Under the Knife by Arnold van de Laar Laproscopic surgeon

Author:Arnold van de Laar, Laproscopic surgeon
Language: eng
Format: epub
Publisher: St. Martin's Press

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Gills

As our bodies develop in the womb, the embryo again passes through the same phases that we experienced in our evolution from single-cell beings to humans. Sometime in the first few weeks of the pregnancy, we are briefly creatures with gills, like fish, five on each side of our head. The gills then close up again and grow together, eventually forming the face and neck. If something goes wrong at this stage in the development of the embryo, the child is left with a defect, a scar or a cleft lip or palate. These are congenital disorders that can only be corrected surgically. A cleft palate is known medically as palatoschisis, a cleft lip (or harelip) as cheiloschisis and a cleft lip, jaw and palate, which can extend as far as the eye socket and eyelid, as cheilognathopalatoschisis. Similar problems can also occur elsewhere, such as in spina bifida (when the tube of the embryonic nervous system does not close completely) or hypospadias (incomplete development of the urethra). Structures evolve from the five gill arches that you would not expect to be related to either fish or gills. The first arch gives rise to the middle ear – two of the three middle ear bones (auditory ossicles) and the Eustachian tube. The second forms the third auditory ossicle (the stapes), the hyoid bone (tongue bone) and the pharyngeal tonsil (adenoid). The parathyroid glands and the thymus are formed from the third and fourth gill arch and the fourth and fifth develop into the thyroid gland and the larynx (with the vocal cords). So anyone who thinks we were created from anything else is simply wrong – we started off as fish.

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