Development of the Heart Flashcards
when does vasculogenesis and hematopoiesis begin?
day 17
where does vasculogenesis and hematopoiesis begin?
in the mesoderm adjacent to the endoderm of the yolk sac- the extraembryonic mesoderm
what is the first step in the process of vasculogenesis and hematopoiesis?
aggregates of hemangioblasts differentiate and give rise to both hematopoietic progenitor cells and endothelial precursor cells (EPCs)
what do the primitive hematopoietic precursor cells differentiate into?
early embryonic erythrocytes, macrophages, and megakaryocytes
where do the early hematopoietic cells populate by day 23 and what is their function?
they populate the developing liver; they primarily function to meet the immediate need for blood cells
what are the definitive hematopoietic stem cells programmed from?
hemogenic endothelial cells of the dorsal aorta in the aortic-gonadal-mesonephric (AGM) region
when do AGM hemogenic endothelial cells appear and when do they seed the liver? and when do they disappear?
first appear: day 27
seed the liver: day 30
disappear: day 40
where are the sites of eventual hematopoiesis?
yolk sac mesoderm, liver primordium, AGM region, liver, lymph organs, and bone marrow
when and where does production of definitive HSCs begin?
~week 5 and continues until birth; occurs in the liver
what is the difference between vasculogenesis and angiogenesis?
vasculogenesis is making new blood vessels de novo; angiogenesis is making new blood vessels when you already have a blood vessel
what is intussusception?
splitting of blood vessels to make more
what are angiomas caused by?
abnormal blood vessel and lymphatic growth via vasculogenesis likely stimulated by abnormal levels of vasculogenic factors
what is a capillary hemangioma?
excessive formation of capillaries
what is a cavernous hemangioma?
excessive formation of venous sinuses
what are hemangiomas of infancy?
benign tumors made of mostly endothelial cells
what are the first signs of the development of the first heart field?
first signs seen with the formation of EPC clusters that are arranged in a horseshoe shape within a cardiogenic area of intraembryonic splanchnic mesoderm
where do the definitive HSCs eventually populate?
the lymph organs and bone marrow
when does hematopoesis of the yolk sac mesoderm begin? and when is it finished?
starts day 17; finished by day 60
when is the liver primordia colonized by primitive HSCs?
day 23
when do the definitive HSCs seed lymph organs and bone marrow?
begins around week 10.5; bone marrow becomes eventual major hematopoietic organ
inside the embryo we have vasculogenesis. What is this coupled with?
nothing (it is not coupled with any hematopoetic stem cells)
when does intraembryonic vasculogenesis begin?
day 18
the EPCs + the adjacent mesoderm (aka the intraembryonic splanchnic mesoderm) form what?
the first heart field (or cardiac crescent)
what occurs to the primary heart field as the anterior/posterior body folding occurs?
the primary heart field and coelom become folded beneath the embryo- pulling some endoderm inside to form the foregut
what do the EPCs of the first heart field differentiate into? and what does this form?
they will differentiate into endothelial cells forming two primitive endocardial tubes
what occurs due to lateral folding?
the two forming heart tubes will fuse midline and together with the adjacent cardiogenic mesoderm, they form a simple tubular heart
what is the heart tube suspended by initially?
the dorsal mesocardium
when the dorsal mesocardium ruptures, what is created that can still be seen in the adult?
the transverse sinus
inflow of blood into the primitive heart is from 3 pairs of vessels. What are they?
the common cardinal veins, the vitelline veins, and the umbilical veins
what does the primary heart tube consist of?
endocardium, myocardium, and the cardiac jelly
what is the endocardium?
it is the inner epithelium that is continuous with the blood vessels
there are remnants of the ruptured dorsal mesocardium that remain caudally. What do they form?
proepicardial organ
what is the significance of the proepicardial organ?
they are going to be the progenitor cells for the epicardium (they will eventually migrate over the surface of the myocardium forming the epicardium)
What is the first major step required for cardiac septation?
cardiac looping
what do the three pairs of vessels- common cardinal veins, vitelline veins, and umbilical veins collectively form?
the left and right sinus horns
what does the combination of the sinus horns form?
the sinus venosus
before cardiac looping, what does the sinus venosus drain into?
the primitive atrium
What drives the cardiac looping?
we are adding new muscle tissue to the anchored outflow and in flow ends
What is the final result of cardiac looping?
the atrium will move cranially and dorsally and the primitive ventricle will be pushed inferiorly
Cardiac looping requires and is driven by the lengthening of the cardiac tube at both ends; how is this accomplished/ what is driving this lengthening process?
by the development of the second heart field that forms at both ends of the rupturing dorsal mesocardium
how do NCCs contribute to heart development?
they are required for maintaining cardiogenic mesoderm proliferation and proper myocardial cell specification within the second heart field- if NCCs are not present you could shorten cardiac looping
normally, lengthening of the heart causes the primitive ventricle to?
move to the left
what is ventricular inversion?
anomaly-reverse cardiac lopping that results in a right-sided left ventricle; the primitive ventricle folds to the right and the outflow tract ends up on the left
what is heterotaxia and what are the different forms?
heterotaxia is any symmetry anomaly; there is situs inversus or situs ambiguous
what is situs inversus?
total reversal anomaly
what is situs ambiguous?
partial reversal anomaly