The atlas and axis support the head on the lower cervical spine while providing for considerable mobility in flexion, extension, rotation and lateral bending. The first two vertebrae also function as conduits for the cervical cord and vertebral arteries.

Superiorly the atlas articulates with the occiput to form the Atlanto-occipital joint which allows the head to nod up and down on the vertebral column. Inferiorly the atlas articulates with the dens which acts as a pivot that allows the atlas and attached head to rotate on the axis.

On the superior surface of the atlas bone are a pair of concave facets. The facets articulate with rounded condyles on the underside of the skull’s occipital bone. This junction allows the head to nod up and down. Directly below the atlas bone is the axis bone (C2).

occipital condyles

The atlas is the topmost vertebra and, with the axis (the vertebra below it), forms the joint connecting the skull and spine. The atlas and axis are specialized to allow a greater range of motion than normal vertebrae. They are responsible for the nodding and rotation movements of the head.

The C1 and C2 vertebrae function together to give your head flexibility. With the atlas and axis relationship, you are able to swivel and rotate your head, as well as support your head. These two vertebrae are more responsible for the head’s rotational range of motion than from any other joint.

The atlas is one of the two upper cervical vertebrae, also known as C1, which is the topmost vertebra of the spinal column. It is the vertebra that is in contact with the occipital bone, a flat bone located at the back portion of the head.

Irregular bones have complicated shapes that cannot be classified as “long”, “short” or “flat”. Their shapes are due to the functions they fulfill within the body e.g. providing major mechanical support for the body yet also protecting the spinal cord (in the case of the vertebrae). Examples: Atlas bone.

The occipital bone is a bone that covers the back of your head; an area called the occiput. The occipital bone is the only bone in your head that connects with your cervical spine (neck). The occipital bone surrounds a large opening known as the foramen magnum.

The atlas is the first cervical (neck) vertebra which is just under the head; it is named for Atlas, the Greek god who supported the world on his shoulders. The joint between the atlas and axis is a pivot type of joint. It allows the head turn from side to side. It is also called the atloaxoid joint.

C1, C2, and C3 (the first three cervical nerves) help control the head and neck, including movements forward, backward, and to the sides. The C2 dermatome handles sensation for the upper part of the head, and the C3 dermatome covers the side of the face and back of the head. (C1 does not have a dermatome.)

The word cervix is derived from the Latin root word “cervix” which means “neck.” For this reason, the word cervical pertains to many areas where tissues narrow to a neck-like passage, and not only in your neck.

temporomandibular joints

Planar, hinge, pivot, condyloid, saddle, and ball-and-socket are all types of synovial joints.

atlanto-occipital joint

The three main features of a synovial joint are: (i) articular capsule, (ii) articular cartilage, (iii) synovial fluid.

Terms in this set (7)

• synovial joints. articulating bones are separated by a fluid-filled joint cavity.
• All bone ends (epiphyseas) have articular cartilage. absorbs compression, keeps bone ends from crushing each other.
• Joint cavity.
• Articular cartilage.
• Synovial fluid.
• Reinforcing ligaments.
• Lots of nerves and blood vessels.

Synovial fluid, also known as joint fluid, is a thick liquid located between your joints. The fluid cushions the ends of bones and reduces friction when you move your joints.

Pivot Joints The joint of the wrist that allows the palm of the hand to be turned up and down is also a pivot joint. Figure 4. The joint in the neck that allows the head to move back and forth is an example of a pivot joint.

There are six types of freely movable diarthrosis (synovial) joints:

• Ball and socket joint. Permitting movement in all directions, the ball and socket joint features the rounded head of one bone sitting in the cup of another bone.
• Hinge joint.
• Condyloid joint.
• Pivot joint.
• Gliding joint.
• Saddle joint.

Circumduction is the movement of the limb, hand, or fingers in a circular pattern, using the sequential combination of flexion, adduction, extension, and abduction motions. Adduction, abduction, and circumduction take place at the shoulder, hip, wrist, metacarpophalangeal, and metatarsophalangeal joints.

There are five types of bones in the skeleton: flat, long, short, irregular, and sesamoid.

Clavicle or the collar bone is the softest and weakest bone in the body.

The four principal types of bones are long, short, flat and irregular. Bones that are longer than they are wide are called long bones.

The bones of the human skeleton are classified by their shape: long bones, short bones, flat bones, sutural bones, sesamoid bones, and irregular bones (Figure 1).

Bones are made of two tissue types:

• Compact bone: also known as cortical bone, this hard-outer layer is strong and dense.
• Cancellous bone: also known as trabecular bone, this spongy inner layer network of trabeculae is lighter and less dense than cortical bone.

The human skeleton is made up of 206 bones, including bones of the:

• Skull – including the jaw bone.
• Spine – cervical, thoracic and lumbar vertebrae, sacrum and tailbone (coccyx)
• Chest – ribs and breastbone (sternum)
• Arms – shoulder blade (scapula), collar bone (clavicle), humerus, radius and ulna.

Classifications of Bones Bones are classified according to their shape.

• Long Bones. A long bone is one that is cylindrical in shape, being longer than it is wide.
• Short Bones. A short bone is one that is cube-like in shape, being approximately equal in length, width, and thickness.
• Flat Bones.
• Irregular Bones.