Video: Main bones of the body

Did you know your skeleton isn’t just a loose collection of bones — it’s a carefully engineered framework that gives your body shape, strength, storage, and stability. It supports your weight, protects what matters, and allows controlled movement rather than collapse, like the framework of a complex building!

So put on your hard hat, because in this tutorial, we’ll explore the main bones of the body!

The adult skeleton is made up of 206 individual bones, which, together with joints, cartilage, and ligaments, form the complete skeletal system. The bones of your body have five important jobs that keep your body running smoothly. It provides support, keeping you upright like the scaffolding of a building. It offers protection, shielding vital organs such as the brain, heart, and lungs. It enables movement, acting as a system of levers for your muscles to pull on. It also serves as mineral storage, holding calcium, phosphorus, and other essential nutrients. Finally, it plays a crucial role in blood cell formation, with bone marrow producing both red and white blood cells.

Before we start touring the skeleton, let’s talk about the structure of bone, and zoom in on what bones are actually made of.

At the core is bone tissue, which forms the framework of the skeleton and contains hematopoetic and adipose tissue. Bone tissue itself comes in two main forms. Compact bone forms the dense outer layer, providing strength and resistance. Spongy bone forms a lattice-like interior, reducing weight while maintaining support. Different bones — and different regions within the same bone — contain varying proportions of compact and spongy bone depending on the loads they need to bear.

With the materials in mind, we can now look at a classic example: the structure of a long bone. At each end are the epiphyses — a proximal epiphysis near the trunk of the body and a distal epiphysis farther away. These widened regions articulate with neighbouring bones and help distribute forces across joints. Their surfaces are covered with articular cartilage, which reduces friction and absorbs shock during movement.

Between each epiphysis and the shaft lies the metaphysis, a transitional zone that plays a key role in bone growth. In growing bones, this region contains the epiphyseal plate — a layer of hyaline cartilage where lengthening occurs. In adults, once growth is complete, this plate ossifies and becomes the epiphyseal line, a visible remnant marking where longitudinal growth once took place.

The diaphysis forms the long, cylindrical shaft, acting as the main weight-bearing column. Running through its centre is the medullary cavity, which houses bone marrow — producing blood cells when filled with red marrow, or storing fat when filled with yellow bone marrow.

Supplying this interior is the nutrient artery, which enters the shaft through a small opening called the nutrient canal, or nutrient foramen. This vessel travels into the medullary cavity to provide essential blood supply to the bone tissue and marrow. Additional medullary vessels help distribute blood throughout the internal structure.

Covering the outer surface of the bone is the periosteum, a tough, vascular connective tissue layer that protects the bone and supports growth, repair, and the attachment of tendons and ligaments — much like protective cladding and anchoring points on a structural column.

Let’s move on now to look at different types and shapes of bones. Just like a building uses different types of beams and supports, bones come in five distinct shapes, each designed for a specific purpose. Long bones, such as the humerus and femur, act as levers for movement. They are characterised by an elongated shaft with expanded ends, making them well suited for weight-bearing and mobility.

Short bones, like the carpals and tarsals, provide stability. They are roughly cube-shaped, allowing them to resist compression and distribute forces evenly.

Flat bones, including the skull and sternum, offer broad protection. They are thin and flattened, and are often slightly curved, providing a large surface area for muscle attachment and organ protection.

Irregular bones, like the vertebrae, have complex shapes for support and articulation. Their varied and asymmetrical forms enable them to perform specialised functions in different regions of the skeleton.

Finally, sesamoid bones, like the patella, are embedded within tendons to protect joints and improve leverage—think of them as specialized reinforcements within the structure. They are small and rounded, forming within tendons at points of high friction and stress.

With that foundation in mind, we’re ready to explore the skeleton’s core structure, which is divided into two major parts. First, there’s the axial skeleton—the central, load-bearing framework that keeps everything upright, like Big Ben, and protects the most vital organs, like the heart and the lungs. It includes the skull, vertebral column, rib cage, sternum, and the bony pelvis.

Then there’s the appendicular skeleton, which consists of the supporting structures and appendages attached to the core, like the wings of a transmission tower. This includes the shoulder girdle, upper limbs, and lower limbs.

Now, let’s lift the roof off this architectural marvel and take a closer look at the axial skeleton!

At the top of this framework is the skull, which itself is divided into two main parts. The neurocranium forms a protective dome around the brain, and includes the frontal bone at the front, the paired temporal bones and parietal bones on the sides, and the occipital bone at the back.

Moving back to the front of the skull, we have the viscerocranium, which forms the ‘facade’ of the building—the face—including the maxilla, or upper jaw, which holds your upper teeth and forms the nose and palate, and the mandible, or lower jaw, which holds the lower teeth. The mandible is the only moveable skull bone, articulated via the temporomandibular joint. These bones not only give the structure its shape but also support chewing and speaking.

Moving down the framework, we come to the vertebral column, or spine—the vertical support column of the structure. In this posterior view of the spine you can see that it consists of 33 vertebrae organized into five regions: 7 cervical vertebrae, 12 thoracic vertebrae, 5 lumbar vertebrae, 5 fused sacral vertebrae, which forms the sacrum, connecting the spine to the pelvic girdle, and 3-4 fused coccygeal vertebrae, which form the coccyx, forming the terminal end.

Next, we have the ribs, a protective lattice that shields the heart and lungs. We can see that the ribs connect to the sternum, or breastbone, which itself is divided into three parts: the manubrium at the top, the body in the middle, and the xiphoid process at the bottom. Together with the ribs, the sternum helps to form a strong, flexible cage—like steel beams surrounding sensitive equipment—while still allowing movement for breathing.

Moving down to the bony pelvis, we see a sturdy, bowl-shaped foundation connecting the lower limbs to the axial skeleton. Each hip bone is composed of three fused parts: the ilium, the ischium, and the pubis. This structure supports the weight of the upper body and transfers it efficiently to the lower limbs.

With the axial skeleton explored, let’s look at the appendicular skeleton!

Starting at the top, we have the shoulder girdle, which connects the arms to the central framework. Each side consists of the clavicle, or collarbone, which stabilizes the arm as it extends outward, and the scapula, or shoulder blade, a broad, triangular support plate that serves as the base for arm movement. Together with the clavicle, it forms the architectural connection between the core and the upper limbs.

The arm itself, or brachium, contains a single long beam: the humerus. This long bone acts as a lever for movement, transferring forces from muscles to the forearm. Speaking of the forearm, or antebrachium, it contains two long bones, the radius on the lateral side and the ulna on the medial side, which together form a flexible yet strong two-column structure.

At the end of the forearm, we reach the hand, which is made up of three levels of small, articulated structures. The carpal bones form the wrist, which is the region that connects the hand to the forearm. The metacarpal bones in turn connect the wrist to the fingers, forming the palm. Finally, the phalanges make up the fingers, allowing fine motor control for gripping and manipulation.

Moving down to the lower limbs, we can see that the thigh, the region between the hip and knee, contains a single long beam: the femur, the longest and strongest bone in the body. It articulates with the pelvic socket via a ball-and-socket joint, providing both stability and a wide range of motion. At the knee, the patella, or kneecap, acts as a protective cover – like a hard hat! – and improves leverage for movement.

Below the knee, the leg contains two long bones: the tibia on the medial side, bearing most of the weight, and the fibula on the lateral side, providing lateral stability. The foot then completes the structural extension, with the tarsals forming a compact base, the metatarsals acting as support beams, and the phalanges giving flexibility for balance and propulsion—just like adjustable scaffolding and support struts in a complex building extension.

With this, we’ve explored the skeleton from the biggest beams to the tiniest nails, seeing how its design provides support, protection, movement, mineral storage, and blood cell formation. If you want to learn more about the different bones of the body, don’t forget to check out our study units and quizzes at Kenhub. See you next time!