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Physiology & Science: Human Growth > Principles of Growth > Flashcards

Principles of Growth Flashcards

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1
Q

Growth can be divided into which 4 periods?

A
  • Intrauterine
  • Infancy
  • Childhood
  • Adolescence
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2
Q

What are examples of non-pathological influences on growth?

A
  • Genetic (family + racial)
  • Age
  • Sex
  • Environmental (altitude, urbanisation, smoking, psych stress)
  • Nutrition
  • Season
  • Diurnal
  • Socioeconomic
  • GH secretion
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3
Q

Which factor is most important from the beginning ie. from foetal growth all the way down to adulthood?

A

Genetics

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4
Q

What is the sequence of events from day 1 to day 12 in the first trimester, in regards to foetal growth?

A
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5
Q

At which point is the developing organism referred to as a foetus?

A

From the 10th week of gestation - all major structures are already formed in the foetus and continue to grow + develop.

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6
Q

When do the foetus’ eyelids close and reopen?

A

Eyelids close around 10-12 weeks + will not reopen until about the 28th week

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7
Q

What can be identified in a foetus at 10-12 weeks?

A
  • Tooth buds appear
  • Limbs long + thin
  • Foetus makes a fist w/ fingers
  • Genitals appear well differentiated
  • RBCs produced in liver
  • Heartbeat detected by ultrasound
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8
Q

What happens at week 15?

A

At week 15, main development of external genitalia is completed

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9
Q

What can be identified in a foetus at 22 weeks?

A
  • 28cm + 500g
  • Eyebrows + eyelashes well formed
  • All eye components are developed
  • Startle reflex
  • Footprints + fingerprints continue forming
  • Alveoli forming in lungs
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10
Q

What can be identified in a foetus at 24 weeks?

A
  • 38cm, 1.2kg
  • Nervous system develops -> control some body functions
  • Eyelids open + close
  • Cochlea developed
  • Resp system develops -> gas exchange
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11
Q

What can be identified in a foetus at 30 weeks?

A
  • 38-43cm, 1.5kg
  • Body fat rapidly increases
  • Rhythmic breathing movements occur
  • Lungs not fully mature
  • Thalamic brain connections form - mediate sensory input
  • Bones fully developed (soft + pliable)
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12
Q

What can be identified in a foetus at 34 weeks?

A
  • 40-48cm, 2.5-3kg
  • Lanugo hair starts to disappear
  • Body fat increases
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13
Q

The foetus is considered full-term at the end of the 39th week of GA. What can be identified on the foetus from 35 weeks until term?

A
  • 48-53cm
  • No lanugo except on upper arms + shoulders
  • Small breast buds on both sexes
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14
Q

List growth factors in foetal life

A
  • Insulin like growth factors (IGF1, 2)
  • Foetal insulin
  • Foetal glucocorticoid
  • Thyroid hormone
  • Growth hormone
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15
Q

What is the role of foetal glucocorticoid?

A
  • Tissue differentiation + prenatal development of organs
  • Eg. lungs - maturation of surfactant
  • Eg. liver - control of glycaemia
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16
Q

What is Karlberg’s ICP model?

A
  • Infancy, childhood + puberty (ICP model) breaks down growth mathematically
  • Components of the human growth curve from birth to adulthood strongly reflect the different hormonal phases of the growth process
  • Model provides an improved instrument fro detecting + understanding growth failure
17
Q

What factor(s) are important in early life for growth?

A

Nutrition

18
Q

What factor(s) are important in infancy and childhood for growth?

A
  • Nutrition
  • IGF 1
  • GH
19
Q

What factor(s) are important for growth during puberty?

A
  • GH
  • Sex hormones
20
Q

Describe the pathway of GHRH and GH

A
  • GHRH release in a pulsatile pattern from hypothalamus
  • Stimulates pituitary to release GH
  • GH acts directly on GHr
  • OR GH combines to form GHBP
  • OR GH goes to liver -> IGF-1

Growth hormone acts in a multitude of ways

21
Q

Why is it bad to measure a random growth hormone level in primary care?

A
  • GHRH release in a pulsatile pattern
  • There is transient augmentation of the pulses during puberty
  • ie. GH levels differ throughout the day so can’t take samples every hour or measure at one point
  • Instead do growth hormone stimulation test
22
Q

What is the structure of growth hormone?

A
  • 4 alpha helices
  • 4 cysteine residue
  • 2 disulphide bridges
  • 2 GHR binding sites
23
Q

What is the cellular action of growth hormone?

A
  • Dimerized GHR
  • -> JAK
  • -> MAP kinase
  • -> STAT5
  • -> translocation of GH responsive genes
24
Q

Which 3 processes does growth hormone stimulate in skeletal growth?

A
  • Subperiosteal apposition
  • Endosteal resorption
  • Remodelling
25
Q

How does growth hormone affect growth plates specifically?

A
  • Increases rate of mitosis of chondrocytes + osteoblasts
  • Increases rate of protein synthesis (collagen, cartilage matrix, enzymes)
26
Q

How does parathyroid hormone (PTH) affect growth plates?

A
  • Increases resorption of calcium from bones -> blood
  • Raises blood calcium levels
  • Increases absorption of calcium by small intestine + kidneys
27
Q

How does calcitonin affect growth plates?

A
  • Decreases resorption of calcium from bones
  • Lowers blood calcium levels
28
Q

How do oestrogen and testosterone affect growth plates?

A
  • Promotes closure of epiphyses of long bones
  • Stopping growth
  • Helps retain calcium in bones
  • Maintains strong bone matrix
29
Q

What is meant by crossing of growth centiles and what does this mean?

A
  • Infants + children stay within 1 or 2 growth centiles
  • Any crossing of height centiles warrants further evaluation
  • Crossing of centiles = normal event in child development
  • Though crossing centiles should be taken seriously
30
Q

What is catch up growth?

A
  • Catch-up growth characterised by height velocity above the limits of normal for age for at least 1 year after a transient period of growth inhibition; complete or incomplete
  • Inc growth rate following IUGR = catch-up growth
  • Complete - result in a mean final height close to mean target height
31
Q

Describe catch down growth

A
  • Seen in children who start off at high percentile in early infancy
  • 6-18 months - show fall on their percentile growth chart
  • Over time they match their genetic programming + then grow at lower percentile, but along genetic potential
  • Have normal physical, psychological + behavioural development
  • However, a fall of more than 2 major percentiles warrants investigations
32
Q

What is puberty?

A
  • Transition from childhood to achievement of adult stature through development of secondary sexual characteristics
  • Influenced by genetic, nutritional, environmental + socioeconomic factors
33
Q

What is the average age of onset of puberty?

A
  • female - 11
  • male - 12
34
Q

What are the events of puberty in girls?

A
  • First sign = breast development
  • Pubic hair
  • Growth spurt
  • Menarche
35
Q

What are the events of puberty in boys?

A
  • First sign = testicular (4ml) (+ penile) enlargement
  • Pubic hair
  • Voice change
  • Growth spurt
  • Spermatogenesis
36
Q

Why might some patients with pubertal development problems also have problems with smell?

A

GnRH neurones arise from the olfactory placode + migrate to the hypothalamus along the olfactory tract - under control of genes (KAL, FGF8)

Physiology & Science: Human Growth (9 decks)

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