Heart Development Flashcards
1
Q
Define vasculogenesis
A
-de novo creation of blood vessels directly from mesenchyme
2
Q
When does extraembryonic vasculogenesis begin?
A
around day 17
3
Q
True or False: extraembryonic vasculogenesis is coupled with hematopoeisis
A
True
4
Q
What are hemangioblasts?
A
progenitor cells of extraembryonic vasculogenesis that can give rise to the hematopoietic lineage or to endothelial cells
5
Q
True of False: intraembryonic vasculogenesis is couple with hematopoeisis
A
False
6
Q
When does intraembryonic vasculogenesis begin?
A
around day 18
7
Q
What are angioblasts?
A
a subset of cells in the intraembryonic splanchnic mesoderm that differentiate directly into endothelial precursor cells
8
Q
Define angiogenesis
A
budding or sprouting of new vessels from existing ones
9
Q
Define intussusception
A
splitting a blood vessels in half to make two vessels
10
Q
How does angiogenesis happen?
A
- tip cells “invade”
- stalk cells follow
- endothelial cells proliferate and migrate
11
Q
Where do embryonic hematopoietic stem cells reside and by what day of development do they reach there?
A
in the primordial liver
by Day 23
12
Q
What types of cells can embryonic hematopoietic stem cells become?
A
erythrocytes, macrophages, and megakaryocytes
13
Q
What are definitive hematopoietic stem cells?
A
cells that can create the full range of myeloid and lymphoid lineages
14
Q
What specialized cells come out of the AGM (aortic-gonadal-mesonephric) region of the dorsal aorta?
A
hemogenic endothelial cells
15
Q
From the AGM, where do hemogenic endothelial cells go?
A
they seed the liver by day 30
16
Q
What do the hemogenic endothelial cells do when they get to the liver?
A
cell-cell interactions with embryonic hematopoietic stem cells
give the stem cells the full capacity to generate both myeloid and lymphoid lineages
17
Q
Where do the definitive hematopoietic stem cells go after their transformation in the liver
A
lymph organs
bone marrow
18
Q
What are the mechanisms by which the vascular plexus expands?
A
sprouting
intussusception
cont’d proliferation of EPC’s
recruitment of new mesoderm into the walls of existing vessels
19
Q
Pathology: Angiomas
A
-abnormal blood vessel and lymphatic capillary growth via vasculogenesis
20
Q
What is the likely cause of angiomas?
A
abnormal levels of angiogenic factors
21
Q
What are the two types of angiomas?
A
Capillary Angioma = excessive growth of a small capillary network
Cavernous Angioma = excessive growth of venous sinuses
22
Q
Pathology: Hemangiomas of Infancy
A
- benign tumors made mostly of endothelial cells
- most regress on their own
-depending on site or degree, can lead to clinical complications
23
Q
What germ layer gives rise to early cardiogenic precursors?
A
intraembryonic splanchnic mesoderm
has neural crest contributions
24
Q
What do neural crest cells do in the development of the heart?
A
- regulate the activity of the 2nd heart field
- play a role in the separation of the outflow tracts into pulmonary A. and aorta (cushion tissue derived from neural crest cells)
25
What are some roles of endoderm during heart development?
- signals the development of early blood vessels
| - signals the formation of early endocardium from splanchnic mesoderm
26
What is the role of endoderm in regards to cardiac looping?
-signaling continual proliferation of splanchnic mesoderm (second heart field) necessary for driving cardiac looping
27
Delineate the process of forming a single cardiac tube from two primitive heart tubes.
- sides of embryo move toward midline and ventrally
- endocardial tubes are brought together and fuse
- adjacent cardiogenic mesoderm is incorporated
- tube sinks into the pericardial cavity
28
List the layers of the heart tube from superficial to deep.
- myocardium
- cardiac jelly
- endocardium
29
What is myocardium?
mesoderm adjacent to the endocardial tubes
30
What is cardiac jelly?
concentration of ECM b/w endocardium and myocardium
31
What is endocardium?
inner epithelium continuous with blood vessels
32
Delineate the formation of endocardium.
mesodermal precursors
specialization of endothelial cells
endocardium
33
From what germ layer is endocardium derived?
intraembryonic splanchnic mesoderm
34
What is the first heart field (cardiac crescent)?
formation of endothelial precursor cells in clusters, plus the adjacent mesoderm
-in a horseshoe shape within a cardiogenic area of intraembryonic splanchnic mesoderm
35
How is the second heart field formed?
as lateral body folding occurs, the location of the second heart field is pulled farther away from the notochord and neural tube; w/o the inhibition from the notochord, the splanchnic mesoderm cells can proliferate at the cranial and caudal ends of the tube
36
What does the proliferation of the cranial and caudal ends of the heart tube induce?
cardiac looping
37
What does the left sinus horn become?
coronary sinus
38
What does the sinus venosus become?
sinoatrial junction
| sinus venarum
39
What does the right sinus horn become?
superior vena cava
inferior vena cava
--from the right vitelline vein
40
What forms the SA node?
cells in the R cardinal vein that serve as a pacemaker in the early heart stages
41
Pathology: Heterotaxia
-any abnormal development of L-R organs
42
Pathology: situs inversus
- a type of heterotaxia
- complete reverse symmetry of heart and GI
- not fatal
- may be asymptomatic
43
Pathology: situs ambiguous
- a type of heterotaxia
- reversal of only some L-R organs
- causes problems with inflow and outflow tracts
- life threatening
ex: visceroatrial heterotaxia
44
Pathology: Ventricular Inversion
- primitive ventricle folds to the R
- outflow tract ends up on the L
- -R-sided left ventricle
45
What structure brings oxygenated blood back into the primitive heart?
umbilical vein
46
What is the first structure to develop that allows blood to bypass the pulmonary circuit?
foramen primum
- low in the septum primum
- -b/w the two atria
47
What is the second structure to develop that allows blood to bypass the pulmonary circuit?
foramen secundum
| -high up in the septum primum
48
What is the third structure to develop that allows blood to bypass the pulmonary circuit?
foramen ovalis
| -in the septum secundum
49
Delineate how most blood flows from R to L in a fetal heart
- enters R atrium
- through foramen ovalis
- between septum secundum and septum primum
- -displaces septum primum
- flows through foramen secundum into L atrium
50
Delineate a minor way that blood flows from R to L in a fetal heart.
- some blood goes into R ventricle so that it gets worked
- most shunted b/w pulmonary trunk and aorta
- -ductus arteriosus
51
How is the transverse sinus formed?
-the heart tube remains attached to the rest of the splanchnic mesoderm by the dorsal mesocardium
- dorsal mesocardium ruptures and allows looping
- makes a space separating inflow from outflow
52
How is the atrioventricular canal partitioned?
- myocardium signals some of the endocardial cells to delaminate (endothelium to mesenchyme)
- mesenchymal cells migrate to fill in the ECM and the two sides fuse
53
What changes in atrial blood flow occur at birth?
- pressure in R atria and R ventricle decrease
- -d/t ease of R ventricle pumping blood to lungs
- blood flow from lungs into L atria increases pressure
- pressure is always greater on L than R
54
How are the foramina between the atria functionally closed at birth?
-b/c the pressure in the L side of the heart is greater than the R side, septum primum is driven up against septum secundum, resulting in a "closed" septum
55
What are the germ layer(s) that contribute to the septation between the atria and ventricles?
-intraembryonic splanchnic mesoderm
56
What are the germ layer(s) that contribute to the septation of the outflow tract?
- intraembryonic splanchnic mesoderm
| - neural crest (endoderm-derived)
57
What are the two parts of the ventricular septum?
- muscular (from the ventricle wall)
| - fibrous (from the AV cushion tissue and proximal conotruncal ridges)
58
How is the outflow tract partitioned?
- conotruncal ridges form on R and L sides
| - as ridges approach the ventricle, they come off at different angles and spiral downward
59
Pathology: Persistent AV Canal
- failure of AV septum fusion; abnormal or missing valve
- normally accompanied by ASD's and VSD's b/c the cushion tissue from the AV septum normally contributes to the fibrous portion of the septa
60
What are the symptoms of a Persistent AV Canal?
```
pulmonary HTN
intolerance to exercise
shortness of breath
cardiac congestion
increased risk of endocarditis
```
61
Having a Persistent AV Canal is linked with what condition?
Down's Syndrome
62
Pathology: Double Outlet Right Ventricle
- both aorta and pulmonary trunk exit R ventricle
| - VSD accompanies b/c the malalignment causes agenesis of the fibrous portion of the septum
63
What is the embryological cause of Double Outlet Right Ventricle?
-insufficient shifting of the AV septum
or
-problem with cardiac looping
64
What are the symptoms of Double Outlet Right Ventricle?
- cyanosis
- breathlessness
- murmur
- poor weight gain (later on)
- occur within days of birth
65
Which type of congenital heart defects are the most common?
VSD's
66
Pathology: Persistent Truncus Arteriosus
- undivided truncus overriding both ventricles
- causes mixing of oxygenated and deoxygenated blood
-causes a VSD b/c the fibrous portion of the septum would've normally come from the ridges
67
What is the embryological cause of Persistent Truncus Arteriosus?
-failure of conotruncal ridge formation or fusion
68
What are the symptoms of Persistent Truncus Arteriosus?
- low degree of cyanosis
- pulmonary congestion
-R ventricle hypertrophy d/t increased R ventricular pressure
69
Pathology: Tetralogy of Fallot
- unequal division of pulmonary trunk and aorta
- pulmonary infundibular stenosis
- overriding aorta
- causes a VSD (missing fibrous portion)
70
What are the symptoms of Tetralogy of Fallot?
- fetal R ventricle hypertrophy
- -increased R ventricle pressure causes the hypertrophy; R pressure eventually exceeds L pressure, so you get R to L shunting at birth = cyanosis of the newborn (most common cause)
71
What is the embryological cause of Tetralogy of Fallot?
-conotruncal ridges form off-center
72
Pathology: Transposition of the Great Vessels
- pulmonary trunk connects to the L ventricle
- aorta connects to the R ventricle
-survival (life expectancy approx 3 yrs) is only possible d/t existing shunts (ex: VSD, ASD, ductus arteriosus)
73
What is the embryological cause of Transposition of the Great Vessels?
-failure of the conotruncal ridges to spiral
74
Pathology: Pulmonary Valvular Atresia
- pulmonary valves are fused
| - -hypoplastic R ventricle
75
In a patient with Pulmonary Valvular Atresia, how does blood get from the R side to the L side?
-patent foramen ovalis
76
In a patient with Pulmonary Valvular Atresia, how does blood get into the lungs?
-by going into the aorta and through the ductus arteriosus
77
Pathology: Aortic Valvular Stenosis
- leads to L ventricle hypertrophy
- eventual cardiac failure
- pulmonary HTN
- congenital, d/t infection, or degenerative
- 4:1 male:female ratio
78
Pathology: Aortic Valvular Atresia
-leads to hypoplastic L ventricle
79
What happens in a fetal heart with Aortic Valvular Atresia?
- R ventricle hypertrophy
- wide ductus arteriosus forms during fetal stage as the only way to get oxygenated blood from the placenta into systemic circulation
80
What are the abnormal features of blood flow in the heart (after birth) in a patient with Aortic Valvular Atresia?
-oxygenated blood flows back into R atrium through an ASD since it can't be ejected via the aortic valve; then it gets into systemic circulation via the pulmonary trunk and a patent ductus ateriosus
81
Pathology: Tricuspid Atresia
- no R atrioventricular orifice
- patent foramen ovalis and ductus arteriosus
- VSD
- hypoplastic R ventricle
- hyperplastic L ventricle
82
How does blood flow in a patient with tricuspid atresia?
- from R atrium to L atrium through foramen ovalis
- from L ventricle into both outflow vessels via VSD
- -d/t location of pulmonary trunk, not much blood enters from L ventricle, and instead get to lungs via ductus arteriorsus after entering the aorta
83
Pathology: Bicuspid Aortic Valve
- initially asymptomatic
- results in regurgitation and valvular stenosis
- eventual L ventricle hypertrophy
- often associated with aortic aneurysm
84
What is the embryological cause of a Bicuspid Aortic Valve?
-three leaflets form, but two fuse
85
Pathology: Hypoplastic Left Ventricle
- small/unformed bicuspid and aortic valves
- underdeveloped ascending aorta
- heart works as a univentricular heart (R side)
- high mortality
86
How does blood flow if a patient has a hypoplastic left ventricle?
- oxygenated blood flows back into R atrium via ASD or patent foramen ovalis
- blood (mixed) can flow into systemic circulation via patent ductus arteriosus
