10 - Physiological adaptation at birth Flashcards
What is the state of the foetus in utero?
o Cushioned in amniotic fluid
o Protected from trauma, cold and infection
o Lungs full of fluid
o Placental transfer of oxygen and carbon dioxide
o Continuous nutrition and mineral acquisition through the placenta
o Elimination of waste products through the placenta
What happens to the foetus at one week of age?
o Efficient respiration through the lungs
o Maintaining own temperature
o Acquiring intestinal microflora and making immune responses
o Feeding orally and putting on weight
o Eliminating bilirubin and urea
What happens to the foetus as it prepares for birth?
o Accumulation of fat and glycogen
o Secretion of surfactant with increased gestation (stimulated by increased glucocorticoids and thyroxine)
o Inhibition of foetal breathing of amniotic fluid during labour
o Switch from secretion to absorption of fluid in the lungs – this is a stress response to normal labour caused by the secretion of catecholamines
What occurs during the first gasp of breath of a baby?
o Very negative pleural pressure from strong diaphragmatic contraction – minus 52cmH2o – 28-105
o High expiratory pressure with crying aids formation of FRC
o FRC establishment takes longer following caesarean section as less stressful so fewer catecholamine secretion so less resorption of the lung fluid
What needs to occur in the lungs of a newborn?
Clearance of lung fluid
Functional residual capacity established
Surfactant needs to be produced
What is surface tension?
In the alveoli - the forces that act at the interface between the alveolar air and fluid
can collapse the alveoili
What is the function of surfactant and what is it secreted by?
Reduces surface tension
Secreted by type II pneumocytes?
What is surfactant?
Monolayer of phospholipid molecules
Mainly consists of DPPC and PG
Stabilised by surfactant protein B
How does the foetus receive oxygenated blood?
From the placenta
via pulmonary vein
How does deoxygenated blood leave the foetus?
Via umbilical artery to the placenta
What is the function of ductus arteriosus?
Joins the pulmonary artery and aorta
Higher pressure in pulmonary artery - blood flows into aorta and then placenta to be oxygenated
What is the function of the foramen ovale?
Connect the two atria
What does the ductus venosus do?
allows blood from umbilical vein to bypass liver
What is the effect of oxygenation of the lungs?
o Increased oxygen levels in alveoli and pulmonary capillary sheer forces
o Drop in pulmonary vascular resistance and smooth muscle relaxation (bradykinin, NO, prostaglandin I2)
o Increase in pulmonary artery blood flow and decrease in pressure
o Reversal of shunt across foramen ovale and ductus arteriosus
o Oxygenated blood from the lungs to systemic circulation
What are innate behaviours newborns have to establish breastfeeding?
o Rooting o Sucking o Swallowing o Intestinal motility o Digestion o Pulsatile increases in intestinal blood flow o Passage of meconium (first faeces)
Why is there a 2 day delay in maternal milk supply?
Baby already has a fat and glycogen store at full term to last 2 days
What is neonatal jaundice?
o Immaturity of glucoronyl transferase in the neonatal liver
o Less conjugation of bilirubin can occur
o Harder to excrete as unconjugated
o Build up of bilirubin in the blood jaundice
What is physiological jaundice?
o Peak levels at 3-5 days
o Rarely causes problems
o Seen with pathological conditions of haemolysis
How do you treat jaundice?
o Can be treated with phototherapy (blue-green light converts bilirubin to harmless water soluble isomers) or exchange transfusion
How does renal function of a baby change in the first few days of birth?
o Low urine out on the first day
o Renal blood flow increases during the first week of life
Which levels are highest in a baby - IgM, IgG, IgA?
IgG high as transferred from mother across the placenta
Low IgM and IgA
What is in breastmilk to protect the baby?
IgA
Lactoferrin
Lysosome
Oligosaccharides
What is the visual acuity of a newborn?
Limited to 6/60
