Skeletal System

  • Provides shape and strength to the body
  • Protects internal organs
  • 206 bones in an adult human body
  • Major bones: Skull, Ribcage, Backbone, Limbs (arms and legs)


Major Bones and Functions

  • Skull: Protects the brain, 22 bones
  • Ribcage: Protects heart and lungs, 12 pairs of ribs
  • Backbone (Vertebral column): Main axis, allows bending and twisting, 33 small bones
  • Jawbone: Largest and strongest bone in face, helps in biting and chewing


Importance of Bones

  • Shape and support: Give shape and strength to the body
  • Protection: Protect soft internal organs like brain, heart, and lungs


Limbs

  • Upper limbs (arms): Humerus, radius, ulna
  • Lower limbs (legs): Femur (thigh bone), connected by girdles (shoulder and hip)


Joints

  • Types: Movable and Immovable
  • Function: Allow movement, protect bones from wear and tear
  • Examples of movable joints: Knees, elbows, hips
  • Examples of immovable joints: Skull joints (except lower jaw)

Exercise

A. Tick (✔) the correct option.

1. The framework of bones that gives support to our body is called.............

i. muscles

ii. skeleton √

iii. ribcage

2. The bony structure that encloses heart and lungs is .................

i. backbone

ii. ribcage √

iii. blood

3. Red blood cells are produced in the ....................

i. muscles

ii. bone marrow √

iii. lower joint

4. Vertebral column is made up of ...................... small bones.

i. 22

ii. 33 √

iii. 11

5. Both smooth an ............. muscles are involuntary muscles

i. rough

ii. cardiac √

iii. skeletal


C. Write ‘T’ for True and ‘F’ for False.

1. 14 flat bones joined together protect the brain. - T

2. The lower jaw enables us to eat and talk. - T

3. Ribcage encloses liver and kidneys. - F (Ribcage protects heart and lungs)

4. Joints of the bones are held together by strong tissue called ligaments. - T

5. Muscles are attached to bones through tendons. - T


D. Match the following.

1. Smooth muscles - iii. stomach and intestines

2. Hinge joint - iv. elbows and fingers

3. Bone marrow - v. blood cells

4. Ball and socket joint - i. hip and shoulder

5. Gliding joint - ii. wrist and ankle


E. Name the following.

1. The frame work of all bones - Skeleton

2. The last two pairs of ribs that are joined to the backbone - Floating ribs

3. The longest bone in our body - Femur

4. It protects the bones from wear and tear Cartilage

5. The muscles whose movements can be controlled by us - Voluntary muscles


F. Differentiate between.

1. Movable and immovable joints.

Ans: The difference between movable and immovable joints is given below.

Movable Joints

  • These joints allow us to move our body parts freely.
  • They help us walk, run, and pick things up.
  • Examples: Shoulder, knee, elbow, and wrist.

Immovable Joints

  • These joints do not allow any movement at all.
  • They provide protection and keep bones firmly in place.
  • Examples: The bones of the skull (except the lower jaw) and the pelvic girdle.

2. Voluntary and involuntary muscles.

Ans: The difference between voluntary and involuntary muscles is given below.

Voluntary muscles

  • You can control these muscles whenever you want. You think, and they move.
  • They can get tired and need rest (like after running).
  • They are mostly attached to your bones (Skeletal muscles).
  • Examples: Muscles in your arms, legs, and hands.

Involuntary Muscles

  • These muscles work automatically. You don't have to think about them to make them work.
  • They work all the time without getting tired.
  • They are found in internal organs like the heart and stomach.
  • Examples: Cardiac muscle, stomach and intestines, blood vessels.

G. Answer the following questions.

1. Write a short note on skeletal system. Name the major bones of the human body.

Ans: The skeletal system is a framework of bones, cartilages, and ligaments that provides support, protection, and movement to the body. It consists of 206 bones in adults.


Major Bones:

- Skull

- Sternum 

- Ribs 

- Vertebral column

- Humerus (upper arm)

- Femur (thigh bone)

- Tibia and Fibula (lower leg)

2. What is floating ribs?

Ans: Floating ribs are the last two pairs of ribs that are not attached to the sternum in the front. They are only connected to the spine in the back.

3. What is sternum?

Ans: The sternum, also known as the breastbone, is a long, flat bone in the center of the chest. It connects the ribs together and protects the heart and lungs.

4. Write down the importance of bones.

Ans: Bones support the body, protect organs, help with movement, store calcium, and produce blood cells. They enable us to stand and function properly.

5. Describe different types of movable joints found in our body.

ANs: We have a few types of movable joints that help us move:

- Ball-and-socket joints (shoulder, hip): Allow rotation and movement in multiple directions

- Hinge joints (knee, elbow): Allow movement in one direction (like a door)

- Pivot joints (neck): Allow rotation

- Gliding joints (wrist, ankle): Allow sliding movements

- Condyloid joints (wrist): Allow flexion, extension, and some rotation.

6. What do you mean by the term “posture”?

Ans: Posture refers to the way you hold your body, like how you sit, stand, or lie down. Good posture means keeping your body aligned and balanced, which helps prevent strain and injury. 

7. How do we keep our bones healthy and strong?

Ans: We keep our bones healthy and strong by:

- Eating a healthy diet rich in proteins, vitamins, and minerals

- Consuming calcium-rich foods for bone and teeth formation

- Ensuring adequate vitamin D for calcium absorption

- Doing regular exercises like running, cycling, swimming, and yoga

- Maintaining good posture to prevent strain on muscles and joints.

8. Draw the diagrams of the following.

i. Forelimbs

ii. Hindlimbs

iii. Ribcage