embryology Flashcards
how are sperm formed?
by spermatogonia which undergo spermatogenesis to form 4 sperm
how are ova formed?
by oogoinua which undergo oogenesis to form 1 ovum and 3 polar bodies which degenerate
what happens in week 1 embryonic phase?
zygote is formed and divides to form a blastocyte which moves through the uterine tube to reach the uterine cavity
what is a morula?
solid ball of cells formed from the zygote
why are mitochondrial diseases inherited from the mother?
because the zygote inherits all of cytoplasm organelles from the mother
how is a blastocyst formed and what is it composed from?
as morula cells increase a blastocytic cavity forms to aid nutrition, cells accumulate at one end to form an inner cell mass, the outer lining is called a trophoblast
what do trophoblastic cells form?
the placenta
what are uterine tubes lined with?
ciliated epithelium
what happens during the week 2 embryonic phase?
- implantation occurs in uterine endometrial layer and placenta starts to develop
- cells form bilaminal disc
- sacs, membranes and cord form to aid nourishment
what is a chorion?
formed from the trophoblast, it develops chorionic vili, forms part of the placenta and secrete HCG (human chorionic gonadotropin) which is used to detect pregnancy
at what point does the blastocysts begin to burrow into the endometrium?
7 days
what is the endometrium called after implantation ?
decidua basali
what does the bilaminar disc consist of?
epiblast and hypoblast
what are the two cavities formed by the bilaminar disc called?
amniotic cavity at the top and yolk sac at the bottom
what is the chorionic cavity?
contains fluid in which the embryo floats, surrounded by the chorion
what’s the allantoic cavity ?
gets rid of waste products
what’s are the roles of the placenta?
foetal nutrition, transport of waste & gas and immunity
describe the two sides of the placenta
foetal facing side- smooth with foetal blood vessels and end of umbilical cord
maternal facing side- residual basalis or endometrium, rough ad with maternal blood vessels
what is gastrulation and neurulation ?
gastrulation- formation of germ layers
neurulation- formation of neural tube
what is the primitive streak?
formed in the midline of the epiblast by the dipping of cells known as invagination
why is the primitive streak important ?
because once it forms the axis of the embryo is also formed
what happens to the bilaminar disc in order to reduce the 3 germ layers ?
it becomes the trilaminar disc
what are the 3 germ layers formed?
ectoderm
mesoderm
endoderm
whats the functions of the notochrome?
induces ectodermal cells in the midline to form the neural tube and it also secretes proteins
describe the process of the formation of the notochord
cells from the primitive streak sink down to form the notochord between the endoderm and the mesoderm
describe the process of neurulation
neural plate at the ectoderm thickens and sinks down to form a neural tube between the ectoderm and mesoderm
what induces the mesoderm to thicken?
neural tube
what are the three parts of the separated mesoderm ?
paraxial mesoderm, intermediate plate mesoderm and lateral plate mesoderm
what happens to the later plate mesoderm?
splits into two leaves with a cavity in between
what happens to the paraxial plate?
it forms a somite which divides into the dermatome(forms skin), myotome(forms muscles) and sclerotome(forms bone)
what systems does the ectoderm form?
epidermis of skin, brain and spinal cord
what systems does the intermediate plat mesoderm form?
kidneys and reproductive
what systems does the endoderm form?
gut and respiratory
what systems does the lateral plate mesoderm form?
pleura, peritoneum and the body cavities
what are teratogens?
environmental factors that cause abnormal development
what are the 3 factors that increase the risk of teratogenesis?
exposure during critical stages of development
dosage of drugs/chemicals
genetic constitution of embryo
what does the respiratory system form from?
ventral wall of foregut part of the primitive gut tube
where does the gut tube form from?
endoderm
what is the oesophageal septum?
develops between oesophagus and trachea and separates them
what happens if the trachea and oesophagus don’t split?
fistula or atresia can form
what are fistulas and artesias?
fistula- abnormal passage between 2 epithelialised tubes
atresia- orifice or passage in the body is closed or absent
what the visceral pleura formed from?
splanchnic mesoderm
what is the parietal pleura formed from?
somatic mesoderm
how do pleural cavities get closed off from the heart?
the pleuropericardial fold separates the pleural cavity and pericardial cavity
what are the foetal period stages involved in the production of alveoli?
pseudoglandular stage- development of lung structure, no gas exchange
canalicular stage- formation of respiratory part and type 1&2 cells, no gas exchange
saccular stage- formation of alveolar sacs, gas exchange begins
describe the postnatal stage involved in the production of alveoli?
alveolar stage- proliferation of alveoli from alveoli sacs
what happens during neonatal distress syndrome?
surfactant deficiency
partial alveoli collapse
hyaline debris accumulates
what happens during lung agenesis?
failure of lung bud to develop/branch
insufficient mesoderm
What closes off the pleural cavities from the peritoneal cavity of the abdomen?
the diaphragm
