Saadia Muzafar, Mamoona Hamid, Nabeela Akhter.
Morphology of Developing Human Occipital Squama.
J Rawal Med Coll Jan ;19(1):67-70.

Background: To study the limits and ossification of developing human occipital bone. Methods: In this descriptive study of the development of Occipital squama, 30 foetal skulls were selected. They were grouped as AG and Am. Gross examination was carried on 15 foetal skulls (Group AG ) with a pre-natal age of 8-20 weeks, A strip was cut 1.5 cm above the lambdoid suture and carried along the line of suture till the foramen magnum. After examination of un-stained specimens under dissecting microscope, the specimens were stained with Alizarin Red -S and Toluidine blue method for gross staining of calcium. Fifteen foetal skulls of (Group Am) were selected for microscopy and circular strip approximately 3mm was cut in a plate like fashion in radius of 5mm2 with external occipital protuberance as a centre of cutting area. It was confirmed that they did not have any congenital or artificial deformity. The specimens were fixed in 10% neutral buffered formalin, decalcified in 2% nitric acid, dehydrated with graded alcohols cleared in inhibisol and embedded in paramat. The sections were placed vertically in the block with the side facing lambdoid suture anteriorly and the side facing foramen magnum posteriorly. Sections were cut at 500µm interval and stained with haematoxylin and eosin. The process of ossification in occipital squama was studied regarding limits, time and type of ossification centres . Results: Occipital squama was seen to consist of two parts, supra-occipital and interparietal. Supraoccipital has dual origin. The upper part of cartilaginous supra-occipital between superior and highest nuchal lines known as intermediate segment or Torus Occipitalis, ossified intra-membranously from two nuclei. The interparietal part (also intramembranous in origin) ossifies above the highest nuchal line from two pairs of nuclei forming medial and lateral plates respectively. Conclusion: The defect in the fusion of ossifying centres results in variation in developmental process:leading to formation of one or more separate bones known as interparietal bones or Inca bones (Type 1-V). I

PakMediNet -Pakistan's largest Database of Pakistani Medical Journals - http://www.pakmedinet.com