S3 Development of CVS Flashcards
What effect does folding (lateral and cephalocaudal) of the embryo have on the early development of the heart?
Lateral - creates a heart tube
Cephalocaudal - brings the tube into the thoracic region
What are the 6 sections of the primitive heart tube?
- Aortic roots
- Truncus arteriosus
- Bulbus cordis
- Ventricle
- Atrium
- Sinus venosus
Describe the folding and looping of the primitive heart tube.
- The tube elongates
- It runs out of room due to the pericardial sac being a set size
- So the tube twists and folds (in a regular and predictable way)
- This places the inflow and outflow in the correct orientation in respect to each other
- The atrium and ventricle expand
How is the transverse pericardial sinus formed?
Folding so the arteries/outflow are in front of the veins/inflow
How does the sinus venosus develop?
- The right and left sinus horns are initially equal sizes
- The venous return shifts to the RHS, the left sinus horn recedes
- The right sinus horn is absorbed by the enlarging right atrium
(Producing superior and inferior vena cava)
How does the atria (right and left) develop?
Right atrium - develops from most of the primitive atrium, sinus venosus and receives venous drainage from the vena cava and coronary sinus
Left atrium - develops from a small section of the primitive atrium, also absorbs proximal parts of the pulmonary veins and receives oxygenated blood from the lungs
How does the oblique pericardial sinus form?
Formed as the left atrium expands absorbing the pulmonary veins (between the heart and pericardial sac)
What is used in the foetus given the lungs don’t work to move oxygenated blood from the right side to the left side of the heart?
Shunts
What are the 3 foetal circulatory shunts? What does each bypass?
- Ductus venosus - liver
- Foramen ovals - right ventricle and lungs
- Ductus arteriosus - lungs
What is the mature circulatory system (after birth)?
- Right atrium
- Right ventricle
- Pulmonary trunk
- Lungs
- Pulmonary veins
- Left atrium
- Left ventricle
- Aorta
- Body
- Right atrium
What is the fetal circulatory system?
- Oxygenated blood from mother
- Placenta
- Bypass the liver - ductus venosus
- Inferior vena cava
- Right atrium
- Bypass the right ventricle and lungs - foramen ovale.
A small amount of blood drains into the right ventricle from the right atrium (to keep the right ventricle developing normally) to the pulmonary trunk, bypass the lungs - ductus arteriosus, aorta - Foramen ovale to the left atrium
- Left ventricle
- Aorta
- Body
- Placenta
- Deoxygenated blood back to mother
What happens after birth that converts the circulatory system from the fetal to the mature?
- respiration begins
- the left atrial pressure increases causing the foramen ovale to close
- the ductus arteriosus contracts
- placental support is removed
- the ductus venosus closes
What are the 4th aortic arch derivatives?
- right - proximal part of the right subclavian artery
* left - arch of aorta
What are the 6th aortic arch derivatives?
- right - right pulmonary artery
* left - left pulmonary artery and ductus arteriosus
What is the left recurrent laryngeal nerve hooked around?
The 6th aortic arch, hooked around the the shunt (ductus arteriosus)