Appendicular Skeleton

Note the differences in the fore and hindlimb bones. These differences are related to the need for flexibility and support. Both limbs have the the same basic plan. A girdle bone articulates with a long bone. The shallow ball and socket joint of the forelimb provides for flexibility, while the deeper joint of the hindlimb provides more support. The proximal long bones of both limbs articulate with two smaller bones. In the hindlimb these smaller bones are sometimes fused to provide support, but in the forelimb where flexibility is important this does not happen. The paws and feet are structurally similar. They begin with small cuboidal bones that form the ankle or wrist. These articulate with a series of intermediate elongate cuboidal bones which support the arch in the foot and form the palm in the hand. The last several bones are the toes and fingers.

Click for a closer examination of the forelimb.

The red arrow is pointing to the deltoid tuberosity and the blue arrow is pointing to the olecranon process. These are important points of attachment for muscles that control the movement of the forelimb.

The bones which form the pectoral girdle do not articulate with each other but are held in place by muscles. This allows for a wider range of motion. Follow this link to learn more about the muscles associated with the scapula.

Click for a closer examination of the hindlimb.

The arrows point to the three bones that make up the innominate bone. The the blue arrow indicates where the innominate bone articulates with the sacrum. And the red arrow indicates where the two innominate bones meet at pubic symphysis forming the pelvic girdle. The green arrow indicates the position of the most caudal of the three bones.

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