Lecture 3: Development Flashcards
after ejaculation
sperm cells make their way through the acidic environment of the vagina to the more hospitable environment of the uterus
ampulla
about 200 sperm cells reach the ampulla of the uterine tube. the ampulla is where fertilization occurs over a 24-hour period
acrosome
located at the tip of the sperm cell. contains enzymes that break down the outer layers of the egg cell
route of the sperm
the sperm and egg cell must fuse. the sperm must first pass through the layer surrounding the egg cell (corona radiata and zona pellucida). once past the barriers, the sperm cell leaves its plasma membrane and enter the cytoplasm of the egg cell
ootid
the egg cell that now contains the nuclei of the female and the male and has a haploid number of chromosomes from the sperm and the egg cell
capacitation
the process by which the sperm cell is prepared to enter the egg
zygote
when the fusion of the nuclei produces a diploid number of chromosomes it is then referred to as a zygote
diploid
the presence of two complete sets of chromosomes in an organism’s cells, with each parent contributing a chromosome to each pair
haploid
the presence of a single set of chromosomes in an organism’s cells
blastocyst
after 4-6 days, before implantation in the uterus, the mass of cells is called a blastocyst
stem cells
stem cells are undifferentiated cells that can turn into virtually any specialized cell. has two main types:
- embryonic stem cells
- adult stem cells
fission
the zygote single cells, or blastomere begins a series of mitotic divisions creating new cells
second week
by the end of the second week, the blastocyst implants itself into the uterus, the blastocyst nestles into the uterine wall, new cells must pass through the existing cells and layers. the cells build up from the inside out
around 9 to 10 weeks
the embryo develops teeth and nails
from 17 weeks
a baby can dream (REM sleep)
end of pregnancy
the baby can close and open its eyes, however a lot can go wrong, such as ectopic pregnancy in the fallopian tube: the embryo must then be removed
totipotent stem cells
they can differentiate into all possible cell types
pluripotent stem cells
they can differentiate into most cell types
multipotent stem cells
they can differentiate into related cell types
oligopotent stem cells
they can differentiate into limited types of cells
unipotent stem cells
they can only differentiate into their own type of cells
invagination
when the embryo begins to assume its multicellular form during the gastrulation phase of the embryonic development. in this process, the folding of the embryonic cells produces three cell layers
ectoderm (outer layer)
the layer of cell or tissue of an embryo in early development. the central nervous system forms from this