Final answer:
Sutural bones are small, irregular bones found within the sutures of cranial bones, providing additional strength to the skull. Irregular bones such as vertebrae and pelvis bones have complex shapes made up of spongey and cortical bone. Sutures eventually ossify, leading to bone fusion in a process known as synostosis.
Step-by-step explanation:
The small bones located within the sutures of certain cranial bones are known as sutural bones. These tiny, irregular bones can be found in the joints that occur between larger bones in the skull—specifically in the fibrous tissue of sutures, which are immobile joints that securely connect skull bones. While they are not always present, sutural bones become part of the intricate structure that helps protect the brain, forming a tight union with surrounding bones. In contrast, irregular bones such as the vertebrae and the bones of the pelvis are characterized by a mix of spongey and cortical bone and do not fit into the other bone category shapes due to their complex forms.
Additionally, during birth, some areas of the skull known as fontanelles allow for flexibility and growth, but these eventually decrease and become sutures as a child grows. Sutures are significant because they tightly interlock to reinforce the strength of the skull, which is crucial for brain protection. Over time, some sutures may ossify in a process called synostosis, causing adjacent bones to fuse for further stability.