Embryology Flashcards
(29 cards)
How is the primitively heart tube moved into the thoracic region?
By cephalocaudal folding
From the cranial to caudal end of the primitively heart tube, name its regions
Aortic roots; truncus arteriosus; bulbus cordis; ventricle; atrium; sinus venosus
What direction is blood pumped through the primitively heart tube?
Caudal to cranial
Describe how the primitively heart tube loops
- Cephalic, cranial portion bends centrally, caudally and to the right
- Caudal portion bends dorsally, cranially and to the left
What does looping of the primitively heart tube achieve?
- Places the inflow and outflow cranially with the inflow behind the outflow
- Causes atrium to communicate with the ventricle via the atrioventricular canal
- Transverse pericardial sinus is formed
What is the transverse pericardial sinus?
The space behind the inflow and in front of the outflow of the heart through which an object can be inserted
How does the sinus venosus develop
- Initially left and right sinus horns are equal in size
- As venous return shifts to the right the left sinus horn recedes
- Enlarging right atrium absorbs the right sinus horn
Describe the development of the right atrium
- Develops from most of the primitively atrium
- Absorbs the right horn of the sinus venosus
Describe the development of the left atrium
- Develops from a small portion of the primitively atrium
- Absorbs the proximal parts of the pulmonary veins
What is the left auricle?
The remainder of the primordial atrium in a fully developed heart, it is situated in the bottom of the left atrium
What is the oblique pericardial sinus?
The oblique sinus found around the back of the heart
How is the oblique pericardial sinus formed?
Formed when the left atrium expands and absorbs the pulmonary veins
What does the 4th aortic arch develop into?
- Right arch develops into the proximal part of the right subclavian artery
- Left arch develops into the arch of the aorta
What does the 6th aortic arch develop into?
- Right arch develops into the right pulmonary artery
- Left arch develops into the left pulmonary artery and Ductus Arteriosus
How do the great vessels develop?
- Early arterial system begins as a bilaterally symmetrical system of arched vessels
- Vessels undergo remodelling to create major vessels
- 6 aortic arches develop into vessels but aortic arch 5 has no derivatives
How does separation occur in the heart?
- Constriction between the primitively atrium and ventricle (atrioventricular canal) creates the first division
- Endocardial cushion develops on the dorsal and ventral sides of the atrioventricular canal
- Endocardial cushions grow towards each other to divide the heart into right and left channels
After division of the common atrium which holes are present?
- Ostium primum is the hole present before the septum primum fuses with the endocardial cushions
- Ostium secundum appears in the septum primum via apoptosis before the ostium primum closes
- Foramen ovale appears in the septum secundum
How does atrial septation occur?
- Septum primum grown down towards the fused endocardial cushions
- Septum secundum grown in a crescent shape
What is the purpose of the holes present after atrial septation?
Allows right to left shunting of blood
What is the fossa ovalis?
The adult reminant of the shunt used to bypass the lungs in utero
Describe ventricular septation
- Muscular portion of the septum grows up towards the fused endocardial cushions and forms the majority of the septum
- Membranous portion is derived from the spiral septum that grows to separate the truncus arteriosus
- Membranous septum fills the gap above the muscular septum and closes the primary interventricular foramen
Describe foetal circulation
- Lungs are non-functional so little blood flows through them
- Foetus receives oxygenated blood via the placenta and umbilical vein
- Deoxygenated blood bypasses the lungs and returns to the placenta via the umbilical arteries
What is the ductus venosus?
Vessel which transports oxygenated blood from the placenta to the inferior vena cavae in a foetus
What is the ductus arteriosus?
Vessel which allows blood to pass from the pulmonary trunk to the aorta in a foetus
