VESTIGIAL GILL TROUBLES?
You`re not going to believe this question. A member of my staff has claimed on occasion that she is ill — due to swelling in her neck caused by “dirt in her gill.” She said her doctor told her that at some point during embryonic development, she had gills, and one gill had some debris in it. The “dirt in her gill” sometimes creates flare-ups. Can this possibly be true? It`s so preposterous that I can`t imagine anyone making it up! (But I really don`t believe a word of it!)
Actually, there is some truth in the statement. It`s not that dirt gets in the “gill” however, but that dirt gets into the space that was between the gills. This involves some complex embryology. If you`re really interested, read on.
Approximately one month after conception, the human embryo has a series of 4 bumps that appear about where you`d think the front of the neck should be. At this time of development the facial structures aren`t very well formed. These bumps are called “pharyngeal arches.” They go on to develop into the muscles of the face and neck, the salivary glands, nerves of the face and neck, and the bones of the middle ear and throat. Fish embryos have these same bumps but, in fish, they develop into the gills.
As you look at the human embryo, there are slits between these bumps (“pharyngeal grooves”). The remains of the first groove can be found after we`re born as the opening into the ear canal. The other grooves usually disappear as the neck develops.
If a pharyngeal groove does not completely disappear, it may be seen in a person as a small tunnel or pit in the skin of the side of the neck — usually near the edge of the long strap muscles that go from the corner of the jaw to the collarbone. The tunnel may end blindly or it may connect to the back of the throat near the tonsils. This is called a “branchial sinus”.
A branchial sinus may have mucous come out of it. If the sinus becomes blocked, the mucous may become infected which will cause swelling and pain. This is probably what your staff member is referring to as “dirt in her gill”.
If a branchial sinus gets infected frequently, it is usually recommended that it be removed surgically by an otolaryngology (ENT) specialist.
If you want to learn more about embryology and to see some photos of what I`ve been describing, the following resources were developed for the general public: Book — Nilsson, Lennart (1977): “A Child Is Born.” Delacorte Press/Seymour Lawrence. New York, NY. Videotape — “The Miracle of Life.” (1986) NOVA. WGBH Educational Foundation.
For more information:
Go to the Inherited Disorders and Birth Defects health topic.