Development of the CVS Flashcards
What are the 4 main stages?
- Development of Primordial Heart Tube
- Looping of the Heart Tube
- Atrial and Ventricular Septation
- Development of the Outflow Tract
What is this?
Bilateral heart primordia
Which part of the lateral plate forms the circulatory system (and other viscera)?
Splanchnic mesoderm
How are the two primitive heart tubes formed?
Angiogenic cell islands collect in the lateral plate splanchnic mesoderm, move towards the midline and coalesce
Why is the cardiovascular system the first major system to function in the embryo?
Diffusion is not enough to satisfy the growing embryo
Where do blood vessels first appear?
In the wall of yolk sac, allantois, connecting stalk and chorion
When and where do the angioblastic chords form?
Appear in the 3rd week in the cardiogenic mesoderm
What do the angioblastic chords do?
Canalize to form heart tubes
How is the primordial cardiovascular system formed?
Tubular heart joins blood vessels in other areas
Where is the pericardium derived from?
The intra-embryonic coelom (space between the splanchnic and somatic mesoderm)
What part of the pericardium is formed from the somatic mesoderm?
Parietal layer of serous pericardium and fibrous pericardium formed from somatic mesoderm.
What is the visceral layer of the serous pericardium formed from?
Splanchnic mesoderm
What are the following structures?
How many horns does the sinus venosus have?
Two horns
Where does each sinus venosus get its venous blood?
The yolk sac (viteline vein)
Placenta (umbilical vein)
Body of the embryo (common cardinal vein)
How many aorta exist in the embryo?
2, the adults only have the left one
How many aortic arches exist initially?
6
What is the truncus arteriosis continuous with?
The aortic sac
How is the u shape of the bulboventricular loop formed?
Bulbus cordis and the ventricle grow faster than the other regions forming a U shaped loop
What is dextrocardia?
Abnormal cardiac looping
How does dextrocardia arise?
Heart tube loops to the left side instead of the right thus coming to lie facing the right.
It is the moset requent abnormality of the heart - •Dextrocardia can be associated with situs inversus (transposition of viscera)
When does partitioning of the primordial heart take place?
Around the 27th and 37th days of embryonic development
What does the endocardial cushion do?
Separates the right atrioventricular opening from the left atrioventricular opening, forming left and right atrioventricular canals
atrial septal defect (ASD)
& ventricular septal defect (VSD) are associated with malfunctinos of development with?
Septum formation
Look
Label the diagram
Label the diagram
What is the ostium primum?
The opening between the septum primum and the endocardial cushion
Where does the foramen secundum form?
The upper end of the septum primum (cell death)
Where does the septum secundum form?
On the right of the septum primum
How does the septum secundum grow?
Grows and overlaps the foramen secundum - But septum secundum is incomplete – perforated by oval foramen (foramen ovale)
Label the diagram
What is the role of the oval foramen before birth?
- Allows most of the blood to pass from the right atrium to the left atrium (non functioning lung)
- Prevents the passage of blood in the opposite direction
What is the function of the oval foramen after birth?
Normally closes allowing for increased pulmonary blood flow and shift of pressure to the left atrium.
Septum primum fuses with the septum secundum
What is the oval fossa?
Remnant of foetal oval foramen
How does hole in the heart arise?
Non closure - no fusino between the septum primum and the septum secundum
What are the 4 clinically significant types of ASD?
A)Foramen secundum defect
B)Endocardial cushion defect with foramen primum defect
C)Sinus venosus defect
D)Common atrium
The first two types are more common
What is the opening called formed by the muscular ventricular septum?
Interventricular septum
How is the membranous interventricular septum formed?
Aorticopulmonary septum rotates and fuses with muscular ventricular septum to form membranous interventricular septum, closing interventricular foramen.
What is the role of the endocarial cushions in partitioning?
Separates the atria from ventricles
Contributes to atrial septation
Contributes to the membranous portion of the interventricular septum
When does partitioning of the bulbus cordis occur?
5th week of development
How is the aorticopulmonary septum created?
Spiralling of the bulbus cordis and the truncus arteriosis resulting in the formation of aorticopulmonary septum. •This septum divides BC and TA in to aorta and pulmonary trunk
What is the most common congenital heart disease?
Ventricular septal defect
When does the SA node develop?
During week 5
Where is the SA node?
•Adult location of SA node – High in the right atrium near the entrance of the SVC
Where do the av node and the bundle of his form?
From cells of AV canal and sinus venosus
What is Cot death or sudden infant death syndrome (SIDS) caused by?
Cause – abnormalities of conducting
tissue
Look
Who are more likely to be affected from congenital heart disease?
Males
ASD more common in females
VSD is more common in males
What are the causes of congenital heart disease?
Aetiology - Multifactorial
- Rubella infection in pregnency (PDA)
- Maternal alcohol abuse (septal defects)
- Maternal drug treatment and radiation
- Genetic - 8%
- Chromosomal – 2% (Down’s and Turner’s syndrome)
What is a common cause of cyanotic disease in newborn infants?
Transposition of great vessels
How does transposition result in complications?
•Permit exchange of systemic and pulmonary circulation
What causes transposition of great vessels?
Failure of aorticopulmonary septum to take a spiral course
Defective migration of neural crest cells
What are the heart defects associated with the tetralogy of fallot?
- Pulmonary stenosis (obstruction of right ventricular outflow)
- Ventricular septal defect (VSD)
- Dextroposition of aorta (“overriding” aorta)
- Right ventricular hypertrophy
What is the cause of tetralogy of fallot?
Unequal division of the conus due to anterior displacement of aorticopulmonary septum
