Strep throat is a contagious disease caused by infection with streptococcal bacteria, which causes inflammation and swelling of the mucous membranes lining the back of the throat and the tonsils.trep throat is a contagious disease caused by infection with streptococcal bacteria, which causes inflammation and swelling of the mucous membranes lining the back of the throat and the tonsils.
Once an egg cell is fertilized by a sperm, it will divide and become an embryo. In the embryo, there are stem cells that are capable of becoming all of the various cell types of the human body. For research, scientists get embryos in two ways. Many couples conceive by the process of in vitro fertilization. In this process, a couple's sperm and eggs are fertilized in a culture dish.
Embryonic stem cells are derived from very early embryos called blastocysts; the diameter of a human blastocyst is roughly four times that of a human hair. A human blastocyst next to a human hair. A mouse blastocyst aged 3.5 days; the inner cell mass is coloured green and the trophectoderm is coloured red. An outer layer of cells, or trophectoderm, will form the placenta that supports the embryo as it grows inside the uterus. 2  An inner clump of cells, called the inner cell mass, is a ball of 10â20 cells. 3  These cells are undifferentiated, or unspecialized.