Development and Inheritance Flashcards
What happens during fertilization?
genetic material of sperm and oocyte merge into a single nucleus
When does fertilization occur?
12-24 hours after ovulation
What must happen before fertilization can occur?
capacitation
acrosomal reaction
what is capacitation?
weakening of cell membrane of spermatozoa head
where does capacitation happen?
female reproductive system
what is the acrosomal reaction?
sperm surrounds oocyte and releases hyaluronidase
what happens after hyaluronidase is secreted?
disruption of the corona radiate and the zona pellucida
what blocks polyspermy?
changing the location of the veils
what is polyspermy?
many sperm
How long do spermatozoa survive?
3-7 days
How long is the oocyte viable once ovulated?
24 hours
What day of the cycle should fertilization occur?
day 15
What happens when sperm enters the secondary oocyte?
fusion of male pronucleus and female pronucleus
what is a male pronucleus?
flagella is shed and head develops
what is a female pronucleus?
nucleus of female oocyte
What happens when the male pronucleus and female pronucleus fuse?
a zygote is formed with 46 chromosomes
How are dizygotic twins formed?
when the mother ovulates 2 oocytes and both are fertilized
Once a zygote is formed, it will undergo
a form of mitosis called cleavage
what is cleavage?>
1 celled zygote will duplicate and split into two cells
How long after fertilization does cleavage occur?
30 hours
what follows cleavage?
more and more cell division until a morula is formed
what is a Morula?
solid ball of blastomeres surrounded by the zona pellucida
Where is the morula?
fallopian tube headed for the uterus
What happens after 5 days of development?
a blastocyst is formed.
what is a blastocoele?
cavity that forms in the middle of the blastocyst
what is a trophoblast?
outer covering of cells on the blastocyst
what causes blastocoele?
movement of blastomeres
what is the embryoblast?
inner covering of cells on a blastocyst
the embryoblast will form the
baby
the trophoblast will become
the placenta
how are monozygotic twins developed?
1 oocyte is fertilized by 1 sperm but 2 areas of embryoblast develop individually
what are conjoined twins?
monozygotic twins that are joined physically
what causes conjoined twins?
abnormal cleavage
When does the blastocyst enter the uterus?
5 days after fertilization
what happens 6-7 days after fertilization?
blastocyst attaches to endometrium
what is the germinal period
first two weeks when the germ layers will form
what is the embryonic period?
3-8 weeks of development
what happens after the embryonic period?
fetal period
What are the three germ layers that the embryoblast differentiates into?
ectoderm
mesoderm
endoderm
what is the ectoderm?
outside layer. skin and nervous system
what is the mesoderm?
middle layer. muscle, bone and connective tissue
what is the endoderm?
middle layer. most viscera
what are the four membranes that develop
yolk sac
amnion
chorion
allantois
what is the yolk sac?
early site of blood formation. comes from the endoderm
what is the amnion?
membrane that surrounds embryo
what fills the amnion?
amniotic fluid
where does the amnion come from?
ectoderm
what is the function of the amnion?
protection
what is the chorion?
membrane that becomes pportion of the placenta
what does the chorion secrete?
human chorionic gonadotropin
what is the function of hCG?
continue progesterone secretion
what are pregnancy tests based on?
human chorionic gonadotropin detection
where does the chorion come from?
trophoblasts
what is the allantois?
early site of blood formation
where does the allantois come from?
endoderm
what is the function of the placenta?
bringing oxygen and removing waste products
what happens to the placenta after 3-4 months?
production of progesterone and estrogen
what do progesterone and estrogen do?
maintain endometrial lining and prepare mammary glands for milk
what is the function of the chorion?
to grab onto the mother
when can hCG be detected on a pregnancy test?
day 22
what is gestation?
time that a zygote, embryo or fetus is carried in the reproductive tract
How long is the human gestation period
266 days or 40 weeks
what is labor proceeded by?
increase in hormones
what are the three stages of labor?
stage of dilation
stage of expulsion
placental stage
what is stage of dilation
dilation of the cervix from 1 to 10 cm
what happens during the stage of dilation?
contractions of the uterus and rupturing of the embryonic sac
what is the stage of expulsion?
when delivery occurs
how long does the stage of dilation last?
hours
how long is the stage of expulsion?
minutes
what is the placental stage?
when the placenta is passed
how long is the placental stage?
minutes