The Human Skeleton

Composed of the body’s

• Bones
• Ligaments ( bone -- bone )
• Tendons ( bone -- muscle )
• Cartilage

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Infants have more than 300 bones at birth

• Bones fuse as babies develop
• 206 bones in the adult human body (==can be less)==

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1. Structure and Support

Leg bones, pelvis, and vertebrae

Supports the body’s weight

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2. Protection

Skull protects the brain

Ribs and sternum

(breastbone) protects the lungs and heart

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<<Functions of the Skeletal System<<

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3. Movement

4. Muscles attach to bones and use them as levers to move the body

5. Storage

   1. Calcium and Fat (Stored E)

6. Blood Cells Production :

   1. Bone marrow produces millions per second

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<<Bone Classification<<

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Each bone belongs to one of two major groups:

• Axial Skeleton
  • Skull, vertebral column, and rib cage
  • Involved in protection, support, and carrying other body parts
• Appendicular Skeleton
  • Bones of upper & lower limbs
  • Involved in locomotion

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^^Types of Bones^^ :

1. Long Bones

   1. Longer than they are wide
   2. All limb bones except the patella (kneecap) and the bones of the wrist + ankle

2. Short Bones

   1. Roughly cube shaped
   2. Bones of the wrists and ankle

3. Flat Bones

   1. Thin; flattened, and usually a bit curved

   2. Scapula (shoulder blade)

      Sternum (breast bone), ribs, and most bones of the skull

4. Irregular Bones

   1. Have weird shapes that fit none of the 3 previous classes
   2. Vertebrae, hip bones, 2 skull bones - mandible, and maxilla

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Long Bone Structure:

• Periostern : Hard outer covering
• Epiphysis : Ends of the bones
• Diaphysis : The shaft of the bone
• Articular Cartilage : Cushions the ends of the bones and allows for smooth movement
• Epiphyseal Plate : Areas made of cartilage allowing for the growth of the bone growth plate

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Collagen (protein) -- provides strength and resillience

Calcium -- provides hardness and resistance to crushing

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<<Three Types of Bone Cells<<

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1. Osteocytes --

   1. Mature bone cells suspended in matrix [ cytes = basic cells ]

2. Osteoblasts --

   1. Build new bone by adding Collagen and Calcium to matrix [ blasts = build ]

3. Osteoclasts --

   1. Breakdown matrix to replace stored Calcium; can also clean up unhealthy or unwanted bone

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Yellow Marrow:

• Largely fat
• In emergencies -- massive blood loss -- convert to red bone marrow

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Red Marrow

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Medullary Canal

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All bones consist of a dense, solid layer known as compact bone and an inner layer spongy bone