Heart Development Flashcards
In what week does the heart form
Wk. 3
In what week does circulation begin
Wk. 4
What is the heart derived from
Splanchnic mesoderm and NC Cells
Heart fields are what in origin
Splanchnic mesoderm
Where do the primary heart fields develop and what do they develop into
Develop from the cranial end mesoderm of the primary streak
Develop into:
LA, RA, LV
Where do secondary heart fields develop from and what do they develop into
Develop from the mesoderm of the pharyngeal arches
Develop into:
RV, outflow tract, and part of the atria
The three layers of the heart are derived from what
Splanchnic mesoderm
What is mesentary
A double layer of splanchnic mesoderm
In utero, the heart is suspended by what?
Dorsal mesoderm which becomes part of the posterior wall
What forms the truncus arteriosus and aorticopulmonary septa
Neural crest cells that originate in the myelechephalan and then migrate through pharyngeal arches 3 - 6
What genes regulate cardiac NC cell migration and differentiation
Hox
Nf - 1
Pax - 3
What do the truncus arteriosus and bulbus cordis do
Fuse together to form the aorta and the pulmonary trunk
Angioblasts are what and are derived from what
Are cardiogenic cords and are derived from splanchnic mesoderm
How do the bulbus cordis and ventricles behave
They separate and move in oposite directions
What is normal heart folding
R folding
How is the atrioventricular canal formed
Endocardial cushions move together and form L and R AV canals which also separate atria from ventricles
What are the endocardial cushions formed from
Mesodermal growth from the dorsal and ventral walls
What can produces AV canal defects
Disruption of retinoid signaling
What does the pectinate muscle come from
Primordial heart tube
What does the cardiac smooth muscle come from
Sinus venosus from the R sinus horn
What does the sinus venosus come from
The R sinus horn
What does the right horn of the sinus venosus give rise to
The sinus venarum - smooth part of the RA
Orifices of superior and inferior vena cave
Orifices of the coronary sinus
What does the left horn of sinus venosus become
The coronary sinus
The R sinuatrial valve of the sinus venosus gives rise to what
Cranial - crista terminalis
Caudal - valve of coronary sinus
What is the sinus venosus
The first chamber that empties into the RA
What does the septum primum and septum secundum meet with
The endocardial cushions
Define the foramen primum
The first shunt of the septum primum
Gone when fused with endocardial cushions
Define the foramen secundum
Second foramen of the septum primum
Formation ensures shunting between LA and RA
Define the foramen ovale
Foramen of the septum secundum
Closes when baby takes its first breaths
What happens in regards to the septums when the baby takes its first few breaths
The septum primum and the septum secundum fuse together, forming the interatrial septum
The foramen ovale also closes
How does the interventricular septum form
Muscular portion extends to meet the endocardial cushions but can’t make it, so membranous part takes over and reaches it
What is the interventricular septum formed from
Splanchinic mesoderm
How does the membranous interventricular septum form
Right and left bulbar ridges fuse, thus creating the membranous part and extending the interventricular septum
Defects in the interventricular septum result from what
A defect in the membranous part
What are the left and right bulbar ridges formed from
NC Cells
Define acyanotic cardiac abnormality
L to R shunt
Define cyanotic cardiac abnormalities
R to L shunt
Ductus arteriosus
Classification:
Why does it occur:
Treatment:
CLinical presentation:
Acyanotic
PDA doesnt close due to PGE2 which is mediated by COX2
Treat with COX - 2 inhibitors
Presents as poor eating, tachycardia, high pressure inlungs - capillary destruction
Define atrial septal defect
Classification:
Why does it occur:
Acyanotic
Occurs due to septums not closing at right time
Define ositum secundum
A patent foramen ovale with a patent foramen secundum (mismatched and do not fuse shut)
Caused by excessive cell death and reabsorption of septum primum
Define ositum primum
Septum primum (foramen primum) does not fuse with endocardial cushion
This is also associated with a mitral valve cleft
Define VSD
Classification:
Why does it occur:
CLinical presentation:
Acyanotic
Membranous part of IVS does not form due to NC Cells
The bulbus ridge did not fuse with the endocardial cushion
Define complete AV septal defect
Primum ASD (ositis primum) that is contiguous with a VSD and a common AV valve
Define partial AV septal defect
Primum ASD (ositis primum) a single AV annulus with 2 separate valve orifieces
What is the embryological basis for AV septal defect and who does it mostly affect
Failure of endocardial cushions to fuse
Mostly affects people with Downs
Define corrected transposition of the great vessels
Embryological basis? Type?
The RA sends blood to the LV and the LA send blood to the RV
The RV then has the aorta and the LV has the PT
Blood flow is correct
Acyanotic
Due to improper rotation of the heart
Define transposition of the great vessels
The great vessels have the wrong ventricles
Cyanotic
Define tet. Of fallot
Features include pulmonary stenosis
IVS defect
Overriding aorta
RV hypertrophy
Oxygenated blood and deoxy blood is mixed and sent to aorta due to no septum and a big, in the way aorta
Why is critical pulmonary stenosis cyanotic
Decreased pulmonary blood flow to lungs
What are the features of critical aortic stenosis
Tachypnea
Poor feeding
Poor perfusion
Hypoplastic Left Heart Syndrome
Cyanotic
Define hypoplastic left heart syndrome
Cyanotic
Has mitral valve stenosis
LV is hypoplastic with a large muscle
Made worse by patent ductus atrial and atrial septal defect
