ICSE Solutions for Chapter 12 Skeleton: Movement and Locomotion Class 9 Biology Selina
Progress Check
1. Fill in the blanks
(i) Our skeleton consists of bones ____ and ____
(ii) ____ is the chief component of our skeleton
(iii) Shape wise the bones can be classified as _____, ____, ____ and ____
(iv) The central hollow part of the long bones is known as _____
(v) A bone becomes soft and flexible when placed in dilute ____
Solution
(i) Our skeleton consists of bones cartilages and ligaments.
(ii) Bone is the chief component of our skeleton.
(iii) Shape wise the bones can be classified as long, short, flat and irregular.
(iv) The central hollow part of the long bones is known as bone marrow.
(v) A bone becomes soft and flexible when placed in dilute weak hydrochloric acid.
2. Mention if the following statements are true (T) or false (F)
(i) Humerus of the upper arm is the longest bone. T/F
(ii) Axial skeleton incudes shoulder and hip girdles. T/F
(iii) There are 10 vertebrae in the neck. T/F
(iv) There are three kinds of ribs — true, false and floating. T/F
(v) The shoulder girdle is large and trough-shaped. T/F
Solution
(i) False. Femur or the thigh bone is the longest bone
(ii) False. Appendicular skeleton consists of shoulder and hip girdles
(iii) False. The neck has 7 vertebrae
(iv) True.
(v) False. The hip pelvic girdle is a large trough-shaped part.
3. Mention if the following statements are true (T) or false (F).
(i) The flexor and extensor muscles of the arm are antagonistic muscles. T/F
(ii) Muscles can contract as well as elongate. T/F
(iii) Muscles are attached to bones by ligaments. T/F
(iv) Cardiac muscle is a voluntary muscle. T/F
(v) Bending of arm on elbow is an example of first order of lever mechanism. T/F
Solution
(i) True.
(ii) False. Muscles can contract and relax but cannot lengthen.
(iii) True.
(iv) False. Cardiac muscles are involuntary muscles.
(v) True.
4. Match the bones (Column I) with the kind of joint (Column II)
|
Column I (Bones) |
Column II (Joint) |
|
(i) Humerus and shoulder girdle |
(a) Partially movable |
|
(ii) Two adjacent vertebrae |
(b) Gliding |
|
(iii) Skull and upper end of the backbone |
(c) Immovable |
|
(iv) Bones of brain box |
(d) Ball and socket |
|
(v) Rib and breast bone |
|
Solution
|
Column I (Bones) |
Column II (Joint) |
|
(i) Humerus and shoulder girdle |
(d) Ball and socket |
|
(ii) Two adjacent vertebrae |
(b) Gliding |
|
(iii) Skull and upper end of the backbone |
(e) Pivot |
|
(iv) Bones of brain box |
(c) Immovable |
|
(v) Rib and breast bone |
(a) Partially movable |
Review Questions
A. Multiple Choice Type
1. Your external ear (pinna) is supported by
(a) Bone
(b) Cartilage
(c) Tendon
(d) Capsule
Solution
(b) Cartilage
Our skeleton consists of bones, cartilages and ligaments. Cartilages are the supporting and the connecting structures,
2. The type of joint found at shoulder is also found at
(a) Elbow
(b) Knee
(c) Ankle
(d) Hip
Solution
(d) Hip
The joint present at the shoulder and the hip is known as the ball and socket joint.
3. Which one of the following categories of vertebrae are correctly numbered
(a) Cervical – 7
(b) Thoracic – 10
(c) Lumbar – 4
(d) Sacral - 4
Solution
(a) Cervical – 7
The cervical or neck vertebrae are 7 in number
4. Human skeleton altogether contains 213 bones. Which of these are the 6 bones?
(a) Neck vertebrae
(b) Ear ossicles
(c) Carpals
(d) Metacarpals
Solution
(b) Ear ossicles
Ear ossicles from a pair of ears i.e., 3×2 = 6 bones
B. Very short answer type
1. Name the parts of the skeleton where the following are located: Transverse process, glenoid cavity, shoulder-blade, acetabulum.
Solution
|
Parts of the skeleton |
Location |
|
Transverse process |
Neural arches in vertebra |
|
Glenoid cavity |
Pectoral girdle |
|
Shoulder-blade |
Shoulder girdle |
|
Acetabulum |
Pelvic girdle |
2. Name any two parts of your body where the supporting skeleton is made of cartilage instead of bone.
Solution
Two parts of your body where the supporting skeleton is made of cartilage instead of bone:
- External Ear
- Tip of the nose
C. Short Answer Type
1. What is the difference between a true rib and a floating rib?
Solution
Difference between a True rib and a Floating rib
|
True rib |
Floating rib |
|
The first seven pairs of ribs are called true ribs. |
The last two, i.e., 11th and 12th pairs of ribs are called floating ribs. |
|
They are attached in front of the sternum by means of costal cartilages. |
They are not attached to the sternum at all. |
2. Do the muscles pull the structures, or push them? Explain briefly.
Solution
Muscles pull the structure. A muscle has two ends; a fixed end where the muscle originates and a movable end that pulls some other part. The movable end is drawn out to form a tough structure known as a tendon that is attached to the bone. When a muscle is stimulated by a nerve, it contracts and becomes shorter and thicker and this pulls the bone at its movable end. Muscles can only contract and relax, they cannot lengthen.
3. Just as the humerus corresponds to femur, what bones correspond to tarsals, metacarpals, ulna and radius respectively?
Solution
|
Bones |
Corresponding bones |
|
Humerus |
Thigh bone (Femur) |
|
Tarsals |
Carpals |
|
Metacarpals |
Metatarsals |
|
Ulna |
Fibula |
|
Radius |
Tibia |
4. What are antagonistic muscles? Give one example.
Solution
Once a structure has been moved by a muscle, it cannot return to its original position without another muscle acting on it. Muscles that cause opposing movements are known as antagonistic muscles.
Example of antagonistic muscles:
When you flex your arm at the elbow, the muscle that lies above the upper arm, i.e. the biceps is seen and felt bulging. This muscle bulges due to contraction and becomes smaller in length, stiffer and thicker. Contraction of biceps draws the forearm towards the upper arm. However, relaxation of biceps cannot push the forearm back to its original position. When the arm is extended or straightened, the muscle at the back of the upper arm, i.e. the triceps contracts. The two muscles work antagonistically or in opposite directions to bend or flex and straighten the arm at the elbow.
5. Some people in old age complain of stiff joints. What do you think could be a possible reason for it?
Solution
Some joints like shoulder joint, knee joint need to be held firmly in position to be well-lubricated. Such joints contain a lubricating fluid called synovial fluid, which serves as a cushion between the bones and removes friction during movements. As we age, the joint movement becomes stiffer and less flexible because the amount of lubricating fluid inside the joints decreases and the cartilage becomes thinner. Ligaments also tend to shorten and lose some flexibility, making the joints feel stiff.
D. Long Answer Type
1. What are the uses of the skeleton in our body?
Solution
Uses of skeleton:
- 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.
- Protection: The skeleton protects the internal delicate and important organs of the body. For example in human beings, the skull protects the brain, ribs protect the heart and lungs, vertebral column protects the spinal cord, etc.
- Movement: The skeletal system helps in movement. It co-ordinates the movement of attached bones and muscles to bring about locomotion.
- Leverage: Some bones and joints of the skeletal system form levers and help in magnifying, either the movement or the force. For example, slight contraction of biceps moves the hand to a distance of about a foot.
- Formation of blood cells: The skeleton is the site of haematopoiesis. Various types of blood cells like red blood cells, white blood cells and platelets are formed in the bone marrow of some long bones.
- Storehouse for minerals: The bones are a storehouse of calcium and phosphorus for the rest of the body.
2. Name the different types of joints? Give one example of each type.
Solution
Types of joints with examples are:
- Immovable joint: Skull bones
- Partially movable joint: Joints between vertebrae
- Freely movable joint: Hip joint
- Gliding joint: Ankle bones
- Pivot joint: Joint between atlas and axis vertebrae
- Hinge joint: Elbow
- Ball and socket joint: Shoulder joint
3. What is the difference between ligament and tendon? (On the basis of their function).
Solution
|
Ligament |
Tendon |
|
Ligament 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. |
|
They are formed of yellow or elastic fibres. |
They are formed of white or collagen fibres. |
|
They help to stabilize joints. |
They carry tensile forces from muscle to bone. |
|
Prevent dislocation. |
Attach muscles to portions of the skeleton. |
4. What are bones made of? Are the bones living or non-living? Give reason.
Solution
(i) Bone is a strong, hollow and non-flexible connective tissue.
(ii) It is hard, greyish-white tissue, composed of 2/3rd of inorganic substances or minerals like calcium, phosphorus, carbonates, etc. and 1/3rd of organic substances.
(iii) The outer surface of the bone is called periosteum. Periosteum is a thin, dense membrane that consists of outer fibrous and inner cellular layer, nerves and blood vessels that nourish the bone.
(iv) The next layer is made up of compact bone. This part is highly calcified, very hard and rigid connective tissue. This tissue gives bones a smooth, white and solid appearance.
(v) The middle layer of bone consists of bone cells called osteocytes, which are arranged in the form of concentric rings. They are embedded in a hard matrix made up of collagen fibre and mineral deposits.
(vi) The innermost hollow cavity of long bones contains bone marrow, which produces blood cells. Red bone marrow is present at the ends of the bone and produces majority of red blood cells, platelets and most of the white blood cells. Yellow bone marrow contains higher amount of fat cells than red marrow and helps in the production some white blood cells.
(vii) Bones are living tissue as long as they are present in the living body. However, when they are taken out of the body, their cells die and the bones are then said to be dead.
5. Identify the parts of the skeleton given below in the diagram.
Solution
1: Cranium/Skull
2: Clavicle, Scapula
3: Sternum
4: Humerus
5: Ulna
6: Coccyx
7: Ribs
8: Radius
9: Femur
10: Fibula
11: Tibia
