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