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Chapter 12

Skeleton - Movement and Locomotion

Class 9 - Concise Biology Selina


Multiple Choice Type

Question 1

Your external ear(pinna) is supported by

  1. Bone
  2. Cartilage ✓
  3. Tendon
  4. Capsule

Question 2

The type of joint found at shoulder is also found at

  1. Elbow
  2. Knee
  3. Ankle
  4. Hip ✓

Question 3

Which one of the following categories of vertebrae are correctly numbered

  1. Cervical — 7 ✓
  2. Thoracic — 10
  3. Lumbar — 4
  4. Sacral — 4

Question 4

Human skeleton altogether contains 213 bones. Which of these are the 6 bones?

  1. Neck vertebrae
  2. Ear ossicles ✓
  3. Carpals
  4. Metacarpals

Very Short Answer Type

Question 1

Name the parts of the skeleton where the following are located: Transverse process, glenoid cavity, shoulder-blade, acetabulum.

Answer

Part of the skeletonLocation
Transverse processNeural arches in the vertebra
Glenoid cavityPectoral girdle
Shoulder-bladeShoulder girdle
AcetabulumPelvic girdle

Question 2

Name any two parts of your body where the supporting skeleton is made of cartilage instead of bone.

Answer

Two parts of your body where the supporting skeleton is made of cartilage instead of bone are:

  1. External Ear
  2. Tip of the nose

Short Answer Type

Question 1

What is the difference between a true rib and a floating rib?

Answer

Differences between a True rib and a Floating rib are as follows:

True ribFloating rib
The first seven pairs of ribs are called true ribs.The last two pairs of ribs (11th & 12th) are called floating ribs.
They are attached in front of the sternum by means of coastal cartilages.They are not attached to the sternum at all.

Question 2

Do the muscles pull the structures, or push them? Explain briefly.

Answer

The muscles in the body provide the means of all movements. Muscles pull the structures. Each muscle usually has two ends- a fixed end where the muscle originates and a movable end which pulls some other part. The movable end is shorter and thicker and hence pulls the bone at the movable end. Muscles can only contract and relax, they cannot lengthen or elongate.
The movable end is projected out to form a tough structure referred to as a tendon which is attached to the bone. When a muscle is triggered by a nerve, contraction of the muscle occurs and it becomes thicker and shorter which causes the bone to be pulled at the movable end.

Question 3

Just as the humerus corresponds to femur, what bones correspond to tarsals, metacarpals, ulna and radius respectively?

Answer

BonesCorresponding bones
HumerusFemur
TarsalsCarpals
MetacarpalsMetatarsals
UlnaFibula
RadiusTibia

Question 4

What are antagonistic muscles? Give one example.

Answer

A structure that has been moved by a muscle cannot return to its original position without the action of another muscle. Such muscles causing opposing movements are called as antagonistic muscles.
Example of antagonistic muscles—
The flexor muscles or the biceps of the upper arm bends the lower arm over the upper arm (flexes). Extension of the lower arm is caused by the extensor muscles or the triceps. Hence these two muscles are antagonistic or work in the opposite direction.

Question 5

Some people in old age complain of stiff joints. What do you think could be a possible reason for it?

Answer

Some joints like shoulder joint, knee joint need to be held firmly in position to be well lubricated. Such joints possess synovial fluid which is a lubricating (loosening) fluid which act as a cushion between the bones and taking away friction while movements. As we get older, the movement of the joints tend to get stiffer with reduced flexibility as the synovial fluids decreases and the cartilage gets thinner. Furthermore, joints tend to get stiffer as the ligaments also shorten and lose some flexibility.

Long Answer Type

Question 1

What are the uses of the skeleton in our body?

Answer

Uses of skeleton:

  1. Support and shape — The skeletal system provides a framework to the body. It provides support to all soft parts and gives a definite shape to the body and all body parts.
  2. Protection — Several delicate and important organs are well protected by a casing of bones.
    Example — The skull provides protection to the delicate brain.
  3. Movement — Some bones are movable on each other which is brought about by the action of muscles that originate on one bone and are inserted into another.
  4. Leverage — Some bones and joints form levers which causes the increase in the speed and distance of the muscle movement.
  5. Formation of blood cells — Certain types of blood cells including red and white blood cells are formed in the marrow of certain long bones such as the femur.
  6. The bones are storehouse of calcium and phosphorus for the rest of the body.

Question 2

Name the different types of joints? Give one example of each type.

Answer

Types of joints with examples are:

  1. Immovable joints — Skull bones
  2. Partially movable joints — Joints between the ribs and breast-bone
  3. Freely movable joints — Hip joint
  4. Gliding joint — Ankle bones
  5. Pivot joint — Joint between axis vertebrae and atlas
  6. Hinge joint — Elbow
  7. Ball and socket joint — Shoulder joint

Question 3

What is the difference between ligament and tendon? (On the basis of their function).

Answer

LigamentTendon
Ligaments connects two or more bones together.Tendon connects muscle to a bone.
They are elastic.They are inelastic.
They are arranged freely.They are arranged in bundles.
Ligaments stabilize joints.Tendons pass tensile forces to the bones from muscles.
Prevent chances of dislocationResponsible to cause the muscles to stay intact with parts of the skeleton.

Question 4

What are bones made of? Are the bones living or non-living? Give reason.

Answer

  1. Bone is a strong, hollow, hard and non-flexible connective tissue.
  2. It is hard, greyish-white tissue and are made of two-thirds of inorganic substances which includes minerals such as phosphorus, calcium, carbonates etc. while one-thirds of it is composed of organic substances.
  3. The outer surface of the bone is known as periosteum which is a thin, dense membrane which consists of an outer fibrous and inner cellular layer, blood vessels and nerves which nourish the bone.
  4. The next layer is made up of compact bone. This part is highly calcified. It is extremely rigid and hard connective tissue which causes the bone to appear as smooth, solid and white.
  5. The middle layer is composed of bone cells known as osteocytes which are arranged as concentric rings which are implanted in a hard matrix composed of collagen fibre and mineral deposits.
  6. The innermost hollow cavity of long bones contains bone marrow responsible for synthesizing blood cells.
  7. Bones are living tissues as long as they are located in the body of a living person. However, when they are taken out of the body, their cells die and the bones are then said to be dead.

Question 5

Given below is a diagram of human skeleton. Name the bones numbered 1-11.

Given below is a diagram of human skeleton. Name the bones numbered 1-11. Skeleton, Concise Biology ICSE Class 9.

Answer

  • 1 → Skull/Cranium
  • 2 → Clavicle
  • 3 → Sternum
  • 4 → Humerus
  • 5 → Ulna
  • 6 → Coccyx
  • 7 → Ribs
  • 8 → Radius
  • 9 → Femur
  • 10 → Fibula
  • 11 → Tibia
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