Physiology of Neonatal Transition

Question 1

Respiratory System

Answer 1

• lungs are filled with fluid in utero
• fluid=contributes to cell maturation and development and influences the size and shape of lungs
• in order to be able to undertake gaseous exchange, the lungs must be sufficiently developed

Question 2

Placenta

Answer 2

as a result of placenta, liver and lungs redundant. therefore temporary structures exist to diver blood to these organs

Question 3

Ductus Venosus

Answer 3

divert tube so instead of all blood reaching liver first, bypasses and guest heart. therefore heart is first organ to get freshly oxygenated blood

Question 4

Umbilical Cord

Answer 4

1 vein and 2 arteries

From the placenta, the newly oxygenated blood enters umbilical vein

• lumens are wide and gape over
• thinner walls, less muscular tissue

Question 5

What is the first breath stimulated by?

Answer 5

• cord flaming
• cooling
• physical discomfort

Question 6

First possible route

Answer 6

Blood reaches right atrium…

• right ventricle
• enters pulmonary trunk ( only small amount as pressure so high)
• lungs filled with fluid, o2 therefore can’t diffuse across, hypoxic state causes arterioles to vasoconstrict (vasoconstriction causes high resistance in lungs)
• therefore majority of blood will take path of leat resistance - ductus arteriosus

Question 7

Second possible route

Answer 7

Blood reaches right atrium…
-foramen ovule
-due to high pressure in lungs = causes high pressure on right side of heart
-again, majority of blood will take path of least resistance (foramen ovule)
=moreover, valve of inferior vena cava enables most oxygenated blood directly foramen ovule. From left to right atrium blood will enter left ventricle and out aorta. some blood will travel up ascending aorta to head and neck

Question 8

From the aorta …

Answer 8

both options lead to descending aorta. This carries blood to lower body, supply will go through internal iliac attires, umbilical artieries, branch off internal iliac arteries. so umbilical arteries then cary deoxygenated blood back to centre to be replenished

Question 9

The Transition

Answer 9

• lung aeration triggers cardiovascular transition at birth, by decreasing pulmonary vascular pressures. because of this pressure change, pressure on right side of the heart is also reduced
• as there is not blood returning to left atrium from lungs. Consequently, the left side pressure is not greater than right, forcing the foramen ovule to shut

Question 10

First Breath

Answer 10

• first breath needs pressure approx 10-15 times more than subsequent breaths
• first few breaths enable any remaining fluid to be forced into interstitial space