Embryology Flashcards
What is embryology
Progression from a single cell to a baby in 9 months
What do the fimbriae do
Their movements helps move the egg from the ovary into the Fallopian tube
Why can the uterus reverse its contractions
To assist the movement of sperm
Why must the opening of the cervix remain closed during pregnancy
So the bay doesn’t fall out. This is a cause of recurrent miscarriages
What is spermatogenesis
The production of 4 spermatids from a spermatogonium
What is produced in oogenesis
I big egg and 3 polar bodies
Why is the egg cell so big
It contains lots of food to be able to survive 12 weeks before it’s supplied nutrients via the placenta
When does meiosis II occur during oogenesis
After fertilisation
When does meiosis I occur in oogenesis
In puberty just priori to ovulation
What happens to the number of germ cells in females are they age
They reduce dramatically
Why does the number of germ cells in females reduce
Many die or contribute to producing a big egg
What helps the movement of the egg through the Fallopian tube
Contractions by the Fallopian tube
How do sperm know which Fallopian tube to travel down
Thermotaxis
True or false; cilia in the Fallopian tube assist the movement of sperm
False, they help the movement of the egg and so waft in the opposite direction to sperm making it harder
What is capacitation of spermatids
When chemicals in the reproductive tract cause the heads of the sperm to change so that they swim faster. This then makes them capable to fertilise the egg
What is the layer of cells covering the egg called
Corona radiata
What is the outer layer of the egg called
Zona pellucida
What happens when sperm burrow into the zona pellucida
They bind to sperm receptors triggering acrosomes to release digestive enzymes
What happens to the zona pellucida once a sperm enters the egg
It hardens stopping other sperm entering
What happens to the female genetic information once the egg is fertilised
It completes meiosis II and then forms a pronucleus
What bring the 2 pronuclei together in fertilisation
Microtubules
Where does fertilisation occur
Ampullary region of the Fallopian tube
How long are sperm viable for
5 days
How long are secondary oocytes viable for
12-24 hours
When are antibodies against sperm produced
When they have contact with blood
What does seminal fluid do
Helps the survival of sperm, contains immunosuppressants, increases likelihood of implantation
What s the embryonic age
Time since fertilisation
What is the gestational age
Time since last menstruation (embryonic age minus 2 weeks)
What is the germinal Stage
Time from fertilisation to end of 2nd week
What is the embryonic period
Time from 3rd to 8th week
What is the foetal period
Time from 9th week to birth
what is a zygote
fertilised ovum
what is a morula
a cluster of 32 cells
what will the trophoblast become
the placenta
what is the function of the zona pellucida
stops implantation occurring in the wrong place and prevents the ball of eggs becoming too large as theres limited food
true or false; the morula and blastocyst undergo both aerobic and anaerobic respiration
true
what is histotrophic nutrition
nutrition provided to the embryo not from maternal blood
how long does the embryo undergo histotrophic nutrition
for the first 12 weeks
what is haemotrophic nutrition
nutrition provided by the mothers blood
what does the morula differentiate into
an outer and inner cell mass
when does the embryo develop into a blastocyst
when a blastocyst cavity form
where does the embryo normally implant
superior posterior wall of uterine cavity
what day does implantation occur
day 6
what is an ectopic pregnancy
when implantation occurs at an abnormal site
what is placenta previa
when implantation occurs at the internal os and so the placenta blocks the babys exit
what does the outer cell mass differentiate into
trophoblast
what does the inner cell mass differentiate into
embryoblast
what does the trophoblast develop into
cytotrophoblast and synctiotrophoblast
when does the trophoblast begin to differentiate
as it burrows into the endometrium wall
what does the embryoblast develop into
bilaminar disc
what are the 2 layer of the bilaminar disc
epiblast and hypoblast
what develops between the cytotrophoblast and the epiblast
amniotic cavity
What do cells from the hypoblast form
the yolk sac
what membrane covers the yolk sac
exocoelomic membrane
true or false the growth of the bilaminar disk is faster than the syncytiotrophoblast and cytotrophoblast
false - its actually the other way round
what is the name of the small holes that form in the syncytiotrophoblast
lacunae
what is the extra embryonic mesoderm
the new cells that form between the yolk sac and cytotrophoblast
what happens to the extraembryonic membrane
a cavity forms creating the chorionic cavity
what joins the bilaminar disk to the cytotrophoblast
connecting stalk
during which period is there the greatest risk of congenital malformation
embryonic stage
what is teratogensis
congenital malformation
what stage occurs in the 3rd weed of development
gastrulation
what occurs in gastrulation
the bilaminar disk is converted into a trilaminar disc
what occurs at the primitive streak
cells from the epiblast migrate here and invaginate into the bilaminar disk forming a new layer
what are names of the 3 layers of the trilaminar disc
ectoderm, mesoderm and endoderm
what does the ectoderm develop into
brain and epidermis
what does the mesoderm develop into
muscle, cartilage, bone and heart
what does endoderm develop into
epitheial lining, respiratory tract
what occurs at the primitive node
ciliated cells waft signals for leftsidedness to the left
what occurs after gastrulation
neurulation
what drive neurulation
the notochord
what does the notochord do
convert the overlying ectoderm into neuroectoderm by releasing signals for these cells to differentiate to become thicker forming the neural plate
how does the neural tube form
edges of the neural plate curl up to form the neural groove and then eventually the neural tube
what does the following mesoderm develop into following the neural tube formation
somites
what step occurs after neurulation
segmentation
at what day do somites start to develop
day 20
how many pairs of somites do you develop
31
what do somites degrade and differentiate into
dermatome, myotome and sclerotome
what is dermatome the precursor of
skin
what is myotome the precursor of
muscle
what is sclerotome the precursor for
bone
what will the buccopharyngeal membrane develop into
mouth
what will the cloacal membrane develop into
anus
what will the intraembryonic coelom develop into
the serous membranes
what stage occurs after segmentation
folding
what type of folding occurs first?
cephalocaudal folding
what drive cephalocaudal folding
growth of the neutral tube
what type of folding occurs second
lateral folding
what drives lateral folding
growth of somites
