Bones and Joints

Human Bones and Skeletal System - structure of our body (skeleton) that holds us up. Without the skeleton we would just collapse. Bones are made up of osteoid (hard or compact), cartilaginous (tough, flexible), and fibrous (threadlike) tissue, as well as elements of bone marrow (tissue in the center of most bones). People start off with around 270 bones, but by adulthood, there are only 206 because some softer and smaller bones become harder and larger single bones.

Function and Development of Bones

Bone development starts before birth, starting out as flexible cartilage and ossifies (cartilage replaced by hard deposits of calcium phosphate and stretchy collagen) into solid bone.

Bones are made of two types of tissue:

• Hard outer layer called cortical (compact) bone
• Spongy inner layer called cancellous bone, that is lighter and less dense than compact bone

Function of bones

• Protects inner organs
• Support the body against the constant pull of gravity
• Marrow inside bones produces blood cells
• Allow movement and posture
• Store minerals
• Skull protects the brain
• Spine protects the nerves in the spine
• Ribs shield our lungs, heart and liver

Bone Structure

By about 25 years of age, human bones are as big as they are going to get. Most bones have 4 parts:

• Outside part of bone (periosteum) - thin but very dense layer that has the nerves and blood vessels which nourish the bone
• Compact bone is next layer - it is smooth and very hard
• Cancellous bone, resembles a sponge but much stronger
• Bone marrow - the very inside of the bone that makes new blood cells for the body

Bones are made of

• Protein
• Minerals (calcium, potassium, manganese, magnesium, silica, iron, zinc, selenium, boron, phosphorus, sulfur, chromium)
• Vitamins (Vitamin D)

Joints

Bones meet each other at the joints. They make the skeleton flexible and help us move. Flexible joints have a lining of cartilage (substance that limits wear and tear of the bones by coating the bones so they don't rub against each other) on top of the bones. Ligaments join bones together and help make the joint stable.

• Fixed joints that don't move - joints in skull
• Low-movement joints - spinal joints
• High-movement joints - knees, elbows, shoulders

There are two kinds of moving joints.

• Hinge joints - knees and elbows
• Ball and socket joints - hips and shoulders

Bone and Join Problems

• Osteoporosis
• Arthritis
• Bone Breaks and Fractures
• Bone Cancer
• Joint Dislocation
• Bone Spurs

Bone and Joint Health

• Good nutrition, especially dairy foods, during pregnancy and years of bone formation
• Eating foods rich in calcium and vitamind D
• Exercise to strengthen the bones
• Don't foget to protect your bones by wearing helmets and protective gear during exercise

Skull

• Protects brain
• Makes the framework for the face
• Some bones in the middle part of your ear carry sound from your eardrum to the inner ear
• Jawbone helps you chew food and is the only bone in the skull that moves

Spine

• Has 26 vertebrae
• Protects the spinal chord of the brain
• Top 7 vertebrae (cervical vertebrae) that support the head and neck
• Next 12 vertebrae are called the thoracic that hold one end of your ribs
• Next 5 are the lumbar vertebrae
• Next 5 are the sacrum
• Last 4 at the bottom of the spine is the coccyx (tail bone), which is one bone made of 4 small vertebrae fused together

Ribs

• Protect the lungs, liver and heart
• There are usually 12 pairs of ribs

Arms and Hands

• Each arm has 3 bones and a number of joints
  • Humerus (funny bone) - bone between your shoulder and the elbow
  • Radius - goes from elbow to the wrist
  • Ulna - goes from elbow to the wrist
• The wrist has 8 small bones which makes it so flexible
• Each hand has 19 bones

Legs and Hips

The legs have a number of bones connected by a few joints at the knees, ankles and hips.

• Feet and ankles have a total of 52 bones
• Femur - largest bone in the body that goes from the pelvis to the knee
• Patella (kneecap) - covers the knee joint to protect it
• Tibia and Fibula - go from knee to the ankle
• Ankle (talus) - largest bone in the body that goes from the pelvis to the knee