CVS 3 (Development) Flashcards
What does lateral embryonic folding do to the developing heart?
Creates a heart tube
What does craniocaudal embryonic folding do to the developing heart?
Brings primitive heart tube into thoracic region
What does embryonic folding do to the developing heart?
Lateral folding - Creates heart tube
Craniocaudal folding - Brings tube into thoracic region
What allows the primitive heart tube to freely move within the pericardial cavity?
It is only tethered at the cranial and caudal ends
Name the 6 sections of the primitive heart tube, from the inflow to the outflow:
1) Sinus venosus
2) Primitive atria
3) Primitive ventricle
4) Bulbus cordis
5) Truncus arteriosus
6) Aortic roots
Between which days after fertilisation does the looping of the primitive heart tube take place?
Days ~ 23-28
What does the sinus venosus become?
The vena cavae and the coronary sinus
In the primitive heart tube, the sinus venosus is highly symmetrical. Why does it become very distorted after folding of the heart tube?
The RHS of the sinus venosus is absorbed to form part of the right atrium
What does the right atrium develop from?
- Most of the primitive atria
- RHS of sinus venosus
What does the left atrium develop from?
- Small % of the primitive atria
- Proximal parts of pulmonary veins
Which vessels drain into the right atrium?
Superior vena cava
Inferior vena cava
Coronary sinus
How many pulmonary veins empty into the left atrium?
4
Name the vessel which supplies the foetus with oxygenated blood from the placenta:
Umbilical vein
Which 2 developing organs must be bypassed by the foetal circulation?
Lungs
Liver
Which foetal shunt allows the circulation to bypass the liver?
Ductus venosus
Which foetal shunt allows the circulation to bypass the lungs?
Ductus arteriosus
Which 2 blood vessels does the ductus arteriosus connect?
1) Pulmonary trunk
2) Aorta
What is the ligamentum arteriosum a derivative of?
Ductus arteriosus
How many aortic arches are present in early foetal life?
5: 1,2,3,4 and 6
From which foetal aortic arch does the adult aortic arch derive from?
4th arch
From which foetal aortic arch does the adult pulmonary arteries derive from?
6th arch
Which foetal aortic arch forms part of the ductus arteriosus?
6th arch
Each aortic arch has a corresponding nerve. Which nerves are paired with the 6th aortic arches?
Recurrent laryngeal nerves
The recurrent laryngeal nerve is a branch of which cranial nerve?
CN X
Why does the left recurrent laryngeal nerve descend further in the body than the right nerve?
The left recurrent laryngeal nerve hooks around the ductus arteriosus
The right subclavian artery is derived from which aortic arch?
The right 4th aortic arch
Which germ layer gives rise to the cardiovascular system?
Mesoderm
In which week of development does embryonic folding take place?
Week 4
What is the name of the junction between the atria and ventricle of the primitive heart?
Atrioventricular canal
What is the name of the tissue which develops to separate the atrioventricular canal into an atrium and a ventricle?
Endocardial cushions
What is the first septation to occur in the developing heart?
Septation between the primitive atrium and ventricle (from the atrioventricular canal)
Name the septa required for normal atrial septation:
1) Septum primum
2) Septum secondum
Septum primum grows from ? and fuses with ?
From the top of the primitive atria,
fuses with the endocardial cushions (which separate the atria from the ventricle)
What is the name of the ‘hole’ present between the atria (of a developing heart), before septum primum fuses with the endocardial cushions?
Ostium primum
What is the name of the ‘hole’ present between the atria (of a developing heart), after septum primum fuses with the endocardial cushions?
Ostium secondum
In which septum does the ostium secondum form?
Septum primum
Describe the shape of the septum secundum:
Cresent-shaped
What is the name of the ‘hole’ that forms in the septum secundum?
Foramen ovale
Name the 3 ‘holes’ present in the atrial septa (at different stages of development):
1) Ostium primum
2) Ostium secundum
3) Foramen ovale
Which direction does blood shunt through the foramen ovale and ostium secundum during foetal life?
R -> L (blood enters RA of heart)
Why is it important that the ‘holes’ of the foetal R -> L atrial shunt are NOT ALINED?
After birth, the pressures in the heart change due to the pulmonary system, the 2 atrial septa are pushed together, and holes are not alined = no shunting of blood between atria.
What are the 2 tissue components of the ventricular septum?
1) Large muscular component
2) Small membranous component
The muscular part of the ventricular septum grows from ? towards ?
From the bottom of the ventricle upwards, towards the endocardial cushions
The muscular part of the ventricular septum does not fuse with the endocardial cushions, forming a hole. What name is given to this hole?
Primary interventricular foramen
What closes the primary interventricular foramen?
Membranous connective tissue, which grows downwards from the endocardial cushions to fill the gap.
What does the conotruncal septum achieve?
Division of the truncus arteriosus into the aorta and pulmonary trunk, creating 2 outflow tracts from the heart
Describe the shape of the aorticopulmonary septum:
Spiral
How does the conotruncal septum grow in a spiral shape?
It forms form ridges either side of the truncus arteriosus, which grow towards each other in a staggered way, forming the spiral
Once the conotruncal septum has formed, what name is given to it?
Aorticopulmonary septum
Name the 4 foetal shunts:
1) Ductus venosus
2) Ductus arteriosus
3) Foramen ovale
4) Umbilical vein
What does the foramen ovale become in an adult?
Fossa ovalis
What does the umbilical vein become in an adult?
Ligamentum teres
What part of the heart does the conus cordis form?
Outflow tracts of the R and L ventricles
Approximately how many babies per 1000 births have congenital heart defects?
~6-8
What is the most common heart defect?
Ventricle septal defect
What are the 4 types of congenital heart defect?
1) Atrial septal defect
2) Ventricle septal defect
3) Transposition of great vessels
4) Tetralogy of Fallot
What proportion of children born with Down’s syndrome also have a congenital heart defect?
~ 50%
Why does Marfan syndrome cause a heart defect?
It causes progressive enlargement of the aorta near the aortic valve, due to the weak vessel walls and high BP. This can rupture.
What are the 3 main types of causes of congenital heart defects?
1) Genetic
2) Environmental
3) Maternal infections
What may happen to the heart of an unborn child if the mother took lithium medication?
Lithium may cause a congenital heart defect, as causes displaced leaflets of the tricuspid valve
What is the %pO2 in the right side of the heart?
~ 67% pO2
What is the %pO2 in the left side of the heart?
~ 99% pO2
Name the 3 acyanotic left to right shunts:
1) Atrial septal defect
2) Ventricle septal defect
3) Patent ductus arteriosus
Name the 4 acyanotic obstructive lesions:
1) Aortic stenosis
2) Pulmonary stenosis
3) Mitral stenosis
4) Coarctation of the aorta
What is the difference between ‘aortic stenosis’, and ‘coarctation of the aorta’?
Aortic stenosis is narrowing of the aortic valve
Coarctation of the aorta is narrowing of the aorta either proximal or distal to the ductus arteriosus
Name the 4 cyanotic right to left shunts:
1) Tetralogy of Fallot
2) Total Anomalous Pulmonary Venous Connection
3) Transposition of the Great Arteries
4) Univentricular heart
What is Total Anomalous Pulmonary Venous Connection?
When the pulmonary veins drain into the right atria (instead of the left), and is associated with an ASD, resulting in cyanosis
In an adult, pulmonary pressure (25/10mmHg) is much lower than systemic pressure (80/40mmHg). However immediately after birth this is not the case. Why?
Immediately after birth the pulmonary and systemic pressures must be almost equal, to force blood around the newly opened lungs.
How does an ASD lead to right ventricular hypertrophy?
- Blood moves from LA to RA due to pressure differences
- RV volume overload
- RV hypertrophy to compensate
Where is the most common site of a VSD?
At the top of the interventricular septum, due to defective membraneous formation
Which congenital heart defect commonly occurs in people with Down’s syndrome?
Atrio-ventricular septal defect
Describe the factors of a Tetralogy of Fallot:
1) Pulmonary stenosis
2) Ventricular septal defect
3) Right ventricular hypertrophy
4) Over-riding aorta
Tetralogy of Fallot is a shunt in which direction?
Right –> Left
Is a Tetralogy of Fallot cyanotic or acyanotic? Why?
Cyanotic:
- Not enough blood can get to the lungs to be oxygenated (pulmonary stenosis)
- Non-oxygenated blood mixes with oxygenated blood and enters systemic circulation (VSD + over-riding aorta)
What is tricuspid atresia?
Complete absence of a tricuspid valve. Therefore an ASD and VSD must be present.
Why must there be a VSD if tricuspid atresia is present?
To allow L to R shunt to get blood to the lungs, for oxygenation
What is hypoplastic left heart?
Hypoplasia of left ventricle and ascending aorta. Therefore ASD and PDA must be present.
What is pulmonary atresia?
Absence of valve to pulmonary trunk. Therefore an ASD and PDA must be present.
