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Human Reproduction > Neonatal physiology and lactation > Flashcards

Neonatal physiology and lactation Flashcards

1
Q

What are the stimuli to lung inflation?

A
  1. Tying/breaking the cord
  2. Cold exposure
  3. Sensory stimuli
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2
Q

What are the circulatory changes in the fetus at birth?

A
  1. Decreased pulmonary vascular resistance
  2. Increased pulmonary blood flow
  3. Closure of foramen ovale and initiation of closure of ductus arteriosus
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3
Q

What are the main neonatal fuel reserves?

A
  1. Liver glycogen
  2. Muscle glycogen
  3. Fat
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4
Q

What are the stimuli for mobilisation of hepatic glycogen?

A
  1. Increased catecholamine levels at birth
  2. Direct splanchnic innervation
  3. Changes in insulin/glucagon ratio
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5
Q

How long can the human neonate survive without significant calorific intake?

A

2-3 days

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6
Q

How do endocrine glands change postnatally?

A
  1. Alter set-point

2. Alter sensitivity

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7
Q

How do neonates survive insults well?

A
  1. Large fuel reserves
  2. Capacity for non-shivering thermogenesis (brown fat)
  3. Resistance to anoxia and hypoglycaemia
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8
Q

What is each mammary lobe subdivided into?

A

Lobules

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9
Q

What connects mammary gland lobes to the nipple?

A

Lactiferous ducts

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10
Q

What triggers breast development at puberty?

A
  1. Ovarian oestrogen
  2. Adrenal steroids
  3. Growth hormone
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11
Q

What occurs to mammary glands during pregnancy?

A
  1. Rapid growth and branching of terminal portions of lobules
  2. Increased vascularity
  3. Formation of glandular acini
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12
Q

When does alveolar secretion begin?

A

Second trimester

Not fully activated until after birth

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13
Q

What is the composition of human breast milk?

A 
90% water
6% lactose
3% fat
1% protein
Trace minerals, hormones, growth factors and amino acids
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14
Q

What is the main energy source in milk?

A

Fat

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15
Q

How does colostrum differ from mature milk?

A
  1. Less fat and lactose

2. More proteins, Ig and fat-soluble vitamins (A, D, E, K)

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16
Q

Which pathways are involved in milk formation?

A
  1. Exocytosis
  2. Lipid transfer
  3. Apical transport
  4. Transcytosis
  5. Paracellular
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17
Q

Which enzymes are required for lactose formation?

A
  1. Lactose synthase
  2. α-lactalbumin
  3. Galactosyltransferase
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18
Q

Which hormones are required for the onset of lactation?

A
  1. Withdrawal of progesterone and oestrogen

2. Presence of prolactin

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19
Q

What causes a decrease in progesterone and oestrogen after birth?

A

Delivery of the placenta

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20
Q

What does prolactin do?

A

Stimulates alveoli protein and fat synthesis

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21
Q

How can lactogenesis be inhibited?

A
  1. Administration of oestrogen

2. Inhibiting prolactin secretion with dopamine agonists, such as bromocriptine

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22
Q

How is lactation maintained?

A

Mechanical stimulation of the nipple

Continued suckling

Removal of milk products removes their inhibition of further synthesis of lactose

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23
Q

How are suckling reflexes mediated?

A

Anterolateral columns in spinal cord

PVN and SON in hypothalamus

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24
Q

Which responses are evoked by suckling?

A
  1. Release of prolactin and other hormones forming the lactogenic complex (ACTH and GH)
  2. Release of oxytocin pulses
  3. Inhibition of GnRH release
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25
Q

What is the effect of oxytocin pulses?

A

Causes contraction of myoepithelial cells around ducts, causing milk let down and milk ejection

26
Q

What is the effect of GnRH inhibition?

A

Inhibits gonadotrophin release and ovulation

Lactational contraception

27
Q

How might lactational reflexes be conditioned?

A
  1. Sound of crying baby

2. Demand feeding

28
Q

How do infants express milk from the nipple?

A

Strip out milk stored in lactiferous sinus using tongues and hard palates

Does not have to generate negative pressure to breast feed (though it does to bottle feed)

29
Q

How does vertical transmission of HIV occur?

A

Most occurs during delivery

Additional risk from breastfeeding is 10-14%

30
Q

What are the factors influencing the circulatory changes at birth?

A

pO2

PGE concentrations

Pressure gradients

Deposition of connective tissue

31
Q

Why is there minimal digestive activity in the first 24 hours of life?

A

Need to absorb macromolecules such as gamma globulins from the colostrum

(not in humans)

32
Q

How can thermogenesis occur in human neonates?

A
  1. Shivering

2. Non-shivering thermogenesis

33
Q

What does non-shivering thermogenesis depend on?

A

Presence of brown fat

34
Q

How much of human infant body weight does brown fat account for?

A

2-6%

35
Q

How does brown fat warm the baby?

A

It is positioned to warm blood entering from the periphery into the main veins

36
Q

How is brown fat stimulated to increase heat production?

A
  1. Circulating catecholamines
  2. Thyroid hormones
  3. Stimulation of the sympathetic nerves
37
Q

How does a baby prevent heat gain?

A

Mechanisms are poorly developed

Little sweating, with a higher threshold

Susceptibility to dehydration

Tendency to gain heat in high ambient temperatures

Requires intelligent parental intervention to circumvent problems

38
Q

Which endocrine glands show changes in activity during the perinatal period?

A
  1. Pituitary-adrenal axis
  2. Thyroid gland
  3. Pancreas
39
Q

How does the pituitary-adrenal axis change perinatally?

A

Prepartum activation essential for neonatal adaptation

40
Q

How does the thyroid gland change prenatally?

A

Prepartum increases in T3 with resetting of the axis after birth in association with the need for thermoregulation

41
Q

How does the pancreas change around birth?

A

Becomes important in the control of glycaemia

Large changes in the insulin and glucagon concentrations at birth which are involved in activating gluconeogenesis

42
Q

What are the clinical problems common to premature infants?

A
  1. Respiratory distress syndrome
  2. Hypoglycaemia
  3. Hypothermia
  4. Immaturity of neural mechanisms
  5. Increased susceptibility to infection
43
Q

How many lobes in a human mammary gland?

A

15-25 irregular lobes radiating out from the nipple and surrounded by connective and adipose tissue

44
Q

Which hormones are required for milk secretion?

A
  1. Prolactin
  2. Adrenal steroids
  3. Insulin
45
Q

How long does it take the contents of milk to reach the mature composition?

A

2-3 weeks

46
Q

What milk components are exocytosed?

A
  1. Lactose

2. Milk proteins, eg. lactalbumin

47
Q

What enzyme is lactose formation dependent on?

A

Lactose synthetase

48
Q

What is lactose synthetase?

A

A combination of α-lactalbumin and galactosyltransferase

49
Q

How are triglycerides made in the SER exported in milk?

A

As fat droplets which form an emulsion with the aqueous phase

50
Q

Which milk components are carried by apical transport?

A
  1. Water
  2. Minerals
  3. Certain monosaccharides
51
Q

Which milk components are transported by transcytosis?

A

Extra-alveoli proteins, such as IgG

52
Q

How does oestrogen affect lactation?

A

Inhibits the action of prolactin

53
Q

How does progesterone affect lactation?

A

Inhibits the action of lactose synthetase

54
Q

What is the milk ejection reflex?

A

Suckling causes release of oxytocin pulses from the posterior pituitary

This causes contraction of the myoepithelial cells surrounding the ducts, which in turn, causes milk let down

55
Q

What is galactokinesis?

A

Milk let down

56
Q

What is the worst feeding regime for HIV positive mothers in Africa?

A

Mixed feeding regime as this exposes the infants to a high risk of enteritis and the damaged gut lining then may allow the HIV virus to enter the infant more readily

57
Q

What is kernicterus?

A

Lack of conjugation of bilirubin post-natally allows it to enter the CNS and cause brain damage

58
Q

How is pre-natal bilirubin excreted?

A

In fat soluble, unconjugated form across the placenta

59
Q

How is post-natal bilirubin excreted?

A

Water soluble, conjugated form into bile and urine

60
Q

Why is prenatal conjugation bad?

A

It traps bilirubin in the fetus

61
Q

How are bilirubin levels controlled after birth?

A

Increase in bilirubin levels after delivery induces enzymes for bilirubin conjugation, so the enzyme is only synthesised when needed

62
Q

What causes neonatal jaundice?

A

Enzyme synthesis takes a while to have an effect, causing bilirubin build up in the first 48-72 hours after birth

Human Reproduction (17 decks)

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