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Most fibrous joints are also called "fixed" or "immovable". These joints have no joint cavity and are connected via fibrous connective tissue. Sutures: The skull bones are connected by fibrous joints called sutures. [1] In fetal skulls, the sutures are wide to allow slight movement during birth. They later become rigid (synarthrodial).
The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. [1] [2] In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human the skull comprises two prominent parts: the neurocranium, and the facial skeleton. [3] which evolved from the first pharyngeal arch.
A syndesmosis (“fastened with a band”) is a type of fibrous joint in which two parallel bones are united to each other by fibrous connective tissue. The gap between the bones may be narrow, with the bones joined by ligaments, or the gap may be wide and filled in by a broad sheet of connective tissue called an interosseous membrane. [1]
The frontal suture is a fibrous joint that divides the two halves of the frontal bone of the skull in infants and children. Typically, it completely fuses between three and nine months of age, with the two halves of the frontal bone being fused together.
The articulating surfaces of synarthroses have little or no mobility, and are strongly united to each other. For example, most of the joints of the skull are held together by fibrous connective tissue and do not allow for movement between the adjacent bones. This lack of mobility is important, because the skull bones serve to protect the brain. [3]
The cartilaginous portion of the ear canal contains small hairs and specialized sweat glands, called apocrine glands, which produce cerumen . The bony part forms the inner two thirds. The bony part is much shorter in children and is only a ring (annulus tympanicus) in the newborn. The layer of epithelium encompassing the bony portion of the ear ...
If certain bones of the skull grow too fast then premature fusion of the sutures, craniosynostosis, may occur. [1] This can result in skull deformities. [1] These deformities include: [3] Brachycephaly (both sides) Plagiocephaly (one side only) Oxycephaly (both sides)
After birth, as the skull bones grow and enlarge, the gaps between them decrease in width and the fontanelles are reduced to suture joints in which the bones are united by a narrow layer of fibrous connective tissue. [1] The bones that form the base and facial regions of the skull develop through the process of endochondral ossification.