7. Coitus & Conception: from ovulation Flashcards
by the time of ovulation, what has happened to the ovum?
ovum (primary oocyte) in the ovulatory follicle has completed its first meiotic division to form a secondary oocyte
what does a secondary oocyte contain?
contains haploid number of chromosomes and the bulk of the cytoplasm of the primary oocyte
where are the remaining haploid chromosomes contained?
in a structure called the first polar body
what is the secondary oocyte surrounded by?
follicular cells
what are the follicular cells surrounding the secondary oocyte called?
cumulus
where are the secondary oocytes surrounded by follicular cells (cumulus) embedded within?
embedded in a gelatinous matrix
where is the secondary oocyte released from and picked up by?
released from an ovulatory follicle and picked up by the fimbria of the uterine tube
what happens to the secondary oocytes after they have been picked up by the fimbria of the uterine tubes?
it is then guided into its lumen by the ciliary movements of the lining cells towards the ampulla
what is significant about the ampulla of the fallopian tube?
the site of fertilisation
where the oocyte and the sperms come together
what is fertilisation?
the sperm and ovum come together in the act of fusion
how does the sperm fuse with the ovum during fertilisation?
only 1 sperm penetrates the cytoplasm of the ovum and the sperm’s nucleus fuses with the ovum’s nucleus
what makes up the bulk of the sperm head?
its nucleus
what is the product of fertilisation?
zygote
what does the entry of the sperm into the ovum set off?
a series of events in the ovum that prevent other sperms from entering the ovum
why is it important to prevent other sperms from entering the ovum?
ensures that the zygote contains diploid chromosomes for the normal development to proceed
within a few hours of fertilisation, what happens to the zygote?
the zygote begins to divide by a series of mitotic cell divisions - known as cleavage
what does cleavage form?
a ball of cells called the morula
what forms after morula?
a hollow structure - the blastocyst
during the transformation of the zygote –> morula –> blastocyst, what happens to the zygote?
it is gradually transported along the uterine tube towards the uterus
what does the blastocyst comprise of?
the earliest rudiments of both the embryo itself (inner cell mass) and the placenta
which cells form the placenta?
trophoblast cells
when does the blastocyst enter the uterine cavity?
4-5 days after fertilisation
by the time the blastocyst enters the uterine cavity, what is significant about the endometrium?
the endometrium is ready to receive the blastocyst for pregnancy to be established
after a day or so in the uterine cavity, what happens to the blastocyst?
the blastocyst attaches itself to the uterine endometrium
what is implantation?
when the blastocyst attaches to the uterine endometrium
what does implantation involve?
involves an interaction between the trophoblast cells and the lining epithelium of the uterus
what is further embedding of the blastocyst into the endometrium dependent upon?
the invasive property of the trophoblast
what happens to the blastocyst by the end of implantation?
it now has an outer syncytium called the syncytiotrophoblast
what is different about syncytiotrophoblast?
differentiated from the underlying cellular cytotrophoblast
when is the blastocyst fully embedded within the endometrium?
by the 10th day after fertilisation
what leads to the establishment of the early placenta?
cellular interactions of the blastocyst and the endometrium and
establishment of relationship between embryonic and maternal tissues
