12. Physiological Adaptation from Foetus to Neonate Flashcards
How does the foetus prepare for birth?
What are the respiratory changes at birth?
What is the significance of the first gasp?
Accumulates fat and glycogen, secretion of surfactant with increase in gestation (increased by glucocorticoids and thyroxine), inhibition of foetal breathing during labour, switch from secretion to absorption of fluid in the lung.
Chest compresses duirng birth, first gasp draws air into lungs, active clearance of lung fluid, establishing a functional residual capacity (more gas accumulated with each breath), regular breathing established.
Establishes FRC, v -ve pleural pressure from strong diaphragmatic contraction
What does surfactant do? What produces it?
What is the structure of surfactant?
Lowers the surface tension at the air/liquid interface within the alveoli of the lung. Produced by lamellar bodies in type 2 pneumocytes, has antigenic properties and is reabsorbed and reused.
Monolayer of phospolipid molecules at air-liquid interface in alveoli, mainly consists of DPPC and PG (phosphatidylglycerol), stabilised by surfactant protein B
Describe foetal circulation.
What do the ductus arteriosus and foramen ovale do?
What are the cardiovascular effects of expansion and oxygenation of the lungs?
Placenta = main exchanger of everything. 1 umbilical vein carries oxygenated blood. 2 umbilical arteries carry deoxygenated blood. [pic]
Ductus arteriosus: connects the pulmonary artery to the proximal descending aorta. Still patent for first few days of life. Foramen ovale: allows blood to enter the left atrium from the right atrium
Increased O2 levels in alveoli and pulmonary capillary shear forces. Drop in pulmonary vascular resistance and SM relaxation. Increase in pulmonary artery blood flow and decrease in pressure. Reversal of shunt across foramen ovale and ductus arteriosis. Oxygenated blood to systemic circulation.
Pulm. blood flw increases rapidly in first few hours then steadies
How does a baby establish breast feeding?
Describe the physiology of breast feeding.
Describe the baby’s metabolic adaptation.
Rooting, sucking, swallow, intestinal motility, digestion, pulsatile increases in intestinal blood flow, passage of meconium
Hormone stimulation from nipple and emotions -> protaclin (increased milk production) and oxytocin (let down reflex)
Abrupt cessation of placental transfer. 2-day delay in maternal milk supply. Hepatic glycogen stores (34g), plentiful fat stores. Brain dependant on glucose and ketone bodies (v imp energy source). Other tissues can use free FAs.
What causes neonatal jaundice?
How is it treated?
How does renal function adapt to birth?
Hb 16-20g/dl at birth (needed to transport O2 in hypoxic intrauterine environment), breakdown of red cell mass after birth, bilirubin formed from breakdown of Haem, immaturity of glucoronyl transferase in neonatal liver - less conjugation and biliary excretion. Bilirubin can cross BBB and affect higher mental function - ataxia, cerebral palsy etc., can cause deafness
Phototherapy - blue-green light 400-450nm converts bilirubin to harmless water soluble isomers. Or exchange transfusion.
Renal blood flow increases during 1st week of life, reaches adult levels by 6m
Describe a new born’s immunity capacity.
What specific immune protection does breast milk have?
What are the visual and auditary abilities of the newborn?
Immunologically naive - every immune response is a primary one. Maternal IgG transferred. Low IgM and IgA levels. Higher neutrophil numbers but less effective nuetrophil killing.
IgA, lactoferrin (binds iron needed for bacterial replication), lysozyme, complement, oligosacharides
Focus 1.5m but acuity 6/60. Normal auditory acuity. Make rapid phonetic distinctions in human speech.
How long do innate reflexes in the newborn last? Give some examples.
What is the Moro reflex?
Most disappear by 3-6m, replaced by conscious control of movements. E.g. rooting and sucking reflex. Palmar and plantar grasp reflexes.
When head dropped back rapidly, arms thrown out and small cry emitted
