Anatomy Essentials For Dummies
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Think people know everything there is to know about human anatomy? Think again. Researchers announced the discovery of two new body parts in 2013 alone.

  • The first new anatomical feature was announced in June, when a previously unknown layer was discovered in the eye’s cornea. Now called Dua’s Layer after Prof. Harminder Dua, who led the study at the University of Nottingham in England, the newly identified section lies between the corneal stroma and Descemet’s membrane. It is strong, impervious to air, and only 15 microns thick, roughly one and a half times the length of a human red blood cell.

    Prior to the discovery, the cornea was believed to have only five layers (from the outside in): the corneal epithelium, Bowman’s layer, the corneal stroma, Descemet’s membrane, and the corneal endothelium. Now that Dua’s layer has been identified, however, doctors are beginning to understand that a malformation or damage to this layer can be related to disorders at the back of the cornea. Eye surgeons also are taking advantage of Dua’s layer by injecting air bubbles needed during some surgeries under the layer rather than above it, where there is a chance of air causing damage to the corneal stroma.

  • The second addition to clinical anatomy textbooks was announced in November, when surgeons at the University Hospitals Leuven in Belgium fully described a knee ligament about which clinicians had been hypothesizing since 1879.

    Two Belgian surgeons had become frustrated that some of their patients who had undergone repairs to their anterior cruciate ligament, or ACL, still experienced trouble with the knee giving way mid-motion even after the surgical recovery appeared to be complete. After doing detailed dissections of 41 knees from cadavers, Dr. Steven Claes and Prof. Dr. Johan Bellemans found that all but one of the knees had a previously unidentified feature, now known as the anterolateral ligament, or ALL. Subsequent studies showed that surgical patients whose knees remained unstable, a condition known as “pivot shift,” still had damage in the ALL. As a result, researchers now believe that the ALL controls the rotation of the tibia (the “shinbone”) inside the knee joint.

    The Belgian surgeons now are working on new techniques to correct those injuries. Tears in the ACL are common among athletes in sports that place demands on the knees for rapid shifts and changes in direction, such as skiing, soccer, rugby, and basketball.

Why are researchers still discovering new things about the anatomical structures of the human body? Because the body is an intricate thing, with sometimes extraordinary variation from one individual to another. One example: An arm muscle known as the palmaris longus simply isn’t there in up to 15 percent of the population. To complicate things further, some people have the muscle in one of their arms, but not the other. And that’s not the only elusive part; the plantaris muscle of the leg is missing from 1 in 10 people, and the levator claviculae in the neck is so rare — only 3 in 100 people have one — that it’s considered to be a vestigial muscle.

Keep in mind, too, that researchers are still delving into the microscopic details of how the brain and the nervous system are put together. In other words, stay tuned for further anatomical updates!

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