FA

Chapter 15 - Support, Movement and Locomotion

Skeletal System

  • It consists of 3 main types of tissues:

    (a) Cartilage

    (b) Bones

    (c) Muscles

  • It’s functions are to:

    • Protection
    • Support
    • Muscle attachment
    • Movement
    • Storage of calcium
    • Blood cells formation

Skeleton of Humans

  1. Axial Skeleton (Skull, back bone, ribs)
  2. Appendicular Skeleton (Limbs)
  3. Girdles (pelvic girdle, shoulder girdle)

Skull : The most anterior part of the body. It encloses and protects the brain. It also holds and protects the main sense organ.

Backbone: It makes the central axis of the body. It keeps us upright and holds the weight of body. It is made of 33 irregular bones stacked one above the other.

Ribs: Encloses and protects the heart, lungs and major blood vessels. They also move to bring inhalation and exhale.

Shoulder Bone: A triangular, flat bone with a shallow cavity on narrower end. It joints the arm to the axial skeleton.

Collar Bone: It prevents the shoulder from bending inward

Ulna and Radius:

  • Ulna is longer than radius

  • Ulna is thicker than radius

  • Ulna has cavity where part of humerus fitted to make hinge joint.

  • Ulna has an extended bone

Humerus: A long bone with a rounded head epiphysis and a long central shaft called endophysis.

Joints:

  • Ball and Socket: moves 360 degrees in all planes.

  • Hinge Joint: function like the hinge on a door, allowing bones to move in one direction back and forth with limited motion along other planes.

    Antagonistic Muscles:

  • Muscles contract and pull the bones. They can never push bones back.

  • When the muscles contract they shorten in length.

  • To move a bone at a joint, muscles contract. They are arranged in pairs called antagonistic pairs i.e. when one contracts, the other relaxes.

Teeth

Types of Teeth:

  • Incisors (8 in number)

    - The front four teeth on each jaw.

    - It is used for biting and cutting the food.

  • Canines (4 in number)

    - One sharp/ pointed tooth on either side of both of the jaws next to the incisors.

    - It is used for cracking nuts

  • Premolars (8 in number)

    - Two premolars next to incisors on either side of both the jaws. On the lower jaw they have two roots whereas on the upper jaw, a single root. The crown has cusps which increase surfaces that come in contact for grinding.

  • Molars

    - 3 molars next to premolars on both sides of each jaw.

Causes of Dental Decay:

  • Intake of sugary foods
  • Oral unhygienic
  • Food, bacteria and mucus deposited on teeth as plaque
  • Bacteria break down sugars to make acids
  • Acids decrease pH of the mouth
  • It corrodes the surface of teeth
  • The minerals deposit in the plaque
  • Plaque is hardened to tartar which is not removed by simple brushing.
  • Tartar roughens the surface of teeth
  • More food deposits. More breakdown of food anaerobically lower pH further
  • It keeps on eroding the enamel
  • Enamel is a harder tissue. It takes longer to be eroded, however once it is eroded, denting is exposed, which makes a tooth sensitive to hot and cold.
  • Erosion of denting exposes pulp, which makes the tooth painful.

Prevention of Dental Diseases:

  • brushing regularly
  • Dental floss
  • Regular visits to dentist
  • Cut down sugar intake
  • Use of fluoride tooth paste
  • Scaling
  • Use of fluoridated water
  • Dietary fibers