Heart development embryo Flashcards
what is used to make blood vessels during vasculogenesis?
mesenchyme
what does vasculogenesis begin and what is it coupled with?
Day 17
hematopoiesis
where does vasculogenesis begin?
mesoderm adjacent to the endoderm of yolk sac wall.
how is the initial vascular network formed?
aggregates of hemangioblastsdifferentiate and give rise to both hematopoietic progenitor cells and endothelial precursor cells(EPCs)
These cells organize to form blood islands that then coalesce, lengthen and interconnect
what structures are visible by the end of week three?
you have a vascularized yolk sac wall, connecting stalk, and chorionic villi.
what are the sites of eventual hematopoiesis?
blood islands of the yolk sac, liver, aortic-gonadal-mesonephric region, lymph organs, and then bone marrow
when do Embryonic hematopoietic cells appear? what do they do?
day 17 and go on to populate and
reside in the developing liver primordia by day 23.
where do hematopoietic stem cells come from?
hemogenic endothelial cells of the dorsal aorta
in the aortic-gonadal-mesonephric (AGM) region
when can stem cells produce both lymphoid and and myeloid lineages?
how do they do it?
about day 30, in the liver
go out to populate lymph organs and bone marrow
how is vasculogenesis in embryos different from people?
blood vessel formation within the embryo is NOT coupled with hematopoiesis, except AGM region
when can you first see blood vessels in embryos? where?
By day 18,
one can begin to see vessel formation in the intraembryonic splanchnopleuric mesoderm
how is blood vessel formation done in embryos?
endothelial precursor cells (EPCs) proliferate and differentiate into endothelial cells that then organize into vasculogenic cords
form angioplastic plexus
how does angioplastic plexus in embryos grow and spread?
(1) continued proliferation of endothelial precursor cells,
(2) angiogenesis, the budding and sprouting of new vessels from existing ones
(3) intussusception(splitting),
(4) the recruitment of new mesodermal cells into walls of existing vessels
other than splanchnic mesoderm, where else can blood vessel development occur in embryos?
paraxial mesoderm
what are angiomas?
abnormal blood vessel and lymphatic growthvia a vasculogenic process, likely stimulated by abnormal levels of angiogenic factors
cavernous hemangiomas.
Excessive growth of venous sinuses
capillary hemangioma
Excessive growth of a small capillary network
Hemangiomas of infancy, what are they? are they important?
benign tumors made of mostly endothelial cells
can lead to clinical complications. However, most regress over the years
what forms the first heart field? where is it in comparison to intraembryonic coelom
formation of EPCsclusters
within a cardiogenic area of intraembryonic splanchnic mesoderm
with the adjacent mesoderm
intraembryonic coelom lies dorsal to this
what happens to first heart field and coelom with anterior/posterior body folding?
what is the consequence of this?
the primary heart field and coelom become folded beneath the embryo
pulling some endoderm inside to form the foregut
limbs of the first heart field now lie ventral the foregutand dorsal the coelom!!
EPCs differentiate into endothelial cells forming two primitive endocardial tubes.!!
what happens to first heart field with lateral folding?
the two forming heart tubes brought together
these heart tubes fuse with mesoderm to form simple tubular heart!
what does simple tubular heart link to? what happens to it as embryo continues to grow?
future pericardial cavity
his heart tube is pulled into the cervical and then the thoracic regions.
cranial ends of the developing dorsal aorta are also dragged ventrally along with the heart thereby forming a loop
FIRST AORTIC ARCH is formed!
how is first aortic arch formed?
cranial ends of the developing dorsal aorta are also dragged ventrally along with the heart thereby forming a loop
. Inflow of blood into the primitive heart is via what vessels?
common cardinal veins, vitelline veins, and umbilical veins.
primary heart tube wall consists of what?
Endocardium: blood vessels
myocardium
cardiac jelly: between the other two
when does the simple tubular heart have its first contraction? heart flow?
Day 22
Day 24
what are the initial parts of the simple heart?
Sinus venosus
Primitive atrium
Atrioventricular (AV) region
Primitive ventricle
Outflow tract
Aortic sac
what does the Sinus venosus do?
made of partially confluent right & left sinus horns
umbilical vein(placental blood–O2enriched),
vitelline vein(blood from gut area–venous blood),
and common cardinal vein
drain into each horn
where is the Primitive atrium?
region between sinus venosus and ventricle
what is the Atrioventricular (AV) region?
region of heart separating theprimitive atrium from primitive ventricle
what is the Outflow tract?
portion between primitive ventricle and aortic sac.
what is the aortic sac?
common confluens of pharyngeal arch blood vessels. These will contribute to the great vessels
what is the Dorsal mesocardium?
suspends the heart tube but eventually ruptures forming the transverse sinus
remnants form the proepicardial organ
what is the Epicardium?
future visceral pericardium
what is the primitive ventricle?
early left ventricle.
Delineated from future right ventricle
by a constriction called theinterventricular sulcus
what is the first major step in cardiac septation? what happens?
Cardiac looping , reverses atrial and ventricular positions as the heart tube lengthen
atrium moves cranially and dorsally
outflow tract initially bends to right, ventrally and inferiorly
primitive ventricle bends left and superior-dorsal to the proximal outflow tract.
what forms future right ventricle?
initial outflow tract
outflow tract forms what two structures?
conus arteriosus at cranial end
truncus arteriosus at distal end
why is second heart field developed?
what does it require?
lengthening of the cardiac tube to allow for cardiac looping
NCC within pharyngeal arches, interaction with pharyngeal arch mesoderm and pharyngeal arch endoderm are required to maintain proliferation
how does Failure of proliferation of splanchnic mesoderm affect looping?
results in several cardiac defects including looping anomalies (discussed below) and
outflow tract defects
what are the two looping anomalies?
Ventricular inversion
Heterotaxia
what is ventricular inversion?
the primitive ventricle folds to the right
and the outflow tract ends up on the left with the outcome being a
right-sided, left ventricle