Chapter 3.
Skeletal System
The skeleton is made up largely of a system of bony levers that are capable of moving on one another.
The adult human skeleton is formed from 206 bones and various other types of connective tissue that hold them together.
The bones consist of hard bone, spongy bone, and bone marrow (which is responsible for the production of blood and stems. Bones are made of calcium (for strength) and collagen (for flexibility), and can repair themselves.
Joints, also called articulations, are the points of contact between bones. They are attached to the bones and stabilized through ligaments and tendons. Joints vary considerably in how much freedom of movement is allowed. The spinal column is made of 33 vertebrae – seven cervical, twelve thoracic, and five lumbar vertebrae in addition to five fused vertebrae of the sacral region and four fused vertebrae forming the coccyx.
There are three types of joints: fibers joints are immovable, found in the sutures, which firmly connect and stabilize the skull bones; cartilaginous joints are slightly movable, and they are found in the intervertebral discs that cushion and connect the vertebrae in the backbone and allow a small degree of flexibility; synovial joints are the most freely movable, and they are found in the knee, elbow, heap, and many other places.
As people age, the bones lose calcium and become more fragile; older people are more susceptible to hip fractures.
Suggested video:
The Skeletal System (Bozeman Science)
Back to Introduction Ch. 2 – Skin System Ch. 4 – Muscular System