Physiological Adaptation from Foetus to Neonate

Question 1

Describe how the foetus obtains nutrition pre-partum (in utero)

Answer 1

Amniotic fluid cushions and protects foetus from trauma and infection, placenta supplies site for exchange between maternal and foetal blood and umbilical arteries and veins supply the foetus (in umbilical cord)

Question 2

How does a foetus prepare for birth?

Answer 2

Accumulates fat and glycogen stores, increased production of surfactant by type II pneumocytes , inhibition of foetal breathing in labour, switch from secretion to absorption of fluid in the lungs

Question 3

What stimulates the increased production of surfactant near the end of gestation?

Answer 3

Increase in glucocorticoid and thyroxine production

Question 4

What causes the switch from secretion to absorption of fluid in the lungs?

Answer 4

Stimulated by a stress response during normal vaginal labour which causes the production of catecholamines (adrenaline and noradrenaline)

Question 5

What fluid(s) supplement the amniotic fluid later on in foetal development?

Answer 5

Urine from the foetal kidneys and secretions from the foetal lungs

Question 6

List the changes that take place in the cardiorespiratory system of the foetus at birth

Answer 6

Lungs inflate, amniotic fluid is replaced, pulmonary vascular resistance drops, umbilical arteries close, umbilical vein and ductus venosus closes and ductus arteriosus closes

Question 7

What substances are actively transported across the placenta from the maternal to foetal circulation?

Answer 7

Amino acids, fatty acids, calcium, phosphate, iron

Question 8

What is the main metabolic energy source for the baby in utero?

Answer 8

Glucose

Question 9

What is the main metabolic energy source for the baby post-delivery?

Answer 9

Fat

Question 10

What is the role of umbilical arteries?

Answer 10

Carry waste-laden blood away from the foetus to the placenta

Question 11

What is the role of umbilical vein?

Answer 11

Carries oxygen and nutrient-rich blood from the placenta to the foetus

Question 12

What is the role of the placenta?

Answer 12

Responsible for gaseous exchange of CO2 and O2, provides nutrients to the foetus (glucose, amino acids, calcium and electrolytes), acts to excrete waste products from the foetus, detoxifies drugs and metabolites, produces molecules such as hCG, progesterone and oestrogens (metabolically active) and is responsible for production of long-chain fatty acids which are essential for brain development

Question 13

Describe the changes that occur to the infant’s environment at birth

Answer 13

Baby moves from near weight-lessness to being in gravity and from being in a warm environment to a cold one

Question 14

What is the ‘first gasp’ at birth?

Answer 14

Where a very negative intra-thoracic pressure is generated and air fills the lungs

Question 15

Describe the respiratory changes that occur after birth

Answer 15

Very negative intrathoracic pressure generated by the first gasp –> and within the first 2-3 breaths much of the foetal lung fluid is expelled and remainder is absorbed into pulmonary lymphatic and capillaries over the first 6-12 hours and surfactant secretion is initiated

Question 16

What is surfactant?

Answer 16

Substance of phospholipids and proteins that is secreted by type II pneumocytes and reduces the surface tension of the alveoli to reduce the likelihood of collapse

Question 17

Describe the circulatory changes that occur at birth

Answer 17

PO2 increases from 2-3.5kPa in foetus to 9-13kPa in the first few breaths, and this hyperoxia causes the ductus arteriosus to close

Question 18

When does the ductus arteriosus functionally close?

Answer 18

Within 12-15 hours of birth

Question 19

When does the ductus arteriosus anatomically close?

Answer 19

4-7 days after birth

Question 20

How is the ductus arteriosus kept open in utero?

Answer 20

Under the influence of prostaglandin E1, but this influence declines as term approaches and bradykinins are released from the distended alveoli and cause the smooth muscle of the ductus arteriosus to constrict

Question 21

When do the umbilical vessels functionally close?

Answer 21

Within 5 minutes of birth (cord is clamped and cut)

Question 22

When do the umbilical vessels anatomically close?

Answer 22

Within 10 days after birth

Question 23

When does the ductus venosus functionally and anatomically close?

Answer 23

Between 1-3 weeks after birth

Question 24

When does the foramen ovale functionally and anatomically close?

Answer 24

Functionally is variable, and anatomically will take 6 months or never, but due to pressure changes very little shunting occurs post-birth

Question 25

What causes the ductus arteriosus to close?

Answer 25

Decline in prostaglandin E1 nearing the end of term and production of bradykinins which are released due to distention of alveoli cause the smooth muscle of the ductus arteriosus to constrict

Question 26

What causes the functional closure of the foramen ovale?

Answer 26

Marked fall in pulmonary vascular resistance shortly after birth –> pulmonary blood flow increases –> drop in pressure on right side of the heart –> no longer an shunting from the right to the left atrium across the foramen ovale

Question 27

What causes the functional closure of the ductus venosus?

Answer 27

Decrease in blood flow to the inferior vena cava due to greater pulmonary blood flow and this causes the ductus venosus to become the ligamentum teres

Question 28

What does the ductus venosus become in an adult?

Answer 28

Ligamentum teres

Question 29

Describe the importance of lipid and carbohydrate stores in a newborn baby

Answer 29

Baby born with plentiful supply of fat and glycogen stores, and in the first few days of life, lipid metabolism to free fatty acids supplies most of the structures of the body (glucose for the brain) whilst breastfeeding isn’t occurring due to the baby mostly sleeping

Question 30

What is the cause of physiological jaundice in newborns?

Answer 30

Common between 2-5 days and this is due to an increased breakdown of RBCs –> more bilirubin in circulation –> immaturity of the enzyme glucuronyl transferase in the liver so the bilirubin cannot be conjugated and excreted into the biliary system –> unconjugated bilirubin levels rise

Question 31

Describe the treatment of physiological jaundice (if necessary)

Answer 31

If there is any doubt that there may be an underlying pathology, phototherapy is used as a precautionary measure which is a bright light at the blue end of the spectrum (400-450nm) and it breaks down the bilirubin into harmless, 2-pyrrol ring (water-soluble) which can then be excreted in the urine

Question 32

Describe the transitional neonatal circulation

Answer 32

Flow across the foramen ovale is reversed, now flow is from the left atrium to the right (increased pressure due to increased flow to systemic circulation) and blood flows upward in the ductus arteriosus, from the descending aorta into the pulmonary artery to provide greater blood flow to the pulmonary circuit in the first days of life

Question 33

How is functional residual capacity established in infants?

Answer 33

First gasp produces a very negative pleural pressure –> draws a large amount of air into the lungs, and this is followed by a very high expiratory pressure (with crying) which helps to establish a functional residual capacity

Question 34

What must the baby be able to do in order to establish breastfeeding?

Answer 34

Root for the nipple, suckle, swallow, have intestinal motility, digest (have pulsatile increases in intestinal blood flow) and pass meconium )first bowel movement which is sterile)

Question 35

Describe how there is renal function adaptation after birth

Answer 35

First day of life there is low urine output due to low GFR, but renal blood flow increases during the first week of life, encouraging improvement of renal function and efficacy

Question 36

Outline how the immune system develops after birth

Answer 36

At birth, immune system is naïve and every response is primary despite IgG transferred by placenta, there are low IgM and IgA levels, and ineffective neutrophils; use of breastfeeding stimulates immune system development

Question 37

Outline the neurological abilities of a newborn

Answer 37

Focus to a distance of 1.5m, 6/60 visual acuity, normal hearing, distinguish rapid phonetic divisions in human speech, innate reflexes

Question 38

What is the ductus arteriosus?

Answer 38

Connects the descending aorta to the pulmonary artery

Question 39

What is the ductus venosus?

Answer 39

Bypasses the liver (umbilical vein) to join IVC

Question 40

What is the foramen ovale?

Answer 40

Hole in the inter-atrial septum

Question 41

What is the umbilical cord?

Answer 41

Cord which carries 1 umbilical vein and 2 umbilical arteries and is encased in Wharton’s jelly

Question 42

What components are higher in breast milk than the human body?

Answer 42

IgA antibodies, lactoferrin (binds to iron needed for bacterial replication), lysozyme, complement antibodies and oligosacharides