The Skeletal System What our bones do and are made of

Functions of the Skeletal System  Protect our soft internal organs  Provide the body with support and structure  Stores important minerals that the body needs  Works with the muscular system to allow movement  Make most of the blood cells for our circulatory system

Protection  There are 206 bones in the human bodies (at least for most of us.  Skull (29 bones) – protects the brain and sensory organs (eyes, ears, tongue, nose)  Spinal Column (26 bones) – protects the spinal cord  Rib Cage (25 bones) – protects the heart and lungs, and allows us to breath by supporting the diaphragm  Shoulders, Arms, and Hands (64 bones) – allow movement for survival  Pelvis, Legs, and Feet (62 bones) – allow movement for survival, so we can escape predators and find food

Bones  There are four layers to your bones:  Pariosteum – the outer layer that is thin and dense. It contains the blood vessels and nerves.  Compact Bone – the next layer that is very smooth and hard. It is made up of round bone cells that have blood vessels running through the center of them.  Cancellous – the next layer down looks spongy, but is still very strong. It protects the bone marrow.  Bone Marrow – the inner most layer that is like a very thick jelly and makes the blood cells

Mineral Storage  Bones are made up of...  30% living tissue  45% mineral deposits  25% water  Bones store calcium and phosphorus. As the blood needs more of these minerals they are released from the bones, but the bones need them as well to stay hard and strong.

Bone Marrow  There are two types of marrow:  Red – this is the site for blood cell production. It makes red blood cells, white blood cells, and platelets.  Yellow – contains fatty connective tissues that can be broken down and used as energy during starvation

Cartilage  Cartilage is the elastic, fibrous tissue that is flexible.  It can be found in joints to cushion and allow smooth movements  Some types of cartilage are used to allow flexibility, like in your ears, nose, and trachea.  Some cartilage is meant to bear weight and squish, so the bones do not crack.  Cartilage has no blood vessels running through it, but is still living tissue.  As a fetus most of your skeleton is made of cartilage.

Breaking Bones  There are several different types of breaks or fractures depending on their severity.  The pain is different for everyone, but usually it is a deep ache and you may feel nausea  The best thing is to not move the area that your think might be broken. Immobilize the area and get to a doctor.  Your osteocytes will start producing more bone cells and eventually your break will heal

Fun Facts  Bones fuse with age, so when you were a baby you had about 300 bones  Bones in the hand and feet vary, so not every one has exactly the same number of bone. It usually ranges between 206 and 216 bones  Half the bones in your body are in your hands and feet  Your femur (thigh bone) is stronger than steel rod of the same size and shape  Standing and sitting squeezes the cartilage between the discs in your spine, so you are about ½ inch shorter at the end of the day

Human Skeleton