S3) Development of the Heart Flashcards
Identify the features of the primitive heart tube
Mnemonic: All The Best Vaccuums Are Silver
Relate the following embryological structures to the corresponding mature derivatives:
- Primitive atrium
- Primitive ventricle
- Primitive atrium contributes a small component to each atrium
- Primitive ventricle forms left ventricle
Relate the following embryological structures to the corresponding mature derivatives:
- Sinus venosus
- Bulboventricular sulcus
- Bulbus cordis (proximal 1/3, Conus cordis, truncus arteriosus)
- Sinus venosus is enveloped by the septum transversum to form the diaphragm
- Bulboventricular sulcus forms to the grooves that separate the ventricles
- Bulbus cordis, etc forms right ventricle & outflow tract
What is septation?
Septation is the process in which the primitive heart tube becomes divided into chambers and the outflow tract is subdivided into pulmonary trunk and aorta
In 3 steps, describe the process of septation
⇒ The junction between the atrium and ventricle constricts to form the atrioventricular canal
⇒ This canal provides a framework for the formation of the inter-atrial and interventricular septa
⇒ Endocardial cushions form in the AV canal, allowing septa to grow inferiorly (inter-atrial) and superiorly (inter-ventricular)
What is the role of endocardial cushions in the truncus arteriosus?
Endocardial cushions form in the truncus arteriosus and contribute to the formation of a spiral septum dividing the outflow tract into pulmonary trunk and aorta
Atrial septation is complicated by the fact that the circulatory needs of the embryo/foetus are different to those of the adult.
How does the body cater for this?
Right – to – left shunt (the foramen ovale) must be maintained during life in utero, but this must be instantly sealable at birth
Describe foetal circulation from the placenta to the body in terms of shunting
Identify the specific shunts which:
- By pass the lungs
- By pass the liver
- By pass the right ventricle & lungs
Describe the formation of the foramen ovale
Describe the closure of the foramen ovale
Describe the formation and looping of the primitive heart tube
- Initially, the cardiogenic field lies at the cranial end of the embryo
- In the 3rd week of development, the endocardial tubes are formed
- Endocardial tubes are brought together during embryonic folding and fuse in the mid-line to create the primitive heart tube
Describe the blood flow through the primitive heart
- Receives blood (inflow) at its caudal pole
- Pumps blood (outflow) from its cranial pole
Briefly describe the process of looping in the primitive heart
Looping places both the inflow and outflow vessels cranially, with the inflow vessels dorsal to the outflow
Be able to identify the regions of the developing heart
Describe, briefly, the development of the great vessels
- Early arterial system begins as a bilaterally symmetrical system of arched vessels
- They undergo extensive remodelling to create the major arteries leaving the heart
Describe 4th aortic arch derivatives
Fourth arch:
- R = proximal part of R Subclavian A
- L = arch of aorta
Describe 6th aortic arch derivatives
Sixth arch:
- R = R pulmonary artery
- L = L pulmonary artery and Ductus arteriosus
Each aortic arch has a corresponding nerve.
Which arch corresponds to the recurrent laryngeal nerve?
- Recurrent laryngeal nerve corresponds to the 6th aortic arch
- Right descends to T1-T2 & left descends to T4-T5
What influences the course of the recurrent laryngeal nerve?
- Caudal shift of the developing heart
- Expansion of the developing neck region
- Need for a foetal shunt between PT & aorta
