Human Skeletal System: Functions, Parts and Diagram

The human skeletal system is a remarkable framework of bones, cartilage, and joints that gives shape to our bodies, protects vital organs, stores essential minerals, and enables movement. While an adult typically has 206 bones, infants are born with about 270 bones that fuse over time. In this comprehensive guide, we will explore the skeleton system in simple terms, understand the skeletal system parts, learn about each skeletal system function, and discover what makes our bones so important for overall health.

Overview of the Skeleton System

The term “skeleton system” refers to the rigid structure within our bodies that includes every bone and the connective tissues that hold them together. This system ensures that our body maintains its shape, supports soft tissues, and provides attachment points for muscles to facilitate movement.

To better understand its organisation, scientists often refer to a human skeleton diagram or a skeletal system diagram. These diagrams visually represent the arrangement of bones and their joints, making it easier for learners of all ages to recognise how each bone contributes to the body’s overall functionality.

Skeletal System Parts

There are two major skeletal system parts in humans:

1. Axial Skeleton

• Skull: Composed of 8 cranial bones and 14 facial bones. The skull also houses 6 auditory ossicles (three tiny bones in each ear) and the hyoid bone, which supports the tongue.

• Vertebral Column: Typically consists of 24 vertebrae, along with the sacrum and the coccyx. This column protects the spinal cord and enables upright posture.

• Thoracic Cage: Includes the sternum (breastbone) and 24 ribs (12 pairs). It safeguards the heart and lungs while allowing the necessary movement for breathing.

2. Appendicular Skeleton

• Shoulder (Pectoral) Girdle: Consists of the clavicle (collarbone) and scapula (shoulder blade), forming the base of the upper limbs.

• Upper Limbs: Comprise the humerus (upper arm), radius and ulna (forearm), carpals (wrist bones), metacarpals (hand bones), and phalanges (finger bones).

• Pelvic Girdle: Composed of two hip bones that support the weight of the upper body and provide a stable base for the lower limbs.

• Lower Limbs: Include the femur (thigh bone), tibia and fibula (leg bones), tarsals (ankle bones), metatarsals (foot bones), and phalanges (toes).

5 Major Functions of the Skeletal System

One fundamental way to remember why bones are so important is by recalling the 5 major functions of the skeletal system:

1. Support: The skeleton provides the framework upon which the rest of the body is built. It upholds the soft tissues and maintains the body’s shape.

2. Protection: Bones like the skull, rib cage, and vertebrae safeguard crucial organs (e.g., brain, heart, lungs, and spinal cord) from external impact or injury.

3. Movement: A key skeletal system function is to facilitate movement. Bones serve as attachment sites for muscles, and joints allow motion in different planes and directions.

4. Mineral Storage: Bones store vital minerals such as calcium and phosphorus. These minerals can be released into the bloodstream as needed, maintaining the body’s mineral balance.

5. Blood Cell Production (Haematopoiesis): Red blood cells, white blood cells, and platelets are produced in the bone marrow, illustrating another crucial skeletal system function that supports overall health.

Additionally, recent research has revealed that bones play a role in endocrine regulation, influencing processes like blood sugar control and energy metabolism.

Axial Skeleton in Detail

• Skull and Facial Bones: Apart from protecting the brain, the skull forms the structure of the face and anchors muscles for chewing and facial expressions.

• Vertebral Column: This stacked series of bones allows flexibility while shielding the spinal cord. It is divided into cervical, thoracic, lumbar, sacral, and coccygeal regions.

• Thoracic Cage: The ribs and sternum protect the heart and lungs. Intercostal muscles between the ribs help in breathing.

Appendicular Skeleton in Detail

• Shoulder (Pectoral) Girdle: Enables a wide range of motion for the arms.

• Upper Limbs: Allow complex movements including lifting, writing, and fine motor skills.

• Pelvic Girdle: Supports body weight during standing and walking, and in females, it aids childbirth.

• Lower Limbs: Essential for standing, walking, running, and balance.

Additional Insights

1. Bone Health and Nutrition: While learning about skeletal system parts is vital, maintaining healthy bones is equally important. A diet rich in calcium, vitamin D, and protein helps preserve bone density. Regular weight-bearing exercises like walking, running, or dancing also promote stronger bones.

2. Differences in Male and Female Skeletons: Although the basic structure is the same, the female skeleton typically has a broader pelvic region to facilitate childbirth. Males often have denser bones, especially in the long bones of the arms and legs.

3. Lifelong Changes in Bone Structure

• Infants start with about 270 bones. As they grow, some of these bones fuse, resulting in 206 bones in adulthood.

• Older adults may experience a decrease in bone density, making them more prone to fractures. A balanced diet and regular exercise can slow this process.

4. Joint Types and Movements: Joints—where two or more bones meet—are crucial for movement. Key joint types include:

• Hinge Joints (e.g., knee and elbow) – Allow movement in one plane.

• Ball-and-Socket Joints (e.g., hip and shoulder) – Permit movement in multiple directions.

• Pivot Joints (e.g., neck) – Enable rotation.