ZIG-ZAG LINES ON HUMAN SKULL, WHAT DO THEY SIGNIFY

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Sci Tech Skull lines QUESTION: There are zig-zag lines on human skull. What do they signify? Moorthy, Madurai, T.N. ANSWER: The skull is made of eight flat bones. These are joined together closely. The zig-zag lines one finds over the surface of human skull are immovable joints exclusively found between the cranial bones which form the human skull. Several types of sutures are recognised according to how the margins of bones unite. In some sutures the bone margins merge smoothly, in others they overlap while in some the margins interlock. This architecture bestows on the skull adequate strength and decreases the chances of their fractures. The four prominent sutures found on the surface of the skull are: — The Coronal suture crossing the skull in the left-right direction in the front. — The Lambdoid suture crossing the skull in the left-right direction in the back. — The Sagital suture running front to back in the middle of the skull. — The Squamous suture running front to back on the sides of the skull. Fontanels are the `soft spots' one finds when he or she feels a newborn's head. They are membrane filled spaces which would, as the child grows, transform into sutures. It is this arrangement that enables the foetal skull to modify its size and shape as it passes through the birth canal and also permits rapid growth of the brain during infancy. J. Mohamed Iq