Embryo Exam 1 Flashcards
What are primordial germ cells?
precursors of the sperm and oocyte
Where do PGCs reside?
Yolk Sac
What ploidy are PGCs?
Diploid
What are male somatic support cells?
Sertoli and Leydig cells
What are female somatic support cells?
Granulosa cells and thecal cells
What is the name for DNA + Histone proteins?
Nucleosome
Chromatin
a higher order structure of DNA and histone
Chromosomes
A higher order structure of chromatin
Chromatid
One of the two identical halves of a chromosome that has been replicated in preparation for cell division
Ploidy
number of sets of chromosomes (haploid, diploid)
n
number of copies of each unique double-stranded DNA molecule
What is the correlation between n and ploidy?
There is NO strict correlation between n and ploidy.
After S phase, is a cell with 4n chromosomes haploid or diploid?
Diploid
Cell growth
increase in cell SIZE
Cell division
Increase in cell number (mitosis and cytokinesis)
Cell proliferation
Cell growth plus division
What are sister chromatids closely held together by?
Cohesins
What enzyme cleaves the cohesin complex at the beginning of anaphase?
Separase
Chiasmata
Sites of crossover
Mitosis
Diploid to diploid
Meiosis
diploid to haploid to haploid
What cellular processes can PGCs undergo?
Mitosis and Meiosis
What cellular processes can somatic cells undergo?
Only mitosis
Do oogonia complete mitosis and meiosis?
Oogonia in the embryonic ovary complete mitotic divisions and enter meiosis 1 by the fifth month of fetal development but are arrested in meiosis 1.
Is a primary oocyte haploid or diploid?
diploid
Is a secondary oocyte haploid or diploid?
haploid
How many primary oocytes does an ovary contain at birth?
1 to 2 million
How many oocytes remain in the ovaries at puberty?
only 300,000
How many primordial follicles develop enough to expel their ova between 13 and 46?
400 to 500
Zona Pellucida
Thin layer of acellular material on the surface of an oocyte secreted both by the follicle cells and oocyte
Where does fluid accumulate in a mature graafian follicle?
Antrum
What is the small mass of follicle cells that surrounds the secondary oocyte called?
cumulus oophorus (second layer)
what is the inner most layer of the cumulus oophorus called?
corona radiata (first layer)
What is the name of the phase of the menstrual cycle that spans from day 28 to day 5?
menstrual phase
What is the name of the phase of the menstrual cycle that spans from day 5 to 14?
Proliferative phase
What is the name of the phase of the menstrual cycle that spans from day 14 to 27?
Luteal phase
What is the name of the phase of the menstrual cycle that spans from day 27 to 28?
ischemia phase
What two hormones peak at day 13 of the menstrual cycle?
FSH and LH
What day does ovulation occur?
Day 14
What cells does LH act on?
thecal cells
What cells does FSH act on?
granulosa cells
What happens to thecal cells when they respond to LH?
Become contractile
What is the function of MMPs?
MMPs help break the membrana granuloosa leading to antral follicle rupture
How is the oocyte/cumulus complex moved into the ampulla by?
- synchronized beating of the cilia on the oviduct wall
- peristalsis
Where do the luteal cells of the corpus luteum derive from?
membrane granulosa cells of the ruptured follicular wall
What two hormones does the corpus luteum secrete?
Progesterone and estrogen
What do progesterone and estrogen from the corpus luteum maintain?
the endometrium in a condition to receive the embryo
What if the oocyte is not fertilized?
the corpus luteum involutes, degenerates 10 to 12 days after ovulation and is converted to a white scar-like structure called the corpus albicans
What is corpus albicans?
white scar-like tissue formed after mature corpus luteum shrivels if not fertilized
What occurs during the proliferative phase?
estrogen secreted by the granulosa and thecal cells will cause the endometrial lining of the uterus to proliferate
What occurs during the luteal phase?
progesterone will stimulate the uterine endometrial layer to thicken further and form convoluted glands and increased vasculature
When does spermatogenesis occur from?
continuously from puberty to death
What connects adjacent sertoli cells?
tight junctions (blood testis barrier)
What does the blood testis barrier do?
seals apical compartment from immune system
What are daughter cells connected by?
cytoplasmic bridges
During male puberty, what happens with some of the daughter cells?
go back to replenish the stem cell pool to continue the process of spermatogenesis
Spermatogenic wave
successive groups of syncytial germ cells progressing through the various stages of differentiation form this
What connects spermatocytes and spermatids to surrounding sertoli cells during spermiogenesis?
inter-cellular junctions called tubulo-bulbar complexes
Acrosome
contains hydrolytic enzymes such as acrosin, hyaluronidase, and neuraminidase (helps break zona pellucida)
where does capacitation occur?
uterus and uterine tubes
What allows for the acrosome reaction to occur?
completion of capacitation
what is capacitation?
- unmasking of sperm glycosyltransferases from surface of acrosome
- removal of adherent plasma proteins coating the surface of the sperm
- sperm become hyperactive
What is the size of an oocyte compared to a sperm?
an oocyte is much larger than a sperm
what is the vaginal pH?
5.7 (acidic)
what regulates sperm entry into vaginal canal?
cervical mucus
what plugs the cervical canal?
mucosal closure at the internal and external cervical OS, as well as by the consistency of the cervical mucus.
When do the chances of conception increase?
in the days leading up to ovulation
Can sperm penetrate through progesterone in cervix?
NO
Can sperm penetrate through estrogen in cervix?
YES
Describe estrogen characteristics in cervix
abundant, clear, stretchable mucus (spinnable)
describe progesterone characteristics in cervix
scant, thick, tacky (nonspinnable)
Isthmus
proximal part of fallopian tube
ampulla
distal part of fallopian tube
where does fertilization occur?
ampulla
What do ovulated follicles contain?
a sperm chemotropic factor and only capacitated sperm is able to respond to this factor
what is ZP3?
sperm receptor glycoprotein expressed by zona pellucida
what does SED1 recognize on sperm?
ZP3
what does ZP3 trigger?
acrosome reaction
How is polyspermy prevented?
- fast block - oocyte membrane depolarization
- slow block - formation of Ca2+ wave, release of cortical granules, inactivation of ZP3, and zona pellucida becomes impermeable
what is the function of the calcium wave in the prevention of polyspermy?
induces the oocyte to complete meiosis II
Maternal and paternal nondisjunction can result in what two clinical considerations?
trisomy 21 (down’s syndrome)
turner syndrome (missing/altered X)
What defines an infertile man?
less than 10 million sperm/mL of semen
what does Hypogonadotropic hypogonadism (HH) lead to?
reduced levels of FSH and LH and underdevelopment of ovaries and testicles
What is the main fertility drug taken by females?
clomiphene citrate
What characterizes premature ovarian failure in females?
loss of function of ovary before age 40
What characterizes pelvic inflammatory disease?
infection of uterus, uterine tubes, or ovaries leading to inflammation and scar formation (affects ciliary motility)
what characterizes endometriosis?
appearance of foci of endometrial tissue in abnormal locations outside uterus
what induces ovaries to superovulate?
administration of gonadotropin or FSH
what is IVF?
ova fertilized in vitro with sperm fraction concentrate. Embryo transferred directly into uterus, bypassing tubal occlusion
When is intra-cytoplasmic sperm injection used?
in cases where the male’s spermatozoa are unable to penetrate zona pellucida
when is gamete intra-fallopian transfer used?
used in cases where the female’s oviduct is normal but the male is infertile because of an innate deficiency in sperm motility
when is zygote intra-fallopian transfer used?
in cases where the female’s oviduct is normal but the male is infertile because of an innate deficiency in sperm motility
what happens to the size of blastomeres during cleavage?
do not increase in size
what is compaction?
the flattening of round blastomeres and increased cell-to-cell contact among adjacent blastomeres
when does hatching occur?
day 5
what is hatching
rupture of the zone of pellucida
what is hatching caused by?
increased mechanical pressure of growing blastocyte and secretion of proteolytic enzymes by trophoblastic cells
totipotency
the ability to form any type of differentiated cell
pluripotency
the ability to form more than one type (but not all types) of differentiated cell
where does implantation occur
superior, posterior portion of the uterus
what is the primary source of the placenta?
blastocytes
what is the inner lining of the uterus called
endometrium (decidua)
what are syncytiotrophoblasts
cells that secrete HCG (pregnancy hormone)
what will hCG support
corpus luteum
what do pregnancy tests detect
hCG
when does implantation occur
day 7
what is syncytium
a mass of cytoplasm containing numerous dispersed nuclei (no cell borders)
what occurs when the embryo becomes fully implanted in the endometrium
- cytotrophoblast secrete MMPs
- active finger-like processes extend from the syncytiotrophoblast then penetrate between the separating endometrial cells
what cells do inner cell mass (embryoblasts) differentiate into
epiblasts (dorsal) and hypoblasts (ventral)
what cells form the yolk sac membrane
hypoblastic cells
what is another name for the yolk sac membrane
Heuser’s membrane
what is the name of the two layered embryoblast
bilaminar embryonic disc
what are the bilaminar embryonic disc, yolk cavity, and amniotic cavity surrounded by
extraembryonic mesoderm
what do the spaces within the extraembryonic mesoderm that get bigger and coalesce form
extraembryonic coelom or chorionic cavity
what does the secondary umbilical vesicle form
yolk cavity proper
what suspends the bilaminar embryonic disc, the yolk, and the amniotic cavity in the chorionic cavity
connecting stalk
by the end of 14 days, what are the 3 cavities formed
amniotic cavity, yolk cavity, chorionic cavity
what are the 4 extraembryonic membranes formed by the end of 14 days
amnion, yolk sac, chorion, allantois
what defines an ectopic pregnancy
- implantation of the embryo in a site other than a normal intrauterine location
- lack of coordination between hatching and movement of blastula to uterine cavity
what is the normal site of embryo implantation
superior and posterior part of uterus
where do 90% of ectopic pregnancies form
fallopian tube
what factors contribute to tubal pregnancy
- 35-50% of ectopic pregnancies form due to prior pelvic inflammatory disease
- appendicitis, endometriosis, and previous surgery
- pregnancy with IUD
difference between complete mole and partial mole
complete mole has loss of genetic material in ovum whereas partial mole has too much genetic material
does a complete mole support a fetus
no, but placental membranes
does a partial mole support a fetus
yes
what must be followed after curettage for molar pregnancy
hCG levels for 6 months to 1 year
what percent of hydatidiform moles are invasive
15%
what structure may embolize to sites such as lungs and brain with invasive moles
hydropic villi
what diagnostic lab value is seen with invasive moles
persistently elevated serum hCG
what is the response rate to chemotherapy with invasive moles
very well
what is the severity of gestational choriocarcinoma
rapidly invasive and can metastasize
where are the two most common sites for the metastasis of gestational choriocarcinoma
lungs (50%) and vagina (30-40%)
how responsive is gestational choriocarcinoma to chemo
100% remission and high CURE rate
what diagnostic lab value is seen with gestational choriocarcinoma
elevated hCG
what term describes female genetics
genetic mosaics
why is one X chromosome inactivated in females
dosage compensation
mosaic
genetically distinct cells arising from one zygote
chimera
genetically different cells arising from two zygotes
what type of disease is duchenne muscular dystrophy
x-linked
what is the timeframe of the embryonic period
15 days to 8 weeks
what is the defining characteristic that can occur during the embryonic period
embryo most susceptible to teratogens
what is the name of the epiblastic thickening that forms along the midsagittal plane
primitive streak
what is another name of the cranial end of the primitive streak that is expanded into the primitive node
Hensen’s node
what does the formation of the primitive streak and hensen’s node determine
right and left side of the embryo
What causes directional left-right asymmetry
asymmetric expression and function of genes
what is situs inversus
sidedness reversed (organs develop on opposite side of body than normal)
what are the 2 outcomes that make up Kartagener syndrome
situs inversus and primary ciliary dyskinesia
what does the formation of the primitive streak mark
the beginning of gastrulation
definition of gastrulation
generation of 3 germ layers (ectoderm, mesoderm, and endoderm)
what does the oropharyngeal membrane later form
the mouth
what does the cloacal membrane later form
the anus
how would you describe the mesoderm in the primitive streak
intraembryonic
what begins the formation of the notochord
the notochordal process
what are the characteristics of the notochord
- a mesodermal derivative
- a transient, embryonic structure
definition of neurulation
formation of the neural tube from the ectoderm
what is secreted by the notochord as a critical inductive signal
Shh
on what day does invagination begin
day 18
on what day does closure begin
day 22
on what day is anterior neuropore closure complete
day 25
on what day is posterior neuropore closure complete
day 27
what should all women of childbearing age consume daily and in what amount
.4 mg (400 micrograms) of folic acid
what is the medullary cord derived from
mesenchymal cells
what is the neural tube derived from
ectoderm
what does the secondary neural tube arise from
the medullary cord (condensed mesenchymal cells)
where do the primary and secondary neural tubes fuse at
lumbo-sacral boundary
what process do cells at the dorsal margins of the neural tube undergo
epithelial-mesenchymal transition (EMT)
what kind of cells does the process of epithelial-mesenchymal transition form
neural crest cells
what can altered neural crest development lead to
neurocristopatheis
what are the 4 neural crest types
- cranial
- vagal
- trunk
- lumbo-sacral
what are somites
segmental axial structures of vertebrate embryos that give rise to body segments
what is the cause of sacrococcygeal teratoma
misplaced germ cells
what is the most common site for a teratoma in infants
sacrococcygeal region
what type of cells are the ones that form sacrococcygeal teratomas
pluripotent
what are the complications associated with sacrococcygeal teratomas
- tumor induced vascular steal syndrome leads to high output heart failure
- polyhydramnios and fetal hydrops
what is the cause of caudal dysplasia
abnormal gastrulation- migration of mesodermal precursors is disturbed
what is caudal dysplasia associated with
VATER (vertebral defects, anal atresia, tracheoesophageal fistula, renal defects)
VACTERL (VATER plus cardiovascular defects and upper limb defects)
what syndrome is caused by caudal dysplasia
sirenomelia (mermaid syndrome)
what causes spina bifida occulta
failure of bony fusion and no displacement of spinal canal contents
where does spina bifida occulta form
lumbo sacral boundary
what causes spina bifida
failure of caudal neuropore closure
where do more severe deficits occur in patients with spina bifida
the more cranial the location the more severe the deficits
characteristic of spina bifida with meningocele
meningeal cyst free of neural elements
characteristic of spina bifida with meningomyelocele
nerve roots protrude into cyst
what is the cause of spina bifida with rachischisis
failure of caudal neuropore closure
what is the cause of anencephaly
failure of cranial neuropore closure
what procedures can diagnose anencephaly prenatally
ultrasound and elevated alpha fetoprotein in maternal blood and amniotic fluid
what is a schwannoma
benign tumor of schwann cells of neural crest origin
what is the most common location for a schwannoma to reside
within the cranial vault in the cerebellopontine angle
what are the schwannomas that form within the cerebellopontine angle called
vestibular schwannomas
what is the primary cause of Hirschsprung’s disease
absence of ganglionic plexus due to absence of caudal migration of vagal neural crest cells
what is a characteristic associated with Hirschsprung’s disease
abnormal colonic dilation or distention (megacolon)
what syndrome can be caused by Hirschsprung’s disease
Trisomy 21
where did somatic support cells acquire their name from
coelomic epithelial cells
what is the function of somatic support cells
support growth of PGCs
what week does the embryo decide which gender it becomes
week 7
what is the process of deciding the gender of the embryo called
sex determination
what are the male PGCs called
sperm
what are the female PGCs called
oocyte
what type of cells contribute to the extraembryonic mesoderm
hypoblast cells
What cells reside in the extraembryonic mesoderm
primordial germ cells
What cells arise from the extraembryonic mesoderm
hematopoietic precursors
what are somites
block-like condensations of paraxial mesoderm
Where are somites derived from
paraxial mesoderm
what process do the ventromedial part of somites undergo
epithelial to mesenchymal transition
what does the sclerotome develop into
the vertebrate and ribs
what are the 3 sclerotome layers
dorsal, lateral, ventral
what is the ventral sclerotome
the rudiment of the vertebral body
what is the lateral sclerotome
vertebral transverse process and ribs
what is the dorsal sclerotome
rudiment of the vertebral arch and vertebral spine
what is resegmentation
the caudal segment of each sclerotome fuses with the cranial segment of the slerotome immediately caudal to it to form a vertebra
what is an intrasegmental boundary (von Ebner’s fissure)
intrasegmental boundary dividing the cranial and caudal portions of the sclerotome
How many cervical vertebrate are produced by the resegmentation of 8 cervial somites
7 cervical vertebrates
How many cervical spinal nerves are there, even though there are 7 cervical vertebrate
8 nerves
what is the core of the fibrous intervertebral discs called
nucleus pulposus
what cells form the nucleus pulposus
notochordal cells
what is the periphery of the intervertebral discs called
annulus fibrosus
what cells form the annulus fibrosus
sclerotomal cells
How are myotome cells formed
the ventral part of the dermomyotome will undergo epithelial mesenchymal transition
what do the dorsal cells of the myotome form
the epimere
what do the lateral cells of the myotome form
hypomere
what does the epimere form
epaxial muscles
what is the epimere innervated by
dorsal ramus
what does the hypomere form
hypaxial muscles
what is the hypomere innervated by
ventral ramus
what is the somatic mesoderm
inner lining of the body wall and to parts of the limbs
what is the spanchnic mesoderm
mesothelial covering of visceral organs
what is the cavity between the somatic and spanchnic mesoderm called
coelom
what is a characteristic of prune belly syndrome
abdominal musculature absent or very hypoplastic
what cells are involved in prune belly syndrome
cells of the hypomere
what type of disease is Duchenne muscular dystrophy
x linked recessive
what is the cause of duchenne muscular dystrophy
mutation in the DMD gene for dystrophin
what is the consequence of a mutated DMD gene in those with duchenne muscular dystrophy
a mutation in the DMD gene destroys the ability of dystrophin to anchor actin to the extracellular matrix
what is a medical consequence of duchenne muscular dystrophy
death as a result of cardiac or respiratory failure
when is the periderm normally shed by
month 5
what is the function of the basal layer of the epidermis
replenish the epidermis through stem cells
what is another name for the basal layer of the epidermis
stratum germinativum
what is the immediate layer of the epidermis replaced by in the 5th month
outer stratum corneum, middle stratum granulosum, and inner stratum spinosum
in the transition from the basal to spinous layer, what keratins are switched
keratins from stratum germinativum (krt5, 14) to stratum spinosum (Krt 1,10)
what envelope proteins are produced in the stratum granulosum
loricrin, envoplakin, and involucrin
what enzyme crosslinks envelope proteins to cell membrane in the spinous to granular layer transition
transglutaminase 3
what 2 components aggregate to form tight bundles in the transition from the spinous to granular layer
filaggrin aggregates with the keratin filaments
compare thick skin versus thin skin
thick skin: covers palms of hands and soles of feet, lacks hair follicles, lacks arrector muscles of hairs, lacks sebaceous glands, has sweat glands
thin skin: covers most the rest of the body, contains hair follicles, contains arrector muscles of hairs, contains sebaceous glands, contains sweat glands
what are the embryonic origins of the dermis
Trunk: somatic lateral plate mesoderm and dermomyotome
face and neck: neural crest cells (ectoderm)
how many more blood vessels than needed does the skin of a neonate contain
20 times
why do neonates have more blood vessels than needed in the skin
required for thermoregulation- keep warm
what are melanocytes
specialized cells derived from neural crest cells
when is the density of melanocytes the highest
during the fetal period
what happens to the density of melanocytes after the fetal period until young adulthood
decreases
what are merkel cells
pressure-detecting mechanoreceptors
what do merkel cells arise from
epidermal cells
what are langerhans cells
specialized immune surveillance cells that appear within the epidermis
what happens to the density of langerhans cells with time
increases
what is a characteristic of collodion babies
covered at birth by a thick, taut membrane resembling oiled parchment (collodion) which is subsequently shed
what causes neonatal morbidity in collodion babies
cutaneous infection, aspiration pneumonia, hypernatremic dehydration
what is ichthyosis
a group of cutaneous disorders characterized by increased or aberrant keratinization of the skin resulting in noninflammatory scaling, dryness, and cracks in skin
what inheritance pattern does ichthyosis vulgaris follow
autosomal dominant
what inheritance pattern does lamellar ichthyosis follow
autosomal dominant
what inheritance pattern does epidermolytic hyperkeratosis follow
autosomal dominant
what gene is mutated with ichthyosis vulgaris
gene encoding for filaggrin
what gene is mutated with lamellar ichthyosis
gene encoding transglutaminase 1
what gene is mutated with epidermolytic hyperkeratosis
gene encoding keratin 1 or keratin 10
what inheritance pattern does harlequin fetus follow
autosomal recessive
what gene is mutated in harlequin fetus
ABCA12 gene
what does the ABCA12 gene encode for
adenosine triphosphate binding cassette transporter, which is a lipid transporter in keratinocytes
what are the clinical features of harlequin fetus
most severe form of ichthyosis, many are stillborn or die shortly after birth
what causes Junctional epidermolysis bullosa
mutation in the gene encoding laminin alpha 5 protein
what is laminin alpha 5 protein a component of
hemidesmosomes
what does junctional epidermolysis bullosa lead to
reduced or loss of adhesion of the stratum basale to the basement membrane
what is the main clinical feature of junctional epidermolysis bullosa
widespread bulla (blister) formation where the epidermis is intact but is separated from the underlying dermis
at the end of meiosis 1, two daughter cells are generated. what is their ploidy and n?
haploid, 2n
at the end of meiosis 2, four daughter cells are produced. what is their ploidy and n?
haploid, 1n
