Every object has an internal structure that provides the actual shape to that object. For example, a building is constructed only when you have a structure of the building to further build it. Similarly, the human skeleton is the internal framework of the human body. On this skeleton, the mass and muscles of a human body start growing. In this particular article, we shall be talking in detail about the Human skeleton system.

Table of Content -

An introduction
What is a Skeletal System
Functions of the Skeletal System
Divisions of the Skeletal System

Axial Skeletal System
Appendicular Skeletal System

Key learnings from the Chapter
Frequently Asked Questions

Skeletal System Definition

The human skeletal system or skeleton is the total number of bones which join together (with the help of joints) in the body. It is the framework that helps in providing support, protection and shape to the body, thereby facilitating movement. Each bone is composed of multiple cells, minerals and protein fibers. Without a skeleton, we would not be able to perform our day to day activities like standing, sitting or walking. It also protects the soft tissues and inner parts of our body. For example, the skull covers and protects the brain which is very soft and ribs protect the lungs and heart. Talking about the number of bones in human body, it’s good to know that a newborn baby has about 300 bones and there are 206 bones in the skeletal system of an adult as they get fused as we grow up; multiple cartilage and ligaments also make up the skeletal system in our body.

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Functions of the Skeletal System

The human skeletal system is responsible for six major functions in our body which include protection, movement, support, storage of minerals, production of blood cells and endocrine regulation. We will further learn about the functions of each kind of bone forming the skeletal system in detail.

There are Two Divisions of the Skeleton or Skeletal System, Namely

The Axial Skeletal System: It includes the skull, spine and rib cage.
The Appendicular Skeletal System: It includes the appendages and the girdles including pelvic girdle bones which are attached with the axial skeleton.

Axial Skeletal System

The axial skeletal system consists of 80 bones that run the midline axis of the body and as we learnt above, it includes regions like skull, spine, sternum, auditory ossicles, hyoid and ribs. Let’s know more about each of these.

Skull

The skull covers and protects the brain which is delicate and soft. It consists of cranium and facial bones where the function of the former kind of bone is to protect the brain and is formed of 8 plate-shaped bones joined together at sutures. The remaining 14 bones along with the cranium, form the facial bones. The only movable bone in the human skull is Mandible which forms the lower jaw and holds the lower teeth in the right position.

Spine or Vertebral Column

The spine or the vertebral column is an interconnected complex of bones, nerves, tendons, muscles, and ligaments. Any damage to these parts may cause pain and show neurological symptoms or even loss of mobility. The vertebral column consisting of 33 bones known as vertebrae are the bony building blocks of the spine. There are 5 categories of vertebrae namely cervical vertebrae, thoracic vertebrae, lumbar vertebrae, sacrum vertebrae and coccyx vertebrae. All of these spinal columns protect the spinal cord and provide stiffening and structural support to the bodyweight. The vertebral column is attached to the pectoral and pelvic girdle bones and muscles.

Sternum

Also known as the breastbone, it is a long flat bone positioned at the central part of the chest or anteriorly to the thorax. It is situated at the midline of the chest. A rib cage is formed with this sternum via cartilage and the ribs. First seven ribs and the clavicle or collarbone are attached to the sternum. It protects the lungs, hearts and major blood vessels from injury.

Hyoid

It is the bone that provides muscle attachment to the floor of the mouth, the tongue, the larynx, the epiglottis and the pharynx. It is a U-shaped bone held in place by the strap muscles of the anterior triangle of the neck. It helps in swallowing as it supports the tongue and it has no articulation with other bones. It is regarded as an intermediary between the post cranial skeleton and the skull.

Auditory Ossicles

Also known as the ossicles, these are the three bones, namely, malleus, incus and stapes present in the middle ear and are the smallest ones in the human body. These help in transmitting sounds from the air to cochlea which is a fluid-filled labyrinth. Hearing loss may occur in the absence of auditory ossicles.

Ribs

Ribs protect the heart and lungs which are the inner organs of our body. These are present as a set of 12 long curved bones forming a protective cage of the thorax. As part of the bony thorax, these protect the thoracic organs. The ribs or the bones here articulate with the vertebral column and terminate as cartilage namely costal cartilage, posteriorly and anteriorly, respectively.

Appendicular Skeletal System

Human skeletal system comprises the appendicular skeleton which supports the appendages. Consisting of 186 bones including those present in the limbs, pelvic girdles and pectoral girdles.The appendicular skeletal system has bones with six divisions as follows:

Shoulder Girdle - It is also called pectoral girdle which is the set of 4 bones connecting to the arm on each side. It is the part of the appendicular skeleton meant for the upper limbs. In humans, it consists of the clavicle and the scapula.
Arms and Forearms - This region consists of 6 bones that include humerus, radius and ulna as large bones.
Hands - It consists of 54 bones and these provide flexibility and support to the soft tissues found in hands. The hand bones are categorized into carpals, metacarpals and phalanges.
Pelvis - It is found in the lower part of the trunk as a ring-like bony structure It comprises two bones, namely coccyx and sacrum. Paired hip bones made of pubis, ischium and ilium are also part of the pelvic girdle. Pelvic girdle functions in transferring the body weight from the axial skeleton to the appendicular component, helping in the movements. It is also attached to multiple muscles and ligaments, facilitating movement.
Thighs and Legs - Bones found here support the muscles of the lower limbs and help in walking, standing, running and jumping. These are strong bones supporting the body weight. Femur or the thigh bone is the largest and heaviest bone found in the human body. Tibia and Fibula are two other long bones present in the lower leg linked closely at the knee and ankle.
Feet and Ankles - Foot is the major and firmm platform that supports the whole weight of the body and the major bones present here include tarsals, phalanges and metatarsals.

Key Learnings from the Chapter

The human skeleton is the total number of bones joined inside a human body
Its function is to provide protection, support, production of blood cells, etc
Skeletons are divided into two parts axial and appendicular skeletons
Axial controls the midline axis of the body that is the skull, spine, sternum, ribs etc
The Appendicular skeleton supports the appendages like arms, forearms, hands, pelvis, thighs, legs etc

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FAQs on Human Skeletal System: Key Functions and Importance

1. What are the primary functions of the human skeletal system?

The human skeletal system performs several crucial functions essential for survival. The main functions include:

Support: It provides a rigid framework that supports the body and maintains its shape.
Protection: It protects vital internal organs, such as the skull protecting the brain and the rib cage safeguarding the heart and lungs.
Movement: It serves as an attachment point for muscles. Bones act as levers, allowing muscles to produce movement at the joints.
Blood Cell Production: The bone marrow within certain bones is the site of haematopoiesis, the production of red blood cells, white blood cells, and platelets.
Mineral Storage: Bones act as a reservoir for minerals, primarily calcium and phosphorus, releasing them into the bloodstream as needed.

2. What are the main components that make up the skeletal system?

The skeletal system is a complex network composed of several types of tissues. Its main components are bones, which form the primary structure; cartilage, a flexible connective tissue that cushions joints and forms structures like the nose and ears; ligaments, which are tough bands of tissue that connect bones to other bones; and tendons, which connect muscles to bones, facilitating movement.

3. What is the difference between tendons, ligaments, and cartilage?

These three are distinct connective tissues with different roles. Tendons connect skeletal muscles to bones, enabling the transfer of force to produce movement. Ligaments are strong, fibrous bands that connect bones to other bones at joints, providing stability and preventing excessive movement. Cartilage is a softer, more flexible tissue that covers the ends of bones at joints, acting as a shock absorber and reducing friction.

4. How are bones classified based on their shape? Please provide examples.

Bones are typically classified into four main types based on their shape, which relates to their function:

Long Bones: Longer than they are wide, they act as levers for movement. Examples include the femur (thigh bone) and humerus (upper arm bone).
Short Bones: Roughly cube-shaped, they provide stability and support with limited movement. Examples include the carpals (wrist bones) and tarsals (ankle bones).
Flat Bones: Thin and often curved, they serve as points of attachment for muscles and provide protection. Examples include the sternum (breastbone), ribs, and most skull bones.
Irregular Bones: These have complex shapes that do not fit into the other categories. Examples include the vertebrae and the pelvic bones.

5. What are some common diseases and disorders that affect the skeletal system?

Several diseases can impact the health and function of the skeletal system. Common examples include Osteoporosis, a condition where bones become weak and brittle due to loss of bone density; Arthritis, which involves inflammation of the joints, causing pain and stiffness; and Rickets (in children) or Osteomalacia (in adults), a softening of bones due to a severe vitamin D deficiency.

6. Besides support and movement, what are some less obvious but vital functions of the skeleton?

Beyond its well-known mechanical roles, the skeleton is a metabolically active organ. A critical but less obvious function is haematopoiesis, the formation of all blood cells in the red bone marrow. It is also the body's primary site for mineral homeostasis, storing and releasing calcium and phosphate to maintain stable levels in the blood, which is vital for nerve and muscle function. Furthermore, it stores fat in the yellow bone marrow and has a role in endocrine regulation.

7. How does the skeletal system work together with the muscular system to produce movement?

The skeletal and muscular systems collaborate in a lever system to create movement. The skeleton provides a rigid structure and framework, with bones acting as levers and joints acting as pivots or fulcrums. Skeletal muscles, attached to bones via tendons, contract and pull on the bones. This pulling action creates torque at the joint, resulting in movement like bending an elbow or lifting a leg. Without the solid frame of the skeleton, muscle contractions would not be able to move the body effectively.

8. If all functions are important, why is the protective role of the skeleton often considered so critical?

While all functions are integrated and vital, the protective role is often highlighted because it ensures the immediate survival of the organism by shielding its most delicate and essential organs. For example, the skull provides a hard, unyielding case for the brain, protecting it from physical trauma. Similarly, the rib cage and vertebral column protect the heart, lungs, and spinal cord, respectively. Damage to these organs is often life-threatening, making the skeleton's protective function a non-negotiable line of defence.

9. How does the structure of a long bone relate directly to its functions?

The structure of a long bone, like the femur, is a perfect example of form fitting function. Its long, hollow shaft (diaphysis) is made of dense compact bone, providing immense strength to bear weight and resist bending. The ends of the bone (epiphyses) are wider and made of spongy bone, which helps distribute forces at the joint. This spongy bone also contains red bone marrow, the site of blood cell production. The hollow cavity in the shaft contains yellow bone marrow for fat storage. This design maximises strength for support while remaining lightweight and serving metabolic needs.

10. What is the significance of studying a labelled diagram of the human skeletal system?

Studying a labelled diagram is crucial because it moves beyond memorising names to understanding the system as a whole. A diagram helps to visualise the spatial relationships between different bones, identify the location and type of various joints (articulations), and comprehend how the skeleton forms a functional, interconnected framework. This visual context is essential for understanding biomechanics, locating points of muscle attachment, and diagnosing injuries or abnormalities.