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Humans have endoskeletons, which may be subclassified as axial (the spine and pelvis) and appendicular (limb) types

In the animal kingdom, there are three types of skeletons:

1. Hydroskeletons (a flexible skeleton supported by fluid pressure)
2. Exoskeletons (outer shell)
3. Endoskeletons (support structure inside the body)

Humans have endoskeletons, which  may be subclassified as axial (the spine and pelvis) and appendicular (limb) types.

What is an endoskeleton?

An endoskeleton is a rigid internal framework that is a part of a larger system called the musculoskeletal system, which is made up of bones, ligaments, tendons, muscles, and cartilage.

Bone

Bones are rigid structures that play an important role in supporting organs and anchoring muscles. They protect the brain, lungs, heart, and spinal cord by enclosing them in protective cage-like structures. The brain is enclosed in the skull, the lungs and heart are supported by the ribs, and the spinal cord is protected by the spine of the vertebrae.

There are 206 bones in the adult human skeleton. Sometimes, this number changes depending on whether the hip bones on each side are counted as 1-3 bones on each side. The tail bone (coccyx) may be sometimes counted as 1 or 4 separate bones. Similarly, the sacrum, which is made up of 5 fused vertebrae, is usually counted as a single bone. Bones form about 13% of total body weight, and 50% of bone weight is water. Although bones are lightweight, they are strong and hard.

The longest bone in the body is the femur which forms a part of the thigh, and the smallest bone is the stapes bone in the middle ear. The femur contains a spongy structure that produces red and white blood cells and stores minerals. Some of the bones in your body are fused bones, which include those of the pelvis (hip bone on each side) and skull.

Cartilage

Cartilage is stiff tissue between the bones in the joints, which prevents the bones from rubbing against each other. Cartilage is found in the rib cage, ears, nose, elbows, knees, ankles, bronchial tubes, and intervertebral disks. While not as stiff as bone, it is stiffer than muscle.

Cartilage lacks blood vessel supply, meaning if it gets damaged, it requires more time to repair and heal itself. Cartilage can undergo degeneration and result in osteoarthritis of the joints.

Ligament

A ligament is a band of rubbery tissue that connects a bone to another bone. Ligament tears are common occurrences in sports and other athletic activities.

Tendon

A tendon is a band of rubbery tissue that connects muscle to bone. Inflammation of the tendon is called tendonitis and is often seen in people who play sports. Tendon damage can cause severe pain and discomfort if not treated right away.