6. Embryology 1 Flashcards
What effect does folding of the embryo have on early development of the heart?
Lateral folding - creates a heart tube
Cephalocaudal folding - brings tube into thoracic region
What happens in the formation of primitive heart tube?
Blood islands on either side come together and form a tube
What are the 6 sections of the primitive heart tube?
List from where blood enters to exits
Sinus venosus (vessels) Atrium Ventricle Bulbous cordis (narrower than ventricle) Truncus arteriosus Aortic roots
What happens during looping?
Tube elongates
Runs out of room
Twists and folds up
Places the inflow and outflow in the correct orientation with respect to each other
Expansion of ventricle and atrium, atrium moves above ventricle
At what stage does the transverse pericardial sinus form from?
Looping
Describe the development of the sinus venosus?
R and L sinus horns equal in size
Venous return shifts to RHS, L sinus horn recedes
R sinus horn absorbed by enlarging RA
What does the right atrium develop from?
Most of primitive atrium
Sinus venosus
Receives venous drainage from body and heart
What does the left atrium develop from?
A small portion of primitive atrium
Absorbs proximal parts of pulmonary veins
Receives oxygenated blood from lungs
How is the oblique sinus formed?
Formed as left atrium expands absorbing the pulmonary veins
Why does fetal circulation differ from mature circulation?
Oxygenation and removal of CO2 occur at placenta
Shunts are required to maintain fetal life
Shunts must be reversible at birth
Which side of the heart does the oxygenated blood arrive into?
Right side of heart via IVC
How does the blood flow round the fetus?
Arrives from placenta
Travels in blood vessel that bypasses liver
Drains into IVC
Enters RA
Most blood moves into LA to bypass lungs, moves into LV, drains into aorta and to the rest of the body
Some blood flows into RV, then into PT then into aorta to rest of body
Why does some blood flow into the RV?
To allow normal development of the RV
What are the 3 shunts and where are they?
Ductus venosus - connects umbilical vein to IVC, bypassing liver
Foramen ovale - RA to LA
Ductus arteriosus - PT to aorta
What happens to the shunts after birth?
Respiration begins
LA pressure increases, foramen ovale closes, ductus arteriosus contracts
Placental support removed, ductus venosus closes
