embryonic period

embryonic period,

the earliest period or phase of lung development in utero, lasting from the third week after conception to the sixth week. It is sometimes not named as a defined period of lung development, which is instead considered to begin with the following pseudoglandular period. During this period, a ventral respiratory diverticulum (lung bud) arises from the caudal end of the laryngotracheal groove and grows into bronchial buds and the primordial trachea. Also called embryonic phase.

---

embryonic period (em″breon´ik pe´reod),

n the stage between the second and eighth week of embryonic development, during which differentiation of organs and organ systems occurs.

---

embryonic

emanating from or pertaining to embryo. See also embryo.

---

embryonic death

see early embryonic mortality (below).

embryonic disk

larger cells of the mammalian blastocyst which develop into the embryo.

early embryonic mortality

death of the embryo, i.e. before it becomes a fetus; a principal cause of temporary infertility in farm livestock. Amongst causes are errors in timing of insemination, chromosomal defects, asynchronous development of the endometrium.

embryonic period

see embryo.

embryonic regulation

ability of embryonic tissues to recognize changes in their size and location and to make the necessary adjustments to form the disk-shaped assembly of appropriate structures.

embryonic stem cell

stem cell of fetal origin.

embryonic vesicle

see chorionic vesicle.