CVS Flashcards
What is the first thing to form?
- Blood islands
Before development of the heart what does the embryo look like?
- Horseshoe shaped region at cranial end - cardiogenic area
- Buccopharyngeal membrane, runs down centre of embryo - future mouth
How does the primitive heart tube form?
- Lateral folding of embryo brings endocardial tubes in midline
- These fuse together to form heart tube
What is the heart tube held in?
- Heart tube is suspended in the pericardial cavity by a membrane that then degenerates
What are the 6 different sections of the primitive heart tube?
- Aortic roots
- Truncus arteriosus
- Bulbus cordis
- Ventricle
- Primitive atrium
- Sinus venosus
The primitive heart tube needs to be contained, so as it elongates how does it bend?
- Cardiac looping
- Cephalic portion: ventrally, caudally and to the right
- Caudal portion: dorsally, cranially and to the left
What does the looping achieve?
- Primordium of RV closest to outflow tract
- Primordium of LV closest to inflow tract
- Atrium dorsal to Bulbus cordis (inflow is dorsal to outflow)
How does the atrium communicate with the ventricle after looping?
- Via an atrioventricular canal
How does the sinus venosus develop?
- R&L sinus horns are equal in size (where inflow enters)
- Venous return shifts to the RHS
- Left sinus horn recedes
- Right sinus horn is absorbed by enlarging RA
How does the RA develop?
- Develops form most of primitive atrium (sinus venosus)
- Receives drainage from body (venae cava) and heart (coronary sinus)
How does the LA develop?
- From small portion of primitive atrium
- Absorbs proximal parts of pulmonary veins
- Receives oxygenated blood from lungs
What is the oblique sinus?
- Oblique pericardial sinus formed as LA expands absorbing pulmonary veins
Outline what foetal circulation looks like.
- Non- functional lungs
- Receives oxygenated blood from mother via placenta and umbilical vein
- By-passes lungs
- Returns to placenta via umbilical arteries
What is the ductus arteriosus?
- Joins the PA to the descending aorta
- So is a shunt
What is the role of the aortic arches?
- Early arterial system
- Bilaterally symmetrical
- Undergo remodelling to create major arteries leavening the heart
The 4th and 6th arches have major role what are these?
- 4th: Right -> proximal part of R subclavian artery
Left -> arch of aorta - 6th: Right -> R pulmonary artery
Left -> L pulmonary artery and ductus arteriosus
What are the nerve that correspond to the 6th aortic arch and what does the right and left section descend to?
- Recurrent laryngeal nerves
- R -> T1 and T2
- L -> T4 and T5
What two factors influence the course of the laryngeal nerve?
- Caudal shift of developing heart and expansion of developing neck region
- Need for a foetal shunt between PT and aorta
What septums need to be formed during septation?
- Interatrial
- Interventricular
- Ventricular outflow tract - pulmonary trunk
- aorta - Hence the 4 chambers of the heart
What is the first step of septation?
- Endocardial cushion forming
- Divide the developing heart into L&R channels
- Develops atrioventricular region
Outline the atrial septation process
- Division of atrium -> 2 septa with 3 ‘holes’
- Septum primum grows down towards the fused endocardial cushions
- Ostium primum is the ‘hole’ present before septum primum fuses with endocardial cushions
- Finally a 2nd crescent shaped septum, septum secundum, grows.
- The hole in the septum secundum is the foramen ovale
What is the foramen ovale remnant called in the adult heart?
- Fossa ovalis
What are the two different components of ventricular septation?
- Muscular
- Membranous
What happens to the muscular component of ventricular septation?
- It grows up towards endocardial cushion -> small gap
- This is the primary interventricular foramen
