The appendicular skeleton includes the legs and pelvis, which are the normal means of human ambulation. It contains 126 bones as compared to the 80 in the axial skeleton. The primary purpose of the axial skeleton is the protection of vital organs like the heart and lungs. Some bones in the axial skeleton are fused together for stability. The appendicular skeleton requires freedom of movement, which would be restricted by the fusion of its components.

The metaphysis is the portion of bone between the ephiphyses at the ends of a long bone and the long diaphysis in the middle. None of the other bone types have this structure.

Sesamoid bones are those that are formed within tendons and/or muscles, like the patella. They usually act as pulleys, providing a smooth and hard surface over which a tendon may slide. A long bone is a bone that is longer than it is wide. A flat bone forms a thin plate. Finally, a short bone is a bone that tends to be equal in width and length. 

The correct answer is flat bone - most bones in cranium.

Bones can be classified according to shape. There are four classifications of bones: long, short, flat and irregular. Long bones have a long shaft (diaphysis) with two bulky ends (epiphyses), such as bones in the arm, forearm, thigh and leg. Short bones are cubed shaped, such as the bones in the wrist and ankle. Flat bones are thin, flattened and usually curved, such as most bones in the cranium. Bones that do not fit into the flat, long or short categories are irregular bones and include bones in the vertebrae and some bones in the skull.

The correct match between bone and bone types for this question are as follows:

• long bone = bones in forearm
• short bone = bones in wrist
• flat bone = most bones in cranium (correct answer choice)
• irregular bone = bones in vertebrae

The endosteum is the layer that is found deep to all layers. It is found in the inner lining of the bone. Meanwhile, the periosteum is the most superficial layer of the bone which compromises the outer covering of bones.

There are three main joint categories: synovial, fibrous, and cartilaginous. Synovial joints have the largest range of movement, and are characterized by the presence of articular cartilage and synovial fluid. Fibrous joints lack cartilage and allow for little to no movement. Cartilaginous joints are formed by bands of cartilage between bones, and generally have some limited movement. The shoulder is a synovial joint, the sutures of the skull are fibrous joints, and the intervertebral joints are cartilaginous joints.

Diarthrosis is used to describe joints with wide ranges of movement. Amphiarthrosis describes joints with limited movement, while synarthrosis describes joints with no movement. Almost all fibrous joints are synarthrotic.

Your fingers are able to flex and extend. This type of motion is bidirectional, but along only one axis. This type of joint is called a hinge joint, at which you are able to flex and extend along an axis, with no side to side motion.

The nucleus pulposus is a gelatinous, spongy material located in the core of the vertebral disk. This material responds directly to the pressures of the spinal joints, allowing for twisting, compressing, and stretching forces acting upon the spinal joints and vertebrae. This material can become less resilient with age, but generally does not disintegrate or die as other structures do.

When the rhomboids contract, they pull on the scapula, causing the inferior angle of the scapula to swing up toward the spine. This causes the glenoid fossa to orient downward. Thus, the scapula is downwardly rotated by the rhomboids at the scapulocostal joint. 

When the psoas minor contracts to flex the lower trunk relative to the upper trunk, this posterior tilting of the pelvis occurs at the lumbosacral joint.