Freely movable joints 

• Ball and socket joint – the rounded head of one bone sits within the cup of another, such as the hip joint or shoulder joint. Movement in all directions is allowed.

• Saddle joint – this permits movement back and forth and from side to side, but does not allow rotation, such as the joint at the base of the thumb. 

• Hinge joint – the two bones open and close in one direction only (along one plane) like a door, such as the knee and elbow joints.

• Pivot joint – one bone swivels around the ring formed by another bone, such as the joint between the first and second vertebrae in the neck.

• Gliding joint – or plane joint. Smooth surfaces slip over one another, allowing limited movement, such as the wrist joints.

Cartilage 

What is cartilage? 

Cartilage is a strong, flexible connective tissue that protects joints and bones. It acts as a shock absorber throughout your body. 

What does cartilage do? 

Cartilage protects your bones and joints. It surrounds the ends of your bones and cushions the spaces in your joints where bones meet. Cartilage has three jobs:

• Absorbing shock: Cartilage cushions your bones and joints when you move and use them. It absorbs force and reduces how much stress an impact puts on your bones. Think about the difference between jumping up and down in bare feet and wearing running shoes. Cartilage acts like the cushion in your sneakers on the inside of your joints and around your bones.

• Reducing friction: Cartilage lubricates your joints. It helps your bones slide past each other without rubbing together. This lets your joints work as smoothly as they should and reduces wear and tear on them.

• Supporting structures in your body: Cartilage helps your joints keep their shape while moving. It also connects other tissue together and to your bones.

Ligaments 

What is a ligament? 

Ligaments are bands of tissue that help connect bones, joints and organs and hold them in place. 

What do ligaments do? 

Ligaments have several important jobs that help you move properly. They:

• Allow the joint to move in the direction(s) it was meant to move.

• Hold bones together.

• Make sure that joints don’t twist.

• Stabilize muscles and bones.

• Strengthen joints.

• Prevent bones from dislocating.

For example, your knee has four ligaments that keep it from moving side to side or backward. They also connect the liver, stomach and intestines and hold them in place. 

Why is calcium important?

Calcium is essential for building and maintaining healthy bones throughout life. Calcium combines with other minerals to form hard crystals giving bones strength and structure. Almost 99% of the body’s calcium is found in the bones.

A small amount of calcium is absorbed into the blood and used for the healthy functioning of the heart, muscles, blood and nerves. 

Bones act like a calcium bank. If there is not enough calcium in your diet the body will take what is needed from your bones for use in other parts of the body. If this happens your bone density (bone strength) will gradually decline and you may be at risk of developing osteoporosis.

Calcium deficiency can reduce bone strength and lead to osteoporosis, which is characterized by fragile bones and an increased risk of falling. 

Calcium deficiency can also cause rickets in children and other bone disorders in adults, although these disorders are more commonly caused by vitamin D deficiency 

Muscle tissue is composed of cells that have the special ability to shorten or contract in order to produce movement of the body parts. The tissue is highly cellular and is well supplied with blood vessels. 

Muscle to bone

A tendon is a fibrous connective tissue that attaches muscle to bone. 

Purpose of gas exchange: To transfer oxygen from the atmosphere to tissues of the body, and to move metabolically produced carbon dioxide from tissues of the body to the atmosphere body to the atmosphere.