CVS Session 2 (Lecutre 2.2) Flashcards
What does lateral folding achieve?
Creates the primitve heart tube
What does cephalocaudal folding achieve?
Brings the heart tube into the thoracic region
What lies near the cardiogenic field?
Pericardial cavity
Why is the cardiovascular system the first to develop?
The neccessity for the rapidly growing embryo to obtain oxygen and nutrients and get rid of waste material.
What is the structure that suspends the primitve heart in the pericardial cavity? What occurs to it eventually?
Dorsal mesocardium which degrades and leaves the heart suspended in the PC by the great vessels
How do the cardiogenic cords develop?
Response from signals from the underlying endoderm cause the mesoderm in the cardiogenic area to form a pair of elongated strands.
What do the cardiogenic cords give rise to?
Cords develop a hollow centre becoming the endocardial tubes.
What do the endocardial tubes give rise to?
Lateral folding causes fusion of the two tubes to fuse forming the primitve heart tube.
What are the 6 distinct regions that are developed and being to pump blood?
From caudal to cephalic (tail to head)
1) Sinus venosus
2) Primitve atrium
3) Primive ventricle
4) Bulbus cordis
5) Truncus arteriosus
6) Aortic roots
What direction is the blood flow through the primitive heart tube?
From tail to head
What do the 5/6 regions develop into?
1) Sinus venosus - part of RA (posterior wall), coronary sinus and SAN
2) Primitve atrium - part of RA (ant wall) right auricle, part of LA (ant wall) and left auricle
3) Primitive ventricle - LV
4) Bulbis cordis - RV
5) Truncus arteriosus - ascending aorta and pulmonary trunk
When does looping start and finish? Which directions do the cephalic and caudal portion move in?
1) Day 23-28
2) Cephalic - ventrally, caudally, right
3) Caudal - dorsal, crainially, left
Why does looping occur?
Enlargement of the heart structures with limited space to move in as the pericardial cavity is a fixed space.
What happens after looping?
Atrium communicates with ventricle via the atrioventricular canal
How do the sinus venosus develop?
1) R & L horns equal in size
2) Venous return shifts to RHS, L sinus horn recedes
3) Rt sinus horn is absorbed by enlarging RA
How is the oblique sinus formed?
LA expands absorbing the pulmonary veins
What are the fetal circulatory shunts?
1) By pass the liver to reach the RA»_space;» majority bypasses lungs and reaches LA»_space;> LV»_space;» aorta
2) Small amount RA»_space;> RV»_space;> PT»_space;» bypass lungs via ductus arteriosus (trains RV)
What do the early arterial system begin as? How do they create the major arteries leaving the heart?
Bilaterally symmetrical system of arched vessels which undergo extensive remodelling.
What do the 4th and 6th archers give rise to?
4th - R = prox part of R subclavian art
L = arch of aorta
6th - R = R pulmonary art
L = L pul art + DUCTUS ARTERIOSUS
What is noted about each aortic arch?
Each arch is associated with a corresponding nerve
Which nerve is corresponds with the 6th arch?
Recurrent laryngeal nerve (branch of vagus)
Describe the course of the right and left RLN.
Right - descends to T1-T2 before returning
Left - descends to T4-T5
Which two factors influence the course of the nerves?
1) Caudal shift of developing heart + expansion of the developing neck region
2) Need for a fetal shunt between PT & aorta
What structures do the LRLN become hooked around?
Shunt between PT and aorta = DA
