Development of the Heart

Formed from _________ layer around week __

It is the first organ to develop and function straight away. Why?

Development begins at ______ end of neural plate as 'heart __________'

Heart Primordium/Crescent becomes the _____ __________

Crescent contains 2 types of cells:

Growth of Crescent:

1. Medial expansion

3. Elongation of tube
(consisting of inner layer of endocardium, cardiac jelly then myocardium)

4. Looping of the tube -
Always coils to the _____ first (except in dextrocardia)

5. Addition of cells:
a) ___________ to separate outflow tract and form nerves
b) __________, originating from below tube, to form visceral ________, coronary vessels and other cell types

By _____ days, chambers are now visible, as parts of the tube have ballooned. Ventricles also now contain __________

6. Septation:
Forming the _______ between chambers

A) AV Septation to separate _____ from ___________

i) _________ cells undergo EMT (______ __________ _________)
and populate ______ ______ to form superior and inferior cushions

ii) 2 cushions fuse to leave tubes either side which become _______ between A + V. Surrounding cells become ________

Failure of AV septation results in AVSDs (_____________ ______ ______), common in babies with ______ __________

B) Atrial septation.
Begins with primary ______ _______, which elongates and fuses with ___ ______

Hole forms at top of septum called _______ ______ to allow __________________

The ______ _______ usually closes at birth. 10% of population have ________ FO, which can be lived with, due to pressure gradient keeping flap closed. Larger hole = _______ _______ type ASD (_____ _______ ______)

C) Ventricular septation:
_________ thicken and extend up to AV cushions.
Small piece of _______ joins septum to AV cushions as final part to fuse.

VSDs (______ ______ ______) can occur if ______ does not fuse. Called __________ VSD (75% cases).
Can also occur if there are holes in the _________. Called _______ VSD, but usually fixes itself at birth (25% cases)

D) OFT Septation (____________ ______)
Very complex - uses cushion system. Separates multiple _____ into 2 distinct ones: ________ ________ and ________ leaving the 2 atria. There are many possible defects with this stage.

TGA (________ of the ______ _________) causes ______ and ________ _______ to be connected to the wrong ventricles. Corrected with surgery.

TOF (______ __ _____) is a group of 4 defects commonly seen together:
1. VSD
2. ________ aorta, so both _______ and __________ blood enter it, with little going to the ______ _______.
3. ________ stenosis
4. RV __________
Corrected by early surgery.

Conduction tissue is derived from _________. Needs insulation.