Embryology Flashcards
Descirbe the development of the sinus venosus
- Right and left sinus horns are equal in size, receiving veins from the yolk sac, placenta and umbilical cord.
- Venous return then shifts to the RHS, the left sinus horn recedes.
- Right sinus horns is absorbed by the enlarging atrium. The left horn becomes a vestigial structure.
Describe the differences in the formation of the right and left atria
Right atrium develops form
- Most of primitive atrium
- Sinus venosus
Left atrium develops from
- Small portion of the primitive atrium
- Absorbs proximal part of the pulmonary veins
Name the foetal circulatory shunts
Ductus venosus
Foramen ovale
Ductus arteriosus
Why is some blood allowed to pass from the RA to the RV and what shunt is used to prevent blood going to the lungs
This is to allow the RV to develop normally as for the muscles of the RV to be normal, they must be in use.
Ductus arteriosus
What are the functions of the foetal circulatory shunts
Ductus venosus - allows blood to enter the inferior vena cava from the unbilical vein
Foramen ovale - stops blood going into the RV, is a passageway between the RA and LA
Ductus arteriosus - stops blood from the RL going to the lungs, this ensures the lungs are protected from the high pressures of the blood supply
What do the circulatory shunts become after birth
Ductus venosus - ligamentum venosum
Foramen ovale - fossa ovalis
Ductus arteriosus - ligamentum arteriosum
What does the 4th arch of the early atrial system become
Right side becomes the proximal part of the right subclavian artery
Left side becomes the arch of the aorta
What does the 6th arch of the early arterial system become?
Forms the pulmonary arch
Right side becomes the right pulmonary artery
Left side becomes the left pulmonary artery
What is PDA, what is it caused by and how does it present
Patent ductus arteriosus
Casued by failure of physiological closure of the ductus arteriosus
Presents in children as sweating, rapid and heavy breathing, fatigue, little interest in feeding and poor weight gain
Mechinery murmur heard on auscultation
What is septation and what does it form in the heart
Septation is the formation of the septum
Forms the interatrial and interventricular septums and forms the pulmonary trunk and aorta
What septa ard holes are formed in the process of atrial septation
Septum primum which has the ostium primum before septum primum fuses with endocardial cushions, and the ostium secundum which forms in the septum primum
Septum secundum has the foramen ovale
How does the interventricular septum form
Muscular portion grows upwards towards endocardial cushions, leaving primary interventricular foramen
Membranous portion is then formed by connective tissue from the endocardial cushions fills the primary interventricular foramen
What is ventricular septal defect
A defect in formation of interventricular septum, most commonly defect in formation of the membranous portion of the septum
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