Class- V Subject -Science

Ch-2 Skeletal System

The human body is the most complex of all organisms present on this earth. A human body is

made-up of nearly 206 bones. https://youtu.be/24jgE9rKE8o

Did you know that new born babies have around 305 bones! A baby’s skeleton is mostly made up of

cartilage. As it grows older cartilage undergoes ossification to form a complete skeletal system, having

206 bones. Let us learn about a human skeletal system.

THE SKELETAL SYSTEM

The skeletal system is a system which supports the framework of bones in our body and gives

it a particular and definite shape.

The human skeleton consists of the skull, the backbone, the ribcage and two pairs of limbs.

Skull: Acts like a helmet and protect the brain.

Forelimbs: Help us to lift various objects.

Ribcage: Protect delicate organs like heart and lungs.

Lower Limbs: Along with muscles they help in movement.

The framework of bones present in our body is known as skeleton.

BONE

Bones are made-up of minerals which include calcium and phosphorus. These make the bones

strong.

Types of Bones

Bones may be short, long, flat or irregular.

Long Bones Short Bones Flat Bones Irregular Bones

Thigh Bone Wrist Bone Breast Bone Backbone Spine

Skull

The skull protects the brain. It is a hallow round structure present in the head.

Functions:

The skull covers and protects the brain.

It gives shape to the face.

It supports the teeth present in upper and lower jaw.

https://youtu.be/Nc5IRj3OJhE

Points to ponder

Our teeth form part of our skeletal system, but are not counted as bones. The

hardest substance in our body is enamel coating on our teeth.

SKULL

22 BONES

8 bones form skull 14 bones form face

https://youtu.be/Nc5IRj3OJhE

NOTE: All the bones that form the skull are fixed and immovable, except for the lower

jaw.

BACK BONE

The bone present on the extreme back of our body is known as backbone. It is also

known as the vertebral column or spine. The skull is attached to the backbone.

Vertebral Column – Long bony structure made – up of 33 bones.

Ribcage

The bony cage present in the chest region is called the ribcage. It is made-up of 12 pairs

of thin curved bones called ribs.

Sternum: The long flat bone present in the centre of chest is called sternum.

Backbone: The bone present at the back supporting the ribs is known as backbone.

Floating Ribs: The last two pairs of ribs that are not attached to sternum are known as

floating ribs.

Function: It protects the delicate organs such as heart and lungs.

Limbs

Human beings have four limbs – These include a pair of forelimbs called arms and pair of

lower limbs called legs.

Forelimbs

The upper part of the arm contains a single bone called HUMERUS.The bones of upper

arm and lower arm join at elbow.

Function: The forelimbs help in lifting things.

Lower limbs

The upper part of the leg contains the largest bone called the FEMUR (Thigh bone). The

lower part of leg also contains two bones. The bones of leg and at knee.

Function: The lower limbs help us to walk, move and run. It also supports the weight of the

body.

Points to ponder

The long bones of the skeleton are hollow and are filled with soft, fatty substance called

bone marrow. Red blood cells are produced in the bone marrow.

Girdles

A bony ring like structure present in our body is called a girdle. There are two types of

girdles present in our body.

FUNCTIONS OF THE SKELETON

The functions of skeletol system are given below:

1.Support : It provides structural support to the

entire body.

2.Protection :It protects the delicate internal

organs like heart and brain.

3.Movement :It helps in the movement of different parts of our body.

4.Storage :The bones of the skeleton store minerals like calcium and phosphorus.

5.Blood Cell Production :Bone marrow helps in

GIRDLE

Shoulder Girdle

It is made-up of the collar bone and

shoulder blade.

Hip Girdle

It is made-up of three bones fused to

form a single bone.

production of red blood cells.

Ever wondered why doctors advise to include calcium in your diet? Our bones are made-up of calcium.So taking calcium rich diet strengthens our bones.

JOINTS

A Joint is a region in the human body where two or more bones meet.Joint allow the

movement of different parts of our body.

Bones are held together at joint with the help of ligaments.

The surface of the bones at the joint have a particular type of connective tissue

called cartilage.

Cartilage protects the bones from the wear and tear and increase the life of

bones.

Types of Joints

There are two types of joints:

MOVABLE JOINTS IMMOVABLE JOINTS

A synovial cavity is present .

A synovial cavity is absent.

Movement can occur in these joints.

No movement can occur in thses joints.

It includes all joints except the bones of skull.

It includes the bones of skull.

TYPES OF MOVABLE JOINTS

There are four main types movable joints.

https://youtu.be/WNBIN3P0VzA

1.Ball and Socket Joint

JOINTS

In this type of joint,one bone has ball shaped end and the other has a cup shaped

socket.The ball shaped end of obe bone fits into the cup-shaped socket of other

bone.This joint allows maximum movement in all directions.

Example : Shoulder joint and hip joint.

2.Hinge Joint

Just like the hinge of the door , this joint allows only back and forth movement and no

rotation.

Elbows,Knees and ankles are examples of hinge joint.

3.Pivot Joint

In a pivot joint,the rounded end of a single bone fits into the ring of tendon.Thiw joint

allows sideways movement.This type of joint occurs at the base of the neck between the

first and second vertebrae.

Pivot joint in the base of the neck.

4.Gliding Joint

This joint has bones that glide against each other but cannot move in a circular

direction.This is the least movable joint.

This type of joint is found between the bones of the verterbral coloumn.

MUSCLES

Muscle is a soft tissue present in human body.There are over 600 different muscles

present in our body.https://youtu.be/3HEn8OKllfE

Types of Muscles

Based on their functions ,Muscles are two types --- Voluntary and Involuntary muscles.

Involuntary Muscles are further of two types.These includes Smooth muscles and

Cardiac muscles.

(Muscles present in arms,legs,

hands and feet)

(Muscles present in (Muscles presnt in heart)

internal Organs)

(A) VOLUNTARY MUSCLES

Voluntary Muscles are those muscles whose movements can be controlled by us.The

skeletal muscles present in arms,legs,hands and feet are examples voluntary muscles.

(B)INVOLUNTARY MUSCLES

Involuntary muscles are those muscles whose movements cannot be controlled by us

and they work on their own.

These are further of two types.

Muscles

Voluntary Muscle Involuntary Muscle

Smooth Muscles Cardiac Muscles

(i) Smooth Muscles: These are involuntary muscles which are found in most of

our internal organs.

Examples are muscles of stomach stomach and intestine.

(ii) Cardiac Muscles:

These are involuntary muscles present inside the walls of heart.These muscles work all

the time,pumping blood to different parts of our body.

CARE OF BONES AND MUSCLE

Skeletal system provides a basic framework to the human body and, therefore, we must

care of our bones.

1. Calcium rich diet like milk, banana should be taken.

2. A regular exercise strengthens the bones and muscles and lubricates the joints.

3. A right posture is essential to keep the body in shape.

Always sit with your back straight.

Do not bend your neck too much while reading.

POSTURE

Posture is the position in which we hold our body when we sit, stand or move.

Work sheet -1

Fill in the blanks

1) The _______ System supports the framework of bones and gives the body

definite shape.

2) The _____ is hollow round structure present in the head.

3) The bony cage present in the chest region is called the ________

4) A bony ring like structure present in our body is called a _____

5) _________ joint is freely movable joint.

6) ______ is soft tissue present in the human body.

7) ______ is a type of connective tissue which connects muscles to bones.

8) ______ is the position in which we hold our body when we sit,stand or move.

9) Exercise is moving the body parts to increase the _______ of blood.

10) The upper arm can be divided in to ____ parts.

11) The upper arm consist of upper arm and _______.

12) The upper arm contains a bone called ________.

13) The humerus is joined at ______ in the lower arm.

14) The skull of human beings consist of _____ bones.

15) The hardest substance present in our body is _______.

16) The bones of _______ jaw are movable.

17) There are _____ pairs of floating ribs.

18) Red blood cells are produced in the _______.

19) _______ girdle is made up of two bones fused to form a single bone.

20) _______ muscles are present in our stomach.

21) _______ is the framework of bones in our body.

22) Hollow bones are formed in the disease called ___________.

23) Rickets disease makes the bones __________.

24) __________ disease causes the inflammation of joints.

25) Long flat bone present in the centre of chest is known as _______.

Q2. Choose the correct answer.

1. The ribs protects the ________.

a. Heart b. Feet

2. The pivot joint allows the movement of _______.

a. Knee b. Head

3. Total number of bones present in the human body is _______.

a. 207 b. 206

4. The longest bone present in human body is ______.

a. Femur b. Humerus

5. An example of irregular bone is _____.

a. Spine b. Wrist bone

6. There are _____types of joints.

a. Four b. Two

7. ________ is the least movable joint.

a. Pivot joint b. Gliding joint

8. How many bones make up the backbone?

a. 33 b. 22

9. Knees and ankle are examples of _______joint.

a. Pivot b. Hinge

Q3. Write True or false.

1. Pivot joint is a freely movable joint. ____

2. Voluntary muscles are under our control. ______

3. Cardiac muscles work all the time. _______

4. Femur is a bone present in the upper arm. ______

5. Our teeth are counted as bones. ____

6. Back bone is made up of small bones called vertebrae. ______

7. Human beings have eight limbs. ________

8. The skull protects the brain. ________

9. The knee joint is an example of pivot joint. _______

10. Two bones fuse together to form a shoulder gridle. _____

11. Gliding joint is the freely movable joint._________

Q4. Match the following.

1. Hinge joint a. joint between bones of vertebral column

2. Gliding joint b. shoulder joint

3. Pivot joint c. ankle joint

4. Ball and socket joint d. joint between first and second vertebrae

Worksheet 1 (Answers)

Q1. Fill in the blanks with suitable words.

1) Skeletal18) Bone marrow

2) Skull19) Shoulder

3) Ribcage20) Smooth

4) Girdle21) Skeleton

5) Ball ans Socket22) Osteoporosis

6) Muscle23) Brittle

7) Tendon24) Rheumatoid Arthritis

8) Posture25) Sternum

9) Circulation

10) 2

11) Lower arm

12) Humerus

13) Elbow

14) 22

15) Enamel

16) Lower

17) Two

Q2. Choose the correct answer.

1. a 5. a

2. b 6. b

3. b 7. b

4. a 8. a 9. b

Q3. Write true or false.

1. False 6. True

2. True 7. False

3. True 8. True

4. False 9. False

5. False 10. True 11. False

Q4. Match the following.

1. c3. d

2. a4. b

Worksheet 2

Q1. Answer in one word.

1. Where is back bone present?

2. Give the other name of back bone.

3. What are the small bones that make back bone known as?

4. Freely movable joint is known as?

5. Which is the smallest bone in our body?

6. Irregular bone forming the main axis of body is known as?

7. Name the joint that connects the neck to the vertebrae.

8. Name two minerals of which our bones are made of.

Q2. Answer the following questions.

1. What are vertebrae?

2. Give the functions of skeletal system.

3. Which ribs are known as floating ribs?

4. Differentiate between movable and immovable joints.

5. Give the function of cartilage.

6. Give the functions of backbone.

7. Define ribcage.

Q3.Can you explain why?

1. Our backbone is composed of 33 small irregular bones. What would happen if

instead of these only one straight bone is present?

2. Sanjam’s friend is suffering from rickets. Doctors advised him to increase the

intake of milk. Why?

Worksheet 2 (Answers)

Q1. Answer in one word.

1. At the extreme back of our body

2. Vertebral column

3. Vertebrae

4. Ball and socket

5. Stirrup

6. Backbone

7. Pivot joint

8. Calcium and phosphorus

Q2. Answer the following questions.

1. The small bones that form the vertebral column are called vertebrae.

2. The functions of skeletal system are:

Support: It provides structural support to the entire body.

Protection: It protects the delicate internal organs like heart and brain.

Movement: It helps in the movement of different parts of our body.

Storage: The bones of the skeleton store minerals like calcium and phosphorus.

Blood cell production: Bone marrow helps in production of red blood cells.

3. The last two pairs of ribs that are not attached to the sternum are known as

floating ribs.

4.

MOVABLE JOINTS IMMOVABLE JOINTS

A synovial cavity is present .

A synovial cavity is absent.

Movement can occur in these joints.

No movement can occur in thses joints.

It includes all joints except the bones of skull.

It includes the bones of skull.

5. Cartilage protects the bones from wear and tear and increases the life of bones.

6. The back bone encloses and protects the delicate spinal cord.

7. The bony cage present in the chest region is called the rib cage.

Q3.Can you explain why? (Answers)

1. The small 33 irregular bones at our backbone help us to bend and twist at wrist. If

only one straight bone is present than we would not be able to bend and sit.

2. Rickets is the condition where the bones become brittle. Taking calcium rich

food make the bones strong. Milk is the rich source of calcium so, Doctor advised him to

increase the intake of milk.