Embryology Flashcards
What is another name for primordial germ cells in women?
Oogonia
what is the name of the first cell that starts the process of oogenesis
primordial germ cell
where are primordial germ cells found in the bilaminar disc?
yolk sac originate from the epiblast
under what process do PGC differentiate to become primary follicles containing primary oocyte?
Mitosis
after birth new oocytes continue to develop (true or false)
false - primary oocytes reach maximum number prior to birth
What is the name of the cell division that causes a primary follicle containing a primary oocyte to develop into a secondary follicle
Meiosis I (held in prophase I )
What is the name of the cell division that causes a secondary follicle to mature and become an ootid
meiosis II (held in metaphase II)
draw out oogenesis cycle
See diagrams
draw the cell of a primordial follicle
primary oocyte surrounded by one cell layer of follicular cells
up until puberty describe what is changing in the follicle and oocyte
the oocyte remains the same, whereas the cells surrounding the oocyte become cuboidal, more layers of follicular cells develop and the zona pellucida also develops
when the primary follicle develops a fluid filled cavity what is the name of the follicle?
Antrum follicle
as the antrum follicle grows and the fluid gets bigger the follicle becomes larger and the oocyte moves closer to the edge of the ovary ready for ovulation. What is the name of the follicle now?
Graffin follicle
what hormone triggers ovulation
LH
following ovulation the related oocyte is now a primary or secondary oocyte?
secondary oocyte
in order for the secondary oocyte to become a zygote what must occur?
fertilisation of the ovum ==> zygote
how many primordial follicles do we have at approximately 20 weeks gestation (5 months)
7 million primordial follicles
what happens to the number of primordial follicles between birth and puberty
decrease
between birth and puberty how do primordial follicles die?
atresia (degeneration) and apoptosis
how many primordial follicles does a female baby have at birth?
2 million
how many primordial follicles will a female just entering puberty have?
40,000
during each menstrual cycle how many primordial follicles are recruited?
15-20
what hormone prevents all 15-20 primordial follicles from developing
OMI (oocyte maturation inhibitor)
how long does embryonic development take
8 weeks
after 8 weeks of embryological development what is the name of the developing embryo
Foetus (after 8 weeks gestation)
what part of the fallopian tube does fertilisation occur
Ampulla
what happens to the secondary oocyte once sperm penetrates it to prevent further sperm being able to fertilise the ovum?
once a sperm penetrates the zona pellucida it sets the zona pellucida hard and firm so that no other sperm are able to penetrate
how many hours after fertilisation does the first cell division occur?
24 hours post fertilisation
what is the name given to the developing zygote on day 3 following fertilisation
Morula (mulberry) contains 16 cells
what day does the blastocyst develop
day 5
what is the inner cell mass of the blastocyst called
embryoblast - this will become the embryo
what are the outer cells of the blastocyst called and what will they become
trophoblast - this will feed the embryo and become the the foetal part of the placenta
On what day in the cycle does early implantation of the blastocyst occur
day 6 - early implantation of the blastocyst occurs on either the anterior or posterior wall of the endometrial cavity
what day does the blastocyst implant into the endometrial lining?
day 7, the blastocyst is now completely implanted into the endometrium and the endometrium will heal over the top
during week two the trophoblast divides into two new layers and the embryoblast divides into two layers
what are the names of these layers
Embryoblast:
1. Epiblast
2. Hypoblast
Trophoblast:
1. cytotrophoblast
2. syncytotrophoblast
during week 2 the blastocyst cavity turns into what structure?
the yolk sac
the hypoblast cells develop into a type of tissue that surrounds the yolk sac. What is the name of this cell layer?
hypoblasts develop into extra embryonic mesoderm (this surrounds the yolk sac)
what is the name of the structure that connects the embryoblast to the trophoblast
extra embryonic mesoderm stalk, this is the precursor to the umbilical cord
during week 3 the bilaminar disc develops into a trilaminar structure - what is the name given to this process
gastrulation
name the three layers of the trilaminar structure
ectoderm - embryonic mesoderm (there is intra and extra embryonic) - ectoderm
what is the rod of tissue called that develops at the primitive streak?
notochord
Neuralation occurs during which week in embryonic development?
week 4
what is made during the process of neuralation
the neural cord - this is the basis of the nervous system
what cell layer does the neural cord develop from?
ectoderm
If a mistake or lack of development occurs in week 4 during neuralation what is the potential consequence for the developing foetus?
NTD (neural tube defect)
what layer of tissue do the somites develop from
paraxial mesoderm
what are the three compartments of the developing digestive tract called
foregut, midgut and hindgut
what is the part of the endometrium called that contributes to the placenta?
decidua basalis
what cell layer makes up the lining of the digestive tract
endoderm
what rotation does the digestive tract undergo between weeks 6-10
270 degree anti-clockwise rotation
what proportion of people are born with a meckel’s diverticulum? what is this an embryological remnant off
2% of the population are born with a meckel’s diverticulum
this is an embryological remnant of the vitelline duct (the connection between the midgut and the yolk sac)n
what does the gubernaculum become in men
upper part degenerates
lower part becomes the scrotal ligament
in women what is the embryological origin of the suspensory and round ligament
upper part of the gubernaculum becomes the suspensory ligament
lower part of the gubernaculum becomes the round ligament
what is the embryological remnant of the median umbilical ligament
Urachus
what is the embryological remnant of the medial umbilical ligament
umbilical artery
what is the name of the embryological structure that develops into the urinary bladder
cloaca forms the urogenital sinus
what structures does the ectoderm develop into
ectoderm is the most distal layer
develops into the nervous system and skin epidermis
what structures does the mesoderm develop
mesoderm is the middle cell layer
It gives rise to the following structures :-
1. Blood vessels
2. connective tissue
3. Bone
4. Reproductive system
5. muscle (skeletal and heart)
what structures does the endoderm develop
endoderm is the proximal cell layer
it develops into:
1. respiratory system
2. GI tract
3. endocrine glands
what are the names of the three layers of somites
dermatome, myotome and sclerotome
what cells develop into the vertebral column
sclerotomes
what cells develop into skeletal muscle
myotomes
