Watch this video to view a rotating and exploded skull with color-coded bones. Which bone (yellow) is centrally located and joins with most of the other bones of the skull? The link of the video at the study guide.
The sphenoid bone is the bone that lies in the midline. It is notable for articulating with the occipital bone and temporal bones to form the base of the cranium and for joining the zygomatic bones to form the lateral walls of the orbits.
View another video to review the two processes that give rise to the bones of the skull and the body. The access of the video is in the study guide. Answer this question:
What are the two mechanisms by which the bones of the body are formed and which bones are formed by each mechanism?
The two mechanisms through which bones form are intramembranous ossification and endochondral ossification. Here, intramembranous ossification occurs happens on or within fibrous connective tissue membranes. In this type, mesenchymal tissue is converted to osteogenic cells, then osteoblasts, and then finally osteocytes. Through this, bones like the flat bones of the skull, face, mandible, and clavicle are formed.
On the other hand, endochondral ossification involves the transformation of mesenchymal tissue into hyaline cartilage. This kind of cartilage is used as a model for bone formation until primary ossification and, later, secondary ossification is achieved. With this type of ossification, the long bones of the axial skeleton and the appendicular skeleton are produced.
Watch another video (link at the study guide) to see an animation of synovial joints in action. Answer the following questions after watching the video.
What are the synovial joints being described in the video?
Which type of synovial joint allows for the widest ranges of motion?
The following types of synovial joints are being demonstrated in the video
1. Plane Joints — these are multiaxial joints whose articular surfaces are mostly flat and would only allow short nonaxial gliding movements. In the video, it appears that the example of this is the vertebral joints.
2. Hinge Joints — these are uniaxial joints whose cylindrical end of one bone forms a trough-like surface on another. With this, motion is on one plane and, as the name suggests, resembles that of a mechanical hinge. In the video, an example of this is the knee joint.
3. Pivot Joints — these are uniaxial joints with a rounded end of one bone that is shaped like a ring with another bone that is rod-like and inserted inside of it. Thus, the only safe movement is a uniaxial rotation of one bone around its own long axis. The example from the video appears to be that of the joint of the first and second vertebrae.
4. Condyloid Joints — these are biaxial joints whose oval articular surface of one bone is mounted into the complementarily-depressed surface in another. Here, it is necessary that both surfaces would fit each other as oval surfaces to allow for all angular motions such as circumduction, abduction and adduction, and flexion and extension. In the video, a wrist joint was seen as the example of the condyloid joint.
5. Saddle Joints — these are biaxial joints that appear close to condyloid joints but allow for more freedom of movement. The articular surfaces here have both convex and concave areas, making them seem like a saddle. Like condyloid joints, the articular surfaces of saddle joints then fit together as concave to convex surfaces. The example shown in the video for this is the carpometacarpal joints of the thumbs.
6. Ball-and-Socket Joints — these are multiaxial joints, in which the “ball”-like head of one bone is articulated with the “socket”-like pocket of another. With this, universal movement is allowed, i.e., movement in all axes and planes, including rotation. The shoulder joint is the example displayed in the video for ball-and-socket joints.
Therefore, with this information, it is safe to imply that the ball-and-socket joint would have the widest range of motion, given its allowance for movement in all axes and planes.