embryogenesis 5 Flashcards
what are the two classifications of heart growth defects
acyanotic and cyantonic
was is a acyanotic and cyanotic defect?
acyanotic- sufficient oxygen – but other issues
cyanotic - insufficient oxygen provided to peripheral vasculature
give two examples of a cyanotic defomity
Large ventricular septal defects including a syndrome called Tetralogy of Fallot (multiple defects)
Transposition of the outflow vessels (reversal of pulmonary and systemic flows)
give two example of an acyanotic deformity
Aortic stenosis (obstruction of the left ventricular outflow) – frequently detected in large breeds of dogs
Pulmonary stenosis (narrowing of the pulmonary outflow) – most common canine cardiac defect
Ventricular septal defects
Atrial septal defects
from where do the heart cells arise?
the primitive streak, cranial to the hensons node and extended caudally.
what initiates the hearts development?
FGF (fibroblast growth factor) and BMP (bone morphogenic protein)
what is FGF and how odes it relate to the hearts development
FGF (fibroblast growth factor) initiates the hearts development by signaling to specificy a region of mesodermal cells that will develop.
what is BMP and how odes it relate to the hearts development
(bone morphogenic protein) woirks in tandem with FGF, they signify the specifiied mesodermal cells to differentiate into cardiogenic mesodermal cells.
How it the primitive heart formed? (the single tube, unfolded)
Two cell clusters (cardiomyocytes) each beside the primitive line come together to form the heart anlage (primord), single long tube. the cells are formed by BMP and segregated by FGF
describe the process of heart looping
the tube which begins symetricle, the bottom (from the ventricles bend to the right and fold the atrial segment upwards. this form a unshape.
from this they twist so the the atrial segment in behind the aortic sac which has now developed into the pulmonary artey and aorta.
describe the segments of the heart tube (top to bottom)
aortic sac, truncus arteriosus, right venrticle, left ventricle, sinus venousus, atrium and vitelline veins.
once the heart has folded (no further development) what is the next step
cushions develop inside the chambers, which at this point have an open flow around the heart.
what do the cushions formed in the heart after folding seperate?
Endocardial cushion forms to separate left and right ventricles (atrioventricular channels)
Primitive atrium separated by two septa which grow towards the endocardial cushion.
post nataly the child first breath has what effect on the heart?
the sudden pressure change shuts closed the Left and right atrium (foreman ovale) as well as the ductus arterious opening.
what is the diffrence betwen vasculogenesis and angiogenesis
Vasculogensis: generation of the blood vessels
Angiogenesis: continued extension and pruning of vessels continues pot-natally
what are the two types of vaculogenesis
Extraembryonic and intraembryonic
describe extraembryonic vasculogenesis.
Formation of blood island in the yolk sac, providing the early embryo with primitive red blood cell types
In birds - vitelline veins
Mammals - umbilical cord
Process:
mesenchymall cells condense and form pritive blood and primitive endothelial cells.
describe intraembryonic vasculogenesis.
Arise from angioblasts in mesoderm surrounding individual developing organs.
Networks develop individually and are joined to the central system later
Formation of the aortic arches beginning with 6 looped vessels, these then turn into the single aortic arch.
why is intraembryonic vasculogenesis needed when we have extraembryonic and the placenta
prepares for birth but also these developing organs have high demand during growth and as such the surronding vascular region aid it.
what are Hemangioblasts and describe their location
precursors of the blood vessels and cells. They are within the primitive streak and arise from the lateral plate of the mesoderm.
describe ECMs role in vascular growth
the extracellular matrix is rather strong and is needed to become softer for the vessels to develop.
what is VEGF and its roll in vascular growth and development
(vascular endothelial growth factor) loosens the ECM and allows for the vessels to grow and move through, into the tissues
what is TGF- Beta and its roll in vascular growth and development
(transforming growth factor) - this stabilses the ECM post development of the vessels
what is PDGF and its roll in vascular growth and development
recruits pericytes to the capillary wall. pericytes wrap around the vessel are are cruical for support, maintentence and regulation.
