Cardiovascular Development Flashcards
Which route for BF has higher pressure?
Left side (systemic)
Purpose of pulmonary route of BF
Oxygenation + removal of CO2
Purpose of systemic route of BF
Delivery system + transport of waste
Characteristics of fetal circulatory system
2 open circuits (contribution of BF to each other = parallel)
Mixing of O2 rich/poor blood
Pressure is higher on the right side
Why is R side pressure higher in fetuses?
Pulmonary vasculature is closed
–> higher resistance on the R side of heart (lungs are non-functional)
Purpose of the placenta - fetal circulation
Exchange site of O2, nutrients + waste
Very well vascularized & low resistance vessel –> reduces overall systemic vascular resistance in fetus
Purpose of foramen ovale
Bypasses lungs
Hole that allows for BF from RA –> LA
Purpose of ductus arteriosus
Connects PT and aorta
Key changes at birth
Opening of pulmonary vasculature (site of gas exchange is the lungs now)
= reduces resistance on R side = more resistance on L side
Removal of placenta
How do the fetal bypasses close?
Pressure differential when the baby is born (takes its first breath)
Postnatal remanent of foramen ovale
Fossa ovalis
Postnatal remanent of ductus arteriosus
Ligamentum arteriosum
Postnatal remanent of ductus venosus
Ligamentum venosum
Postnatal remanent of umbilical arteries
Medial umbilical ligaments
Postnatal remanent of umbilical vein
Ligamentum teres
What is the fossa ovalis?
Depression the interatrial septum
Pressure increase on L side after birth closes the flap door of the foramen ovale
How does the ductus arteriosum close?
Vasoconstriction after birth (due to decrease in PGs from placenta and increase in O2 after birth)
How does the ligament venosum form?
After the ductus venous collapses
How does the ligamentum teres form?
After the umbilical vein collapses
How does the aorticopulmonary septum form?
Bulbar ridges grow towards each other & fuse
The septum takes on a spiral shape
What does the aorticopulmonary septum do?
Separates the truncus arteriosus into the aorta and PT
Spiral shape = aorta and PT twist around eachother
How are SL valves formed?
Tissue outgrowth of TA divides into post. ant. right and left sections
Aorticopulmonary septum goes through the middle –> now 2 vessels with 3 cusps each
Persistent truncus arteriosus
Aorticopulmonary septum fails to develop –> no division
Result is a large arterial trunk that overlies R + L ventricles = mixing of blood
Infant becomes cyanotic
When does valve stenosis occur?
During truncus arteriosus development - either aortic or pulmonary valves
Unequal partitioning = aorticopulmonary septum deviation
Treatments for valve stenosis
Give PGs –> dilation of SM
Balloon valvuloplasty to stretch the valve
Patent ductus arteriosus
Ductus ateriosus stays open
Due to the pressure differential, this can cause volume overload in the pulmonary circuit (right side, L –> R shunting)
Formation of interatrial septum
Septum primum grows down to approach endocardial cushion (leaves an opening for the foramen primum, which allows for BF from R –> L)
2 holes come together to form the foramen secundum
Septum secundum comes down + partially covers the foramen secundum, but leaves small space for the foramen ovale (which allows for R –> L flow)
What makes up the valve foramen ovale?
Superior portion of the septum primum regresses (lower edge becomes the valve)
What causes the valve of the foramen ovale to close?
Higher pressure on the left side causes the valve to close (happens right after birth)
Patent foramen ovale
Foramen ovale fails to close –> so L to R blood shunting
Deoxygenated blood does not enter the systemic circulation –> acyanotic
Formation of the interventricular septum
Starts as a growth of tissue at the bottom of the heart, grows towards the endo. cushion
Membranous portion (derived from endo. cushion) stretches out.. Plays a large role in truncus arteriosus formation
Relationship between membranous portion and great vessels
Malformation of membranous portion = malformation of great vessels
Ventricular septal defect
Blood shunts from L –> R
Usually occurs in the membranous portion (its thinner)
What are the AV valves made up of?
Subendocardial mesenchymal tissue
Valves are sculpted by programmed cell death
What is the tetralogy of fallot composed of?
- Pulmonary valve stenosis: reduction in BF in PT
- Overriding aorta: picks up blood from LV & RV (mixed blood entering the systemic circulation)
- VSD: post-natal L –> R shunting = volume overload in RV = increased pulmonary pressure
- RV hypertrophy: natural response to increased pressure
Why does ToF occur?
Abnormal development of the interventricular septum
