Akademik

An outer covering.

- cytotrophoblastic s. the external layer of fetally derived trophoblastic cells on the maternal surface of the placenta.

- diffusion s. a small vessel made of a semipermeable membrane through which peptone, but not serum albumin, can pass; used in performing the Abderhalden test.

- K s. the innermost electron orbit or s.; it can hold two electrons.

- L s. the next lowest energy level of electrons in the atom, after the K s. (q.v.).

- M s. the lowest energy level at which electron transitions give rise to x-rays.

- O s. the outermost s. of electrons, so called because displacement of electrons causes an emission in the visible or optical range.