Frank Solutions for Chapter 17 The Skeletal System Class 9 Biology ICSE
Exercises
1. Bones of which part in the axial skeleton?
Answer
Answer
Bones of skull, vertebral column, sternum and ribs.
2. Name the longest and the smallest bone of the human body.
Answer
Answer
- Longest bone – Femur
- Smallest bone – Stapes of middle ear.
3. How many vertebrae are found in human neck? Give their names.
Answer
Answer
There are seven cervical vertebrae. First vertebra is called atlas, second is axis while the
rest are called typical cervical vertebrae.
rest are called typical cervical vertebrae.
4. What is the role of the skeletal system in an animal?
Answer
Answer
The skeletal system performs the following functions in an animal:
- It provides a framework to support the body and gives a definite shape and form to the body.
- It helps to protect some of the vital organs like heart, lungs, brain and spinal cord.
- It provides the base for attachment of muscles and several bones so as to make body movements possible.
- Bones act as storehouse of some minerals like calcium and phosphorus.
- Red bone marrow of long bones of limbs produces red blood cells and granulated white blood cells in their hollow cavities.
5. What is the role of the skeletal system in an animal?
Answer
Answer
- Axial skeleton
- Appendicular skeleton
6. What are the various parts of human skeleton?
Answer
The various parts of a human skeleton are:
- Axial skeleton: This consists of skull, vertebral column, sternum and ribs
- Appendicular skeleton: It consists of pectoral and pelvic girdles and bones of limbs.
7. What are the various parts of a typical vertebra?
Answer
Answer
A typical vertebra has a main body or centrum and a neural canal in the centre of the neural arch, arising from the sides of the centrum. Neural spine is a flat, longitudinal projection. There are side projections called transverse processes. The articular facets help in joining the two adjacent vertebrae.
8. According to position, endoskeleton is divided into how many parts? Explain each part.
Answer
Answer
On the basis of position, endoskeleton is divided into two main parts:
- Axial skeleton: This consists of skull, vertebral column, sternum and ribs. Human skull has 22 bones of which 8 are present in the cranium and 14 on the face. Brain is present in the cavity called cranium. In the occipital region is an opening called foramen magnum through which spinal cord passes. Cranium has 8 bones which covers the brain from all sides.
(i) Facial bones: These bones form the face and protect the sensory organs present in the head. It has 14 bones.
(ii) Vertebral Column: It makes the axis of the body and provides support like a pillar. Vertebral column is divided into following five parts:
(a) Cervical Region: It has 7 cervical vertebrae. First vertebra is called atlas, second is axis and rest are called typical cervical vertebrae.
(b) Thoracic Region: It has 12 thoracic vertebrae. Neural spine of these vertebrae is long and pointed, which provides surface for muscle and attachment.
(c) Lumber Region: It has 5 lumber vertebrae.
(d) Sacral Region: It has 5 sacral vertebrae which are permanently fused to each other. These are situated on both halves of pelvic and form a joint with pelvic girdle.
(e) Caudal Region: It has 4 caudal vertebrae. These are also fused to form a triangular structure which is called coccyx. - Sternum and Ribs: Sternum is the bone at the mid-ventral line of the thorax to which most of the ribs are attached at their ventral ends. Ribs are formed by vertebral and sterna part. First seven pairs of ribs are called true ribs. These are joined on one side with sternum and on second side with thorax.
- Appendicular skeleton: It consists of limbs, shoulder or pectoral girdle and hip or pelvic girdles and bones of limbs.
(a) Bones of the fore arm: Humerus, radius, Ulna, Carpals, Metacarpals, finger bones, etc.
(b) Bones of hind limb: Femur, Tibia, Fibula, Tarsal, Metatarsal, etc.
(c) Pectoral Girdle: In mammals, two halves of pectoral girdle are situated at equal distance from the ribs on the dorsal plane. Each of it is called shoulder bones. Each half of it made up of a triangular flat bone called scapula. From its outer side a projection arises called acromion and has a cavity called glenoid cavity.
(d) Pelvic Girdle: It consists of two similar halves. In each, three bones are found, ilium, ischium and pubis. Pubis bones of both halves are joined and are called pubic symphysis. Ilium and ischium form acetabulum cavity in which head of femur articulates by forming ball and socket joint. A hollow space is found between pubis and ischium, which is called obdurate foramen, which provides passage for obturator artery, vein and nerve.
9. Describe the bones of vertebral column.
Answer
Answer
The vertebral column is made up of 33 ring shaped bones called vertebrae. A typical vertebra has a main body or centrum and a neural canal in the centre of the neural arch, arising from the sides of the centrum. Neural spine is a flat, longitudinal projection. There are side projections called transverse processes. The articular facets help in joining the two adjacent vertebrae.
10. What are the five regions of the vertebral column?
Answer
Vertebral column is divided into the following five parts:
- Cervical region - It has seven cervical vertebrae. First vertebra is called atlas, second is axis while the rest are called typical cervical vertebrae.
- Thoracic region - It has 12 thoracic vertebrae. Neural spine of these vertebrae is long and pointed, which provides surface for muscle attachment.
- Lumbar region - It has 5 lumbar vertebrae.
- Sacral region - It has 5 sacral vertebrae which are permanently fused to each other.
- Caudal region - It has 4 caudal vertebrae which are fused to form a triangular structure called coccyx.
11. What is the importance of pectoral and pelvic girdle?
Answer
Answer
Importance of pectoral girdle:
- It provides support to the anterior portion of the body.
- Provides surface articulation of fore arms.
- Provides surface for muscle attachment.
- Provides protection to vital organs like heart and lungs.
- Provides surface articulation of hind limbs.
- Provides surface for joining of muscles.
- Provides protection to the uterus.
- Protects from shocks.
12. What is a joint?
Answer
Answer
The place of joining of two or more than two bones is called joint.
13. Describe the following terms: flexor, extensor, levator, rotator.
Answer
Answer
Flexor is a muscle that causes bending of a limb or other part e.g. thigh muscle.
Extensor is the muscle that causes the straightening of a limb or other part. Example: for extending the foot.
Levator is the muscle that raises any part of the body.
Rotator is a muscle that rotates one part on another.
Extensor is the muscle that causes the straightening of a limb or other part. Example: for extending the foot.
Levator is the muscle that raises any part of the body.
Rotator is a muscle that rotates one part on another.
14. Explain axial and appendicular skeleton
Answer
Answer
Axial skeleton: This consists of skull, vertebral column, sternum and ribs. Human skull has 22 bones of which 8 are present in the cranium and 14 on the face. Brain is present in the cavity called cranium. In the occipital region is an opening called foramen magnum through which spinal cord passes. Cranium has 8 bones which covers the brain from all sides.
- Facial bones: These bones form the face and protect the sensory organs present in the head. It has 14 bones.
- Vertebral Column: It makes the axis of the body and provides support like a pillar. Vertebral column is divided into following five parts:
(a) Cervical Region: It has 7 cervical vertebrae. First vertebra is called atlas, second is axis and rest are called typical cervical vertebrae.
(b) Thoracic Region: It has 12 thoracic vertebrae. Neural spine of these vertebrae is long and pointed, which provides surface for muscle and attachment.
(c) Lumber Region: It has 5 lumber vertebrae.
(d) Sacral Region: It has 5 sacral vertebrae which are permanently fused to each other. These are situated on both halves of pelvic and form a joint with pelvic girdle.
(e) Caudal Region: It has 4 caudal vertebrae. These are also fused to form a triangular structure which is called coccyx. - Sternum and Ribs: Sternum is the bone at the mid-ventral line of the thorax to which most of the ribs are attached at their ventral ends. Ribs are formed by vertebral and sterna part. First seven pairs of ribs are called true ribs. These are joined on one side with sternum and on second side with thorax.
- Bones of the fore arm: Humerus, radius, Ulna, Carpals, Metacarpals, finger bones, etc.
- Bones of hind limb: Femur, Tibia, Fibula, Tarsal, Metatarsal, etc.
- Pectoral Girdle: In mammals, two halves of pectoral girdle are situated at equal distance from the ribs on the dorsal plane. Each of it is called shoulder bones. Each half of it made up of a triangular flat bone called scapula. From its outer side a projection arises called acromion and has a cavity called glenoid cavity.
- Pelvic Girdle: It consists of two similar halves. In each, three bones are found, ilium, ischium and pubis. Pubis bones of both halves are joined and are called pubic symphysis. Ilium and ischium form acetabulum cavity in which head of femur articulates by forming ball and socket joint. A hollow space is found between pubis and ischium, which is called obdurate foramen, which provides passage for obturator artery, vein and nerve.
15. Describe the fore and hind limbs of man.
Answer
Answer
Forelimbs consists of one humerus (anterior arm bone), one radius and one ulna (posterior arm bones), 8 carpals (wrist bones), 5 metacarpals ( palm bones) and 14 phalanges (finger bones).
Hind limb consists of one femur bone or thigh bone, one tibia and fibula which are bones of the leg, 8 tarsals (bones of ankle), 5 metatarsals (bones of feet), and 14 phalanges (bones of fingers).
Hind limb consists of one femur bone or thigh bone, one tibia and fibula which are bones of the leg, 8 tarsals (bones of ankle), 5 metatarsals (bones of feet), and 14 phalanges (bones of fingers).
16. Name three types of levers found in the human skeleton.
Answer
Answer
The three levers found in the human skeleton are:
- First order levers
- Second order levers
- Third order levers
17. Name any two types of movable joints found in the body of man.
Answer
Answer
- Ball and socket joint
- Pivot joint
18. What is the ball and socket joint and where are they present in the body?
Answer
Answer
In a ball and socket joint, the ball of one bone is fitted into the socket of another bone such that the ball can move in the socket. Such a joint always involves a long bone, which can move in all planes. This type of joint is found in pectoral girdle, glenoid cavity, femur and acetabulum of pelvic girdle.
19. Name the bones that make up upper arm and lower limb of man.
Answer
Answer
Forelimbs consists of one humerus (anterior arm bone), one radius and one ulna (posterior arm bones), 8 carpals (wrist bones), 5 metacarpals (palm bones) and 14 phalanges (finger bones).
Hind limb consists of one femur bone or thigh bone, one tibia and fibula which are bones of the leg, 8 tarsal (bones of ankle), 5 metatarsals (bones of feet), and 14 phalanges (bones of fingers).
Hind limb consists of one femur bone or thigh bone, one tibia and fibula which are bones of the leg, 8 tarsal (bones of ankle), 5 metatarsals (bones of feet), and 14 phalanges (bones of fingers).
20. How do biceps and triceps work?
Answer
Answer
Biceps muscles first contract to bend the arm, following which the triceps muscles act to straighten the arm. Thus act in opposite ways and are antagonistic muscles, since they counteract each other’s action. The muscles of biceps are called flexor muscle while that of the triceps is the extensor muscle. This whole coordination of muscular action is under the nerve impulse and brain control.
21. What are antagonistic muscles? Name any two of them.
Answer
Muscles which counteract each other’s actions are known as antagonistic muscles. Biceps and triceps are two such muscles.
22. State the functions of biceps and triceps.
Answer
Answer
Biceps cause bending of a limb or other part. Triceps cause straightening of a limb or other part.
23. Name the three types of muscles tissue.
Answer
Answer
Striped, Unstriped and cardiac muscles.
24. Alongside is shown a diagrammatic skeletal of synovial joint.
(a) What is a synovial joint?
(b) Where do you find such a joint?
(c) What is the function of cartilages?
(d) Name the parts 1 to 5.
Answer
(a) Synovial joint is a movable joint present between the adjoining bones which can move independently. The articulating surfaces of the two bones are covered with articular cartilage. The joint is covered with a synovial membrane which secretes synovial fluid for lubrication.
(b) These are found in elbow joint, knee joint, femur and pelvic girdle, etc.
(c) The cartilages cover the ends of the adjoining bones. They function to absorb shock and reduce friction during movement.
(d) 1- and 5-epiphyseal bone
2- synovial cavity
3- synovial fluid
4- synovial membrane
(c) The cartilages cover the ends of the adjoining bones. They function to absorb shock and reduce friction during movement.
(d) 1- and 5-epiphyseal bone
2- synovial cavity
3- synovial fluid
4- synovial membrane
25. The diagram below represents the forelimb of man.
(a) Label the parts marked 1 to 9.
(b) Mention the antagonistic muscles.
(c) Which muscle will contract when the hand is bent?
(d) Name the main bone of pectoral girdle.
(e) Name the type of joint present in shoulder girdle.
Answer
(a) 1. Scapula;
2. Shoulder joint;
3. Humerus;
4. Bicep;
5. Tricep;
6. Radius;
7. Tricep
8. Elbow Joint;
9. Ulna.
(b) Bicep muscles and triceps are antagonistic muscles.
(c) Bicep muscles.
(d) Shoulder bones.
(e) Ball and socket joint.
2. Shoulder joint;
3. Humerus;
4. Bicep;
5. Tricep;
6. Radius;
7. Tricep
8. Elbow Joint;
9. Ulna.
(b) Bicep muscles and triceps are antagonistic muscles.
(c) Bicep muscles.
(d) Shoulder bones.
(e) Ball and socket joint.
26. Every question has four options. Choose the correct answer:
(i) In mammals each half of pelvic girdle consists of
(a) ilium
(b) ischium
(c) pubis
(d) all the above
Answer
(d) all the above
(ii) How many ribs are found in man?
(a) 10
(b) 12
(c) 24
(d) 36
Answer
(c) 24
(iii) In mammals, the number of cervical vertebra is
(a) 5
(b) 7
(c) 10
(d) 12
Answer
(b) 7
(iv) Sutural joints are found between
(a) Parietals of skull
(b) Humerus and radio-ulna
(c) Glenoid cavity and pectoral girdle
(d) Thumb and meta tarsal
Answer
(a) Parietals of skull
(v) Smallest bone of man is
(a) Parietal
(b) carpal
(c) Nasal
(d) stapes
Answer
(d) stapes
(vi) Which of the following is not part of appendicular skeleton?
(a) Femur
(b) Cranium
(c) Humerus
(d) Tarsals
Answer
(b) Cranium
(vii) Which of the following is not true for the elbow joint?
(a) It is a synovial joint.
(b) It is a hinge joint.
(c) It allows movement in all directions.
(d) It is surrounded by a fibrous capsule.
Answer
(c) It allows movement in all directions.