Skeletal  System

1.

The Spine

The spine is the central support for the body. Another word for the spine is the backbone. The spine is made of separate irregular bones called vertebrae. The vertebrae are made up of spongy or cancellate bone surrounded by a layer of compact bone. In between each vertebrae is a layer of cartilage that keeps the bones from rubbing against each other.

There are twenty six vertebrae in the spine. Although each vertebrae can only move a little bit, the total spine is very flexible. The spine of a human being is curved. Most other mammals have a straight spine. The curves allow the spine to support and balance the body on only two legs.

Many people develop back problems as they get older. The discs start to wear away. The vertebra come out of place causing pain. The back gets stiff and makes it difficult to move.

2.

The Ribs

The breastbone, or the sternum, is linked to the bones which make up the ribs. The sternum is a flat bone that is about 6 inches long. The ribs curve around from the spine to the front of the body. This makes a bony framework which is known as the thoracic case. This case helps protect your chest.

Most people have 12 pairs of ribs. The ribs are connected to the sternum by cartilage. This makes the ribs more flexible, which is necessary during breathing. The first seven pairs of ribs are attached directly to the breastbone. The eighth, ninth and tenth pairs are attached to the sternum by a cartrilage band. The last two pairs of ribs are not attached to the sternum or cartilage. The last five pairs of ribs are called false ribs.

3.

The bones of the hands and feet are flexible. The foot has twenty-six bones, one less than in the hand. The bones in the toes are shorter and fatter than the bones in the fingers. This helps us to balance on two feet.

The seven bones in the ankle are called tarsal bones. The main part of the foot is made of metatarsal bones. Phalanges are the bones in the toes. The arch in the foot helps to support the body's weight.

Each hand has twenty-seven separate bones. These are connected with muscles and tendons. Hand bones are also called the metacarpus. Just like the foot, the bones in the fingers are called phalanges.

The fingers have three phalanges and the thumb has two. These joints allow the finger to flex. Because of this, the human hand can make more precise and finer movements than other creatures.

4.

Hips & Legs

The hip bones help us stand upright and move. They support much of the body's weight. Each hip is made up of three bones. These bones are called the ilium, ischium, and pubis. When you are born, these three bones are separated. As you get older, they begin to join together.

The main bones of the legs are the femur, tibia and fibula. Another name for the femur is the thigh bone. The femur extends from the hip joint to the knee This is the longest bone in the body.

The tibia and fibula are the bones of the lower leg. As it helps to support the body's weight, the tibia is the strongest bone in the body. The thinner bone is the fibula and helps to control the movement of the ankle. Another name for the fibula is the shin bone.

The bone that is at the middle of the leg is the patella, or knee cap.

5.

Arm

Just like the bones in the hand, the arms bones are also very flexible. The arm is made up of three bones. These are the ulna, radius, and humerus. In the humerus, there is a deep groove near the top that holds the biceps in place.

The lower bones are connected with the humerus at the elbow and with the carpal bones at the wrist. As the arm turns, so do the bones in the lower arm. There is a membrane between the two bones. The elbow allows the arm to bend and straighten.

At the shoulder are two bones that form the shoulder joint. These are the clavical (collar bone) and the scapul (shoulder blade). This is a ball and socket joint. This joint allows the arm to move in circles.

6.

Joints

We can bend, swivel, stretch, pivot, and point. Our bodies can perform more than one kind of motion because we have joints.

A hinge joint allows movement in a certain spot to take place. This joint is similar to the opening and closing of a door. Some examples of hinge joints are the elbow, knee, ankle and joints between the fingers. Hinge joints allow the body parts to bend and straighten.

Ball and socket joints allow twisting and turning movements. In a ball and socket joint, one of the bones has a rounded head which is the ball. The other bone has a cup-like area that is known as the socket. Some of these joints are the shoulder and the hip. The shoulder joint is the most flexible joint in the entire body. It allows movement in any direction.

There are other types of joints in the body. Gliding joints allow two flat bones to slide over each other like in the bones of the foot and wrist. A condyloid joint allows the head to nod and the fingers to bend. The thumbs has a saddle joint that allows enough flexibility for the thumb to touch any other finger.