Neonatal physiology and lactation Flashcards Preview

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Flashcards in Neonatal physiology and lactation Deck (62):
1

What are the stimuli to lung inflation?

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

2

What are the circulatory changes in the fetus at birth?

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

3

What are the main neonatal fuel reserves?

1. Liver glycogen
2. Muscle glycogen
3. Fat

4

What are the stimuli for mobilisation of hepatic glycogen?

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

5

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

2-3 days

6

How do endocrine glands change postnatally?

1. Alter set-point
2. Alter sensitivity

7

How do neonates survive insults well?

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

8

What is each mammary lobe subdivided into?

Lobules

9

What connects mammary gland lobes to the nipple?

Lactiferous ducts

10

What triggers breast development at puberty?

1. Ovarian oestrogen
2. Adrenal steroids
3. Growth hormone

11

What occurs to mammary glands during pregnancy?

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

12

When does alveolar secretion begin?

Second trimester

Not fully activated until after birth

13

What is the composition of human breast milk?

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

14

What is the main energy source in milk?

Fat

15

How does colostrum differ from mature milk?

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

16

Which pathways are involved in milk formation?

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

17

Which enzymes are required for lactose formation?

1. Lactose synthase
2. α-lactalbumin
2. Galactosyltransferase

18

Which hormones are required for the onset of lactation?

1. Withdrawal of progesterone and oestrogen
2. Presence of prolactin

19

What causes a decrease in progesterone and oestrogen after birth?

Delivery of the placenta

20

What does prolactin do?

Stimulates alveoli protein and fat synthesis

21

How can lactogenesis be inhibited?

1. Administration of oestrogen
2. Inhibiting prolactin secretion with dopamine agonists, such as bromocriptine

22

How is lactation maintained?

Mechanical stimulation of the nipple

Continued suckling

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

23

How are suckling reflexes mediated?

Anterolateral columns in spinal cord

PVN and SON in hypothalamus

24

Which responses are evoked by suckling?

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

25

What is the effect of oxytocin pulses?

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

26

What is the effect of GnRH inhibition?

Inhibits gonadotrophin release and ovulation

Lactational contraception

27

How might lactational reflexes be conditioned?

1. Sound of crying baby
2. Demand feeding

28

How do infants express milk from the nipple?

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

How does vertical transmission of HIV occur?

Most occurs during delivery

Additional risk from breastfeeding is 10-14%

30

What are the factors influencing the circulatory changes at birth?

pO2

PGE concentrations

Pressure gradients

Deposition of connective tissue

31

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

Need to absorb macromolecules such as gamma globulins from the colostrum

(not in humans)

32

How can thermogenesis occur in human neonates?

1. Shivering
2. Non-shivering thermogenesis

33

What does non-shivering thermogenesis depend on?

Presence of brown fat

34

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

2-6%

35

How does brown fat warm the baby?

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

36

How is brown fat stimulated to increase heat production?

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

37

How does a baby prevent heat gain?

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

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

1. Pituitary-adrenal axis
2. Thyroid gland
3. Pancreas

39

How does the pituitary-adrenal axis change perinatally?

Prepartum activation essential for neonatal adaptation

40

How does the thyroid gland change prenatally?

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

41

How does the pancreas change around birth?

Becomes important in the control of glycaemia

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

42

What are the clinical problems common to premature infants?

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

43

How many lobes in a human mammary gland?

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

44

Which hormones are required for milk secretion?

1. Prolactin
2. Adrenal steroids
3. Insulin

45

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

2-3 weeks

46

What milk components are exocytosed?

1. Lactose
2. Milk proteins, eg. lactalbumin

47

What enzyme is lactose formation dependent on?

Lactose synthetase

48

What is lactose synthetase?

A combination of α-lactalbumin and galactosyltransferase

49

How are triglycerides made in the SER exported in milk?

As fat droplets which form an emulsion with the aqueous phase

50

Which milk components are carried by apical transport?

1. Water
2. Minerals
3. Certain monosaccharides

51

Which milk components are transported by transcytosis?

Extra-alveoli proteins, such as IgG

52

How does oestrogen affect lactation?

Inhibits the action of prolactin

53

How does progesterone affect lactation?

Inhibits the action of lactose synthetase

54

What is the milk ejection reflex?

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

What is galactokinesis?

Milk let down

56

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

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

What is kernicterus?

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

58

How is pre-natal bilirubin excreted?

In fat soluble, unconjugated form across the placenta

59

How is post-natal bilirubin excreted?

Water soluble, conjugated form into bile and urine

60

Why is prenatal conjugation bad?

It traps bilirubin in the fetus

61

How are bilirubin levels controlled after birth?

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

62

What causes neonatal jaundice?

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