This lesson introduces the anatomy and functions of the skeletal system. This lesson also explores how bone forms, remodels, and constantly changes as a person grows.
A human is born with roughly 270 bones. As a person grows, this number decreases to approximately 206. This is because many of the bones fuse.
Half of the pelvic bone has three separate bones at birth: the ilium, ischium, and pubis. By adulthood, these bones fuse into one bone called the hipbone.
Anatomically, the skeletal system is divided into two major divisions: axial skeleton and appendicular skeleton. The axial skeleton consists of the bones of the skull, sternum, vertebral column, and ribcage. The appendicular skeleton comprises the bones of the upper and lower extremities and the associated girdles that connect the extremities to the vertebral column. The following table summarizes the number of bones found in each skeletal division.
Twenty-four of the bones in the vertebral column are called the pre-sacral vertebrae. These consist of 7 cervical, 12 thoracic, and 5 lumbar vertebrae. The last two bones of the vertebral column are the sacrum and coccyx.
|Inner ear ossicles||6|
|Skull and Hyoid||23|
|Sternum and Ribs||25|
The skeletal system consists of bones, cartilage, and ligaments that are tightly bound together to form a strong, yet flexible, framework. Bone is an active form of connective tissue. This tissue plays a role in many of the functions of the skeletal system:
The following image illustrates the anatomy of the skeletal system.
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Which of the following is part of the axial skeleton?