The Skeleton and Muscles

The Skeleton and Muscles

1. Functions of the skeleton

   • Support: skeleton supports the body and keeps it upright
   • Protection: skull protects the brain, backbone protects spinal cord, ribs protect the lungs
   • Manufacture of blood cells: red cells, white cells and platelets are made in bone marrow of the long bones
   • Movement: bones provide rigid levers against which the muscles can pull

2. The Axial Skeleton

   • Composed of the skull (cranium), facial bones, vertebral column (spine), rib cage and sternum (breastbone)
   • Spine
     • A pad of fluid enclosed by cartilage, called a disk act as shock absorbers and protect the vertebrae from rubbing each other

3. The Appendicular Skeleton

   • Consists of the pectoral and pelvic girdles, and their attached limbs
   • Pectoral (shoulder) girdle
     • Consists of scapula (shoulder blade) and clavicle (collar bone)
     • Function is to give upper body mobility and strength
   • Pelvic (hip) girdle
     • Consists of the pelvis (made up of three fused bones called innominate bones)
     • Gives strength and support to the body and allows mobility of lower limbs

4. Structure of a Long Bone

   • Compact Bone
     • The inorganic material gives strength to the bone
     • The organic material gives the bone flexibility
     • Contains blood vessels and nerve fibres
   • Medullary Cavity
     • Contains a soft material called bone marrow
     • Red marrow is active in making blood cells
     • Yellow marrow is inactive and contains numerous fat-storage cells
       • Can convert to red marrow if needed
   • Spongy Bone
     • Consists of a mixture of compact bone with pockets of bone marrow
     • Function is to give strength and rigidity to bones without making them too heavy
   • Cartilage
     • It protects the end of long bones and acts as a shock absorber
     • Made of collagen

5. Bone Growth

   • Osteoblasts produce and lay down new bone
   • Osteoclasts digest and remove old bone
   • Cartilage slowly converted to bone (ossification)
   • In growth plate, osteoblasts form bone matrix to extend the length of bones

6. Joints

   • A joint is where two or more bone meet
   • Immovable Joints: allow no movement between the bones. Their function is strength and protection
   • Slightly Movable Joints: allow a small amount of movement between bones. e.g. joints between vertebrae
   • Freely Movable Joints: contain synovial fluid in joint cavity which allows greater friction-free movement
     • Hinge Joints: allow movement in one direction only
     • Ball and Socket: allow movement in all direction

7. Muscles

   • Cardiac muscle: located in the heart
   • Voluntary (skeletal) is the muscle that cause body movement. They work as antagonistic pairs
     • Antagonistic muscle pairs are composed of two muscles that have opposite effects to each other
   • Involuntary (smooth) muscle is located in the intestines, bladder and blood vessels
   • Muscles can only contract

8. Arthritis

   • Caused by swelling of joints
   • Prevention: reducing wear and tear
   • Treatment: rest; surgery to repair damage in severe cases

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