Embryo Flashcards
In vasculogenesis, blood islands appear in the ____________ mesoderm during the __________ week of development.
Lateral plate mesoderm
3rd week
In vasculogenesis,
Blood islands at the cranial end of the embryo merge to form a ___________ shaped tube lined with _________________. This tube is then surrounded by __________, forming the cardiogenic field.
Blood islands @ cranial end merge → horseshoe shaped tube
- lined w endothelial cells
- surrounded by myoblasts
→ cardiogenic field
After formation of the cardiogenic field, the early heart tube expands into the new forming ________________, before folding into its 4 chambers.
Pericardial cavity
Once surrounded by the pericardial cavity, the primitive heart tube folds to develop 2 bulges:
1) _____________________
2) _____________________
These continue to bend to create the cardiac (bulboventricular) loop during the ___________ week of development
1) Cranial budge → bulbus cordis
2) Caudal bulge → primitive ventricle
4th week of development
What is the order of structures in the early heart tube from cranial to caudal?
1) Truncus arteriosus
2) Bulbus cordis
3) Primitive ventricle
4) Primitive atrium
5) Sinus venosum
(Blood flows in opposite direction)
What does the truncus arteriosus give rise to?
Pulmonary artery and ascending aorta
What does the bulbus cordis give rise to?
RV and outflow tracts
What does the primitive ventricle give rise to?
LV
What does the primitive aorta give rise to?
RA/LA
The sinus venosus is formed by ____________________________.
The major embryonic veins:
1) common cardinal
2) umbilical
3) vitelline
With time, venous draining is prioritise to the (L/R) side of the embryo and the (L/R) sinus horn becomes smaller to form the __________________ which _____________. The other becomes part of the ______.
Venous draining prioritise R →IVC
L smaller → coronary sinus
A single pulmonary vein on the (R/L) side of the ___________ divides to form the 4 pulmonary veins.
L side of primitive atrium
The process of dividing the heart tube into its 4 chambers is known as _____________ and involves the inward growth of the __________ (cushions) to meet and split the atrium, ventricles, bulbus cordis, and atrioventricular canal.
Septation (~5weeks)
- inwards growths of endocardium (endocardial cushions)
Describe the formation of the L and R atria from the primitive atrium.
1) Septum primum (tissue from roof of primitive atrium) extends to meet the endocardial cushions
→ ostium primum (gap btwn septum primum and endocardial cushions)
2) Septum secundum (2nd tissue from roof) extends to lean against septum primum
→ ostium secundum (gap btwn septum secundum and endocardial cushions)
→ 1-way valve allowing blood to shunt from RA to LA
→ Foramen ovale
What is the foramen ovale?
A one-way valve formed by septum primum and secundum that allows for shunting of blood from RA to LA during fetal development?
How does the foramen ovale close physiologically?
Change in pressure between atria at birth holds the septum primum closed against septum secundum → foramen ovale permanently sealed
Describe the formation of the left and right ventricle.
1) Muscular interventricular septum arise from floor of ventricles towards endocardial cushions → temporary interventricular foramen
2) Endocardial cushion extends inferiorly → complete interventricular septum
→ close interventricular foramen
What does the sinus venosus give rise to?
Left horn → Coronary Sinus
Right horn:
Umbilical vein → degenerate
Common cardinal vein → SVC
Vitelline vein → IVC
Describe the splitting of the primitive outflow tracts to form pulmonary and systemic circulatory systems.
1) Ridge forms from inner part of truncus arteriosus → aorta
2) Ridge forms between either sides of bulbus cordis → pulmonary trunk
What is the tetralogy of fallot formed by?
Abnormal division of truncus arteriosus
Describe the process of vasculogenesis.
1) Mesodermal cells differentiate → hemangioblasts differentiate → haematopoietic stem cells + angioblasts
2) Angioblasts →blood vessels
What is the difference between angiogenesis and vasculogenesis?
Angiogenesis:
- formation of new blood vessels from exisiting blood vessels
Vasculogenesis
- formation of blood vessels from angioblasts (from mesodermal cells)
What is the function of the vitelline vessels?
Blood flow between embryo and yolk sac
What do the vitelline arteries give rise to?
3 anterior branches of abdominal aorta:
celiac, superior mesenteric, inferior mesenteric
What do the vitelline veins give rise to?
IVC and hepatic veins
What is the function of the umbilical vessels?
Blood flow between chorion of placenta and embryo
Umbilical veins carry (de-/O2) blood to the embryo.
Umbilical vein: O2 blood to fetal heart
Umbilical artery: De-O2 blood to placenta
What does the umbilical vein give rise to?
Ligamentum teres
What do the umbilical arteries give rise to?
Internal iliac, Superior vesical arteries, Ligaments
What is the function of the cardinal veins?
Drain head, shoulder, abdomen, pelvis, lower limbs
What do the cardinal veins give rise to?
1) Vena cavae
2) Brachiocephalic veins
3) Azygos veins
4) Hemiazygos veins
Describe the flow of oxygenated blood form the placenta to the aorta.
Umbilical vein → ductus venosus
→ 1/2 go liver, 1/2 go to IVC
IVC → RA → FO → LA → LV → Aorta
Describe the flow of de-oxygenated blood from the SVC to the umbilical arteries.
SVC → RA (mixes w O2 blood from IVC)
→ RV → DA → Aorta → Umbilical arteries
At birth, the ductus venosus closes via ________________, and degenerates to become _________________.
Ductus venosus closes via sphincter @ umbilical vein end
→ forms ligamentum venosum
What does the foramen ovale form in an adult?
Fossa ovalis in right atrium
What causes a atrial septal defect?
Failure of foramen ovale to close anatomically within 6 mths of birth
In a px with an ASD, what would exacerbate the backflow of blood form the left to right atrium?
Whatever ↑intrathoracic P
eg. sneezing, coughing
