammation in the joints.

Cartilage is a flexible, avascular connective tissue. It is less flexible than muscle, but softer and more flexible than bone. These properties make it an ideal candidate for joints, providing a medium between the muscles and bones that enact forces on the joint. Cartilage is found on the epiphyses of long bones and between certain bones, such as vertebrae, to cushion the motion of the joints.

Due to its avascular nature, cartilage does not easily regenerate. It is formed by chondroblasts (cartilage cells) in a chondrin matrix. In endochondral ossification, cartilage can be used as a precursor to bone, but will never be formed as a result of bone breakdown. Finally, there are three types of cartilage: elastic cartilage, hyaline cartilage, and fibrous cartilage.