Unit 13
The Skeletal System
Question: Explain the skeletal system and its functions.
Answer:
The skeletal system is the framework of the body made up of bones, cartilages, joints and ligaments. It gives shape, support and protection to the body. The adult human body contains 206 bones. The skeletal system is divided into axial skeleton and appendicular skeleton.
The axial skeleton consists of skull, vertebral column, ribs and sternum. It forms the central axis of the body. The appendicular skeleton consists of bones of upper limbs, lower limbs, pelvic girdle and pectoral girdle.
Bones are hard structures made of connective tissue rich in calcium and phosphorus. Cartilage is a soft flexible connective tissue present in joints, nose and ear. Ligaments connect bone to bone and help in joint stability.
Functions of Skeletal System
• Gives shape and support to the body.
• Protects vital organs such as brain, heart and lungs.
• Helps in movement by providing attachment to muscles.
• Produces blood cells in red bone marrow.
• Stores minerals like calcium and phosphorus.
• Maintains posture and body balance.
• Provides framework for the body.
Thus, the skeletal system is essential for protection, support and movement of the body.
Question: Describe the structure of a long bone.
Answer:
A long bone is a bone that is longer than it is wide. Examples are femur, humerus and tibia. Long bones help in movement and support body weight.
The structure of a long bone consists of the following parts:
Diaphysis
• It is the shaft or middle portion of the bone.
• It is made mainly of compact bone.
• It provides strength to the bone.
Epiphysis
• These are the two ends of the long bone.
• They are made mainly of spongy bone.
• They help in joint formation.
Metaphysis
• It is the region between diaphysis and epiphysis.
• It contains the epiphyseal plate responsible for growth in length.
Periosteum
• It is a tough fibrous membrane covering the outer surface of bone.
• It contains blood vessels and nerves.
• It helps in nourishment and repair of bone.
Compact Bone
• It forms the hard outer layer of bone.
• It gives strength and support.
Spongy Bone
• It is present inside the epiphysis.
• It contains spaces filled with bone marrow.
Bone Marrow
• Red bone marrow produces blood cells.
• Yellow bone marrow stores fat.
Medullary Cavity
• It is the hollow cavity inside the shaft of long bone.
• It contains yellow bone marrow.
Articular Cartilage
• It covers the ends of bones.
• It reduces friction during movement.
Thus, a long bone is specially designed to provide support, movement and protection.
Question: Classify bones with examples.
Answer:
Bones are classified according to their shape and structure. The human body contains different types of bones performing different functions.
Long Bones
• Long bones are longer than they are wide.
• They help in movement and support body weight.
• Examples are femur, humerus, tibia and radius.
Short Bones
• Short bones are cube-shaped bones.
• They provide stability and limited movement.
• Examples are carpals and tarsals.
Flat Bones
• Flat bones are thin, broad and flattened.
• They protect internal organs and provide surface for muscle attachment.
• Examples are skull bones, ribs, sternum and scapula.
Irregular Bones
• Irregular bones have complex shapes.
• They perform special functions.
• Examples are vertebrae, pelvic bones and facial bones.
Sesamoid Bones
• Sesamoid bones are small round bones embedded in tendons.
• They reduce friction and modify pressure.
• Example is patella.
Pneumatic Bones
• Pneumatic bones contain air-filled spaces.
• They make the skull lighter.
• Examples are frontal bone and sphenoid bone.
Thus, bones are classified into different types based on their shape and functions.
Question: Explain the types of joints with examples.
Answer:
A joint is the place where two or more bones meet. Joints help in movement and provide flexibility to the body. Joints are classified into fibrous joints, cartilaginous joints and synovial joints.
Fibrous Joints
• In fibrous joints, bones are connected by fibrous connective tissue.
• These joints allow little or no movement.
• They are strong and stable.
• Example is sutures of the skull.
Cartilaginous Joints
• In cartilaginous joints, bones are connected by cartilage.
• These joints allow slight movement.
• They provide flexibility and support.
• Examples are joints between vertebrae and pubic symphysis.
Synovial Joints
• Synovial joints are freely movable joints.
• The ends of bones are covered by articular cartilage.
• A synovial membrane secretes synovial fluid which reduces friction.
• These joints allow maximum movement.
Types of Synovial Joints
Ball and Socket Joint
• Allows movement in all directions.
• Example is shoulder joint and hip joint.
Hinge Joint
• Allows movement in one direction only.
• Example is elbow joint and knee joint.
Pivot Joint
• Allows rotational movement.
• Example is joint between atlas and axis vertebrae.
Gliding Joint
• Allows sliding movements.
• Example is wrist joint and ankle joint.
Saddle Joint
• Allows movement in two directions.
• Example is thumb joint.
Thus, joints are important for body movement, flexibility and stability.
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