embryo

embryo /em·bryo/ (em´bre-o)

1. in animals, those derivatives of the zygote that eventually become the offspring, during their period of most rapid growth, i.e., from the time the long axis appears until all major structures are represented.

2. in humans, the developing organism from fertilization to the end of the eighth week. Cf. fetus.

3. in plants, the element of the seed that develops into a new individual.em´bryonalembryon´ic

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presomite embryo  the embryo at any stage before the appearance of the first somite.

previllous embryo  the embryo before the placental chorionic villi develop.

somite embryo  the embryo between the appearance of the first and the last somites.

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em·bry·o (mbr-) n. pl. em·bry·os 1. An organism in its early stages of development, especially before it has reached a distinctively recognizable form. 2. An organism at any time before full development, birth, or hatching. 3. The fertilized egg of a vertebrate animal following cleavage. 4. In humans, the prefetal product of conception from implantation through the eighth week of development.

embryo Clockwise from top left: human embryo at five, seven, and eight weeks of development

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Embryo

In humans, the developing individual from the time of implantation to about the end of the second month after conception. From the third month to the point of delivery, the individual is called a fetus.

Mentioned in: Birth Defects, Childbirth, Echinococcosis, Ectopic Pregnancy, Gene Therapy, Human Chorionic Gonadotropin Pregnancy Test, Hypogonadism, Infertility, Miscarriage, Pregnancy, Puberty, Stem Cell Transplantation

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embryo

[em′brē·ō]

Etymology: Gk, en, in, bryein, to grow

1 any organism in the earliest stages of development.

2 In humans the stage of prenatal development from the time of fertilization of the ovum (conception) until the end of the eighth week. The period is characterized by rapid growth, differentiation of the major organ systems, and development of the main external features. Compare fetus, zygote. embryonal, embryonic, embryonoid, adj.

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embryo,

n the fertilized ovum, while in its primary developmental stage, two to eight weeks after implantation in the mother's womb.

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embryo

(em´brēō),
n an organism in the earliest stages of development; the stage between the time of implantation of the fertilized ovum until the end of the seventh or eighth week of gestation.

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embryo

a new organism in the earliest stage of development, i.e. from the time that the fertilized embryo begins to develop a long axis up to the time that the major structures have begun to develop, when it becomes a fetus.

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embryo collection

collection of an embryo from the genital tract for the purposes of embryo transfer; surgical and nonsurgical techniques available.

embryo cryopreservation

preservation of embryos by freezing.

hexacanth embryo

the larva with six hooks present in the cestode egg when it escapes from the uterus of the adult tapeworm. Called also oncosphere.

embryo micromanipulation

handling of an embryo under a microscope, for examination, dissection.

embryo transfer

collection of fertilized ova from one female before they become implanted and transfer to another female to complete the gestation. The donor is usually superovulated and then inseminated. Collection may be surgical via a laparotomy or nonsurgical by flushing through the cervix. Collected embryos must be stored carefully. They are evaluated in terms of fertilization, possibly cleaved artificially to create clones, and washed to eliminate the possibility of transferring infection with the embryo. Long-term storage by freezing is a practicable procedure. The recipient needs to be in appropriate stage of uterine receptivity, effected by synchronizing the estrus cycle with that of the donor.

embryo transplant

see embryo transfer (above).

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embryo

An early stages of a developing organism, which follows fertilization of an egg including implantation and very early pregnancy–ie, from conception to the 8^th wk of pregnancy. See Preembryo. Cf Fetus.