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Uncovering the Secret of the Human Skeleton: Why Does the Skull Stay So Strong as It Grows?
The human skeletal system is an amazing structure that carries our bodies and protects internal organs. Of all the parts that make up the skeleton, the axial skeleton occupies a key position, which leads us to wonder: Why does the skull remain so strong as it grows?
What is the axial skeleton?
The axial skeleton is composed of the head and trunk bones of vertebrates. For humans, this part contains 80 bones, including the skull (28 bones, including skull, mandible and middle ear bones), spine ( 26, including the vertebrae, sacrum, and coccyx), the thorax (25, including the ribs and sternum), and the hyoid bone. The axial skeleton is connected to the appendage bones through the shoulder girdle and pelvis, supporting the movement of the limbs.
Characteristics of the skull
The human skull is composed of skull and facial bones. The main function of the skull is to protect the brain, and this function is achieved through the solid structure of the brain's cranial cavity. The skull is made up of eight lamellar bones that join together tightly at junctures, known as sutures. The facial bones are made up of 14 bones and form an important structure in the front of the skull.
A human skull contains 22 bones, which gradually fuse during growth to form a strong protective structure.
The special thing about the skull is that the pieces of the human skull are separated at birth. This feature allows the skull to maintain a certain degree of flexibility as it passes through the birth canal. As we age, these bone fragments gradually fuse into a complete skull structure, with only the mandible remaining independent.
Structure and function of ribs
The ribs are composed of 12 pairs of ribs plus the sternum, a total of 25 bones. Their main function is to protect important organs such as the heart and lungs. The ribs are crescent-shaped, with different shapes and functions at both ends. The back end is connected to the thoracic vertebrae and the front end is connected to the sternum. According to the different connection methods of the ribs, the ribs can be divided into "true ribs" (directly connected to the sternum), "false ribs" (connected through non-rib cartilage) and "floating ribs" (freely suspended and not connected to any bones). .
The first pair of ribs is considered the shortest, but has the strongest structure and plays an important protective role.
The evolution and structure of the spine
At birth, the human spine has 33 separate vertebrae. However, as an individual grows, some of the vertebrae fuse, resulting in the adult spine being roughly composed of 24 separate vertebrae. The lower part of the spine contains the sacrum and coccyx, which are formed by the fusion of several smaller bones. The spine is composed of five parts: cervical vertebrae (7 vertebrae), thoracic vertebrae (12 vertebrae), lumbar vertebrae (5 vertebrae), sacral vertebrae and coccygeal vertebrae (3 to 5 vertebrae, depending on the individual).
As the backbone of the body, the spine not only supports the entire body, but also protects the important nerves in it.
Why is the skull so strong?
Throughout the skeletal system, although many bones become weaker and more fragile as we age, the skull retains its structural strength. This is largely due to the design and structure of the skull, including its strong sutures and high degree of density. The solidity of the skull is to better protect the enemy's brain, making it one of the most important parts of the entire skeleton.
Skull strength is not only a biological requirement, but also reflects selective pressure during evolution.
Summary
By studying the human skeletal system, we can not only understand the basic structure and function of the human body, but also understand how the skeleton continuously adapts to changes in the environment and lifestyle during the long process of evolution. The unique robustness of the skull leads us to consider a fundamental question: Will our bones evolve again in the future as our lifestyles change?
