Principles of growth Flashcards

1
Q

What are the influences on growth?

A
  • Race
  • Family
  • Puberty- diff hormone secretion
  • Gender- males taller than girls
  • Nutrition
  • Seasonal changes- some grow more in summer than winter
  • Environmental changes
  • Hormones
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2
Q

Why do boys grow taller than girls?

A
  • bc males have puberty later in life
  • more time to grow
  • have longer growth spurt
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3
Q

What are the patterns of growth?

A
  • genetics
  • nutrition
  • environmental
  • hormones
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4
Q

How do genetics affect growth?

A
  • if genetic problem from birth = can prevent growth= shunted growth throughout life
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5
Q

What happens if the mother at birth is anorexic and stressed?

A
  • very small baby born
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6
Q

What happens if mother at birth has diabetes and is obese?

A
  • fat baby
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7
Q

When does nutrition play the most important part in life?

A
  • 1st year of life

- e.g. if GH deficiency= growth no happen

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8
Q

How do hormones affect growth?

A
  • childhood= growth and thyroid hormones

- puberty= sex hormones = more growth hormone- growth spurt

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9
Q

Which phase is the most rapid growth phase?

A
  • prenatal
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10
Q

What happens in the first trimester?

A
  • rapid growth of organs
  • differentiation of organs
  • form embryonic disc layers:
  • ectoderm (skin, hair, brain, nerves)
  • mesoderm (cardiac, skeletal, renal, bloods)
  • endoderm (lung, gut, thyroid, pancreas)
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11
Q

What happens in the 2nd trimester?

A
  • cellular hypertrophy (rapid cellular division)

- get peak foetal length velocity of 2.5cm per week

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12
Q

What happens in the 3rd trimester?

A
  • maturation of organs
  • max weight gain
  • near term= subcutaneous fat added to the embryo
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13
Q

What factors affect prenatal growth?

A
  • in utero, extrinsic factors play bigger role than intrinsic factors
  • hormones
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14
Q

What are the extrinsic factors in utero?

A
  • placenta
  • blood flow
  • nutrition to baby
  • maternal anatomy
  • maternal size
  • maternal nutrition
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15
Q

What are intrinsic factors?

A
  • genetics

- hormone function of embryo

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16
Q

What hormones are involved in utero prenatal growth?

A
  • growth hormone
  • IGF I and II
  • thyroid
  • foetal glucocorticoid (cortisol)
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17
Q

Growth hormone:

A
  • GH secretion high in foetus

- not too big influence on foetal growth

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18
Q

Insulin like growth factors I and II:

A
  • big role in foetal growth and development
  • higher IGFII secretion
  • IGFI more closely related to foetal growth
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19
Q

Thyroids:

A
  • normally Thyroid hormone not present in foetus

- doesnt affect foetus growth

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20
Q

Foetal glucocorticoid (glucose):

A
  • in utero tissue differentiation

- development of organs e.g. liver, lung

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21
Q

What does birth size depend on?

A
  • in utero environment
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22
Q

What is the average birth size?

A
  • 48-51cm
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23
Q

What is the average birth weight?

A
  • 2.7kg to 4.1kg
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24
Q

What are the variations babies can be born with?

A
  • small for gestational age

- large for gestational age

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25
Q

What is the correlation between birth size and adult size?

A
  • WEAK
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26
Q

What is difference between males and females?

A

males normally:

  • 150g heavier
  • 0.9cm longer
  • slightly greater muscle mass
  • maybe bc of more testosterone near term (called mini adolescence)
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27
Q

What is the kalberg’s ICP model?

A
  • I: infancy
  • C: childhood
  • P: puberty
  • it breaks down growth mathematically
  • allows you to detect and understand growth failure
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28
Q

What is height velocity?

A
  • records how much child grows in a year
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29
Q

What is the height velocity of children?

A
  • in the first 2 years of life= VERY FAST
  • childhood= SLOWS DOWN becomes nearly constan (4cm to 8cm a year)
  • Puberty = GROWTH SPURT
    = girls smaller growth spurt
    = girls have it before boys
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30
Q

If you measure the area beneath a height velocity graph, what do you see?

A
  • area is larger for boys than girls
31
Q

What is infancy?

A
  • Birth to 1 year old
32
Q

What happens to growth in first year?

A
  • rapid 25cm growth
33
Q

What happens to weight gain in first year?

A
  • 3 fold weight gain (weight x3)
34
Q

What happens to the height velocity in babies during infancy?

A
  • deceleration
  • at birth= growth rate= 20cm/year
  • at 1y/o = growth rate= 10-12cm/year
35
Q

At infancy, what are the main causes for growth?

A
  • environment

- genetics

36
Q

What is childhood?

A
  • First year to puberty
37
Q

What is the height velocity in childhood?

A
  • near constant

- about 4-8cm per year

38
Q

What influences growth in the childhood stage?

A
  • hormones more than nutrition
39
Q

What is the difference between boys and girls in childhood?

A
  • girls taller until age of 4

- girls have advanced skeletal maturity (bc adrenal glands mature faster in girls)

40
Q

What is the GH pathway?

A
  • Hypothalamus secretes GHRH

- Stimulate pituitary gland to release GH

41
Q

Where does GH act?

A
  • directly act on growth plates at bones
  • some stabilised by binding proteins to work on growth plate
  • act on liver to increase IGF1
  • IGF1 acts on growth plates on bones
  • IGF1 reacts with other substances to make stable complexes
42
Q

Can GH be measured?

A
  • GH levels fluctuate in day

- so IGF1 measured

43
Q

What is canalisation?

A
  • can catch up or catch down to growth

- after canalisation, the child normally stays in 1 centile or across 2 growth centiles

44
Q

What happens if at childhood a child is crossing over more than 2 centiles?

A
  • get this checked out

- can be pathological

45
Q

What is catch up growth?

A
  • a period of fast growth to catch up with the slow growth before lol
46
Q

Why will a baby need to go through catch up growth?

A
  • restricted growth in uterus bc maternal environment e.g. anorexia/stress
  • baby born with hypothyroidism= stunted growth
47
Q

If a baby has stunted growth because it was born with hypothyroidism, what do you do to make sure it enters catch up growth?

A
  • give thyroxine
48
Q

What is catch down growth?

A
  • baby born at high centile (e.g. bc of diabetic mother)

- over time, need to go to lower centile

49
Q

When does catch down growth happen?

A
  • starts at 3–6 months of age and is completed by 9–20 months old
50
Q

What is puberty?

A
  • transition from childhood to the achievement of adult stature through the development of secondary sexual characteristics
51
Q

What are the hormones in puberty?

A
  • pulsatile activation of HPG axis

- increase in sex hormones

52
Q

What is HPG like in the foetus?

A
  • GnRH neurones arise from olfactory placode (precursor to nasal epithelium)
  • migrate to hypothalamus along olfactory tract
  • this is under control of KAL and FGF8
  • important bc some children born with genetic hypothalamic hypogonadism
  • cause smell problems
53
Q

What happens to the HPG in infancy?

A
  • when the baby is first born= have high gonadotrophins (high LH, FSH, testosterone)
  • this is window of opportunity to test for problems with the HPG axis
  • after 3-6 months, it goes down and remains like that for the rest of childhood until puberty
  • very low levels of LH and FSH
54
Q

What happens to the HPG during puberty?

A
  • many neurotransmitters e.g. kisspeptin (+), neurokinin B (+), MKRN3 (-)
  • signal receptors to hypothal
  • switch HPG axis on
  • GnRH pulsatile release
  • initially only at night, later in day too
55
Q

What does the female go through during puberty?

A
  • puberty start at 11y/o
  • breast development
  • peak growth spurt occurs beginning to mid puberty
  • puberty end with menarch (FIRST PERIOD)
56
Q

What does the male go through during puberty?

A
  • puberty start at 12-13 y/o
  • testicular enlargement more than 4mls
  • growth spurt mid to late puberty= testes become 6-10mls
  • peak growth spurt 14y/o
57
Q

How are breast stages followed?

A
  • breast bud stage (stage II)
  • juvenile smooth contour (stage III)
  • adult phase (seen in picture)

The peak growth spurt occurs early on in women (between stage II and III of breast development)

58
Q

What is osteogenesis and when does it start?

A
  • bone development

- start 6-7 weeks gestation

59
Q

What are the 2 ways bones grow?

A
  • intramembranous ossification of the flat bones

- endochondral ossification of long bones

60
Q

What is intramembranous ossification of the flat bones?

A
  1. mesenchymal cells in the embryonic skeleton gather together
  2. differentiate into specialized cells= OSTEOBLASTS
  3. osteoblasts appear in cluster called OSSIFICATION CENTER
  4. osteoblasts secretes OSTEOID (uncalcified matrix= calcifies by depositing mineral salts and traps osteoblasts within)
  5. when osteoblasts entrapped, osteoblasts becomes OSTEOCYTES
  6. osteoid secreted around capillaries makes trabecular matrix
  7. osteoblasts on surface of spongey bone become periosteum
  8. periosteum creaes protective layer of compact bone
    superficial to trabecular bones
  9. the trabecular bone crowds nearby blood vessels, which eventually condense into red marrow
61
Q

What is endochondral ossification of long bones?

A

the mesenchymal cells differentiate into chondrocytes (cartilage producing cells)−these chondrocytes produce cartilage and a layer forms around this cartilage called the perichondrium−the cartilage forms a model of the future bone that will replace the cartilage−blood vessels carry osteogenic cells (which will become osteoblasts bone making cells) to the cartilage−the perichondrium converts to the bone making periosteum−the osteoblasts form a collar of bone around the cartilage forming the primary ossification centre (this is the diaphysis)−at the same time, cartilage and chondrocytes continue to grow at the ends of the bone (the future epiphyses ie growth plate)−blood vessels invade this area and the process begins again at the end of the bones forming the secondary ossification centre−cartilage remains at the epiphyseal growth plate and at the surface of joints (articular cartilage)-articular cartilage is the cartilage at joints between two bones

62
Q

What is the epiphyseal plate?

A
  • hyaline cartilage layer

- where ossification occurs

63
Q

What 2 things can the epiphyseal plate be split into?

A
  • epiphyseal side

- diaphyseal side

64
Q

What is the epiphyseal side?

A
  • side of plate close to outside of bone

- where cartilage is formed

65
Q

What is the diaphyseal side?

A
  • side of plate close to inside of bone
  • where cartilage is ossified and converted to bones
  • diaphysis grows in length bc of ossification
66
Q

The epiphyseal plate is composed of 4 zone of cells and activity. What are they?

A
  • reserve zone
  • proliferative zone
  • the zone of maturation and hypertrophy
  • the zone of calcified matrix is closest
67
Q

What is the reserve zone?

A
  • closes to outside of bone (to epiphyseal end of plate)

- contains small chondrocytes within the matrix

68
Q

What is the proliferative zone?

A
  • next layer torwatds the centre of bone
  • contains stacks of large chondrocytes
  • divide by mitosis
  • to replace ossified chondrocytes at diaphyseal end of plate
69
Q

What is the zone of maturation and hypertrophy?

A
  • has chondrocytes that are older and larger than the previous zone
  • the growth of the bone is a result of cellular division in the proliferative zone, and cellular maturation in the zone of maturation and hypertrophy
70
Q

What is the zone of calcified matrix?

A
  • closes to centre of bone (diaphysis)
  • contains ossified chondrocytes (the matrix around these cells has calcified)
  • capillaries and osteoblasts from the diaphysis penetrate this zone and osteoblasts secrete bone tissue on the remaining calcified cartilage-a bone grows in length when osseous (bone) tissue is addedto the diaphysis
71
Q

How does body fat change?

A
  • birth both females and males same amount

- puberty= girls get more body fat

72
Q

Where does fat deposit more in men and women?

A
  • women= increased amount of brown adipose tissue and an enlarged deposition of fat in the peripheries like hips
  • men= more fat deposition in the intra-abdominal area (around the abdomen)
73
Q

What is secular growth?

A
  • trend seen in increasing growth through time
  • trend is that growth is increasing as time goes forward

bc

  • environment
  • better sanitation
  • healthcare
  • nutrition