Embryology Heart and Fetal Circulation Flashcards
When does the primordial heart and vascular system appear?
week 3, 1st major system to develop
When do cardiac progenitor cells derive? Where do they migrate to?
Lateral to primitive streak
Move towards cranium in the splanchnic layer of lateral plate of mesoderm→ cardiac myoblasts. Become surrounded by blood islands
What is the cardiogenic field?
The islands untie and form a horse shoe shaped endothelial lined tube surrounded by myoblasts
What forms the endocardial tube
Continous tub with inner endothelium kinin (future endocardium) and outer muscular layer (future myocardium) separate ny cardiac jelly
When is the partying of the heart chambers complete?
Week 8
During the portioning of the atrium, when mechanism allows R to L shunting of fetal blood?
In the first instance, the septum primum grows from the roof down towards the endocardial cushion, leave ing a space foramen primum.
Eventually the septum premium closes the foremen primum but a opening forms foramen secondum. A septum secundum grows which acts like a valve over the ovum secondum → foreman ovale
When is the portioning of the ventricles complete?
The inter ventricular septum closes at week 7, after this the pulmonary artery communicate with the right ventricle and aorta with the left.
What is the truncus arteriosis?
Aotra and pulmonary artery joined and drain both L&R ventricle
When does the conducing tissue originate?
From the sinus venous, which is then incorporated by the right atrium.
Name some environemental foctors that can cause heart defects.
ETOH Rubella Thalidomide Isotretinoin (vitamin A) 1st Trimester - high blood glucose and HTN
ASDs - more likely to affect girls or boys
2 x more likely to affect females
When is the incidence of patent foramen ovale?
25% - asymptomatic
How well is Foramen Secundum ASD tolerate
Well in childhood, often develop PHTN in 3rd decade of life
What is sinus venous ASD
Failure of incorporation of sinus venous into the R atrium.
Are VSDs more are less common than ASDs? More common in boys or girls?
More common than ASDs
More common in boys
What are can VSDs cause?
Dysponea
Pulmonary HTN
Heart failure
What is the most common form of VSD. Prognosis?
Membranous VSD - failure of development of membranous part of IV septum. 30-50% close in 1st year of life.
Where does the swiss cheese VSD develop?>
Muscle part of IV septum
What type of VSD is commonly seen in Downs Syndrome. Why does it occur?
Atrioventricular septal defect (AVSD) - failure of fusion of endocardial cushions → large defect in heart. 20% downs
What are the 4 features of tetralogy of fallot?
- Pulmonary stenosis
- Overrdiing aorta
- Ventricular hypertrophy
- VSD
What happens in persistent truncus arteriosis?
Failure of division of truncus arteriosos aorta and pulmonary artery joined + VSD
What is the most common cause of cyanotic heart disease of the newborn infant?
Transposition of the great vessels.
Has to be treated surgically
What is the most common cause of sudden infant death syndrome in developed countries
Abnormality of the conducting system.
Explain the fetal circulation
85% oxygenated blood enters through the umbilical vein.
Mostly bypasses the liver via the ductus venous which joins the inferior vena cava.
The inferior vena cava enters into the R atrium, passes through the forman ovale into the L atrium.
Then passes out L ventricle through the aorta.
Some blood still leaves the R side of heart via the pulmonary artery. Resistance in lungs s high so blood passes into the aorta via the ductus arteriosis.
Blood from aorta enters placenta via 2 x umbilical artier 58% oxygenated.
When do the umbilical arteries close? What do they form?
Close within a few minutes of birth, obliteration takes 2-3 months. Form medial umbilical ligament. Proximal part stay patent - superior vesical artery
When does the closure of the umbilical vein & ductus venous occur? What does it form?
Both close shortly after umbilical artery. After obliteration
umbilical vein → ligament teres hepatis (round ligament of liver) in lower margin of falciform ligament
Ductus venous → ligamentum venosum
How does the closure of ductus arteriosis occur?
As the lungs are used they release bradykinin which causes muscular contractions around the ductus arteriosis, complete closure takes 1-3 months.
Ligament arteriosum
What is the cause of cyanotic periods of the new born?
Oval foremen not completely fused, during crying there is R to L shunt.
Constant appoistion gradually leads to fusion of the 2 septum.
