Reproduction Flashcards
gametogenesis
the formation and development of germ cells–oocytes and spermatocytes
meiosis
produce cells with a haploid number of 23 chromosomes
phases
2 sequential meiotic cell division occur during gametogenesis
prophase
homologous chromosomes pair
anaphase
homologous chromosomes separate
first meiotic division
reduction division in which each new cells form a secondary oocyte or spermatocytes retaining the haploid number of chromosomes
second meiotic division
each chromosome divides to form two chromatids that are drawn to a different poles of the cell
ovum
egg
oogenesis
process of egg formation begins during fetal life
how many ova mature during women’s reproductive stage life?
400-500 ova
primary oocytes
begins their first meiotic division before birth but remain suspended in prophase until puberty
menarche
first menstrual cycle (monthly cycles)
one oocyte matures and completes the first meiotic division
when does second meiotic division begin?
division begins at ovulation but progress only to metaphase when division is arrested
zona pellucida
inner layer
penetrated by sperm, the second meiotic division is completed.
spermatogenesis
formation of germ cells to a sperm cells
when does spermatogenesis begin
begins at puberty under the influence of testosterone and continues throughout adult life
where does spermatogenesis take place in?
the seminiferous tubules within the testes
where does sperm cells travel through?
the efferent tubules to the epididymis, where they mature
where does mature sperm cells move to?
the ejaculatory duct through the vas deferens, where they wait ejaculation
what regulates female menstrual cycles
hypothalamus, anterior pituitary gland, and ovaries and occurs in four stages that repeat every 28 days.
stage I (menstrual phase)
the shedding of the endometrium (caused by decreased in estrogen and progesterone) triggering menstrual bleeding
stage II (follicular phase)
the preovulation phase, whereby the ovary and follicles prepare for the release of an ovum through the influence of follicle-stimulating hormone and estrogen
stage III (ovulation phase)
the ovum is expelled from follicles (triggered by a sharp rise in estrogen and luteinizing hormones) and is drawn into the fallopian tube
stage IV (luteal phase)
cilia in fallopian tubes are stimulated by high estrogen levels, which propel the ovum toward the uterus. The follicle transforms into the corpus luteum during this phase and release progesterone, which cause the uterine wall to thicken in the anticipation of supporting a fertilized egg.
what happens if fertilization does not occur
corpus luteum disintegrates and is usually absorbed by the women’s body
with degeneration of the corpus luteum, estrogen and progesterone decrease, thus triggering the shedding of the uterine wall and start the next menstrual cycle.
pregnancy
begins with fertilization and in the absences of complications, involves a 40-week gestation period (measured from the first day of the last menstrual period) and results in live birth.
trend in pregnancy rates
vary by population subgroup
age
influenced by factors such as changes in
sexual activity
new contraceptive methods
change in marital/cohabitation trends
social and economic context of childrearing
public health threats
how many sperms are ejaculated during intercourse?
500 million
where does fertilization occur?
lower third of the fallopian tube
cortical reaction
sperm and ovum are enclosed after sperm penetrate the ovum membrane
prevents other sperm from entering the ovum
ovum nucleus
become female pronucleus, and second meiotic division is complete
head of sperm
enlarges to form male pronucleus and the tail degenerates.
zygote
new cells after fertilization
has two set of chromosomes
when does cleavage begin?
30 minutes after fertilization
division of zygote into two blastomeres
soon after divide again to form four blastomeres
rapid cellular division occurs while blastomeres travel down the reproductive tract.
increase in number of cells, no increase in mass.
morula
3 days after fertilization
a cell mass of 12-16 blastomeres, enter women’s uterus
4 days after fertilization
A cavity is formed within morula
becomes a blastocyst and float freely within the uterus for 2 days
implantation
spaces form between the central cells of the morula and fluid pass through the zona pellucida, collecting in these spaces
the zona pellucida then lyses and degenerates.
trophoblast
cells separate into an outer layer after zona pellucida lyses and degenerates.
what dose the trophoblast form
placenta and an inner layer known as embryoblast, that develop to form embryo.
when does implantation occur
6-10 days after fertilization
where does blastocyst receive nourishments from
endometrial glands in uterus
includes carbohydrates, pyrimidines, purines, and amino acids by active and passive transport
decidua
what the endometrium is called after blastocyst is totally covered
embryonic period
stage of pregnancy development from day 15-8 weeks after fertilization
development of body systems and organs occur
when pregnancy is most vulnerable to malformations caused by teratogens
teratogens
substances, exposures, certain infections, and some health problems that can cause abnormal fetal development.
