CADE EXAM 3: Fetal Circulation (Embryo)

clinical correaltion : closure and persistence of the ductus arteriosus (DA) :the DA constricts at birth but theres is often

a small shunt of blood via the DA from the aorta to the pulmonary trunk for 24-48 hours in a normal full-term infant

during the transition stage, the closure of

fetal vessels and the oval foramen is initially a functional change. Later, anatomic closure results from proliferation of endothelial and fibrous tissues.

fetal circulation: from the placenta, through the umbilical vein,

highly oxygenated, nutrient-rich blood returns to the fetus -on approaching the liver, approximately half of the blood passes directly into the Ductus Venous, a fetal vessel connecting the umbilical vein to the inferior Vena Cava -> consequently, this half of the blood bypasses the liver. (allowing more oxygenated blood to go straight to the IVC) ->the other half of the blood in the umbilical vein flows into the sinusoids of the liver and enters the IVC through the hepatic veins.

PGE 1

is used to keep DA patent in ductal dependent cardiac anomalies, like transposition of great arteries

ductus venosus becomes

ligamnetum venosus the ductus venosus (DV) becomes the ligamentum venosum. This ligament passes through the liver form the left branch of the portal vein and attaches to the IVC.

in premature infants the DA

may remain open much longer. failure of the PDA to close leads to hemodynamically significant left to right shunting of blood and undesirable pulmonary, renal and gastrointestinal effects. inhibitors of PG synthesis, such as indomethacin, are used for the pharmacological closure of a patent DA (PDA) in premature infants

the small amount of well-oxygenated blood from the IVC in the right atrium that DOES NOT enter the oval foramen...

mixes with poorly oxygenated blood from the SVC and coronary sinus and passes into the RIGHT VENTRICLE. this blood, with a medium oxygen content, leaves through the PULMONARY TRUNK.

Foramen ovale becomes

oval fossa the oval foramen usually closes functionally at birth. anatomic closure occurs by the third month and results from tissue proliferation and adhesion of the septum primum to the left margin of the septum secundum. the septum primum forms the floor of the oval fossa. the inferior edge of the septum secundum forms a rounded fold, the border of the oval fossa (limbus fossae ovalis), which marks the former boundary of the oval foramen.

Q: What are some of the factors contributing to the closure of the ductus arteriosus

prostaglandin E2

the output of the right ventricle now flows into the

pulmonary trunk because the pulmonary vascular resistance is lower than the systemic vascular resistance, blood flow in the DA reverse, passing from the descending aorta to the pulmonary trunk.

because of the changes in the cardiovascular system at birth,

some vessels and structures are no longer required. the change from the fetal to the adult pattern of blood circulation is not sudden occurrence. Some changes occur with the first breath; other take place over hors and days.

Ater a short course in the IVC

the blood enters the Right Atrium of the heart. because the IVC also contains poorly oxygenated blood from the lower limbs, abdomen and pelvis, the blood entering right atrium is nat as well oxygenated as that in the umbilical vein, but it still has a high oxygen content.

from the left atrium

the blood then passes to the Left Ventricle and leaves through the ascending aorta. the arteries to the heart, neck, head, and upper limbs receive relatively well-oxygenated blood from the ascending aorta

as soon as the baby is born,

the foramen ovale, ductus venosus, ductus arteriosus are no longer need. occulsion of the placental circulation (clamping of the umbilical cord) causes an immediate decrease in blood flow to the IVC and right atrium (Systemic circulation)

the ductus arteriosus becomes

the ligamentum arteriosus

APPROXIMATELY 10% of this blood flow goes to

the lungs (LOW PULMONARY BLOOD FLOW during fetal life); most blood passes through the Ductus Arteriosus into the Descending Aorta to the fetal body and returns to the placenta through the umbilical arteries.

because of increased pulmonary blood flow and loss of flow from the umbilical vein...

the pressure in the left atrium is now higher than in the right atrium. the increased left trail pressure functionally closes the oval foramen by pressing the valve of the oval foramen against the septum secundum.

describe an alternate blood pathway from the placenta to the fetal body

umbilical vein ductus venous inferior vena cava right atrium right ventricle pulmonary trunk ductus arteriosus aorta

the fetal lungs

use the oxygen from the blood instead of replenishing it

which of the following events are happening at birth? -increase in the systemic blood flow -increase in the pulmonary blood flow -increase in the right atrail pressure, higher than the left atrium -increase in the blood flow through the ductus venosus -increase in the blood flow through the ductus arteriosus

-increase in the pulmonary blood flow

Aeration of the lungs at birth

-or first breath/cry of the new born is associated with dramatic decrease in pulmonary vascular resistance and makes increase in pulmonary blood flow

describe the blood pathway from the placenta to the fetal body

1. umbilical vein 2. ductus venous 3. inferior vena cava 4. right atrium 5. foramen ovale 6. left atrium 7. left ventricle 8. aorta

Q: The abdominal ligament is a derivative of:

A: umbilical artery

during fetal life, which structure contains the most oxygenated blood

Inferior Vena Cava

umbilical arteries become

abdominal ligaments the umbilical arteries remain patent for a short period after birth (days) and may be used for catheterization soon after birth in sick newborns most of the intra-abdominal parts of the umbilical arteries becomes medial umbilical ligaments; the proximal parts of these vessels persist as the superior vesicle arteries, which supply the urinary bladder

umbilical vein

becomes round ligament of the liver the umbilical vein remains patent for a short period after birth (days) and may be used for catheterization soon after birth in sick newborns the intra-abdominal part of the umbilical vein eventually becomes the round ligament of the liver (ligamnetum trees)

the effects of oxygen the ductal smooth muscle appears to be mediated by

bradykinin (constriction of the ductus) and prostaglandin (dilation of the ductus)

most blood from the inferior vena cava is directed

by the crista dividens (inferior border of the septum secundum), through the Oval foramen into the left atrium. Here it mixes with the relatively small amount of poorly oxygenated blood returning from the lungs through the pulmonary veins.

clinical correlation: umbilical arteries and umbilical vein can

can be catheterized in sick newborns. Umbilical arterial and venous catheters are commonly used in neonatal ICU's

in full-term infants, oxygen is the most important factor in controlling

closure of the DA.