12. Which bone is considered part of the axial skeleton? A. Humerus B. Femur C. Sternum D. Clavicle E. Scapula 13. What type of cartilage is primarily found in the intervertebral discs? A. Hyaline Cartilage B Elastic Cartilage C. Fibrocartilage D. Articular Cartilage E. Costal Cartilage 14. The main structural units of compact bone are called: A. Lamellae B. Trabeculae C. Osteons D. Spicules E . Canals 15. What type of ossification occurs directly from mesenchymal tissue? A. Endochondral Ossification B. Intramembranous Ossification C. Perichondral Ossification D. Subperiosteal Ossification E. Chondral Ossification 16. Which movement occurs when the angle between two bones increases? A. Flexion B. Extension C. Abduction D. Rotation E. Circumduction

12. The correct answer is C. Sternum. The sternum is part of the axial skeleton, which includes the bones located along the body's central axis, such as the skull, vertebral column, and rib cage.<br /><br />13. The correct answer is C. Fibrocartilage. Intervertebral discs, which are located between the vertebrae in the spine, primarily consist of fibrocartilage. This type of cartilage is specialized for areas that require both flexibility and strength.<br /><br />14. The correct answer is C. Osteons. The main structural units of compact bone are called osteons, also known as Haversian systems. Osteons are cylindrical structures that contain a central canal, known as the Haversian canal, surrounded by concentric rings of calcified matrix.<br /><br />15. The correct answer is B. Intramembranous Ossification. Intramembranous ossification is the type of ossification that occurs directly from mesenchymal tissue. This process is responsible for the formation of flat bones, such as the bones of the skull and the clavicles.<br /><br />16. The correct answer is B. Extension. Extension is the movement that occurs when the angle between two bones increases. It is the opposite of flexion, which is the movement that decreases the angle between two bones.