Purposes of the skeleton Supports and moves the body Significantly protects internal organs Cranium protects brain, ribs protect lungs etc. Holds the body in shape Provides muscles with connection points Creates levers for the muscles to push on and attachments for tendons Ventilates lungs by means of the muscles between ribs Blood cells created inside bones in the bone marrow Used to store mineral ions, calcium and phosphorous
Long and short bones Long bones – Long cylinders in the limbs, such as the femur. Short bones – Bones whose structures are undefined but generally cubic or rectangular. They can be found in the wrist and ankle.
Flat bones Flat bones or Membranous bones – These bones are shaped like a curved board and build a cavity to protect organs inside. They have three layers, outer, inner, and middle. The middle layer is spongy. Examples include the forehead and cranial bones.
Irregular bones Complex structure with a lack of uniform, such as, vertebrae and lower jaw bones.
Cartilage Cartilage – Dense and flexible connective tissue. Formed from collagen, cartilage cells, and intercellular substance. The structure is similar to bone tissue, but it does not have calcium or phosphate. A lack of cartilage causes Arthritis.
Marrow Marrow – Soft tissue found in internal cavities of some bones in the body. Blood cells are produced in bone marrow.
Skeletal related problems and diseases Fracture – A lesion, or partial break, in the bone Stress fracture – Erosion of bone caused by constant pressure. For example, by walking “a bunch”. These are microscopic fractures that can grow into a complete fracture. Osteoporosis – When the bone tissue thins. Bone mineral density decreases due to a disorder of calcium metabolism. As a result, bone structure changes and the bone is more easily fractured. Affected by lack of Estrogen.
The lever – A simple machine Levers give the user a mechanical advantage, requiring less energy to do more work. It’s one of the simple machines of physics. Parts of a lever: Load or weight Fulcrum or pivot Resistance arm needs to be moved Effort arm is pushed against
Types of levers The type of lever depends on the relationship between pivot, effort, and load. The type of lever depends on the relationship between pivot, effort, and load. First order – Pivot between load and effort Second order – Load between pivot and effort Third order – Effort between pivot and load
First order lever in body Pulling the head backwards over the neck:
Second order lever in body Pushing up on the toes
Third order lever in body Lifting weights with arm
Types of joints Fibrous joint – No mobility, short fibers link bones together and are pressed together tightly, like between bones in the cranium. Cartilaginous joint – Limited mobility connected by cartilage like spinal vertebrae. Synovial joint – Joints that enable high mobility. Minimal friction, smooth cartilage over each bone and a structural matching between the two bones. Synovial fluid formed by a membrane in the joint cavity also reduces friction in the cavity. Examples include, arm and shoulder joint.
Types of Synovial joints Hinge joint – Allows movement on one level only, such as elbow. Ball and socket joint – Allows movement in all directions, such as arm and shoulder joint.
Other types of synovial joints Articulatio Trochoidea – Built like a door hinge to allow two bones to move around each other. Examples include, the ulna twisting against the humerus. Articulatio Sellaris – A joint that looks like two adjacent saddles and a ball and socket joint.
Damage to joints Sprain – Caused by a sudden twist in a joint that results in a torn ligament or tendon. Dislocation – This occurs when a joint bone moves out of place. Following the dislocation, the joint loses its mobility and any attempt to move the joint causes pain. Lower back pain – Back pain is caused by many things and many people have lower back pain. Causes of pain: disc and joint degeneration between the vertebrae; a herniated disc: a disc between the vertebrae contains gel surrounded by a ring. If the ring tears, the gel may erupt and press on nerves in the spinal cord. Pain may be caused by injury in muscles after exertion or from the vertebrae itself following an illness or fracture.