Session 3-Development Of Heart And Great Vessels Flashcards
What is the cardiogenic field?
Zone within mesoderm that can differentiate into the CVS
True or false: congenital birth defects can be either structural abnormalities or complete absence of a structure
TRUE
What are the potential causes congenital birth defects? (2)
1) genetic
2) exposure to chemicals/drugs/infectious agents
When can a congenital heart defect occur? (3)
When there is:
1) a structural defect of the chambers or vasculature
2) obstruction
3) communication between pulmonary and systemic circulations
What is the primitive heart tube?
Essentially a modified blood vessel with no chambers or valves
What are the different zones of the primitive heart tube, from inlet to outlet tubes? (6)
1) sinus venosus
2) atrium
3) ventricle
4) bulbus cordis
5) truncus arteriosus
6) aortic roots
What does cardiac looping allow?
Septation
What happens in cardiac looping?
Heart tube elongates, runs out of room and twists and folds up
Why is the RA rougher than the LA?
RA has more primitive atrium (trabeculated tissue) than LA
What does the RA develop from? (2)
1) most of the primitive atrium
2) sinus venosus
What dos the LA develop from? (2)
1) small portion of primitive atrium
2) absorbs proximal parts of pulmonary veins
True or false: lungs don’t work in the foetus
TRUE
What is required to allow oxygenation and removal of CO2 at the placenta in a foetus?
Shunts
In foetal circulation, where does blood with the highest PO2 arrive and where does it travel to?
At the umbilicus, travels through the umbilical vein and up to the liver
Why is a shunt created around the liver?
To pump blood into the inferior vena cava because the liver is highly metabolically active during foetal life and would otherwise use up most of the O2 supply
Why does a small amount of blood flow from the RA to RV?
To allow the muscle in the RV to contract and to ensure normal development of the ventricle
What is the name of the shunt between RA and LA?
Foramen ovale
What is the name of the shunt between the pulmonary trunk and aorta?
Ductus arteriosus
What is the name of the shunt between the placenta and the inferior vena cava?
Ductus venosus
What does the early arterial system begin as?
Bilaterally symmetrical system of arched vessels
Which nerve becomes hooked around the shunt between the pulmonary trunk and aorta?
Left recurrent laryngeal nerve
What is patent ductus arteriosus? (PDA)
Persistent communication between descending aorta and pulmonary artery and the failure of physiological closure
What does ostium primum mean?
First hole
What leads to the formation of the ostium secundum?
Apoptosis
True or false: blood flows through the foramen ovale when pressure in LA > pressure in RA
FALSE - flows when pressure in LA < pressure in RA
After birth, why can blood not flow through the foramen ovale?
Pressure in LA > pressure in RA and septum primum is pushed against septum secundum and as the holes aren’t aligned, no blood can flow through
What is atrial septal defect?
Ostium secundum defect-
Septum primum is resorbed and is too short and the septum secundum is too small
What is hypoplastic left heart syndrome?
Left heart is underdeveloped
What are the potential causes of hypoplastic left heart syndrome? (2)
1) defect in development of mitral and aortic valves resulting in atresia and limited flow
2) ostium secundum is too small therefore R to L flow is inadequate in utero
What are the two components of the ventricular septum?
Muscular
Membranous
True or false: membranous portion of the ventricular septum forms most of the septum and grows upwards towards the fused endocardial cushions
FALSE - muscular, not membranous
Complete the sentence:
The ____________ portion of the ventricular septum grows upwards towards the endocardial cushions leaving a small gap called the primary ________________ __________
Muscular
Interventricular foramen
How is the membranous part of the interventricular septum formed?
By connective tissue derived from endocardial cushions to fill the gap
Which portion of the interventricular septum is most commonly affected by ventricular septal defect?
Membranous
Complete the sentences:
Endocardial cushions also appear in the truncus ___________. As they grow towards each other they twist around each other, forming a ________ _______
Arteriosus
Spiral septum
Which operation may be carried out to treat cyanosis?
Arterial switch operation
What happens in tetralogy of Fallot? (5)
1) Large ventricular septal defect
2) Aorta straddles both ventricles
3) RV outflow tract obstruction
4) RV hypertrophy
5) Conotruncal septum formation is defective
What does the 4th aortic arch develop into?
R=Proximal part of right subclavian artery
L=arch of aorta
What does the 6th aortic arch develop into?
R=right pulmonary artery
L=left pulmonary artery and ductus arteriosus
