2.5 Cardiovascular embryology Flashcards
What are the 3 stages of heart formation?
- Formation of primitive heart tube.
- Cardiac looping.
- Cardiac septation.
Describe what happens in the formation of the primitive heart tube.
Two endocardial tubes form (day 19). The tubes fuse together and the heart beats (day 22).
Describe what happens in cardiac looping.
Nodes secrete nodal, this circulates to the left due to ciliary movement. Nodal causes a cascade of transcription factors that transduce looping.
Describe what happens in cardiac septation.
Endocardial cushions form. Fuse at mid-line to form atrio-ventricular septum. Muscular ridge in the floor of the primitive ventricle migrates to endocardial cushions forming interventricular septum.
What does the ecoderm (outer layer) form?
Skin, nervous system, and neural crest (which contribute to cardiac outflow and coronary arteries).
What does the mesoderm (middle layer) form?
All types of muscles, most systems, kidneys, blood, bone
What does the endoderm (inner layer) form?
gastro-intestinal tract (including liver and pancreas but not smooth muscle) and endocrine glands.
The cardiovascular system is derived from cells situated in…
The mesoderm
and some contribution from the neural crest in the ectoderm
What layer of the tri-laminar disc forms the cardiovascular system?
Mesoderm
What does the first heart field produce?
The left ventricle
What does the second heart field produce?
The right ventricle, atria and outflow tracts.
What are the 3 types of capillaries
Continuous (most common),
Fenestrated (kidneys, small intestines and endocrine glands),
discontinuous (liver sinusoids)
What is the ligamentum teres a remnant of?
The umbilical vein.
What is the ligamentum venosus a remnant of?
The ductus venosus.
Briefly describe foetal circulation.
Maternal circulation - umbilical vein (oxygenated blood) - ductus venosus - IVC - RA - LA/RV - aorta - umbilical artery (deoxygenated blood) - maternal circulation.
What does the sinus venosus form?
The coronary sinus and RA.
What does the primitive atrium form?
RA and LA.
What does the primitive ventricle form?
Forms most of LV.
What does the bulbus cordis form?
Part of the ventricles.
What does the truncus arteriosus form?
The aorta and pulmonary trunk.
What do the 1st and 2nd aortic arches form?
Minor vessels in the head.
What does the 3rd aortic arch form?
The common carotid arteries.
What does the left and right 4th aortic arch form?
Left - aorta. Right - Right subclavian artery.
What does the 5th aortic arch form?
There is no 5th arch!
What does the left and right 6th aortic arch form?
Left - left pulmonary artery and ductus arteriosus. Right - right pulmonary artery.
What does the 7th segmental aortic arch form?
Left and right subclavian arteries.
What does the dorsal aortae form?
Left dorsal aortae - descending aorta. Right dorsal aortae - part of right subclavian artery.
Where is the SAN located?
In the Right Atrium under the crista terminalis.
What does the left coronary artery divide into?
The left anterior descending, and the circumflex.
Why is the O2 saturation in coronary venous blood very low?
O2 extraction by the heart muscle is very high.
What surface of the heart does the right coronary artery supply?
The inferior surface (underside) of the heart.
What valve prevents high pressures developing in the jugular veins during ventricular systole?
Tricuspid valve.
Why does an increase in LVEDV signify heart failure?
Heart failure is the inability to pump blood out of the heart. There is blood remaining at the end of systole. The blood therefore accumulates and so LVEDV increases.
Which pressure is most likely to increase in left sided heart failure?
LV EDP.
Which pressure is most likely to decrease in left sided heart failure?
Mean aortic pressure.
Less blood is being pumped into the aorta
What is stenosis?
Narrowing.
Which pressure is most likely to increase in mitral valve stenosis?
Left atrial end-systolic pressure.
What does it mean if a heart valve is incompetent?
It is regurgitant.
Which pressure is most likely to increase when the aortic valve is incompetent?
Left ventricular end-diastolic pressure.
Pulmonary oedema is a sign of what?
Left heart failure.
What can severe pulmonary hypertension cause?
Right heart failure.
The heart has to pump harder to get blood into the pulmonary circulation due to an increased afterload.
Shortness of breath, severe peripheral oedema and ascites after a heart attack can indicate what?
Biventricular failure.
What is ascites?
Accumulation of fluid in the peritoneal cavity, this can cause abdominal swelling.
What branch does the right coronary artery give off as it reaches the inferior border of the heart?
The right marginal branch.
What artery does the RCA anastomose with on the diaphragmatic surface of the heart?
The circumflex artery.
What does the LAD anastomose with on the diaphragmatic surface of the heart?
The posterior inter-ventricular branch of the RCA.
Where is the coronary sinus found?
Between the LA and LV - left atrio-ventricular sulcus.
What does the coronary sinus drain into?
The RA.
What artery arises from the RCA in 90% of hearts, the circumflex in 30% and in 20% arises from both the RCA and circumflex?
The posterior inter-ventricular branch.
Define ischaemia.
A decrease in blood flow to a tissue.
Define infarction.
No blood flow to a tissue - tissue death.
Explain the formation of fluid exudate in inflammation.
Chemical mediators cause vasodilation of vessels and an increase in permeability.
What reaction does adenyl cyclase catalyse?
The conversion of ATP into cAMP.
How do muscarinic M2 receptors cause a decrease in cAMP?
They inhibit adenyl cyclase.
What surface of the heart does the RCA supply?
Inferior.
