1.2.2 Development of Heart and Cardiovascular System Flashcards
When does the heart first beat in embryological development?
Day 22
List the most common congential anamolies.
VSD - 42%
ASD - 10%
Pulmonary stenosis - 7%
PDA - 7%
Tertralogy of Fallot - 5%
Aortic valve stenosis - 4%
Atrioventricular septal (canal) defect - 4%
TGA - 4%
Persistent truncus arteriosus - 1%
At day 20, when the embryo begins to fold both cranially on itself and medially, what structures are being formed?
- Cranial fold starts the formation of the aortic arch
- right and left endocardial tubes start to come towards each other
- endocardial tubes are developing adjacent to fluid filled sack, the pericardial cavity
At day 21, the fusion of the right and left endocardial tube in the cardiogenic region leads to the formation of what?
a single heart tube
Draw the pericardial sac at day 21-22.
Include aortic sac, bulbis cordis, ventricle, atrium, sinus venosus
Describe how the pericardial sac twists and folds into the heart structure.
At day 22 the heart starts to beat, what are the four layers of the heart at this point?
- Endocardium (primitive endocardium)
- Cardiac jelly (ECM)
- Myocardium (heart muscle)
- Epicardium (visceral pericardium)
The breakdown of what structure leads to the formation of the transverse pericardial sinus?
Dorsal mescardium
Another image of how the heart tube twists into form.
Typically twist to the left.
In what two conditions is the base of the heart directed to the right side of the body as opposed to the left? What differentiates the two conditions?
Dextrocardia (1/12,000 births) - increased risk of additional heart defects
Situs Inversus - all organs are completely reversed (1/7000 births) - only slight increased risk of additional heart defects
What helps form the septum intermedium (which helps separate atrium from ventricles)?
Endocardial cushions (posterior and anterior), Day 28
Abnormalities in endocardial cushions can lead to what type of defects?
ASD, VSD, AV canal defects, and TGA
What type of cells contribute to the cells that form the endocardial cushion?
Neural crest cells
People who have a variety of craniofacial defects are at greater risk of having endocardial cushion defects. What condition could lead to increased risk of atrioventricular septal (canal) defects?
Trisomy 21, Downs
What is believed to impair/inhibit neural crest cell migration?
Binge drinking alcohol
What causes atrioventricular septal (canal) defects? What is true about the four chambers of the heart?
Endocardial cushion defect; no separation of the four chambers
What are the main clinical symptoms of the atrioventricular septal (canal) defects?
Tachypnea, poor feeding, growth retardation around 6 weeks of age as pulmonary vascular resistance continues to fall
What two structures help to separate the R and L atria? Describe the characteristics of each.
Septum primum and septum secundum. The secundum is stiffer than the primum. The primum is more pliable.
The interface b/t the septum primum and septum secundum forms what structure? As an embryo this allows blood to travel in what direction?
Oval Foramen
It allows blood to flow from the R atrium to the L atrium. After birth, the L atrium becomes a higher pressure system stopping this flow.
What type of shunt is ASD? What murmur is commonly associated with ASD?
L to R shunt
“split” S2
What is the most common type of ASD? What is the male to female ratio?
Secundum; 2 females for every male
Why is a patent foramen ovale not considered an ASD?
B/c no septal tissue is missing, it is just that the two atrial septa fail to fuse with each other. Interatrial shunting cannot occur as long as L atrial pressure exceeds R atrial pressure.
What structure grows into the right atrium? The left atrium?
R atrium: sinus venarum
L atrium: pulmonary veins
What begins to grow up from the inferior wall of the ventricles towards the septum intermedium during the 4th week?
Muscular interventricular septum
Most common heart defect? Type of shunt?
VSD, L to R shunt
What is different about the presentation of small VSDs and large VSDs?
Small VSD: systolic murmurs by 48 hrs after birth
Large VSD: present at 3 to 12 wks with tachypnea, grunting respiration, and slow weight gain
What ultimately divides into the aorta and pulmonary trunk?
Truncus Arteriosus
What is the most common type of interventricular septal defect?
Membranous (thin) portion of interventricular septum
What are some possible of congential heart defects that come as a result of failure of the sepetation of the truncus ateriosus outflow tract?
TGA
Pulmonary stenosis
PTA
TOF
What happens in TGA? What is their saving grace?
Aorta sits of the right ventricle and pulmonary artery sits over the left ventricle. The PDA will help the patient get some oxygenated blood until surgery can be done to swap the position of the arteries
For newborns w/ TGA to survive, there must be communication between the two sides of the heart. What two structures can help with this communication?
Peristent or patent foramen ovale or PDA
What is PTA? How do newborns present and what will happen without surgical intervention?
Persistent truncus arteriosus is a congenital cardiac malformation in which the outflow of the heart is through a single vessel rather than a pulmonary trunk and aorta.
Present w/ cyanosis. Most die of CHF unless surgically corrected
What is the clinical presentation of TOF?
Newborns can be cyanotic and fail to thrive
Most often: detected during well baby checks, months after they leave the hospital. Sudden incidences of cyanosis w/ hyperpnea are common from 2 mo to the 2 y. Surgery is necessary for survival into adulthood.
What determines the severity of TOF?
degree of pulmonary stenosis
How will more severe pulmonic stenosis affect heart sounds?
More pulmonic stenosis, greater splitting of S2
What is aortic stenosis?
Condition in which the leaves (cusps) of the aortic valve become stiff or fuse together, leaving only a smaller opening for blood to leave the L ventricle
In adults, aortic valvular stenosis can lead to what?
Enlargement of the aortic arch due to jetting of blood
What is coarction of the aorta?
Constriction in the aorta 95% of the time just above or just below the attachment of the ductus arteriosus
What is the hallmark that leads to diagnosis of coarction of the aorta in an adult?
HTN in upper extremities and hypotension in the lower limbs, murmur heard posteriorly in the interscapular regions, notching of the under surface of ribs
What are III, IV, VI arch of the of the aorta
III - common and part of internal carotid artery
IV - right subclavian artery (R) and arch of the aorta (L)
VI (pulmonary arteries)
