Graphics Reference
In-Depth Information
Ball-and-Socket Joint
Ball-and-socket joints are triaxial joints that allow movement through
three axes. These joints comprise a spherically shaped bone that fits into a
reciprocal cup shape within the adjoining bone, enabling a swivel type of
action. Such joints are to be found at the hip and the shoulder.
There are other joints that are cartilaginous, fibrous, or ligamentus in nature
that unite two bones by means of interconnecting cartilage or fibrous tissue.
The most important of these as far as movement and mobility are concerned
are those that make up the vertebral column. The thickness of the vertebral
disks allow for a degree of movement that is not dissimilar to that achieved
with a ball-and-socket joint.
The Skull
The skull's role is to provide protection for the brain. Made up of 22 bones, the
skull is joined together by ossified material that only occurs in the skull. Part of
the skull is composed of air-filled sinus cavities that offer strength and reduce
the skull's weight.
The jaw is held in place by the temporomandibular joint, which is composed
of fibro-cartilaginous tissue that offers a great deal of flexibility.
The Spine and the Rib Cage
The spine is a remarkable structure that provides support, strength, and
a degree of flexibility to the entire body. It is primarily a mechanism for
maintaining our upright position and permitting a range of movements for
the head, neck, and trunk. The spine's flexible action allows the entire figure to
maintain balance throughout many actions. The level of flexibility also allows
for the transmission through the body of forces that enable locomotion. It is
often the position and orientation of the spine that animators use to identify
the “line of action” within the figure.
The normal human spine consists of around 33 different and irregularly
shaped vertebrae. These are grouped in four regions, from top to bottom:
cervical, thoracic, lumbar, and sacrum, as follows:
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Seven cervical vertebrae
•
Twelve thoracic vertebrae
•
Five lumbar vertebrae
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Five fused sacrum vertebrae
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Three to five fused vertebrae that make up the coccyx, which forms part of
the sacrum region of the spine
The vertebrae of the spine are classified as irregularly shaped bones, the
spaces between which are filled with a cartilaginous material. This material
provides a form of lubrication that enable humans' high degree of flexible
movement.
