Session 3 - Heart Development (2) Flashcards
What does the following embryonic structure form in adult heart? Ductus Arteriosus
Ligamentum arteriosum
What does the following embryonic structure form in adult heart? Foramen ovale
Fossa ovalis
Why is the LA smooth?
Due to its absorption of the pulmonary veins
Why is the RA trabeculated?
Due to its formation from the primordial atrium - also absorbs sinus venosus
What does the following embryonic structure form in adult heart? Primitive atrium
Left and right auricles
Describe the initial process of septation
* Neural crest cells form the endocardial cushions which develop in the atrioventricular region * These grow towards one another and divide the developing heart into right and left channels
What needs to happen after the heart has been developed into right and left channels?
Atria, ventricles and outflow tract must be divided.
What happens in the outflow tract during septation?
In outflow tract: endocardial cushions also appear in the truncus arteriosus, as they grow towards each other they twist around each other to form a spiral septum
Give four steps of inter-atrial septation
- Septum primum grows down towards the fused endocardial cushions 2. The ostium primum is the first hole present before the septum primum fuses with the endocardial cushions 3. Before the ostium primum closes, a second hole, the ostium secundum appears in the septum primum via apoptosis 4. Finally a second crescent shaped septum, the septum secundum grows,; the hole in the septum secundum is the foramen ovale
What are the two components of the ventricular septum?
* Muscular * Membranous
Describe fromation of the interventricular septum
- Muscular portion grows towards the endocardial cushions leaving a small gap – the 1° interventricular foramen 2. Membranous portion of the interventricular septum formed by connective tissue derived from endocardial cushions to “fill the gap”
How are the lungs bypassed in foetal circulation?
Via foramen ovale, a right to left shuntq
In utero, how does left atrial pressure compare to right?
In utero: pressure LA < pressure RA
What occurs at first breath?
At birth: first breath causes pressure LA > pressure RA Þ septum primum pushed against septum secundum. Foreman ovale shuts.
What does the foramen ovale become after birth?
Fossa ovalis
What does the ductus arteriosus become after birth and why?
* Ductus arteriosus > ligamentum arteriosum o At birth, high oxygen in the lungs and reduced pulmonary vascular pressure trigger closure
What happens to ductus venosus after birth?
Ligamentum venosum
What happens to the umbilical vein after birth
Ligamentum teres
What is A?
The foramen ovale
What is the location and purpose of the foramen ovale?
The foramen ovale is formed from two holes in the septum primum and septum secundum in the atrial septum. Its purpose is to provide allow blood to move from the right atrium to the left, down a pressure gradient.
What is B?
The ductus arteriosus
What is the ductus arteriosus and what is its purpose?
The ductu arteriosus is a blood vessel connecting the pulmonry artery to the aortic arch. Allows most of the blood from the right ventricle to bypass the lungs in the foetus
What is C?
The ductus venosus
Where is C found, and what is its purpose?
The ductus venosus shunts half of the blood flow from umbilical veins to inferior vena cava, thus avoiding the liver.
