Embryology 👶 Flashcards
What is the time of the development of the Primitive heart?
At the beginning of 4th week
What is the origin of the primitive Heart?
The cardiogenic plate of mesoderm (Angioblastic cells )
What are the steps of the development of the primitive heart?
- Cells in the cardiogenic area collect into two-heart tubes (one on each side).
- Then the two heart tubes will fuse together to give a single heart tube with 2 ends
- one end is venous that receives blood and the other is arterial ejecting the blood.
- Constrictions appear in the heart tube dividing it to 5 segments
- Growth of the heart tube, resulting in its bending into an S-shape.
“After U-shaped, Due to attachment with the esophagus with elongation”
What are the segments of the Primitive heart from causal to cranial?
- Sinus venosus “receive venous blood”
- Primitive atrium.
- Primitive ventricle.
- Bulbus cordis.
- Truncus arteriosus.
What does the S-shaped heart consist of?
- The right limb: which is formed by truncus arteriosus and bulbus cordis.
- The transverse limb: which is formed by the primitive ventricle.
- The left limb: which is formed by the primitive atrium and sinus venosus.
When does the heart first beat?
starts at early 4th week (22 days).
When are heartbeats first heard?
1st detected heartbeat by ultrasound can be done as early as 6th week.
What Is the time of development of the truncus arteriosus?
5th week “Last thing to develop”
What are the steps of development of the truncus arteriosus?
- 2 ridges (Rt & Lt) appear in the cephalic part of TA
- Grow distally, undergo 180 spiraling, and fuse→form spiral aortico-pulmonary septum
- The septum divides TA into ascending aorta & pulmonary trunk.
What are the anomalies of truncus arteriosus?
1- Transposition of the greater vessels (TGA)
2- Persistent truncus arteriosus (PTA)
3- Fallot’s Tetralogy (FT)
What are the characteristics of TGA?
- Failure of the aortico-pulmonary septum to spiral.
- Aorta arises from the RT ventricle & the Pulmonary arises from the Lt ventricle.
- Common cyanotic heart disease.
- Associated with PDA and or, VSD, ASD, to mix oxygenated and deoxygenated blood.
What are the characteristics of PTA?
- Failure of development of the aortico-pulmonary septum.
- TA persist as single trunk overrides both ventricles→ receives mixed blood
- Accompanied by the membranous ventricular septal defect.
What are the Characteristics of FT?
- Anterior displacement of the aortico-pulmonary septum leads to unequal division of the TA.
- May be accompanied with PDA.
- Characters:
1) Pulmonary stenosis.
2) Hypertrophy of the Rt ventricle.
3) Overriding of the aorta.
4) Ventricular septal defect.
What is Fallot’s pentalogy?
FT+ASD
What are the steps of development of the aortic and pulmonary valves?
▪ 4 endocardial cushions; Rt, Lt, Ant, Post developed in the cephalic part of bulbus cordis (BC) at its junction with truncus arteriosus (TA).
▪ The Rt & Lt ridges fused dividing the orifice into anterior→pulmonary, posterior→Aortic orifices
▪ Rotation of aorta and pulmonary trunk 45-degree→ rearrangement of their cusps.
▪ The cusps are hollowed out at their upper surface.
What are the anomalies of aortic and pulmonary valves?
1- Pulmonary stenosis
2- Aortic stenosis
→Partial fusion of the valves
3- Pulmonary atresia
4- Aortic atresia
→Complete fusion of the valves
“underdevelopment of the cusps —-> blood regurgitation”
What is the definition of fetal circulation?
Circulation of the blood between fetus and mother and also through the fetus.
What does the umbilical cord contain at early embryonic life?
- Two umbilical veins: carry oxygenated blood (80%) from the placenta to the fetus (The Rt umbilical vein disappears early).
- Two umbilical arteries: carry non-oxygenated blood (60%) from fetus to placenta.
Describe the fetal circulation
- The Lt. umbilical vein carries oxygenated blood from the placenta → Lt portal vein → ductus venosus → Rt atrium → MOST BLOOD passes from foramen ovale → Lt atrium → Lt ventricle → Aorta → Upper part of the body with well-oxygenated blood.
- SMALL AMOUNT of blood in the Rt atrium (mixed) → Rt ventricle → Pulmonary trunk:
→Small amount supplies the lung
→A large amount passes through the ductus arteriosus → descending aorta → lower part of the body with mixed blood. - The umbilical arteries carry deoxygenated blood from the fetus (internal iliac arteries) to the placenta
What are the changes that happen in fetal circulation after birth?
I. Immediate Changes After Birth:
- Establishment of pulmonary circulation
- Functional closure of foramen oval
- Functional closure of ductus arteriosus
II. Late Fibrotic Changes
- Changes to The left umbilical vein
- Changes to The ductus venosus
- Changes to The ductus arteriosus
- Changes to The umbilical arteries
How is the pulmonary circulation established?
Immediately after birth, exposure to cold & anoxia occurs due to the stoppage of placental circulation → stimulating the respiratory center in the brain stem → establishment of pulmonary circulation.
How is the foreman ovale closed?
This occurs due to:
- Increase pressure in the left atrium (due to establishment of pulmonary circulation)
- Decrease pressure in the right atrium (due to stoppage of blood coming from the placenta)
- this will press the septum primum against the septum secondum leading to firm physiological closure.
What are the causes of the closure of ductus arteriosus?
Due to strong contraction of the muscle layer in the ductus arteriosus
What are the results of the closure of ductus arteriosus?
- Block the communication between the aorta and left branch of the pulmonary.
- Directing all the blood in the pulmonary trunk to the lungs.
What happens in the first year postnatal?
some vessels become fibrosed and change into ligaments
What is the fate of the left umbilical vein?
becomes the ligamentum teres of the liver.
What is the fate of ductus venosus?
becomes the ligamentum venosum, connecting the left branch of the portal vein with the IVC.
What is the fate of ductus arteriosus?
becomes the ligamentum arteriosus.
What is the fate of the umbilical arteries?
- The proximal parts remain patent and give the superior vesical arteries to the bladder.
- The distal part fibrosed and give the lateral umbilical ligaments connected to the umbilical cord.
