JD5037

Skeletal System

Diagram of the human skeletal system

The skeletal system is the framework of bones and cartilage that supports and protects the body of an organism. In humans, the skeletal system is composed of 206 bones in the adult body, which are organized into two main divisions: the axial skeleton and the appendicular skeleton.

Functions

The skeletal system serves several vital functions:

• Support: It provides a rigid framework that supports the body and cradles soft organs.
• Protection: It protects vital organs, such as the brain, heart, and lungs.
• Movement: It provides attachment points for muscles, allowing for movement.
• Mineral Storage: It stores minerals, such as calcium and phosphorus, which can be released into the bloodstream as needed.
• Blood Cell Production: It contains bone marrow, which produces red blood cells, white blood cells, and platelets.

Structure

The skeletal system is divided into two main parts:

Axial Skeleton

The axial skeleton consists of 80 bones and includes the following:

• Skull: Protects the brain and forms the structure of the face.
• Vertebral Column: Composed of 33 vertebrae, it protects the spinal cord and supports the head.
• Rib Cage: Consists of 12 pairs of ribs and the sternum, protecting the heart and lungs.

Appendicular Skeleton

The appendicular skeleton consists of 126 bones and includes the following:

• Pectoral Girdle: Composed of the clavicles and scapulae, it connects the arms to the trunk.
• Upper Limbs: Includes the humerus, radius, ulna, carpals, metacarpals, and phalanges.
• Pelvic Girdle: Formed by the hip bones, it connects the legs to the trunk.
• Lower Limbs: Includes the femur, tibia, fibula, tarsals, metatarsals, and phalanges.

Bone Types

Different types of bones in the human body

Bones are classified into several types based on their shapes:

• Long Bones: Found in the arms and legs, they are longer than they are wide.
• Short Bones: Found in the wrists and ankles, they are roughly cube-shaped.
• Flat Bones: Found in the skull, ribs, and sternum, they are thin and flat.
• Irregular Bones: Found in the vertebrae and some facial bones, they have complex shapes.
• Sesamoid Bones: Found embedded in tendons, such as the patella.

Bone Composition

Bones are composed of several types of tissue:

• Compact Bone: Dense and forms the outer layer of bone.
• Spongy Bone: Lighter and found inside bones, containing red bone marrow.
• Bone Marrow: Soft tissue inside bones, responsible for blood cell production.

Related Pages

• Muscular system
• Nervous system
• Circulatory system
• Endocrine system