Fetal Circulation Flashcards
The placenta is composed of a maternal & fetal component. What is the fetal component derived from? The maternal?
- Chorionic Sac
2. Endometrium
What is the function of the placenta?
- Gas exchange
- Nutrients
- Removal of wastes
- hormones & Immunologic exchange
How does oxygenated fetal blood enter the fetus? How does this deoxygenated blood then LEAVE the fetus?
Umbilical VEINS
Umbilical Arteries
What does the ostium premium form from? The foramen scandium?
- Inerior extension of septum premium
2. Fenestrations in the septum premium form Foramen Secundun
What does foramen ovale connect?
Right Atrium to Left Atrium
What is the flow of blood from the Fetal Branch Villi to the Aorta? (9)
- Fetal Branch Villi
- Umbilical Vein
- Ductus Venosus
- IVC
- Right Atrium
- Foramen Ovale
- Left Atrium
- Left Ventricle
- AORTA
Because the lung has high pressures and is collapsed in the fetus, where is blood shunted as it enters as it travels from the right atrium –> right ventricle –> pulmonary artery?
Ductus Arteriosus!
What structure connects the umbilical vein to the IVC?
Ductus Venosus
Uterine contractions that clamp the cord and decrease pressure in the umbilical vein, and thus decrease pressure where? (forming a pressure gradient in the heart)
Right Atrium
What is the result of clamping the Umbilical Artery? Where does pressure increase?
Increase Systemic Vascular resistance, increasing pressure in the LEFT ATRIUM
What is the main result of clamping both the umbilical vein & the umbilical artery?
DECREASEs flow across foramen ovale
- increasing pressure in Left Atrium forces this SHUT
septum primum presses against septum scandium
What happens to pulmonary resistance as the first breath is taken (and alveoli & capillaries expand)?
Pulmonary Resistance DROPS
Decrease in pulmonary resistance causes flow from right ventricle to pulmonary and increases pressure in the LEFT Atrium. What is the result?
Further facilitates closure of FORAMEN OVALE
What does Bradykinin do?
Causes close of Ductus Arteriosus
What are the remnants of the following:
- Umbilical Artery
- Umbilical Vein
- Ductus Arteriosus
- Ductus Venosis
- Medial Umbilical Ligament
- Ligamentum Teres
- Ligamentum Arteriosum
- Ligamentum Venosus
Describe the structure of Fetal & Adult Hemoglobin.
- Fetal = 2 alpha & 2 gamma
2. Adult = 2 alpha & 2 BETA
What has a higher affinity for oxygen HbF or HbA? Which direction is the oxygen dissociation curve shifted?
- HBF!
2. Shifted LEFT! (fetus wants to hold on to oxygen)
What is the effect of 2,3 DPG on HbF? on HbA?
- NO affect on fetal
2. HbA –> curve shifts RIGHT (decreases binding affinity)
Up until 30 weeks of gestation, where does fetal hematopoiesis occur? Where is it after this?
- Fetal Liver & Spleen
2. Bone Marrow!
As fetal hemoglobin shifts to adult hemoglobin, how is the oxygen dissociation curve changed?
SHIFTS RIGHT
2,3 - DPG
What is the function of 2,3-DPG? Is the affect the same in fetal and adult hemoglobin?
2,3-diphosphoglycerate lowers the affinity of Hb for oxygen by binding to and stabilising deoxyhemoglobin.
The gamma chains of HbF allow less 2,3-DPG binding. Therefore, HbF has a higher O2 affinity/ decreased unloading in the presence of 2,3-DPG than HbA
What are the 5 cyanotic lesions?
Cyanotic lesions (“5-Ts”):
Transposition of the Great Vessels Truncus Arteriosis Total Anomalous Pulmonary Venous Return Tricuspid Atresia Tetrology of Fallot
How does the pressure change in the right ventricle as the umbilical vein is clamped?
Decreased pressure in right ventricle from clamping the umbilical vein.
What are the pressure changes regarding Dustus Arteriosus?
Increased SVR secondary to crying, moving, and clamping the umbilical arteries.
Decreased PVR secondary to opening of the lungs.
Reversal of flow in the ductus arteriosus.
