The skeletal system is a system which includes all the bones in the body, and their joints(where they attach to each other). Our skeletons are used to protect our internal organs, provides a frame that allows movement, acts as a storehouse for minerals, and produces red and white blood cells. Without skeletons, a simple bump to the head/chest could create injuries for the vital internal organs. The skeletal system is composed of 206 different bones that come in 4 different shapes! Long bones - (like the femur) Short bones - (like the wrist and ankle) Flat bones - (like the skull) Irregular bones - (like the vertebrae)
There are TWO types of bone tissue, compact bone and spongy bone! Compact bone is dense, smooth and very strong, whereas spongy/cancellous bone is spongy and lightweight. Both types contain what is called, living cells. Living cells help repair injuries to the bone. An average long bone has a shaft called, the diaphysis. The diaphysis is made of compact bone. A long bone will also have two ends called, epiphyses. Those are composed of spongy bone. The main shaft of a long bone is covered in a membrane of living cells called periosteum. Periosteum is where muscles/tendons attach themselves. Inside the main shaft a cavity called the medullary cavity, holds bone marrow. The bone marrow stores fat, produces blood cells, and plays a role in the immune system of the body.
AXIAL SKELETON: The Axial Skeleton is made up of 80 bones. These 80 bones come from the skull, vertebral column, and thorax. APPENDICULAR SKELETON: Is made up 126 bones from the shoulders, upper extremities, hips, and lower extremities. Upper Extremities: The arm is composed of the humerus(upper arm), radius, and the ulna. The wrist and hand consists 27 bones. Because of these large number that is formed from small bones, our hands are capable of moving more than any other part of the body. Lower Extremities: The leg is made up of the femur(aka: the heaviest and strongest bone of the body), tibia, and fibula. The tibia bears ALL the weight of our body, whereas the fibula bears no weight at all. The patella/kneecap is a large bone in between the femur, and tibia and fibula.