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Crocodilian form of crurotarsal ankle. The astragalus (pink) is fixed to the tibia (green) by a suture. Adapted with permission from Palaeos. In the type of crurotarsal ankle, which is found in crocodilians and some other archosaurs, the astragalus is fixed to the tibia by a suture, and the joint bends around a peg on the astragalus, which fits into a socket in the calcaneum.
Bones are commonly described with the terms head, neck, shaft, body and base. The head of a bone usually refers to the distal end of the bone. The shaft refers to the elongated sections of long bone, and the neck the segment between the head and shaft (or body). The end of the long bone opposite to the head is known as the base.
The cancellous part of bones contain bone marrow. Bone marrow produces blood cells in a process called hematopoiesis. [53] Blood cells that are created in bone marrow include red blood cells, platelets and white blood cells. [54] Progenitor cells such as the hematopoietic stem cell divide in a process called mitosis to produce precursor cells.
Fontanelles allow for stretching and deformation of the neurocranium both during birth and later as the brain expands faster than the surrounding bone can grow. [2] Premature complete ossification of the sutures is called craniosynostosis. After infancy, the anterior fontanelle is known as the bregma.
A suture is a type of fibrous joint that is only found in the skull (cranial suture). The bones are bound together by Sharpey's fibres. A tiny amount of movement is permitted at sutures, which contributes to the compliance and elasticity of the skull. These joints are synarthroses. [1]
The frontal and parietal bones are joined by the coronal suture. The two separate parietal bones are connected at the sagittal suture. The blowhole of sperm whales is located on the crown of the head and allows the whale to breathe. Below the crown, the frontal bone and the parietal bones are separated by a range of fibrous joints called ...
At birth, the bones of the skull do not meet. If certain bones of the skull grow too fast, then craniosynostosis (premature closure of the sutures) may occur. This can result in skull deformities. If the lambdoid suture closes too soon on one side, the skull will appear twisted and asymmetrical, a condition called "plagiocephaly". Plagiocephaly ...
The pterion is the region where the frontal, parietal, temporal, and sphenoid bones join. [1] It is located on the side of the skull, just behind the temple.It is also considered to be the weakest part of the skull, which makes it clinically significant, as if there is a fracture around the pterion it could be accompanied by an epidural hematoma.