Fetal adaptations

Question 1

State 4 ways the fetus prepares for external environment

Answer 1

1. Alveolar cells produce surfactant at 34 weeks for breathing
2. Stores glycogen in the liver
3. Produces catecholamines
4. Deposition of brown fat

Question 2

Describe the fetal blood circulation

Answer 2

Umbilical vein carries oxygenated blood to fetal heart. Blood crosses fetal heart ducts in right to left direction (small % goes to lungs).
The Ductus arterioles joins pulmonary artery to aorta so most blood goes through aorta.
Blood can travel directly from right atrium to left atrium via foramen oval in arterial septum then into left ventricle and out the aorta.

Question 3

State 5 stages of respiratory changes extrauterine

Answer 3

1. Lungs take over placenta so decrease in pO2, increase in pCO2 and decrease in pH
2. Lungs begin to exchange gas
3. First breath inflates lungs and causes circulatory changes
4. Lungs inflate which decreases resistance to blood flow in lungs and increases resistance in pulmonary arteries
5. Newborn circulation is established

Question 4

State 5 effects of clamping the umbilical cord

Answer 4

1. Decrease O2 concn
2. Increase CO2 concn
3. Decrease blood pH
4. This stimulate fetal aortic and carotid chemoreceptors
5. This activates the respiratory centre in the medulla to initiate respiration

Question 5

What causes passive inspiration upon birth.

Answer 5

1. Mechanical compressions of chest during delivery forces a third of the fluid out of the fetal lungs.
2. As chest is delivered it re-expands to generate a negative pressure which draws air into lungs
3. As the infant cries it establishes a positive intrathoracic pressure to keep alveoli open which forces remaining fetal lung fluid into the lymphatic circulation

Question 6

3 components for effective respiration in the neonate?

Answer 6

1. Adequate pulmonary blood flow
2. Adequate surfactant
3. Respiratory musculature strong enough to support respiration

Question 7

State 2 cardiovascular adaptations of the neonate

Answer 7

1. Increased aortic pressure and decreased venous pressure secondary to clamping of umbilical cord
2. Increased systemic pressure and decreased pulmonary artery pressure with initiation of respirations

Question 8

State the changes the 3 shunts in the neonate

Answer 8

1. Ductus venous - shunts blood from umbilical to IVC to allow blood oxygenated by the placenta to pass the liver
2. Ductus arteriosus - moves blood from pulmonary artery to aorta
3. Foramen oval - opening between right and left atrium

These close

Question 9

State 4 factors that predispose a newborn to heat loss

Answer 9

Large surface area (especially head)
Blood vessels closer to the surface
Less fat
Limited ability to control their metabolic rate