Heart Development - Dr. Brauer Flashcards
Hear conditions make up how much of congenital birth defects
20%
What do Hemangioblasts give rise to what day in development
Become progenitor hematopoietic (RBC+ macrophage) and endothelium precursor (BV) cells
= organize into blood islands and BVs
DAY 17
Hematopoietic progenitor cells day 23
Populate in the liver = make immediate Blood cell needs for body
Definitive Hematopoietic stem cells (HSCs) are made by what
Are made from AGM homogenized endothelial cells (located in dorsal AORTA)
They go to the liver to colonize = make HSCs (can make any hematopoietic cells)
HSCs when made go where
Ones made in the liver by AGM cells ——> BM and Lymph organs
First hematopoietic cells are found where
In the yolk sac day 17 (early RBC and macrophages) from primitive HSCs
2nd place you see the hematopoietic cells
LIVER PRIMORDIA (day 23) The primitive HSCs go to the liver (from yolk sac) to continue making primitive RBCs and macrophages
3rd place you see the hematopoietic cells
the AGM (Aortic Gonadal Mesonephric) DORSAL AORTA makes Hemogenic endothelial cells (day 27-40)
4th place you see the hematopoietic cells
The hemogenic endothelial cells (in AGM) go to the LIVER
Liver makes DEFINITIVE HSCs from these hemogenic endothelial cells (week 5 —> birth)
5th place you see the hematopoietic cells
The Definitive HSCs go from the liver to the BM and Lymph organs (around week 10.5)
Major hematopoietic organ in the adult
BM
Blood vessel formation (intraembryonic vasculogenesis
Day 18
Endothelial precursor cells —> EPC attach with adhesion molecules into blood islands —> forms vasculogenic cords
*making BVs de novo from mesoderm
Blood vessels made by angiogenesis (intussusception)
New BVs made from existing BVs (expanding existing BV)
Intussusception = BV splits in half
Angiomas
Abnormal vasulogenesis of BV and lymphatic capillaries
- Capillary hemangioma (excessive capillaries)
- Cavernous hemangioma (excessive formation of venous sinuses
- Hemangiomas of infancy : this happening in neonates, and then regresses after birth
First Heart Field
the Angiogenic clusters or (EPC, endothelial progenitor cells) = forming a Cardiac Crescent in splanchnic mesoderm
how is the tubular heart made
- the angiogenic clusters become Endocardial tubes + Precardiomyocytes
- the endocardial tubes fuse
- tubular heart formed (Endocardium,Cardiac Jelly, Mesocardium)
Periepicardial Organ
becomes the epicardium around the heart
initial heart formation steps
- A is below V
- heart grows caudally and cranially causing it to loop
- V goes under A (turing counterclockwise)
- sinus horns –> sinus venosus —-> into A
what drives the lengthening of the heart development
secondary heart field
Secondary Heart Field
does not have initial cardiogenic markers
- adds SM to the heart
- DRIVES cardiac looping
Heterotaxia
any asymmetry thats abnormal
- Situs inversus : total reversal of organs (normal physiology)
- Situs ambiguous : partial reversal of some organs (
Visceroatrial heterotaxia
right heart, normal GI
Ventricular inversion
cardiac looping reversed
LV on right ride
sinoatrial growth happens most where
most differential expansion in the left side, causing the SA node to be located more right
The coronary sinus if remanent of the what
Left sinus horn
Right sinus horn incorporates to what
the posterior wall of future RA
Bicuspid Aortic Valve
Aortic semilunar (tricuspid) valve is BICUSPID = regurgitation = LV hypertrophy or valve stenosis
can develop LV hypertrophy later in life
can cause aortic aneurism
inheritable in some cases
Hypoplastic LV
underdeveloped LV + ascending aorta
small not well formed mitral valve + aortic valve
has patent ductus arteriosus + patent foramen ovale
*RV does all the work
*has patent ductus arteriosus + open FO
Left sinus horn becomes the
coronary sinus
sinus venosus opens into
RA in the sinoartrial orifice
crista terminalis
pectinate (rough) and smoothed wall part junction in the RA
inferior of right valvular fold
becomes the valve of IVC
SA node comes from
right sinus horn and right common cardinal vein
AV node comes from
left sinus horn
first step in 4 chambers partitioning of heart
Differential growth : making muscular interventricular septum and muscular atrial septum (not closing all the way)
grows caudal –> cranial * as the heart expands up with differential expansion
Second step in 4 chambers partitioning of heart
Endocardial Cushion Tissue : new CT formed in the AV region
fibrous septa formed by:
1. mesenchymal cells of endocardium (ECT)
what separates the A and V
the AV region (septum fusion)
fusion happens from
cushion cells
Conotruncal ridges
in outflow tract
- Conus Arteriosus : proximal, make sure RV and LV blood are flowing separate
- Truncus Arteriosus : distal, dives to make aorta and pulmonary a (with aorticopulmonary septum)
Septum primum
from A wall (top) to AV septum, has a hole near AV septum (OSTIUM PRIMUM)
- cushing cells close this hole
- new hole (ostium secundum or foramen secundum) forms on superior end of septum
* RA and LA formation
Septum Secundum
septum grows from A wall (top) to AV septum(NOT ALL THE WAY) also (over the foramen secundum)
* the hole formed right above the AV septum = foramen ovale
foramen ovale how it works
the septum primum is the flap over it that only opens to allow blood to move RA –> LA, not the other way around
the hole is formed by the septum secundum
BLOOD GOES : RA —-(foramen ovale, foramen secundum)—-> LA
1st breath of infant causes what
LA BP increases
RV and RA BP decreases
LEFT SIDE has higher P then right side= causing the septum primum into septum secundum = the close the hole
patent foramen ovale
should permanently seal within 3 months
however this is when it doesn’t happen within a year
Probe patency
foramen ovale doesn’t close completely only partially
2 places cushion tissue forms
- AV setpum
- close the septum primum ostium primum
- in the conotruncal endocardial cushion tissue (when it divides the BF) + NCC cushion cells*
Persistent AV Canal
AV septum does not fuse due to failed cushion cells AV valves degenerate = Pulmonary HTN = X exercise = SOB = cardiac congestion (mixing blood) = linked to down syndrome
Atrial Septation
O2 coming into RA BYPASSES pulmonary circuit in embryo (right to body system) DUCTUS ARTERIOSUS (RV --> Descending Aorta)
Ostium Primum Defect
Cushing cells dont form to close the septum primum or (foramen primum) hole
Cyanosis
bluish skin due to low O2 blood saturation
due to mixing of blood, like when the shunt of foramen ovale does not close
also cause : finger clubbing, bluishs nails, lips
Double Outlet RV
both pulmonery A and Aorta connect to RV
this is due to the AV canal or septum not shifting midline to allow the aorta to be in the LV
= cynosis
= murmus, SOB
aortic arches : 1st 2nd 3rd 4th 5th 6th
6th aortic arch = connects to lung
3rd + 4th aortic arch = Systemic circulation to body
the outflow tract formation
- the conotruncal ridges (swellings) spiral 180 degrees around eachother (the tubes)
- they fuse in the midline with the muscular septum (bottom of Vs) and the grow down from AV septum
4 things NCC do
- help with spiraling of the outflow tract
- septation of the outflow tract
- semilunar valves cusps
- ANS nerves
Ventricular septal defect
the ventricular septum (fibrous part) does not fuse with AV septum
CAUSE : LV –> RV pressure flow (Blood flow)
= RV works harder = RV hypertrophy and Pulmonary HTN
= Cynosis and Congestive Heart Failure (can take some months to years to see)
in the embryo, fetus where does blood go from the RV
RV —-> Pulmonary trunk —-Ductus Arteriosus—-> Descending Aorta
*skips pulmonary As and lung
Persistent Truncus Arteriosus
the conotruncal ridges dont form = no separation in the outflow tract of aorta and pulmonary trunk
+ Fibrous ventricular septum doesnt form
= separation happens more distally
= quick pulmonary HTN. cardiac hypertrophy, cyanosis
part of ventricular septum usually is not developing in a septal defect
the fibrous part, not the muscular part
Tetralogy of Fallot
outflow track divides so aorta gets more space and some gets into RV (conotruncal ridge does not from midline and therefore does not meet the muscular part the V septum)
4 hallmarks of Tetralogy of Fallot
*most common defect that presents as cyanosis at birth
- Pulmonary Stenosis : since Pulmonary outflow is so small
- overriding aorta
- Ventricular septal defect (septa does not close)
- RV hypertrophy ( work hard to push blood into small pulmonary a) = cyanosis
2 defects showing cyanosis at birth
- TOF * most common
2. Transposition of Great Vessels/ Pulmonary Valvular Atresia
- Transposition of Great Vessels/ 2. Pulmonary Valvular Atresia
- the conotruncal ridges fuse with septum however dont spiral = aorta to RV and pulmonary a to LV
- the pulmonary semilunar valves dont form and are closed = blood cant get into pulmonary a from RV = RV hypoplasia and foramen ovale stays open*, LV hypertrophy
* patent ductus arteriosus
Aortic Valvular stenosis
Aortic Valvular Atresia
- partial semilunar valve of aorta, doesnt open well (small opening) = LV hypertrophy, try to get blood in to aorta
- X semilunar valve or opening of aorta = LV hypotrophy, RV hypertrophy, does all the work, * Patent ductus arteriosus stays*
Tricuspid Atriesia
X tricuspid valve (between RA and RV), it is closed
= you have blood RA –> LA–> LV–> RV
*patent ductus arteriosus
