THE BIG STORY ON BONES
 FUNCTIONS OF BONES:
**shape and support
**movement
**protection
**stores certain materials
**produces blood cells
Almost all bones are made of the same materials:
*The outer surface of the bone=periosteum. It’s a thin, dense
membrane that contains nerves and blood vessels that nourish the bone.
*The next layer is made up of compact bone. It’s smooth and very
hard.
*Within the compact bone are many layers of spongy bone. It looks
like a big sponge and is very strong.
*The innermost part of the bone=bone marrow. It’s like thick jelly and
makes blood cells.
 HOW BONES GROW
* A baby’s body has about 300 SOFT bones at birth. Some of these
bones are made of cartilage, which is soft and flexible.
*As a child grows, the cartilage grows and is slowly replaced by bone,
with help from calcium. By the time you are 25, this process will be
complete.
*The adult human body has 206 bones.
 YOUR SPINE
*Let’s you twist and bend and holds your body upright.
*Protects the spinal cord, a large bundle of nerves that sends info from
your brain to the rest of your body.
*It’s special b/c it is made of 26 bones called vertebrae.
*5 types of vertebrae:
1. cervical=the first seven vertebrae at the top.
2. thoracic=below the cervical. There are 12 and they
anchor your ribs in place.
3. lumbar=below the thoracic. There are 5.
4. sacrum=beneath the lumbar. There are 5 joined together.
5. coccyx=at the bottom of the spine. Made of 4 fused
vertebrae.
*Between each vertebrae are small disks made of cartilage. They keep
the vertebrae from rubbing against each other and act as shock
absorbers.
 YOUR RIBS
*Protect your heart, lungs, and liver.
*Each person has 12 pairs of ribs which attach in the back to the
spine.
*The first 7 pairs attach to the sternum.
*The very last two sets of ribs are called floating ribs b/c they are
not connected to the sternum or the ribs above them.
 YOUR SKULL
*Protects the brain.
*Contains the smallest bone in your body called the stirrup (behind
your eardrum).
 Teeth – not considered bones, but is part of the skeletal system
 YOUR HANDS
*Each arm is attached to a shoulder blade (scapula), a large triangular
bone.
*The arm is made up of 3 bones: humerus, radius, and ulna.
*Your wrist is made up of 8 small bones.
*The center of your hand is made up of 5 separate bones.
* Each finger has 3 bones, except the thumb which has 2.
*Between your wrists, hands, and all your fingers, you’ve got 54 bones.
 YOUR LEGS
*Your legs are attached to your pelvis, a bowl-shaped structure. It is
made up of 2 hip bones and protects the digestive, urinary, and parts of
the reproductive system.
*Femur=pelvis to knee and is longest bone in your body.
*Patella=kneecap
*Tibia & Fibula=below the knee.
*Ankle has 3 larger bones and 4 smaller ones. The foot has 5 bones.
*Each toe has 3 bones, except the big toe has 2.
*52 bones in your feet and ankles.
 YOUR JOINTS
*The place where 2 bones meet.
*Fixed joints do not move.
Ex: sutures, parieto-temporal
*Moving joints move.
Ex: hinge joint-elbow and knees
Ball & socket joint-shoulder, hips
*Synovial fluid helps joints move.
*ligaments=where bones are held together at the joints. (rubber bands)