Embryology Of The Heart Flashcards
What is the first functioning organ to develop in the body
The heart
When does the heart begin beating and pumping
21 to 22 days after fertilisation
What does the heart develop from
The prominent heart bulge
Where is the predominant heart bulge found on the embryo
The anterior surface
What does the heart develop from
The heart develops from embryonic tissue called the mesoderm
What is the mesoderm
1 of the primary germ layers
Where does the development of the heart start
Towards the head end of the embryo in the cardio genie area
How does the mesoderm begin to develop the heart
The cardiogenic area receives signals from the endoderm which begins the process of forming 2 strands known as the cardiogenic cords
As the cardiogenic cords develop what happens to them and what do they become
As they develop a lumen forms around the meaning they become the endocardia tubes
What forms the primitive heart tube
The proactive heart tube is formed by the 2 endocardia tubes migrating towards each other and fusing to form one single tube
How many regions does the primitive hear tube from
5
What are the 5 regions the primitive heart tube forms
Tructus arteriosus
Bulbous cordis
Primitive ventricle
Primitive atrium
Sinus venosus
In the early heart where does blow flow into
The sinus venosus
What does the turn us arteriosus become in the fully developed heart
The ascending aorta and the pulmonary trunk
What does the bulbus cordis become in the fully developed heart
The right ventricle
What does the primitive atrium become in the fully developed heart
The right and left atria
What does the posterior of the sinus venous become in the fully developed heart
The sinoatrial node and the coronary sinus
How many days after fertilisation does the primitive heart tube begin to fold
The primative heart tube begins to elongate and begins to fold with the pericardium between day 23 and 28
What does the folding of the primitive heart tube become and why is it important
The folding of the primitive heart tube with the pericardium forms an s-shaped structure which is important as it places the chambers and major vessels in the correct alignment which is close to the adult heart
When does partitioning of the heart happen
5 weeks after fertilisation
What are the 3 blood shunts in a foetus
Ductus arteriosus
Ductus venous
Foramen ovale
When do the atrioventricular valves form
Between 5 and 8 weeks after fertilisation
When do semilunar valves form
Between 5 and 9 weeks after fertilisation
When does the heart begin to receive blood
At the end of the 4 weeks after initial fertilisation
How is the primary hear field formed
Mesoderm cells travel through the primitive heart tube to the embryo head which forms 2 horseshoe shapes known as 2 limbs and is known as the primary heart field
What does vascular endothelial growth factor do
This signals to the 2 limbs of the primary heart field to form 2 tubes
What forms the somatic splanchnic layers
The lateral mesoderm splits to form the somatic splanchnic layers
How does the heart fold to fuse the endocardial tubes
The heart folds in a cylindrical shape so the lateral borders meet in the midline and so the endocardial tubes fuse
How is the sinus venosus formed
The left and right Vitelline veins fuse
What is the sinus venosus known as
The inflow tract
How is the aortic sace formed
The aortea fuse
What is the aortic sace also known as
The outflow tract
What becomes the pericardial cavity
The primitive pericardial cavities fuse around the heart tubes which become the pericardial cavity
How do the heart tubes stay attached to the pericardial cavity
Via a sheet of mesoderm known as the dorsal mesocardium
Describe craniocaudal folding
This is when the primitive heart tube folds down length ways to form a shrimp-like shape which pushes the heart towards the chest, this happens around 4 weeks after fertilisation when blood can be seen traveling through the heart tube
When the heart loops what shape does it become
A c-shape
In the looping of the heart where do the truncus arteriosus and bulbus cordis move to
They form the top of the c-shape and move down and to the right
Where does the primitive ventricle move to during looping of the heart
This forms the middle of the c-shape and bends to the right of the midline slightly to the front
Where does the primitive atrium and sinus venous move to during looping of the heart
They form the bottom of the c-shape
During looping of the heart where does the enlarging ventricle move to
It moves to the left crossing over the midline and covers the atrium
Describe how the atria and ventricles become individual in the developing heart
During partitioning of the heart the mesoderm proliferates on both the anterior and posterior walls of the atrioventricular canal. This forms the anterior and posterior endocardial cushions which begin to grow towards each other and fuse. This fusion leads to the left and right atrioventricular canal.
The endocardial cells proliferate on the ventricular side of each canal which form the leaflets of the mitral and tricuspid valves.
The division of the canals causes the formation of the individual atria and ventricles
Describe how the atria are formed
The crescent septum primum grows downwards between the future left and right aria. As the endocardial cushions grow and fuse the ostium primum closes. As this closes the ostium secundum then appears in the centre. This grows cowards too but leaves a small opening known as the foramen ovale.
What is the septum secundum
This acts as a one way valve allowing blood to flow from the left to right atrium via the foramen ovale
When does the foramen ovale close
This closes after birth
What stimulates the closure of the foramen ovale
The decrease in right atrial pressure due to the occlusion of the placental circulation and an increase in the left atrial pressure due to an increase in the pulmonary venous return
Describe how the ventricles form
Muscular ridges grow upwards from the apex which fuse with the thin membranous regions hanging from the endocardial cushions which forms the right and left ventricles
Describe the development of the aorta
The aorta develops from the truncus arteriosus, when the 2 endocardial cushions appear on the right superior and left inferior walls they begin to grow with spiralling trajectory and so wrap around each other. This forms the artiopulmonary septum which then divides into the root of the aorta and the pulmonary artery
Where do the arteries of the head and neck region originate
They come from 5 aortic arches
What branches from the 1 aortic arch
The maxillary artery
What branches from the 2nd aortic arch
The stapedial artery
What branches from the 3rd aortic arch
2 common carotid
Part of the internal carotid
What branches from the 4th aortic arch
The left becomes the aortic arch
The right becomes the right subclavian artery
What branches from the 6th aortic arch
The pulmonary arteries
Ductus arteriosus
Where do the remaining arteries develop from
They develop from the right and left dorsal aortae
What does the left and right dorsal aortae form
They fuse to form the dorsal aorta
What branches from the dorsal aorta
Posterolateral arteries
Lateral arteries
Ventral arteries
Where does the venous system develop from
The sinus venosus
When does the sinus venosus start to receive deoxygenated blood
Week 4 of gastrulation
Where does the sinus venosus receive deoxygenated blood from
The sinus horns which open into the primitive atrium
Where do the sinus horns receive blood from
From the Vitelline/omphalomenteric veins and the common cardiac veins
Why does the sinus venosus become asymmetric and shifts to the right
Due to the left to right shunt
What does the right sinus horn become
This sinus horn is enlarged and becomes the smooth-wall of the right atria and the opening of the superior and inferior vena cava
What does the left sinus horn become
This sinus horn shrinks and persists as the coronary sinus and the oblique vein of the left atrium
Describe the development of the conducting system in the heart
A group of specialised myocardial cells in the wall of the sinus venosus synchronise their electrical discharge to form pacemaker centres
What do cells in the sinus venosus become in relation to the conducting system of the heart
Sinoatrial node
What do cells in the atrioventricular septum become in relation to the conducting system
Atrioventricular node
What do cells of the intraventricular septum become in relation to the conducting system
Bundle of HIS
What do the rest of the ventricular myocytes become in relation to the conducting system
They form modified cardiac myocytes which become the purkinje fibres
