Circulation Review

Foundational Nursing Knowledge

Fetal Circulation

ObjectivesAt the end of this session, student should be able to;

1. define key terms.2. identify fundamental structures

of fetal circulation.3. describe the mechanism of fetal

circulation.4. describe the immediate changes

to the fetal circulatory structures after birth.

Introduction

Placenta + umbilical cord +Fetal Heart

gas exchange

nutrition

elimination endocrine

Placenta thick and disc shaped. 2 surfaces: fetal / maternal surface.

weight: 1/6 baby’s weight at birth. functions: nutrition / protection/ metabolic/endocrine/respiration.

2 membranes: amnion (inner) / chorion (outer).

approx 20- 28 lobes.

Umbilical Cord

cushioned by Wharton’s Jelly. made of 2 arteries and 1 vein. central insertion- normal. ½ inch diameter , average length 2 feet (50 cm long).

Umbilical Cord

Wharton’s Jelly

Vein

Arteries

Temporary Structures of Fetal Circulation

Umbilical vein Ductus venosus (vein to vein) Foramen Ovale Ductus Arteriosus (artery to artery)

Hypogastric arteries

Mechanism of Fetal Circulation 1. Umbilical Vein

Umbilical vein carries blood rich in oxygen and nutrient.

Goes through portal vein to the liver.

2. Ductus venosus (vein to vein)

connects umbilical vein to IVC.

Here, the blood mixes with deoxygenated blood returning from the lower parts of the body.

Thus, the blood throughout the body is partially deoxygenated.

3. Foramen Ovale (oval opening) is a temporary opening between the atria which allows the majority of blood entering from the IVC (right atrium) to pass across into the left atrium.

The reason for this diversion is that the blood does not need to pass through the lungs since it is already oxygenated.

4. Ductus Arteriosus (artery to artery)

leads to the bifurcation of the pulmonary artery to the descending aorta, entering it just beyond the point where the subclavian and carotid arteries leave.

5. Hypogastric Arteries.

Branch off from the internal iliac arteries and become the umbilical arteries when they enter the umbilical cord. They return blood to the placenta.

Structural Changes (after birth) Baby takes a breath and blood is drawn to the lungs through the pulmonary artery.

Placental circulation ceases soon after birth and so less blood returns to the right side of the heart. In this way, the pressure in the left side of the heart is greater whilst the right side of the heart becomes less. This results in the closure of a flap….

over the foramen ovale, which separates the two sides of the heart and stops the blood flowing from the right to left.

The cessation of the placental circulation results in the collapse of the umbilical vein, ductus venosus and the hypogastric arteries.

Umbilical vein becomes ligamentum teres

Ductus Venosus ligamentum

venosum

Ductus arteriosus ligamentum arteriosum

foramen ovale fosa ovalis

hypogastric arteries obliterated hypogastric arteries.

Changes involved after birth respiratory changes circulatory changes nutrition elimination

Amniotic Fluid Function cushion against impact from maternal abdomen.

provide a stable temperature. allows development of fetus. keeps membranes from adhering to fetal parts.

provides room for fetal movement.

derived from fetal membranes and fetal urine.

normal volume= 500 – 1000 mls.

Review Objectives1. define key terms.2. identify fundamental

structures of fetal circulation.3. describe the mechanism of

fetal circulation.4. describe the immediate

changes to the fetal circulatory structures.