Superfetation
An extremely rare situation in which a pregnant woman becomes pregnant a second time with another (younger) fetus. Superfetation is characterized by the fertilization and the implantation of a second oocyte in a uterus already containing the product of a previous conception. Superfetation is different from the process of twinning or multiple gestation and involves the conception of an additional fetus during an established pregnancy. With superfetation, the two fetuses have different gestational ages and due dates. Superfetation can occur in some animals but is so rare in humans that fewer than 10 cases have been reported in the medical literature.
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- Superficial
In anatomy, on the surface or shallow. As opposed to deep. The skin is superficial to the muscles. The cornea is on the superficial surface of the eye. For a more complete listing of terms used in medicine for spatial orientation, please see the entry to “Anatomic Orientation Terms”.
- Superficial spreading melanoma
One of the four clinical types of malignant melanoma, the most common type in white people, which typically presents as a raised, irregular, colored area that starts in a mole-like shape and spreads across the skin.
- Superfluous
Beyond what is sufficient. A sixth finger is superfluous.
- Superior
In antomy, above or over top of. As opposed to inferior. The heart is superior to the stomach. The superior surface of the tongue rests against the palate. For a more complete listing of terms used in medicine for spatial orientation, please see the entry to “Anatomic Orientation Terms”.
- Superior vena cava
A large vein that receives blood from the head, neck, upper extremities, and thorax and delivers it to the right atrium of the heart.