The sternum, often called the breastbone, is indeed a flat bone located in the central part of the chest. It plays a significant role in the human skeletal system, providing both structural support and protection for internal organs. Situated at the front of the rib cage, this bone is easily felt just beneath the skin. Its classification as a flat bone relates directly to its shape and primary functions within the body.
Understanding Flat Bones
Flat bones are characterized by their relatively thin, flattened, and often curved shape. These bones are composed of two thin layers of compact bone with a layer of spongy bone in between. Unlike long bones, which are designed for support and movement, flat bones primarily serve two main purposes. They provide extensive areas for muscle attachment and offer protection for underlying soft tissues or internal organs.
The design of flat bones allows them to effectively shield sensitive areas of the body. For example, the flat bones of the skull protect the brain, while the ribs form a cage around the heart and lungs. Their broad surfaces also act as anchors for various muscles, enabling a wide range of movements.
The Sternum: Structure and Role
The sternum is a long, flat bone positioned in the middle of the chest, commonly known as the breastbone. It forms the front portion of the rib cage and protects the heart, lungs, and major blood vessels. The sternum is composed of three distinct parts that fuse during development.
The uppermost section is the manubrium, a broad part that connects to the collarbones and the first pair of ribs. Below the manubrium lies the body, or gladiolus, which is the longest segment, articulating with the remaining ribs through cartilage. The xiphoid process is the smallest and most variable part, largely cartilaginous in youth and ossifies into bone with age.
Why the Sternum Is a Flat Bone
The sternum is classified as a flat bone because it exhibits the characteristic features and functions of this bone type. Its thin, broad, and somewhat flattened shape aligns perfectly with the definition of a flat bone. The sternum’s primary role in the human body is to provide a protective shield for the vital organs within the thoracic cavity, such as the heart and lungs.
The structure of the sternum, with its relatively flat surfaces, also offers ample sites for the attachment of chest muscles. This combination of protective ability and broad surface for muscle attachment makes the sternum an archetypal example of a flat bone. Its design enables it to withstand external forces, safeguarding delicate internal structures.
Other Flat Bones in the Human Body
Beyond the sternum, several other bones in the human skeleton are classified as flat bones, serving similar protective or muscle attachment roles. The bones that make up the skull, such as the frontal, parietal, and occipital bones, are prominent examples. These cranial bones form a robust casing that protects the brain.
The ribs, which extend from the spine to connect with the sternum, are also flat bones that collectively form the rib cage, shielding the thoracic organs. Additionally, the scapulae, or shoulder blades, are large, triangular flat bones located in the upper back. They provide broad surfaces for the attachment of numerous muscles involved in arm and shoulder movement.