Embryology (Organogenesis) Flashcards
The key events in cardiac development are:
folding of embryo and heart tube fusion
heart looping
septation and division of outflow tracts.
cardiogenic cells developp where and it what manner
Cardiogenic cells develop in a horseshoe shape outside the embryo.
how is the sinle heart tube formed and when
pair of
heart tubes which fuse to form a single heart tube by 21 days fertilisation;
the tube is able
to pump blood uni-directionally.
what gives rise to the 4-
chambered structure of the normal human heart.
Looping of the heart tube and septation
what are 2 unique features of the heart in development
foramen ovale and ductus arterious
what does forman ovale do
allows blood returning to the heart (relatively high oxygen) to pass form the
RA to the LA, then to LV, then pumped though aorta to the rest of the body.
what does ductus arterious do
conects Main artery
from RV to aorta
(diverts blood that would
normally go to the lungs.)
what happens at birth to these structures
foramen ovale and ductus arteriosus should close, diverting blood to the lungs.
what succesive phases are involved in kidney development
Pronephros= most immature form of kidney
Mesonephros= intermediate phase
Metanephros= most developed, persists as the definitive adult kidney.
when does the metanephros appear
appears by the fifth week.
where do the excretory units develop from
mesonephric mesoderm;
where does collecting duct develop from
ureteric bud.
what else does the uteric bud give rise to
penetrates the metanephric tissue and gives rise to the ureter, renal pelvis, major and minor
calyces and the collecting tubules.
how do the kidneys move through development
initially form near the tail of the embryo but migrate upwards through the developing body to their
final place;
sending out a new and slightly more cranial branch of blood supply.
what is the consequence of kidney movement to vasculature
form new connections with the developing arterial system as they move, so that renal arteries break down and re-form during this process.
describe face developmet
Initially, eyes are on the side of the heads by then move inwards.
The two sides of the face
form separately at either side of the head.
how does facial tissue move to its correct place in development
repeated formation of clefts in the face, and then filling in of the clefts,
leads to sequential loss of tissue from the centre of the face, and the movement of tissues to the correct places.
what are 2 periods of lung development and what time frames do they occur
Saccular period= 26 weeks to birth
alveolar period= 8 months to
childhood
when does surfactant production begin
early in the
third trimester and gradually increases.
what is the clinical significance of surfactant production
essential for normal lung function; reduces the surface tension in
alveoli; produced by type II cells (pneumocytes).
what happens in Respiratory distress syndrome
surfactant levels are low or absent so the alveoli are
unable to function.
RDS declines in incidence as amount of surfactant increases.
give a treatment option for RDS
Artificial
surfactant is a good treatment as it works very quickly.
where do they gonads initally arise from
intermediate mesoderm within the urogenital ridges of the embryo.
where do they geneticl ducts arise from
from paired mesonephric (male) and paramesonephric (female) ducts;
mesonephric ducts give rise to ….. which turns into reproductive tract tissue
wolffian (male) ducts
paramesonephric ducts give rise to ….. which turns into reproductive tract tissue
mullerian (female) ducts
when do gonadal and reproductive tracts begin to change into male/female
Gonads and reproductive tracts are indifferent up to 7 weeks of development
i.e. after 7 weeks
what is gonadal/reproductive tract differentiation dependent on
SRY presence or absence
what are the implications of SRY positive
development
proceeds towards male (7 weeks onwards)
SRY converts gonads to testes… mullerian duct breaks down and the wolffian duct is
integrated into the developing gonad. (MALES).
what are the implications of absence of SRY
gonad develops into and ovary with oogonia and stromal cells.
Wolffian ducts regress
Mullerian ducts persist giving rise to the oviducts, uterus, and upper third of the vagina.
what do leydig cells produce
testosterone
what do sertoli cells produce
anti-
mullerian hormone.
what is significanct about these hormones in female tract development
Mullerian ducts persist as there
is not anti-MH present;
Wolffian ducts regress as there is no testosterone present.
what affect will testosterone and AMH have
cause male development
what gives rise togametes in gem cells
Primordial germ
where do PGC originate and migrate
originate in the
epiblast, but then migrate to the caudal part of the yolk sac.
Once the main caudal
structures of the embryo have developed, the PGC migrate…..
through the hind gut and dorsal
mesentery to the mesonephros and then the developing gonads.
by week 7 embryo has
indifferent reproductive system.
how long does it take for SRY to cause conversion of the
indifferent system to the male tract,
during next 3 weeks.
femaletract development starts later or earlier
later
SRY influences
tract, gonadal and genital pattern
what hormone is a key regulator of male development and what is it under the influence of
Testosterone under influence of hCG
