Class 9 Lecture on Skeleton and Skin

Introduction

• Introduction to skeleton movement, locomotion, and skin for Class 9 students.
• This is a one-shot revision series where we will also practice questions.

Skeleton Movement and Locomotion

Importance of the Skeleton

• The main function of the skeleton is to provide framework and support to the body.
• It maintains the shape of various parts of the body, such as the skull, upper body, hands, and legs.

Functions of the Skeleton

• Support and Shape: Providing support and shape to body parts.
• Protection: Protecting delicate organs like the brain, lungs, and spinal cord.
• Movement: Movement is possible through the combined function of bone and muscles.
• Leverage: Increasing the speed and distance of body movement.
• Formation of Blood Cells: Production of blood cells within the bone marrow.
• Storage of Minerals: Storage of calcium and phosphorus.

Parts of the Skeleton

• Endoskeleton: Internal skeleton, such as that of humans.
• Exoskeleton: External skeleton, such as that of a cockroach.

Skeleton Tissues

• Bone: The main element of bones, composed of organic and inorganic materials.
• Cartilage: Softer structure compared to bone, such as ears and nose.
• Ligament: Connective tissue that joins bones.
• Tendon: Tissue that connects muscles and bones.

Skin

Structure of Skin

• Epidermis: Outer layer, composed of dead cells.
• Dermis: Inner layer, with the presence of blood vessels and nerves.

Functions of Skin

• Protection: Protection from germs and UV rays.
• Secretion: Production of sweat and oil.
• Sensation: Presence of various receptors.
• Heat Regulation: Regulation of heat through blood vessels and sweat glands.
• Excretion: Elimination of waste products through sweat.

Derivatives of Skin

• Hair: Structure of hair root, hair shaft, and hair bulb.
• Nails: Keratinous plate and nail bed.
• Glands:
  • Sebaceous Glands: Keep skin moisturized and oily.
  • Sweat Glands: Help in expelling body heat.
  • Mammary Glands: Milk production.

Joints and Movement

Types of Joints

• Immovable Joints: No movement possible. Example: Cranium.
• Partially Movable Joints: Limited movement.
• Freely Movable Joints: Like ball and socket, hinge joints, etc.

Lever Mechanism

• Lever Action: To facilitate movement
• 3 Orders of Lever:
  • Lever 1: Fulcrum in the middle
  • Lever 2: Resistance in the middle
  • Lever 3: Effort in the middle, such as movement of the hand

Conclusion

• Both skeleton and skin are essential parts of the body and were revised along with question practice in this lecture.
• More detailed information will be provided in future classes.