“foreign” and that stimulates a specific immune response when it enters the tissues of an organism.


– See Assisted reproductive technologies

Artificial insemination

– See Donor insemination

Assisted reproductive technologies (ARTs)

– Fertility treatments or procedures that involve laboratory handling of gametes (eggs and sperm) or embryos. Examples of ARTs include in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI).

Autoimmune disease or disorder

– A category of diseases and disorders in which one’s own cells are mistakenly identified as “foreign” by the body and are therefore attacked by the immune system, causing tissue damage.


– The fluid-filled cavity within the blastula.


– A preimplantation embryo in placental mammals (about 3 days after fertilization in the mouse, about 5 days after fertilization in humans) of about 30–150 cells. The blastocyst stage follows the morula stage, and can be distinguished by its unique morphology. The blastocyst consists of a sphere made up of a layer of cells (the trophectoderm), a fluid-filled cavity (the blastocoel or blastocyst cavity), and a cluster of cells on the interior (the inner cell mass, or ICM). The ICM, consisting of undifferentiated cells, gives rise to what will become the fetus if the blastocyst is implanted in a uterus. These same ICM cells, if grown in culture, can give rise to embryonic stem cell lines. At the time of implantation the mouse blastocyst is made up of about 70 trophoblast cells and 30 ICM cells.

Blastocyst cavity

– The fluid-filled cavity within the blastocyst, sometimes referred to as the blastocoel.


– A cell from a morula-stage embryo.


– Term (often used in lower vertebrates) to describe an early stage in the development of an embryo consisting of a hollow sphere of cells enclosing a fluid-filled cavity called the blastocoel. The term blastula sometimes is used interchangeably with blastocyst.

Cell line

– A general term applied to a defined population of cells that has been maintained in culture for an extended period and usually has undergone a spontaneous process, called transformation, that

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