Growth Flashcards
What does the foetus use as fuel when it is near term?
- uses ~5g glucose/kg/d
- substrates are principally glucose and amino acids
- insulin is the dominant hormone
What are the actions of insulin?
- increased glucose uptake in muscle, fat and liver
- decreased lipolysis
- decreased amino acid release from muscle
- decreased gluconeogenesis in liver
- decreased ketogenesis in liver
What are the energy stores by weight in a baby?
about 1% glycogen
about 16% fat
How are stores converted to fuels?
Anabolic actions of insulin are opposed by the counter-regulatory (catabolic) hormones:
- glucagon
- adrenaline
- (cortisol)
- (growth hormone)
What is the glucagon surge?
- as plasma glucose levels fall at birth, plasma glutton levels rise rapidly
- this activates gluconeogenesis, opposing insulin
What happens during a postnatal fast?
- the baby will need to utilise stores to provide glucose as an energy source for the tissues
- gluconeogenesis is the process of providing glucose from stores - muscle (amino acids and glycogen) and fat via substrates such as lactate, pyruvate, alanine and glycerol
- ketogenesis is the process of providing ketone bodies (which act as a fuel) from the breakdown of fat
What happens in the oxidation of fat?
- terminal two carbon group removed from fatty acid and bound to coenzyme a, ax acetyl CoA (beta oxidation)
- acetyl groups can then be utilised to form ketone bodies (acetone and beta hydroxybutyrate)
- acetyl groups can also enter the kerb’s cycle as an energy source
How care ketone bodies formed?
- beta oxidation removes 2-carbon units
- these are used to make ketone bodies
What happens in the fasting (post-absorptive) state?
- substrates are mobilised peripherally through action of counter-regulatory hormones
- insulin is opposed
What happens in the fed (post-prandial) state?
- infant diet is 50% fat and 40% carbohydrate
- CHO is mainly lactose
- breast milk contains a lipase
What happens as a result to babies who have problems in terms of switching fuel supply?
- demand exceeds supply
- hyperinsulinism
- counter-regulatory hormone deficiency
- inborn errors of metabolism
What does the extremely small preterm baby require?
- high demand
- small nutrient stores
- immature intermediary metabolism
- establishment of enteral feeding delayed
- poor fat absorption
What does the IUGR baby have?
- high demands (especially brain)
- low stores (liver, muscle, fat)
- immature gluconeogenic pathways
What are the results on an infant of a diabetic mother?
- high maternal glucose
- therefore high fatal glucose
- fetal and neonatal hyperinsulinism
- neonatal macrosomia and hypoglycaemia
- look chubby in the face like the michelin man
What are other causes of hyperinsulinism (other than diabetic mother)?
- beckwith wiedermann
- islet cell dysregulation: nesiodioblastoma
What are symptoms of beckwith wiedermann?
- macroglossia (large tongue)
- macrosomia
- midline abdominal wall defects (exomphalos, umbilical hernia, diastasic recti)
- ear creases or ear pits
- hypoglycaemia
What are other deficiencies of counter regulatory hormones?
- hypothalamic-pituitary-adrenal insufficiency: septo-optic dysplasia
- waterhouse-friderichsen: severe adrenal haemorrhage with adrenal gland dysfunction secondary to sepsis or hypoxia
What are causes of neonatal hypoglycaemia?
- glycogen storage disease (usually type I)
- galactosaemia
- MCCAD (medium chain acyl-CoA dehydrogenase deficiency)
What is glycogen storage disease (type I)?
- deficiency of glucose-6-phosphatase
- hypoglycaemia and lactic acidosis in newborn
- hepatomegaly in older child
What is galactosaemia?
- lactose in milk is broken down to galactose and glucose
- galactose is then broken down to glucose by galactose-1-phosphate
- Uridyl Transferase (Gal-1-put) which is missing in Galactosaemia, leading to toxic levels of galactose-1-phosphate
What does galactosaemia present with?
- hypoglycaemia
- jaundice and liver disease
- poor feeding and vomiting
- cataracts and brain damage
- E Coli sepsis
What is the basic anatomy of the breast?
- about 20 radially arranged lobes with duct system draining down to nipple
- more recent evidence suggests about 9 lobes (4-18) are functional, the rest are vestigial
- each lobe can be considered a separate functional unit
- non-lactating breast about 50% fat, lactating breast about 30% fat
What is the mammary gland drainage system?
- ductal sytem drains into ‘lactiferous sinuses’ beneath areola of the breast
- sub cutaneous, intraglandular and retromammary fat deposits
What is the in vivo anatomy of the lactating breast?
- ‘lactiferous sinuses’ not found
- about 9 ducts emerge at the nipple
- the ducts are tortuous and branch near the nipple
- about 70% of glandular tissue within 8cm of the nipple
What is the structure of the mammary glands?
- mid-trimester view
- basic secretory unit is the alveoli set within connective tissue structure
- lined by mammary epithelial cells (cuboidal or low columnar)
- myoepithelial cells surround the alveoli
- these are contractile and responsible for milk ejection
What preparation for breast feeding is done during pregnancy?
- ‘lactogenesis I’
- placental lactogen and prolactin promote development of the breast
- progesterone and oestrogen inhibit milk secretion
What is lactogenesis postpartum (lactogenesis II)?
- fall in progesterone ad oestrogen levels reduces inhibition
- suckling stimulus releases prolactin driving milk synthesis
- suckling (and higher centres) release oxytocin driving milk ejection
- some autocrine inhibition from duct cells
if you do not remove milk from the breast you will not make more.
What controls milk synthesis?
- prolactin released in response to sucking
- milk synthesis is led by infant demand
suckling causes more synthesis of milk for next feed.
What is the ‘let down’ reflex?
- oxytocin release causes milk ejection
- reflex may become conditioned
sends signal to hypothalamus, to posterior pituitary which will release oxytocin. Control from higher centres, still get let down reflex when baby cries.
How do drugs suppress lactation?
- decrease prolactin secretion
- dopamine agonists
- eg bromocriptine, cabergoline
How do drugs augment lactation?
- increase prolactin secretion
- dopamine antagonists
- eg domperidone, metoclopramide
What is the secretory pathway?
major nutritional component in milk is protein which is packaged in a vesicle to the golgi where calcium and phosphate are added, lactose is synthesised. Lactose can’t travel across so goes in later. The vesicle fuses with the cell membrane and the contents go into the limen
What are the components of breast milk?
- nutrients – macronutrients and trace elements (low “solute load”)
- immunoglobulin (secretory IgA)
- cells (macrophages and lymphocytes)
- non-specific immune components
- growth factors
What changes occur to the volume and composition of breast milk?
Can produce enough milk to fully feed child to 6 months of age. Initially milk has lower levels of lactose which will increase over time. Salt and other ions will drop over time.
What changes in milk composition occur during the feed?
Fat concentration increases as the baby feeds. If baby not growing well, can express the milk first then use the hind milk for the baby to help it to grow
What is the nutritional value of breast milk?
- Protein
- human milk: whey 70%, casein 30%, cows milk: whey 18%, casein 82% (casein low solubility in acid media)
- lactoferrin, lysozyme and sIgA are whey proteins important in host defence
- Lipids
- human milk contains LCPUFA important for brain/retinal development (AA, C20, n-6, DHA, C22, n-3). Cow’s milk contains only C18 LCPUFA, linoleic (n6) and linolenic (n3) precursors
- bile salt activated lipase
What is the GI benefits of breastmilk?
- human milk improves gastric emptying
- human milk is important in preventing NEC in the preterm infant
What are the immunological benefits of breastmilk?
bugs really like iron, so when iron is removed there is less bacterial growth - lactoferrin, trying to stop sepsis. (lactoferrin: inhibits bacterial growth by binding iron)
What effects do the various immune factors have?
sIgA: specific immune response, binds bacterial adherence sites
Complement: C1 to C9 present in low concentration milk, with high amounts of C3 (able to opsonise bacteria in conjugation with IgA)
Lactoferrin: inhibits bacterial growth by binding iron
Lysozyme: cleaves peptidoglycans of bacterial walls
Cytokines: anti-inflammatory cytokines predominate in human milk, allows human milk to protect but not injure the gastrointestinal tract
PAF acetylhydrolase: inhibits platelet activating factor
Oligosaccharides: inhibit binding of enteric/respiratory epithelium
Cellular elements: neutrophils and macrophages
What are the short term benefits of breastfeeding?
• Improved immunity, less infections and infectious morbidity
- Gastro-intestinal infection: dujits et al, 2010, Dutch study
- Respiratory infections: galton bachrach VR et al (2003). Developed world study
- Urinary tract infections (Marild S et al (2004)). Swedish study
SIDS: the German study of sudden infant death is a case-control study of 333 infants who dies of sudden infant death syndrome. This study shows that breastfeeding reduced the risk of sudden infant death syndrome by about 50% at all ages throughout infancy and for as long as the infant is breastfed
What are the long term infant benefits of breastfeeding?
• Type 1 and 2 diabetes
• Obesity: breastfeeding has been found to generally reduce the risk of obesity
• Allergic disease: there is evidence that breastfeeding for at least four months, comparted with feeding infant formula made with intact cow’s milk protein, prevents or delays the occurrence of atopic dermatitis, cow’s milk allergy, and wheezing in early childhood
• Childhood leukaemia: a meta-analysis has concluded that both short term and long term breastfeeding reduce the risk of childhood acute lymphoblastic leukaemia (ALL) and acute myeloblastic leukaemia (AML).
• Cholesterol levels: adolescents have a reduction of 14% in their ratio of LDL to HDL cholesterol if they were fed breastmilk in infancy.
Blood pressure: a review from the USA investigated the effects of breastfeeding in developed countries
What are the benefits of breastfeeding for the mother?
• Breastfeeding releases oxytocin, which causes the uterus to contract, and reduces the risk of postpartum haemorrhage
Women who breastfeed are at lower risk of:
• Breast cancer: good evidence to suggest that breastfeeding protects against breast cancer
- 47 epidemiological studies including 50,000 controls and 97,000 cases showed a 4.3% decreased risk of breast cancer with duration of lactation (95%Cl: 2.9-5.8, p
What are the primitive reflexes?
Rooting and suckling.
rooting: touch cheek and baby turns to the side of the stimulus - this is a reflex
What are the signs of good attachment?
- Mouth wide open
- Mouth full
- Chin is close to breast
- Lower lip everted
- Suching changes
- More of the areola is visible above the baby’s mouth than below
Positioning is the relationship between the baby’s body and the mother’s
What are the patterns of sucking?
Non-nutritive sucking – short bursts of sucking, 5 seconds?
Nutritive sucking – long periods of sucking
What can happen when latching-on goes wrong?
- Incorrect positioning and attachment
- Traumatised nipple
- Ineffective breast drainage
- Leads to infection of breast tissues or ‘mastitis’
What is required for lung development at birth?
Simultaneous growth
- Vascular elements
- Tubular airway elements
- Different cell types
Variety of growth factors required
- Hepatocyte nuclear factor 3beta – foregut
- Fibroblast growth factor-10, sonic hedgehog, bone morphogenetic protein 4 (BMP4) – outgrowth of new end buds
- Gli proteins – branching
- Vascular endothelial growth factor (VEGF) – angiogenesis
What alveolar development occurs at birth?
- 24 weeks, saccules develop: capillaries develop around each (VEGF)
- 32 weeks, shallow indentations
- most development post term: mainly by growth in number, adult numbers by 4 years
- Pneumocytes: type 1 and 2 presetn at 22 weeks, from 24 weeks lamellar bodies are present
What is the secretion of lung liquid?
- secondary active transport of Cl from interstitium to lumen Na and H2O passive
- liquid production allows for positive pressure of 1cmH2O
- lung fluid is required for lung growth but not branching
What is the absorption of lung liquid?
- active sodium transport in apical membranes
- labour and delivery: adrenaline release reduced secretion and resorption begins
- thyroid hormone and cortisol required for maturation of the foetal lung response to adrenaline
- exposure to postnatal oxygen increases sodium transport across the pulmonary epithelium
What are examples of lung liquid pathology?
Oligohydramnios
- early rupture
- kidney abnormalities
Foetal breathing abnormalities
- neuromuscular disorders
- phrenic nerve agenesis
- CDH
- Foetal breathing slows lung liquid loss – maintains expansion
Delivery without labour
- Elective caesarean section – TTN (transient tachypnoea newborn)
About surfactant…
Produced by type 2 pneumocytes
- Surfactant phosphatidylcholine (PC) produced in endoplasmic reticulum
- Stored in lamellar bodies
Degraded in alveoli
- Absorbed and recycled by alveolar cells
- > 90% PC is reprocessed
- turbover time is 10 hours
Negative feedback system to regulate release
- also stretch receptors
- B adrenergic receptors on type 2 cells – increases with gestation
Why do we need surfactant?
- Prevents atelectasis – reduces work to breathe
- Achieved by reduced surface tension solid at body temperature – becomes a solid monolayer, stabilises alveoli
- Laplace equation internal pressure = 2xsurface tension/radius
What is surfactant?
• Mix of phospholipids, neutral lipids and protein
• Lipids most important:
- PC comprises ~80%, PG ~10%
- 60% PC disaturated, predominantly palmitic acid
- therefore dipalmitoyl phosphatidycholine is the major component of surfactant
What is the composition of surfactant?
other lipids: neutral lipids such as cholesterol, alters fluidity of membranes
proteins: 4 types, SP-A……D. 5-10% of surfactant by weight