Human Skeleton System

The skeletal system is the framework of the body made of bones and connective tissues. It protects and supports the body’s organs and tissues. The human skeleton has 206 bones. The skeletal system is made up of bones and cartilage. It has two important functions:

• Supports the body by giving it shape and strength.
• Facilitates movement by helping the body move.

Each bone is a living part of the body made up of cells, protein fibers, and minerals. The skeleton acts like a scaffold, providing support and protection for soft tissues like muscles and organs.

1. Gives shape and support to our body.

2. Protects internal organs:

• The skull protects the brain.
• The rib cage protects the heart and lungs.
• The backbone protects the spinal cord.

3. Allows movement of different body parts by working with muscles.

4. Bone marrow inside hollow bones makes blood cells.

1. Skull

The skull acts like a helmet to protect the brain. It supports and protects the face and brain. The skull is made up of 22 bones that are joined together and do not move.

2. Rib cage

The rib cage protects the heart and lungs. It has 24 ribs arranged in 12 pairs. The rib cage has three main functions:

• Protection of organs.
• Support for the upper body.
• Helps in breathing (respiration).

The sternum is a long, flat bone in the front of the rib cage.

3. Backbone

The backbone surrounds and protects the spinal cord. It runs from the skull to the pelvis. It supports the body’s weight and helps distribute it evenly. The backbone has an "S" shape when viewed from the side, which helps balance the body.

4. Limbs

Limbs include arms (upper limbs) and legs (lower limbs). They help us do many activities, like walking, running, and climbing. Arms and legs are attached to the torso, allowing us to move from one place to another.

Key components of the skeletal system:

• Bones: Hard structures that make up the skeleton and give the body support and shape.
• Joints: Places where two bones meet, allowing the body to move.
• Cartilage: Soft, flexible tissue that cushions bones and allows smooth movement in joints.
• Ligaments: Strong tissues that connect bones to other bones and help hold joints together.
• Tendons: Tough tissues that connect muscles to bones, helping in movement.

5. Joints

There are two kinds of joints:

1. Immovable Joints: Also called fixed joints, these joints do not allow any movement between bones. The bones are interlocked and held together by connective tissue or are fused together. For example: Joints in the skull and ribs.

2. Movable Joints: Most joints in the body are freely movable. The ends of the bones in these joints are covered with cartilage, which provides a smooth surface for easy movement. Examples of movable joints:

• Ball-and-socket: Found in shoulders and hips, allowing a wide range of movement.
• Pivot joint: Allows rotation, like in the neck.
• Hinge joint: Works like a door hinge, allowing movement in one direction, like in the elbows and knees.
• Gliding joint: Allows bones to slide over each other, like in the wrists.

Bones have a hard outer layer called cortical (compact) bone, which is strong and tough. Inside the bone, there is a spongy inner layer called trabecular (cancellous) bone, which is lighter.

• Bones have their own blood supply and nerves, which help them grow and repair themselves as we age.
• Bones are made of calcium, phosphorus, and collagen (a fibrous substance), making them strong but lightweight because they are hollow inside.
• Bone marrow, found inside bones, produces red blood cells.
• A child is born with 300 soft bones, which fuse together as the child grows, leaving 206 bones in an adult.
• The smallest bone in the human body is the stape, found inside the ear.