Week 3 - Development of the Heart and Congenital Heart Defects Flashcards
What is the coronary sinus a remnant of?
The left sinus horn
How is the oblique pericardial sinus formed?
It is formed as the left atrium expands and absorbs the pulmonary veins.
Why does the fetal circulation allow blood to bypass the lungs?
- The lungs are non-functional
2. The blood received from the placenta is already oxygenated: there is no requirement for oxygenation
Outline the embryonic development of the major arteries leaving the heart.
Aortic arches:
The aortic arches are remodelled to create the mature disposition
1. Each arterial system begins as a bilaterally symmetrical system of arched vessels
2. These undergo extensive remodelling to create the major arteries leaving the heart
Name the derivatives of the fourth aortic arch.
Right: Proximal part of right subclavian artery
Left: Arch of aorta
Name the derivatives of the sixth aortic arch.
This is referred to as the pulmonary arch.
Right: Right pulmonary artery
Left: Left pulmonary artery and the ductus arteriosus
Which nerve corresponding to the sixth aortic arch?
Recurrent laryngeal nerve: Branch of the vagus nerve (CN X)
-Right descends to T1-T2, Left descends to T4-T5
What factors influence the course of the recurrent laryngeal nerve on the right and left sides?
- Caudal shift of the developing heart and expansion of the developing neck region
- Need for a fetal shunt between PT and aorta
What is the position of the left recurrent laryngeal nerve (within the heart)?
The left recurrent laryngeal nerve becomes hooked around the shunt between the PT and the aorta
Outline the embryonic development of the right and left atrium (i.e. what structures are they formed from)?
- Right atrium: Forms from most of the primitive atrium and the sinus venosus
- Left atrium: Develops from a small portion of the primitive atrium and absorbs the proximal portions of the pulmonary veins
Which week does the embryo fold in?
Week 4
Briefly outline the process of embryonic folding.
Cephalocaudal folding occurs, where the head and tail fold under. This occurs in conjunction with lateral folding, where the edges fold under and meet each other.
Describe the changes that occur in the fetal circulatory shunts after birth.
- Respiration begins: opening of the pulmonary circulation
- Pressure in the left atrium increases
- Foramen ovale closes: pressure in the left atrium rises above the pressure in the right atrium, and the septum primum is pushed against the septum secundum
- DA contracts in the presence of higher oxygen saturation after birth
- Placental support removed: the ductus venosus closes (it does not receive blood from the umbilical cord)
Name the adult derivatives of the following fetal shunts:
- Foramen ovale
- Ductus arteriosus
- Ductus venosus
- Umbilical vein
- Fossa ovalis
- Ligamentum arteriosum
- Ligamentum venosum
- Ligamentum teres (hepatis)
What is the adult derivative of the sinus venosus?
Right atrium, except for the left horn
What are the adult derivatives of the primitive atrium?
Auricles of definitive atria
What is the main adult derivative of the primitive ventricle?
The left ventricle
What is the adult derivative of the bulboventricular sulcus?
Primary interventricular foramen
Name the adult derivatives of the bulbus cordis.
- Proximal 1/3: Right ventricle (Trabeculated)
- Conus cordis: Outflow tract of left and right ventricles
- Truncus arteriosus: Roots and proximal aorta and pulmonary trunk
Which cardiac defect is the most commonly occurring congenital heart defect?
Ventricular septal defect
What is the embryological basis for transposition of the great vessels?
The conotruncal septum does not adopt a spiral course.
What is the embryological basis for Tetralogy of Fallot?
Unequal division of the conus cordis occurs.
