Development Of The CV System 11 Flashcards
(26 cards)
How many weeks after conception does the heart begin to beat ?
3 weeks
What is interatrial septation ?
Septum needed to divide the atria
What is the first step of septation?
The inter atrial septum
Outline step 1 inter atrial septation
1) endocardial cushions develop in the atrioventricular region.
- this divides the developing heart into right and left channels.
Division of the common atrium invokes the formation of how many septa? And how many holes ?
Two septa and 3 holes
Outline the process of atrial septation
1) septum primum grows down towards the fused endocardial cushions
2) the ostium primum is the hole present before the septum primum fuses with the endocardial cushions
3) before the ostium primum closes , a second hole ( ostium secundum) apppears in the septum primum near the roof of the septum primum.
4) finally , a second crescent shaped septum called the septum secundum grows on the right side of the atria - again , this septum does not completely fuse with the endocardium cushions so this leaves a hole called the foramen ovale.
What is an example of the left and right atria both having components that are derived from the primitive atrium ?
Auricles
What does the inter atrial septum form ?
The right and left atria
What does the right atrium absorb ?
The sinus venosus
What does the left atrium absorb?
The pulmonary vein which then grows to absorb it and it’s first 4 branches
What are the remnants of the foreman ovale and the ductus arteriosus
1) fossa ovalis
2) ligamentum arteriosum
What is the relative pressures in the atria in Utero
Right atrial pressure is greater than left atrial pressure. This is because oxygenated blood from the placenta is arriving at the right atrium via the umbilical vein draining into the inferior vena cava
After birth , what are the relative pressures in the atria ?
Pressure in the left atria is greater than pressure in the right atria because septum primum is pushed against the septum secundum,
What are a few causes of atrial septal defect ?
- septum primum is resorted or too short
- ostium secundum defect
- septum secundum is too small
Hypoplastic left heart syndrome cause
The cause is unknown
- however embryological speculation states that there could be a defect in the development of mitral and aortic valves resulting in limited flow or atresia
- ostium secundum could be too small therefore right to left flow inadequate in utero
= results in underdeveloped left heart
Outline the process of ventricular septation
- starts off with a single ventricular chamber
- ventricular septum forms which has two components ( muscular and membranous)
1) muscular portion forms most of the septum and grows upwards towards the fused endocardial cushions, leaving a small gap called the 1 degrees interventricular foramen.
2) closure of the interventricular foramen occurs when the membranous portion of the interventricular septum which is formed by connective tissue derived from the endocardial cushions fill the gap.
Which is more common : ventricular septal defect or atrial septal defect ?
Ventricular septal defect
What is the common cause of ventricular septal defect ?
Most commonly the membranous portion of interventricular septum involved
Outline the process of septation of the outflow tract
Endocardial cushions also appear in the truancy’s arteriosus
As they grow towards eachother , they twist around eachother to form the spiral septum
What is the most common birth defect?
Congentpital heart defect
What is congenital heart defect?
Defect in the structure of the heart or vessels present at birth,
How many of those who have congenital heart defect survive to adulthood ?
90%
What could be a few possible causes of congenital birthdefects ?
- genetic
- exposure to chemicals , drugs , infectious agents
- unexplained cause
What is the most common cause of indirect maternal death ?
Congenital heart defects
