Cardiac Development Flashcards
Vasculogenesis
Creation of blood vessels
Angiogenesis
Remodelling and pruning of vessels into a recognisable circulatory system
Fistula
Abnormal connection between organs
VEGF
Vascular Endothelial Growth Factor
RA
Retinoic Acid
Circulation , according to Harvey, is ?
One of the first FUNCTIONAL systems to form in the embryo
Why?
Embryo is too big by 3rd week (d14+) to survive without its own circulatory system
What is the most vulnerable time for major heart deformations?
3.5 -6.5 weeks
Formation of a tube
As development progresses the two heart tubes from either side come together and fuse to give one cardiac tube. (d21)
•The cardiac tube then needs to loop and be partitioned
Cardiac tubes start to loop to form the primitive heart: changing from a straight tube to a complex, 4 chambered heart. What drives this?
Changes in Bine Morphogenetic Protein (BMP) signalling which allows cellular shape change by changing cell adhesion
Role of Retinoic acid
Specifies posterior (atrial) region
Function of Looping
Responsible for forming main chambers: atria and ventricles
What process is responsible for the formation of the main heart chambers?
Looping
When does looping begin?
After initiation of rhythmic heart contractions and blood flow
What helps with looping ?
Pressure
The division of the heart occurs via which 3 mechanisms?
- Endocardial cushions
- Single outgrowth (septum primum and secundum)
- Expansion of surrounding areas
Cells in the atrioventricular canal derive from?
Endocardium
Cells in the outflow tract derive from?
Neural crest cells
Valves form from?
Endocardium fusion
Mesenchymal tissue becomes fibrous, whilst the softer tissue below “erodes”, leaving valves and muscular cords.
What are Septa?
Septa are formed at boundaries to subdivide the heart into chambers. (d27-37)
Which disease has the following characteristics:
- Autosomal dominant mutation in Tbx5
- Associated with various cardiovascular defects (75%)
- Atrial septal defects,
- Ventricular septal defects
- Cardiac conduction: brachycardia or fibrillation
- Limb (thumb) defects
- Shoulder girdle defects
- Extent depends on mutation point
Holt- Oram syndrome
Division between the atria is not complete until after birth.
True or false
True
Two septa form in the atria:
Septum Primum
Septum Secundum
CEll death creates a hole called?
Foramen ovale
Function of Foramen ovale
Allows blood flow between the RA and LA
Consequences of partitioning failure
Atrial septal defects
Ventricular septal defects
Primum and secundum septa form via
Outgrowth
A ridge at the back of the atria grows out to occlude the space Tissue grows from the back wall to split the chamber completely
Septal divisions are created via ?
- Outgrowth
- Expansion: of surrounding tissue
Surrounding tissue expanding beyond a fixed point will lengthen a septum. The space will never be completely occluded this way
Congenital heart defects
Stenosis:
•Eg Narrowing
Septal defects (6.4/10,000) •“holes”
Valve defects:
• Stiffening of valves/fusion
•Lack of valve
Vessel defect:
•In the wrong place (transposition)
What is the Tetralogy of a fallout?
- Pulmonary valve stenosis
- A large VSD (ventricular septal defect)
- An overriding aorta. ie aorta is between L and R ventricles, directly over the VSD. Oxygen-poor blood from the RV flows into the aorta instead of the pulmonary artery.
- Right ventricular hypertrophy
Ectopia Cardis
Heart outside of body
Heart progenitor cells move in the primitive streak to form?
Primary heart field- above the embryo
This structure:
Forms centrally to pharynx
Contributes to cardiac lengthening
Right ventricle and outflow tracts
Forms the dorsal mesocardium, anchoring the cardiac tube to the wall
Secondary heart field
Secondary heart field forms?
Forms the dorsal mesocardium, anchoring the cardiac tube to the wall
Explain formation of heart tube
- CElls in Primary heart field form a horseshoe-shaped tube and induce myoblasts in the surrounding mesoderm, giving two of the heart’s layers
ENDODERM
MYOCARDIUM
- Folding of the embryo brings the tubes together
Function of Tbx 5
Express division for Septa.
What happens to the High concentration at the bottom of mesoderm of Retinoic acid?
Diminishes as it moves up
Low concentration of Retinoic acid at the top in the mesoderm specialises
Ventricles
The mesoderm will initially produce its win Retinoic acid, what happens next?
Cardiac tube will produce its own Retinoic acid to help patterning
Endocardial cushion
Outgrowth into cardiac tube - valves are formed this way
Cardiac tube is made of three regions:
Truncus arteriosus - top
Bolbus cordis
Sinus venosus with atria, vitelline veins
Which gene okay a role in position when Selta are formed?
Tbx 5 genes
Septum primum and secudnum form in what way?
Outgrowth
A ridge at the back of the atria grows out to occlude the space
Creation of septa can occur in two ways:
Outgrowth
Expansion of surrounding tissue
Creation of septa (septal division)via outgrowth
Tissue grows from the back wall to split the chamber completely
Creation of septa (septal division) via expansion of surrounding tissue
Surrounding tissue expanding beyond a fixed point will lengthen. The space will never be completely occluded this way
Name the process:
Tissue grows from the back wall to split the chamber completely
Outgrowth to create septa
Name the process:
Surrounding tissue expanding beyond a fixed point will lengthen. The space will never be completely occluded this way
Expansion of surrounding tissue to create septa
Congenital heart defects statistics
1% infants have heart/vascular defects
30% associated with other abnormalities
