Cardiovascular Embryology Flashcards
1
Q
what is the epicardium derives from?
A
(visceral pericardium) is derived from cells of the dorsal mesocardium
1
Q
Describe the early circulatory outflow track:
A
the truncus opens into the aortic sac, from which arise the aortic arches that in turn open into the paired dorsal aortae.
1
Q
How does blood return to the heart from the yolk sac and developing foregut?
A
vitelline veins
2
Q
How does the cardiac tube form the bulboventricular loop?
A
by bending upon itself and to the RIGHT
3
Q
How is blood distributed to the developing gonads?
A
by the lateral segmental arteries
3
Q
what forms the sinus venarum?
A
the sinous venosus incorporated into the definitive right atrium
3
Q
what does the 4th aortic arch give rise to?
A
left: arch of aorta right: proximal part of the right subclavian (distal part of the right subclavian artery is derived from the right dorsal aorta and the right 7th intersegmental artery)
4
Q
what does the muscular interventricular septum arise from? describe its formation
A
dilations of the ventricle on each side form the septum; then the septum grows actively toward (but DOES NOT reach) the fused AV cushions, leaving an interventricular foramen that is then completed by the membranous part of the interventricular septum
4
Q
What is dextrocardia?
A
an anomaly in which the primitive heart tube folds into the left in a mirror image o a normal bulboventricular loop; this usually occurs when all o the organ systems are reversed (situs inversus)
5
Q
What is the primitive heart tube?
A
an endocardial tube
6
Q
what do the vitelline veins represent in the adult?
A
portal and hepatic veins
6
Q
where do the endocardial cushions form? how/what do they form into?
A
on the dorsal and ventral walls of the AV canal; they then approach each other and fuse dividing the single canal into R and L av canals
6
Q
what is the septum primum?
A
sickle shaped; grows from the roof of the atrium towards the endocardial cushions?
6
Q
What does the first aortic arch give rise to?
A
largely disappears; remainder forms the maxillary arteries
6
Q
what does the 3rd aortic arch give rise to?
A
common carotid and part of the internal carotid arteries
7
Q
what does the right and left horns of sinus venous receive blood from?
A
the common cardinal vitelline and umbillical veins
8
Q
what does the second aortic arch give rise to?
A
remnant gives rise to stapedial arteries
8
Q
what occurs as a result of aortic or pulmonary stenosis?
A
left/right ventricular wall (respectively) becomes thickened (hypetrophied), stenosis (narrowing) of the valve restricts flow; these together result in a heart MURMUR; if severe the heart may show evidence of “strain” and the valve may require treatment to open it up
10
Q
what does cardiac jelly separate?
A
myocardium from the heart tube
11
Q
what is cardiac jelly composed of?
A
glycosaminoglycan and matrix proteins
12
Q
what does the sinus venous receive blood from?
A
three pairs of vessels: common cardinal veins, vitelline veins, and umbilical veins
13
Q
Describe fetal circulation:
A
- umbillical vein carries OXYGENATED blood from placenta to fetus 2. blood is shunted through ductus venosus to the IVC through the foramen ovale to the left atrium where it mixes with a small amount of deoxy blood from lungs 3. Blood courses through the left ventricle and into ascending aorta and is distributed to the head, heard, neck and upper limbs 4. rest of blood to aorta to arteries to tissue 5. DEOXY blood returns to heart through SVC to right atrium to right ventricle and pulmonary trunk 6. High pulmonary resistance restricts blood from entering the developing lungs 7. blood goes from pulmonary trunk to ductus arteriosus to the descending aorta to the umbilical ARTERIES to the placenta BARELY ANY BLOOD TO LOWER LIMBS/TRUNK!
14
Q
how do the dorsal aortae form?
A
form in the paraxial mesoderm and unite from behind the heart to the level of lumbar vertebra 4
14
Q
How does the embryonic left atrium expand?
A
by incorporaing the primitive pulmonary vein and its branches
16
What defines the outflow tract?
dorsal aortae
17
what causes cardiac looping?
many factors including: 1. asymmetrical distribution of actin bundles 2. pressure of cardiac jelly 3. cell deformation 4. hemodynamic factors
17
Where do the umbilical arteries arise from? what is their function?
arise from the dorsal aortae; conduct 50% of the cardiac output to the placenta
17
what is foramen ovale?
the opening between the lower edge of septum secundum and the fused AV cushions
18
what does the aortico pulmonary septum divide?
divides the the bulbus cordis and truncus arteriosus into ascending aorta and pulmonary trunk
19
Which veins disappear in embryonic development?
most of the posterior cardinal veins (only part of the RPCV), right and left umbilical veins, and the left vitelline vein
19
What is secundum ASD ? what is it caused by?
it is a defect in fossa ovalis; caused by: 1. excessive resorption of septum primum 2. defective formation of septum secundum
20
what is patency of the ductus arteriosus and ductus venosus in the fetus maintained by?
prostaglandins
21
what does the aorticopulmonary septum fuse with?
the AV cushions (participates in the formation of the membranous interventricular septum)
21
What is transposition of the great vessels? what is caused by?
a condition in which the aorta arises from the RIGHT VENTRICLE and the pulmonary trunk from the LEFT; this is an anomaly due to the failure of the truncoconal swellings to grow in the normal spiral direction; there is also a ventricular septal defect and a patent ductus arteriosus. Not detrimental to life (still allow for oxygenated blood to reach the entire body)
22
What happens to the left umbilical vein?
it disappears, so it shunts 80% of its blood via the ductus venosus to the inferior vena cava; the remained 20% circulates through the liver and returns to the IVC via the hepatic veins
24
How is the newly formed heart tube attached to the pericardial cavity?
via the dorsal mesocardium
25
How do the endocardial tubes form?
splanchnic mesoderm (from the lateral mesoderm layer) in the cardiogenic plate region responds to signals from the underlying endoderm and aggregates into two longitudinal angioblastic cell clusters ventrolateral to the neural plate.
26
what is cardiac jelly?
a layer of acellular matrix that invests the fused endocardial tubes (a derivative of splanchnopleuric mesoderm)
26
what is the most common cause of "blue baby"
tetralogy of Fallot
27
What holds the cardiac tube in place? where?
at the sinus venosus: constrained by septum transversum at the truncus region: by its connection with the aortic arches
28
what does cutting the umbilical cord result in?
an immediate cessation of blood entering the body via the umbilical vein and thus greatly reduces the mouth of blood entering the right atrium; SO the pressure in the right atrium DROPS
29
what does the proximal portion of the bulbus cordis form?
the trabeculated part of the right ventricle
30
What prevents endothelium mesenchyme transformation?
inactivation of transforming growth factor B3
31
what invests the fused endocardial tubes?
splanchnopleuric mesoderm which differentiates into two layers: 1. myocardium (heart muscle) 2. cardiac jelly
32
what are teh four main characteristics of tetralogy of Fallot?
1. pulmonary stenosis 2. ventricular septal defect (VSD) of the membranous portion (the septum is displace too far anteriorly to contribute to the septum) 3. overriding aorta (the aorta staddles the VSD) 4. right ventricular hypertrophy due to the shunting of blood from right to left; (the pressure in the right ventricle is increased due to pulmonary stenosis causing the walls of the right ventricle to expand)
34
what is the trabeculated left ventricle derived from?
the primitive ventricle
34
What is the most vulnerable period of cardiovascular development for a congenital defect?
week 3-7
35
what are 80% of cardiovascular malformations?
1.atrial septal defects 2.ventricular septal defects 3.pulmonary and aortic stenosis 4. fallots tetralogy 5. persistent ductus arteriosus 6. coarctation of the aorta 7. abnormalities of position
36
What is the aortico pulmonary septum derived from?
neural crest mesenchym
37
what induces endothelium to transform into mesenchymal cells that eventually migrate into cardiac jelly?
large proteoglycan particles (adherons) produced by the myocardial cells and accumulates in the endocarial tissue
38
Describe the aortic arch development
first two arches develop between day 22-24; when the first arch regresses, the 3rd and 4th arches appear; when the 6th arch forms, the second arch refresses except for a small remnant which gives rise to the stapedial artery; fifth aortic arch is absent 50% of the embryo's; it regresses completely
40
As the heart tube is remodeling, which direction does the sinus venous shift? When does it stop shifting?
to the right (with the sinatrial orifice) until the sinus venosus communicates with only the right atrium
41
what is a muscular VSD caused by?
excessive cavitation of myocardial tissue during formation of muscular IV septum
43
How is blood distributed to the neural tube?
by dorsal intersegmental branches of the dorsal aortae
45
what is the first asymmetric structure to appear in the embryonic body?
the heart
46
what is tetralogy of Fallot caused by?
results from the conus spetum developing too far anteriorly giving rise to two unequally proportioned vessels-- a large aorta a smaller stenotic pulmonary trunk
47
where do the vitelline arteries bring blood to?
the yolk sac and future gut
47
what doe the overlapping edges of the septa primum form?
fuse to form the limbus of fossa ovalis
48
what is the vale of foramen ovale? how is it present in postnatal life?
it is the persistent part of septum primum, below foramen secundum; in postnatal life it forms the floor of fossa ovalis,
49
what defines the inflow tract?
sinus venous
51
what is foramen primum?
an opening between the lower edge of septum primum and AV cushions that befomes progressively smaller and is obliterated when septum primum fuses with the fused AV cushions
51
How to diagnose coarctation of the aorta
Always suspect in young adults with hypertension; femoral pulses are reduced and delayed; may be able to hear blood flow through epigastric arteries with a stethoscope and observe enlarged intercostal arteries
52
what occurs in coarctation of the aorta?
narrowing of the aorta as hypophasia of arch of the aorta; usually the narrowing is located proximal to the ductus arteriosus; may remain unidentified till early childhood
54
What effect does cephalic folding have on the endocardial tubes? lateral folding?
cephalic folding brings the two endocardial tubes into the thoracic region; lateral folding brings the endocardial tubes close together where they fuse to form a single heart tube
56
what is the endocardium derived from?
the gelatinous CT tissue (cardiac jelly) that separates the myoepicardial mantle from the endothelial heart tube
57
what does the Right Vitelline Vein become? wehre is it located?
located between the liver and sinus venosus, it forms the IVC in this region
57
what is the most commone type of cardiac defect?
ventricular septal defects (VSD)
58
what is the combined effect of the first inspiratory effort and cutting of the umbilical cord?
the pressure in the left atrium is much higher than the pressure in the right atrium; this causes the valve of foramen ovale to be pushed tightly against septum secundum and foramen ovale to be functionally closed
60
what are the functions of cardiac jelly?
1.substrate for cell migration in cardiac septation and valve formation 2.Accumulates to form the endocardial cushions at the atrio-ventricular (AV) junction and in the outflow tract 3. stimulates endothelial cells to migrate into the cushion matrix where they transform into mesenchyme that will form the fibrous basis of the mitral and tricuspid valves
60
What does the terminal portion of the Right Posterior Cardinal Vein persist as?
the azygous vein which enters the SVC
62
Describe the inflow track of the early circulatory system
the sinus venosus receives the paired umbilical, vitelline, and common cardinal veins
63
In coractation of the aorta, how does blood reach the lower parts of the body after the ductus closes?
through collateral pathways 1. scapular anastomosis which connects with intercostal arteries and thus blood flows into the thoracic aorta 2.internal thoracic / superior epigastric/ inferior epigastric/ femoral arteries
65
what is the dorsal mesocardium?
a derivative of the foregut splanchopleuric mesoderm that attaches the heart to the pericardial cavity but eventually it ruptures and leaves the heart tube suspending in the pericardial cavity to form the transverse pericardial sinus
66
How is blood distributed to the somite?
by dorsal intersegmental branches of the dorsal aortae
67
what is aortic or pulmonary stenosis?
the aortic of pulmonary valve is thickened and narrowed leading to the developed of abnormally high pressure in the left or right ventricle
69
what does the dorsal aortae form?
the first arotic arch
70
which tract is connected with the endocardial tubes before folding?
the outflow tract (before folding begins)
71
what does the dorsal mesocardium give rise to?
once it ruptures and leaves the heart suspended in the pericardial cavity; it leaves a space known as the "transverse sinus"
71
what does the right venous valve of the sinoatrial orifice form?
1. crista terminalis 2. valve of the IVC 3. valve of the cornonary sinus
72
what does the myoepicardial mantle form from? what does it become?
formed from the mesenchyme surrounding the endocardial tube; gives rise to the myocardium
73
Describe the order of blood flow in the newly formed heart, just as the endocardial tubes fuse (when it starts to form dilations and constrictions)
From bottom to top: (first thing to last thing blood flows through) 1. Sinus venosus 2. Primitive atria 3. Primitive ventricle 4. Bulbus cordis 5. Truncus arteriosus 6. Aortic sac 7. Dorsal aorta
75
what cells form the definitive mitral and tricuspid valves?
mesenchymal cells
76
What are the vitelline arteries represented as in the adult?
celiac, superior, and inferior mesenteric arteries
78
what are endocardial cushions formed by?
accumulation of cardiac jelly
80
how is blood shunted to the right anterior cardinal vein?
via an anastomosis between the left and right anterior cardinal veins (which drain blood from the brain) note: left anterior cardinal vein disappears below the anastomoses
81
why is the baby's first inspiratory effort significant?
it opens up the pulmonary vascular bed so that blood in the pulmonary trunk enters the lungs; the pressure in the ductus arteriosus drops a ton and it constricts,; this allows the blood leaving the lungs via the pulmonary veins to enter the left atrium and thus the pressure in the left atrium INCREASES a ton
82
where is septum secundum located?
to the right of septum primum and overlaps foramen secundum
83
What occurs in a persistent ductus arteriosus?
(normally functionally closed); failure to close results in blood flow from the aorta to the pulmonary artery normally associated with premature births and rubella;
85
what is the SVC formed by?
a small segment of Right Anterior Cardinal Vein between the junction of the right and left brachiocephalic veins and the right atrium
86
What happens to the right/left horns of the venous sinus as it shifts towards the right atrium? what is the end result of the right/left horns?
the right enlarges and the left horn shrinks; left horn = coronary sinus of the heart right horn = incorporated into right atrium and all blood returning to the heart via IVC SVC and coronary sinus enter the right atrium
87
How does the septum primum adhere to the edge of the septum secundum?
initially by FIBRIN deposits along the line of contact; later on: the fibrin is replaced by fibrous CT over several months
88
What is a persistant trunus arteriosus defect result from?
when the truncoconal swellings fail to grow; the single artery , the truncus arteriosus, arises from both ventricles above the ventricular septal defect allowing pulmonary and systemic blood to mix; distally the single artery is divided into the aorta and pulmonary trunk by an incomplete septum
90
How does blood flow through the atria in a developing embryo?
from the right atrium through foramen ovale and then between the overlapping edges of septum secundum and septum primum into the left atrium BLOOD CAN ONLY FLOW FROM RIGHT TO LEFT ATRIA
91
what is the anastomotic channel formed by?
left brachiocephalic vein and right anterior cardinal vein
93
What is foramen secundum formed by?
genetically programmed cell death that creates perforations in septum primum (before septum primum is obliterated)
95
How is blood distributed to the developing kidneys?
by the lateral segmental arteries
95
what does cavitation of the ventricular walls lead to?
the formation of trabeculae carneae, papillary muscles, and chordae tendinae
96
How does oxygenated blood from the placenta return to the heart?
via the umbilical vein
97
what does the original embryonic left atrium give rise to?
the left auricular appendage
98
what does the bulbus cordis give rise to?
the trabeulated part of the right ventrile (from the proximal bulbis), the conus arteriosus in the right ventricle, and the aortic vestibule in the left ventricle
99
Where do the vitelline arteries arise from?
the dorsal aortae
101
What does probe patency of foramen ovale result from?
incomplete adhesion between overlapping edges of septum primum an septum secondum NOT CLINICALLY SIGNIFICANT
102
what is the membranous part of the IV septum derived from?
AV cushion tissue that fuses with the aorticopulmonary septum and the muscular interventricular septum
103
what is endocardial cushion defect with primum ASD?
incomplete fusion of AV endocardial cushions prevents proper fusion o septum primum with the cushions; thus a foramen primum persists Defects are associated with abnormal mitral valve and often occurs with Down Syndrome
104
what does the sixth aortic arch give rise to?
branches to the lungs; (the full lengths of the arteries proximal to the lungs become the pulmonary arteries) 1. on the right = distal part of 6th arch disappears 2. on the left = persists as the ductus arteriosus and then the ligamentum arteriosum
105
How is the primitive atrium divided into right and left atria?
by the formation of the itneratrial septum
106
what is the aortico pulmonary septum formed by?
fusion of ridges that appear in the bulbus and truncus; the spiral nature of septum results in the "twisting" of the pulmonary trunk with respect to the aorta
108
How effective is the initial heart beating? How does blood enter/leave the heart?
initial heart beating is ineffective; the blood enters via the sinus venosus and leaves via the dorsal aorta
109
what is membranous VSD?
defect in the formaiton of membranous part of IV septum
110
what does the original embryonic right atrium become?
pectinate auricular appendage
111
How does blood return to the heart due to general circulation in the developing embryo?
via anterior an posterior cardinal veins, which join to become the common cardinal vein
112
what is the function of foramen secundum?
it allows blood to continue to flow freely from the right to the left atrium and thus avoid loading of the pulmonary circulation
113
Describe how the conduction system of the heart develops
Nodal tissue develops as modified myocardial cells in the sinus venosus and condenses at the entry of the SVC as the SA node and near the right AV orifice as the AV node; As the AV node is formed the bundle of His appears and sends one branch into the right ventricle and the other into the left ventricle
