Embryo 3 Flashcards
What day does the heart first beat?
22
What does splanchnic mesoderm produce?
ALL the HEART
What does angioblastic tissue produce?
blood vessels
Primary Heart Fields: origin, purpose
- formed due to mesoderm migration during gastrulation
- develop into L/R atria, and L ventricle
- established in cranial end of embryo
- aka cardiogenic cord
Secondary Heart Fields: origin, purpose
- formed from pharyngeal arches
- develop into R ventricle, outflow tract, and part of atria (venous pole)
Outflow tract eventually becomes…
aorta and pulmonary trunk
Mesentery
- double layer of splanchnic mesoderm
- provides route for BVs, lymphatics, and nerves to get to/from organs
What happens to the endocardial heart tubes during lateral folding?
they fuse together
What is: endocardium? myocardium? epicardium? What are they all made from?
- internal endothelial lining
- muscular wall
- outer covering of heart (visceral pericardium)
- Splanchnic mesoderm
What forms when the dorsal mesentery degenerates?
transverse pericardial sinus–>separates outflow tract form venous flow
*dorsal mesentery connects the heart to the posterior body wall
What is the path of the NC cells to help form specific heart structures?
- originate in the myelencephalon (medulla) 2. migrate thru pharyngeal arches 3, 4, & 6
- end in the aorticopulmonary septa (separates outflow tract) and trunks arteriorsus
What four things regulate cardiac NC migration/differentiation?
Retinoic acid, Hot genes, Nf-1, and Pax 3
Primitive divisions include…
- Truncus arterioles and bulbus cordis (outflow tract)
- Ventricle and atrium
- Sinus Venosus (embryo veins bring blood to the heart)
What causes formation of the Bulboventricular loop?
- the fast growth of the bulbus cordis and ventricles
- the heart bends on itself
- right folding is normal
What is Dextrocardia?
- heart folding to the left
- if the abdomen is opposite as well, there are no problems (situs inversus)
Septation events start and end
mid 4th week and 8th week
*septation events happen all at the same time
What is the origin of endocardial (AV) cushions? Their purpose?
- mesodermal growth from the dorsal and ventral walls
- invaded in wk 5 by mesenchyme
- they will grow together to form R/L AV canals
Formation remodeling of the AV cushions is dependent on ____
retinoic acid
Anything smooth comes from the…
sinus venosus
What does the right horn of the sinus venosus give rise to?
- Sinus centrum
- Orifices of superior and inferior vena cava veins
- Orifice of coronary sinus
What does the left horn of sinus venosus become?
coronary sinus
What muscular valves are on either side of the sinuatrial orifice? How do they fuse?
- left and right sinuatrial valves
- both fuse cranially with septum spurious
- the right fuses cranially to form the crista terminalis, and caudally to form the valve of coronary sinus, and most of the valve of the inferior VC
Septum primum vs. Septum secundum
- 2 foramen (ostium)
a. Foramen primum: shunt between R/L atrium; disappears when endocardial cushions fuse
b. Foramen secundum: forms before foramen primun disappears; ensures shunting - Overlaps septum primum
a. Foramen ovale
*leads to shunt from R to L atrium
In embryonic life, when does the patent foramen ovale fuse? In fetal life?
Trick question: it does not fuse in either
What is the role of the inter ventricular septum in ventricle septation?
-muscular portion migrates up, but doesn’t make it all the way leaving an inter ventricular foramen
Bulbar ridges are also called…
conotruncal ridges
Aorticopulmonary septum
- NC derived
- divides bulbus cordis and truncus arteriosus into ascending aorta, and pulmonary trunk
- fuses with endocardial cushion
Incorporated bulbus cordis forms…
Right: conus arteriosus (infundibulum)
Left: aortic vestibule
What events lead to the formation of the membranous portion of the inter ventricular septum?
- complete fusion of the right and left bulbar ridges with endocardial cushion results in disappearance of the inter ventricular foramen
- functions to separate L + R ventricles, and L Ventricle from R atrium
Formation of Semilunar Valve
- Begins once the partition of truncus arteriosus is nearly complete
- Between bulbus cordis + truncus arteriousus
- Valve swellings – blood hits the wall
- Erosion to cusps
* AV valves form in the same process
Cyanotic
right to left shunt
Acyanotic
no shunt or left to right shunt
No shunt
anomalies of aortic arches; coarctation of aorta
Patent Ductus Arteriorsus (PDA)
- Acyanotic
- Does not close due to low O2 content, and circulating PGE2 (mediated by COX-2)
- treatment: Cox-2 inhibitors
- Characteristics: continuous murmur; large defects include poor eating, rapid HR…
Persistent Ductus Arteriosus
-high BP blood in aorta goes into pulmonary trunk–> pulmonary HT, which can damage lungs
Atrial Septal Defect (ASD)
- Acyanotic
- a. Ostium secondum: includes patent foramen ovale, very common, due to excessive cell death and resorption of septum primum, or by inadequate development of septum primum
b. Probe patent foramen ovale: common; incomplete adhesion b/t foramen ovale and septum secundum after birth
c. Ostium primum: septum primum doesn’t fuse w/ endocardial cushions; associated with mitral valve cleft
- Hallmark: fixed, split S2
- *Kids with Down Syndrome often have this
Ventricle Septal Defects
- Acyanotic
2. NC problem; no membranous portion because buds didn’t fuse
AV Septal Defects: Complete vs. Partial
- Complete: characterized by primum ASD that is contiguous with a VSD, and a common AV valve
- Partial: characterized by a primum ASD, and a single AV valve annulus with 2 separate valve orifices (anterior leaflet of the mitral valve typically is cleft)
AV Septal Defect
- Acyanotic
- Endocardial cushions do not fuse
- 20% of people with Down Syndrome are affected
“Corrected” Transposition of the Great Vessels
- Acyanotic
2, Improper septation of outflow tract; reverse rotation of heart
Transposition of the Great Vessels
- Cyanotic
- Improper spiraling of NC
- Great vessels from “wrong” ventricles; septal defects; PDA
Double Outlet Right Ventricle
- Cyanotic
- Abnormal migration of bulbar ridges during septation; muscular portion is misaligned
- Great vessels from “right ventricle”; ventricular septal defect in most cases
Truncus Arteriosus
- Cyanotic
- NC - absence of bulbar and truncal ridges to form/migrate to the midline
- Single great vessel; inter ventricular septal defect
Tetralogy of Fallot
- Cyanotic
- Abnormal septation of outflow tract
- Pulmonary stenosis; inter ventricular septal defects; over-riding aorta; right ventricle hypertrophy
*very serious, and very common
Critical =
Cyanotic
Critical Pulmonary Stenosis
- Cyanotic
2. Cusps of pulmonary valves are fused or thickened
Critical Aortic Stenosis
- Cyanotic
2. Tachypnea, poor feeding, poor perfusion, may lead to hypoplastic left heart syndrome
Hypoplastic Left Heart Syndrome
- Cyanotic (no left ventricle)
- Mitral valve stenosis or atresia; left ventricle hypo plastic; aortic valve stenosis or atresia; aortic arch hypoplastic
