Intermediate
Technical
In the Industry Vocabulary Test
blastocyst
Pronunciation: BLAS-to-sist
Day 5-6 embryo stage characterized by inner cell mass and trophectoderm formation.
Full Definition
A blastocyst is an embryo that has developed to approximately day 5-6 after fertilization, characterized by formation of a fluid-filled cavity (blastocoel), an inner cell mass that will become the fetus, and an outer layer of cells called the trophectoderm that will form the placenta. This developmental stage is preferred for preimplantation genetic testing as it allows biopsy of trophectoderm cells without affecting the inner cell mass. Blastocyst culture and transfer have become standard practice in many IVF programs due to improved pregnancy rates.
Usage
Usage note: One word; not hyphenated.
In Context
- "The blastocyst showed excellent morphology with a clearly defined inner cell mass." — Embryology laboratory report
- "Genetic testing was performed on cells biopsied from the blastocyst trophectoderm." — PGT procedure documentation
Also known as
blastula
Don't confuse with
morula
embryo
zygote