Lect. 3: Cardiovascular System Flashcards
1
Q
When does organogenesis occur?
A
middle of 3rd week until 8th week
2
Q
Which 2 organ systems develop first?
A
nervous system and cardiovascular system
3
Q
What are the 3 divisions of mesoderm after gastrulation?
A
medial (paraxial), lateral (lateral plate), and intermediate (central) region
4
Q
What is paraxial mesoderm also called?
A
somites
5
Q
What does intermediate mesoderm become?
A
urogenital system
6
Q
What two divisions form from lateral plate mesoderm?
A
splanchnic and somatic divisions
7
Q
What forms the CV system?
A
primarily splanchnic mesoderm of lateral plate mesoderm
8
Q
What primarily supports embryo before development of the CV system in the 3rd week?
A
diffusion of nutrients and oxygen from lacunar blood vessels and glands from mother’s uterine wall to embryo
9
Q
Describe how the CV system begins its development during gastrulation.
A
during gastrulation, some of the epiblast forms mesoderm and this cardiogenic mesoderm runs toward cranial end under the epiblast and concentrates at most cranial end of the disc.
10
Q
Where does the heart actually begin to develop?
A
heart develops cranial to oral region and the neural tube
11
Q
Describe the action of the cardiogenic mesoderm. What does it form?
A
cardiogenic mesoderm invades into splanchnic mesoderm and condenses to form 2 primary tubes (paired primordia of heart tubes)
12
Q
What is the relative shape of the developing embryo at the end of week 3?
A
still a flat disk, body folding starts at the start of week 4
13
Q
What are the 2 main body foldings that start in week 4?
A
1) head to tail folding
2) lateral body folding
14
Q
How does the paired primordia of heart tubes form a single tube?
A
during the fourth week body foldings, the paired heart tubes fuse from cranial to caudal forming a single heart tube, but caudal end stays unfused
15
Q
What does the unfused caudal end of the heart tube form?
A
right and left horn of sinus venosus
16
Q
When does the heart tube become contractable?
A
by 4th week
17
Q
Describe the flow of blood through the developing heart?
A
in through caudal end and out through cranial end
18
Q
What are the consequences of head to tail folding for the CV system?
A
cardiac structure pulled ventrally into chest region to lies in chest cavity
19
Q
What is significant about the movement of the heart from a cranial region to a thoracic region?
A
explains why sympathetic innervation is via cervical cardiac nerves and direct thoracic cardiac nerves (pulls its innervation with it)
20
Q
Where is the heart located in the 4th week?
A
the chest cavity
21
Q
What two portions of the developing heart form the veins and atrial chambers? What are their relative positions at 4th week?
A
atrium and sinus venosus (these are most caudal at 4th week)
22
Q
What 3 portions of the developing heart for the ventricles and vascular outflow (aorta and pulmonary)? What are their relative positions at 4th week?
A
truncus arteriosus, bulbus cordis, and ventricle (more cranial at 4th week)
23
Q
What is the normal direction of the s-shaped folding of the heart?
A
to the right
24
Q
Describe the movement of the primitive ventricle during cardiac looping?
A
ventrally, inferiorly, and to the right
25
Describe the movement of the artial and sinus venosus regions during cardiac looping?
move dorsally, upward and to the left
26
By the end of the 4th week, are the atria or ventricles in a dorsal position?
atria are dorsal/superior and ventricles are ventral
27
What adult structure is derived from the truncus arteriosus (neural crest)?
1) aorta
2) pulmonary trunk
3) semilunar valves
28
What adult structure is derived from the bulbus cordis?
1) smooth part of right ventricle (conus arteriosus)
| 2) smooth part of left ventricle (aortic vestibule)
29
What adult structure is derived from the primitive ventricle?
1) trabeculated part of the right ventricle
| 2) trabeculated part of the left ventricle
30
What adult structure is derived from the primitive atrium?
1) trabeculated part of the right atrium (pectinate muscles)
| 2) trabeculated part of the left atrium (pectinate muscles
31
What adult structure is derived from the sinus venosus? What is different about this?
1) RIGHT- smooth part of right atrium (sinus venarum)- MAJOR PORTION OF RA
2) Left- coronary sinus and oblique vein of left atrium
*only embryonic dilation that does NOT have to septate (already septated)
32
What are the 3 main contributions of the neural crest cells to CV development?
1) truncus arteriosus
2) endocardial cushion
3) parts of aortic arches
33
Name the 3 shunts involved in fetal circulation.
1) ductus arteriosus
2) foramen ovale
3) ductus venosus
34
What is the role of the ductus venosus?
shunts blood from umbilical vein to IVC, bypassing the liver
35
What is the role of the foramen ovale?
shunts blood from the right to the left atrium, bypassing the lungs
36
What is the role of the ductus arteriosus?
shunts blood from the pulmonary trunk (comes from the blood that gets into the right ventricle) to the aorta
37
What is weird about blood coming from the SVC and IVC in the fetal heart?
Blood from the SVC and IVC never really mix.
- Blood from the IVC goes to the left atrium via the foramen ovale.
- Blood from the SVC goes to the right ventricle.
38
What is significant about the placement of the ductus arteriosus?
because the ductus arteriosus (with more deoxygenated blood from the SVC) is connected to the aortic arch at a position DISTAL to the brachiocephalic trunk and left common carotid and left subclavian arteries, the most highly oxygenated blood (from the umbilical vein via IVC) is being delivered directly to the brain.
39
Describe fetal circulation.
1) Blood enters via umbilical vein
2) Blood goes through ductus venosus and into IVC
3) Blood passes from IVC into right atrium
4) blood passes directly through foramen ovale and into the left atrium.
5) blood goes into ascending arch of aorta to distribute to brain.
6) deoxygenated blood from brain returns to RA via SVC
7) blood from SVC goes to RV and into pulmonary trunk
8) blood shunted to descending arch of aorta via ductus arteriosus
9) blood from descending aorta gets transported to umbilical arteries and OUT of fetus
40
What does the ductus venosus become after delivery?
ligamentum venosum
41
What does the foramen ovale become after delivery? How long does this take to close?
fossa ovalis, 1-2 minutes
42
What does the ductus arteriosus become after delivery?
ligamentum arteriosum
43
Overall, how long does it take for the ductus venosus, foramen ovale, and ductus arteriosus to close after birth?
24-36 hours
44
What does the closure or right and left umbilical arteries form in adults?
medial umbilical ligaments
45
What does the closure of the umbilical vein form in an adult?
ligamentum teres of liver
46
When do septation events occur? What time period is the most critical?
4th-8th weeks, 5th and 6th weeks are most critical
47
In the fetal heart, pressure on which side is higher?
right atrial pressure is higher than left
48
What leads to the pressure differential in the fetal heart?
1) Umbilical flow to right atrium via IVC is high
| 2) High pulmonary resistance backs up pressure on the right side
49
What shunts blood between the right and left atrium? When can this close?
the foramen ovale, it MUST remain open during fetal life!
50
Describe the formation of the septum primum.
septum 1 grows as mass of mesoderm from common roof to a mass of mesoderm at center of heart (endocardial cushion- from neural crest cells)
51
Why are endocardial cushions so important?
they play critical roles in septation, AV canal formation, AV valve formation
52
Does septum 1 initially reach all the way down to the endocardial cushion?
NO, foramen primum separates the 1st septum from the endocardial cushion
53
What must occur before septum 1 and the endocardial cushion can fuse?
foramen 2 must form (via programmed cell death of some cells from septum 1)
54
Describe the formation of septum secundum.
to right of the first septum, septum 2 (growth of mesoderm from the roof) begins to grow down and overlap the upper margin of septum 1
55
What does the overlapping growth of the 2nd septum over the 1st septum create?
foramen ovale (blood passes over septum 2 and under septum 1 to reach left atrium)
56
Describe the physical properties of septum primum.
very thin flap that is pushed into LA every time there is a fetal heart beat
57
Describe the physical properties of septum secundum.
very thick and muscular
58
What happens 1 minute after birth to the foramen ovale?
dynamic change of pressure so left atrial pressure is higher than right (foramen ovale is pushed close and will eventually scar down over the first few months of life)
59
Describe the location of the fossa ovalis.
fossa ovalis is actually septum 1 (in left atrium)
60
Describe the word for left to right shunting.
non-cyanotic (oxygenated blood keeps going to lungs via the right side over and over)
61
Describe the word for right to left shunting.
cyanotic (blood that is not oxygenated getting pushed into circulation)
62
What are the two major forms of ASD? Which is more common?
1) secundum type ASD* more common!
| 2) primum type ASD
63
What is secundum type ASD?
A form of atrial septum defect that occurs in the central atrial septum ABOVE the limbus and fossa ovalis
64
What are the 2 causes of secundum type ASD?
1) Excessive resorption of the septum 1
2) Reduced size of septum 2
(OR BOTH)
65
What are the 2 effects of secundum type ASD?
1) patent foramen ovale
| 2) left to right shunting (non-cyanotic)
66
Is secundum type ASD a neural crest defect?
NO!
67
What is primum type ASD?
Second most common type of atrial septum defect that occurs in the LOWER atrial septum below the fossa ovalis.
68
What is the cause of primum type ASD?
failure of the first septum and endocardial cushion to fuse
69
What are the 2 effects of primum type ASD?
1) persistent foramen primum
| 2) left to right shunting of blood (non-cyanotic)
70
Is primum type ASD a neural crest defect?
YES, it is a problem with the endocardial cushion
71
What is different between atrial and ventricular septation?
you have to septate the right and left ventricles completely and quickly, NO SHUNT
72
What are the two parts of the interventricular septum?
1) upper membranous
| 2) lower muscular
73
Describe the formation of the muscular part of the IV septum.
the muscular part is mesoderm upgrowth from the floor of the common ventricle toward the endocardial cushion (BUT DOES NOT INITIALLY REACH IT)
74
What is the gap called between the endocardial cushions and the muscular part of the IV septum?
interventricular foramen
75
Describe the formation of the membranous part of the IV septum.
neural crest cells from cushion grows downward to close off the interventricular foramen (right and left conotruncal ridge involved, but he did not go in to this)
76
What is the most common form of ventricular septal defects?
membranous VSD
77
ARe VSDs more common in males or females?
males
78
What causes membranous VSD?
failure of the membranous septum to develop (neural crest migration problem)
79
What are the initial effects of membranous VSD?
1) left to right shunting (non-cyanotic)
| 2) increased blood flow and pressure to the lungs (pulmonary hypertension)
80
What can occur is the pulmonary hypertension gets too high in a membranous VSD?
pressure can back up into the right ventricle so you can get a reversal in shunting, leading to right-to-left shunting of blood and late cyanosis.
81
What is Eisenmenger complex?
the late cyanosis that occurs if you do not correct membranous VSD before pulmonary hypertension gets out of control
82
What is a PDA?
patent ductus arteriosus
83
What occurs with patent ductus arteriosus?
the ductus arteriosus never closes, so blood from the aortic arch is allowed to flow from the aorta into the pulmonary trunk
84
What can lead to PDA?
1) premature birth
| 2) moms with measels
85
What is the direction of flow in a PDA?
left to right shunt (non cyanotic)
86
What keeps the ductus arteriosus open prenatally?
Prostaglandin E
87
What can be used to treat PDA?
prostaglandin inhibitors
88
What is different between truncal septaiton and atrial/ventricular septation?
not a straight vertical septation, spiral septation
89
What is the aorticopulmonary septum?
two spiral ridges come out of endocardial cushions and goes up the truncus arteriosus
90
The aorticopulmonary septum divides the truncus into what 2 parts?
1) aorta
| 2) pulmonary trunk
91
Describe the position of the aorta and pulmonary trunk after truncal septation.
1) Aorta is posterior initially and extends to the right and superiorly to the pulmonary trunk
2) Pulmonary trunk crosses anteriorly to the aorta to get on the left side
92
Name the 3 cyanotic defects.
1) tetralogy of Fallot
2) transposition of the great vessels
3) persistent truncus arteriosus
93
Are cyanotic defects neural crest derived?
YES
94
What is the direction of blood flow in a cyanotic defect?
right to left
95
What is the most common of all cyanotic defects?
Tetralogy of Fallot (but the level of cyanosis is moderate to minimal)
96
What causes the tetralogy of Fallot?
the AP septum fails to align properly and shifts to the right. This leads to a wide aorta and a narrow pulmonary artery
97
How can you fix a tetraology of fallot?
no surgical correction, can live a normal life but you have to moderate physical activity. Squat down in fetal position to change the load of blood in the lungs/heart.
98
What are the 4 classic defects of the Tetralogy of Fallot?
1) Pulmonary stenosis
2) Ventricular septal defect
3) Hypertrophied right ventricle (because it pumps against increased pressure)
4) Overriding aorta
99
What is the appearance of a heart with Tetralogy of Fallot?
boot-shaped heart with a murmur
100
What is the most severe of the cyanotic defects?
transposition of the great vessels
101
What leads to transposition of the great vessels?
the AP septum fails to spiral, resulting in the aorta opening into the right ventricle and the pulmonary trunk opening into the left ventricle
102
What can accompany transposition of great vessels to lead to survival?
ASD, VSD, or PDA (this can allow for some mixing of oxygenated and deoxygenated blood to survive long enough for surgery)
103
What is a closed defect?
right and left heart are completely separated
104
Will an infant with transposition of the great vessels survive?
NO, unless they have an ASD, VSD, or PDA
105
What is persistent truncus arteriosus?
a cyanotic defect where the is partial or no development of the AP septum
106
What is the effect of persistent truncus arteriosus?
one large vessel exits the heart, leads to right to left shunting of blood with cyanosis
107
What ALWAYS accompanies persistent truncus arteriosus?
ventricular septal defect
108
How severe is persistent truncus arteriosus?
it depends on the degree of the split, you need a large pulmonary portion to get enough blood going to lungs for oxygenation
109
Name the 3 major venous systems that flow into the sinus venosus.
1) cardinal veins
2) umbilical vein
3) viteline veins
110
What do the cardinal veins form?
1) brachiocephalic veins
2) SVC/IVC
3) azygos vein
4) renal vein
111
What do the umbilical veins form? What did these once do?
they form the ligamentum teres in adult (initially carried oxygenated blood from the placenta)
112
What do the viteline veins form? What did these once serve?
veins of the liver (hepatic portal vein, sinusoids, hepatic vein).
Viteline veins served the yolk sac in the embryo.
113
What does the aortic sac split into?
left and right dorsal aorta that lead to aortic arches
114
Do you ever see all of the aortic arches at once?
NO, they have waves of development from cranially to caudal and regress
115
What are the roles of the 1st and 2nd arch?
they do not do much, he said forget about them
116
What does the 5th arch form?
nothing, they form and regress and never develop anything
117
What do the right and left 3rd arches form?
common carotid arteries and first part of the internal carotid arteries
118
What do the right and left 4rd arches form?
Left: arch of aorta from left common carotid to left subclavian
Right: right subclavian artery (proximal portion)
119
What do the right and left 6th arches form?
Left: DUCTUS ARTERIOSUS and left pulmonary artery
Right: right pulmonary artery
120
What leads to the right recurrent laryngeal looping so much superiorly than the left?
deficit of 6th arch on the right side (no ductus arteriosus on the right side)
