Skeleton - Movement and Locomotion
ICSE Class 9 · Biology · Chapter 13
What this chapter covers
- Movement and locomotion
- The human skeleton and its functions
- Divisions of the skeleton
- The axial skeleton
- The appendicular skeleton
- Joints and their classification
- Immovable joints
- Slightly movable joints
- Freely movable joints
Key points
- Movement is a change in the position of the body or a part of it; locomotion is movement of the whole organism from one place to another.
- Bones act as levers, joints decide the direction of movement, and muscles, which can only pull, work in pairs and are attached to bones by non-elastic tendons.
- The adult human skeleton is an endoskeleton of 206 bones, made of bone and cartilage.
- Functions of the skeleton: shape and support, protection, movement, muscle attachment, blood cell formation in red bone marrow, mineral storage, breathing and hearing.
- The axial skeleton (80 bones) is the skull (22), ear ossicles (6), hyoid (1), vertebral column (26), ribs (24) and sternum (1).
- The cranium (8 bones) encloses the brain; the mandible is the only movable bone of the skull.
- The vertebral column has 33 vertebrae in a child (7 cervical, 12 thoracic, 5 lumbar, 5 sacral, 4 coccygeal) and 26 bones in an adult after fusion of the sacrum and coccyx.
- There are 12 pairs of ribs: 7 true, 3 false and 2 floating; with the sternum and thoracic vertebrae they form the rib cage.
- The appendicular skeleton (126 bones) is the pectoral girdle (clavicle and scapula on each side), the pelvic girdle (two hip bones, each of ilium, ischium and pubis) and the four limbs of 30 bones each.
- Upper limb: humerus, radius, ulna, 8 carpals, 5 metacarpals, 14 phalanges. Lower limb: femur, patella, tibia, fibula, 7 tarsals, 5 metatarsals, 14 phalanges.
- A joint is where bones meet; ligaments (slightly elastic) join bone to bone.
- Immovable joints: sutures of the cranium.
- Slightly movable joints: between vertebral bodies (intervertebral discs), pubic symphysis, ribs and sternum.
- Freely movable joints have articular cartilage, a synovial cavity with synovial fluid, a synovial membrane, a capsule and ligaments.
- Hinge joint (one plane): elbow, knee, phalanges. Ball and socket (all directions): shoulder, hip. Gliding (sliding): carpals, tarsals, vertebral articular processes. Pivot (rotation): atlas and axis, radius and ulna.
Questions answered
Distinguish between movement and locomotion, with one example of each.
Movement is a change in the position or posture of the body or any part of it, without the organism necessarily going anywhere, for example bending the elbow. Locomotion is the movement of the whole organism from one place to another by its own effort, for example walking to school.
List any five functions of the human skeleton.
Any five of: giving shape and support; protecting delicate organs (brain, spinal cord, heart, lungs); allowing movement and locomotion; providing attachment for muscles; forming blood cells in the red bone marrow; storing calcium and phosphorus; helping in breathing (rib cage); helping in hearing (ear ossicles).
Define the axial skeleton and name its parts.
The axial skeleton is the part of the skeleton that lies along the long axis of the body. Its parts are the skull, the vertebral column, the ribs and the sternum (with the ear ossicles and the hyoid), totalling 80 bones.
How many bones are there in the adult human skeleton, and how are they divided between the axial and appendicular skeleton?
206 bones: 80 in the axial skeleton and 126 in the appendicular skeleton.
Name the only movable bone of the skull and state one use of its movement.
The mandible (lower jaw). Its movement allows chewing (also speaking and yawning).
Name the five regions of the vertebral column and give the number of vertebrae in each in a child.
Cervical 7, thoracic 12, lumbar 5, sacral 5 and coccygeal 4, a total of 33.
Differentiate between the atlas and the axis.
The atlas is the first cervical vertebra, a ring-like bone on which the skull rests; it allows nodding. The axis is the second cervical vertebra; its peg-like odontoid process fits into the ring of the atlas and lets the head turn from side to side.
Why are ribs 11 and 12 called floating ribs?
Their front ends are not attached to the sternum, either directly or through the cartilage of another rib; they are joined only to the thoracic vertebrae at the back.
Past board exam questions
ICSE 2019 sample paper · 5 marks
Complete the following paragraph by filling in the blanks (i) to (x) with appropriate words: The hind limb consists of a long bone (i) ____________ in the thigh, two long bones, the inner (ii) ____________ and the outer (iii) ____________ in the shank, seven (iv) ____________ bones in the ankle, five long (v) ____________ bones in the middle of the foot and fourteen (vi) ____________ in the toes. The forelimb consists of a long bone (vii) ____________ in the upper arm and two long bones (viii) ____________ and (ix) ____________ in the lower arm. The wrist has eight bones called (x) ____________.
Show answer
(i) Femur
(ii) Tibia
(iii) Fibula
(iv) Tarsal
(v) Metatarsal
(vi) Phalanges
(vii) Humerus
(viii) Radius
(ix) Ulna
(x) Carpals