Fetal in the context of "Lecithin–sphingomyelin ratio"

In neuroanatomy, a sulcus (Latin: "furrow"; pl.: sulci) is a shallow depression or groove in the cerebral cortex. One or more sulci surround a gyrus (pl. gyri), a ridge on the surface of the cortex, creating the characteristic folded appearance of the brain in humans and most other mammals. The larger sulci are also called fissures. The cortex develops in the fetal stage of corticogenesis, preceding the cortical folding stage known as gyrification. The large fissures and main sulci are the first to develop.

Mammals that have a folded cortex are known as gyrencephalic, and the small-brained mammals that have a smooth cortex, such as rats and mice are termed lissencephalic.

The digit ratio is the ratio taken of the lengths of different digits or fingers on a hand.

The most commonly studied digit ratio is that of the 2nd (index finger) and 4th (ring finger), also referred to as the 2D:4D ratio, measured on the palm side. It is proposed that the 2D:4D ratio indicates the degree to which an individual has been exposed to androgens during key stages of fetal development. A lower ratio (relatively shorter index finger) has been associated with higher androgen exposure, which would be the physiological norm for males but may also occur in some exceptional circumstances in females. The latter include developmental disorders such as congenital adrenal hyperplasia.