the heart Flashcards
(17 cards)
from what tissue is the heart derived
the lateral mesoderm of the head
what defines a vertebrate heart
separate and defined chambers for the inflow tract (atrium) and outflow tract (ventricle)
what are the building blocks from which the vascular system forms
the pharyngeal arches are the initial building blocks for vertebrate vasculature. whilst they function in gills in fish, they will form the great blood vessels in mammals and birds
In lung breathers, the most caudal aortic arch will form the pulmonary artery
what is the primary and secondary heart
the primary heart is the initial structure that forms and then pumps blood
the secondary heart arises as cells are added to the heart whilst it is beating
do all bilateral animals have a heart
yes, all bilateral animals have an organ that pumps blood
only vertebrates and molluscs have hearts with chambers (these evolved separately)
how does the initial aminote primary heart precursor tissue form the head mesoderm
heart is derived from the lateral mesoderm
mesoderm splits into the somatopleura (dorsal) and the splanchnopleura (ventral)
the splanchnopleura then folds inwards towards the embryos midline
it will then differentiate into the endocardium and myochardium
the endochardium will develop into the endchardial tubes and the myocardial cells will form a contractile tube around them
these tubes will then fuse together at the ventral midline
what is cardia bifida
when the endocardial tubes don’t fuse together properly resulting in the heart being split on either side of the embryo
in what direction does the initial tube heart loop
the heart starts out as a simple tube, then it becomes asymmetrical and loops to the RIGHT
this forms the atrium and ventricle and the inflow and outflow tubes
where is the secondary heart field located
cells will migrate from tissue surrounding the inflow and outflow tubes and nearby pharyngeal tissue
who discovered the secondary heart field and how
Waldo provided the first evidence for a secondary heart field by injecting micro markers into the mesoderm around the head. These cells were then clearly added to the heart
how do we know cardiac genes are highly conserved
although only vertebrates and molluscs posses chambered hearts, all bilateral animals posses basic pumps to efficiently move blood
what is an example of a cardiac gene that is conserved between species
Nkx2.5 and its drosophila orthodolog Tinman
what does Nkx2.5 (and Tinman) do
cells expressing Nkx2.5 will form cardiogenic cells that contribute to the primary and secondary heart fields
what role does BMP play in Nkx2.5 expression
the only cells that are able to receive uninhibited BMP signals (and no Wnt signals) are lateral head mesoderm
Only these cells can become cariogenic cells
what role does Wnt signalling play in Nkx2.5 expression
Wnt signals prevent Nkx2.5 expression and is only expressed in the caudal end of the embryo due to the inhibitor Crescent
This ensures only rostral cells can form cariogenic cells
what will cells affected by both BMP and Wnt differentiate into
the caudal end of the embryo is exposed to both Wnt and BMP
this will cause cells to differentiate into blood and vasculature precursors as opposed to cardiogenic cells
what role does retinoid acid (VitA) in heart development
retanoic acid specifies the inflow tract (atrium) and suppresses the outflow tract (ventricular side)
only the caudal end of the embryo is under the control of retanoic acid signas
