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Block 11 > Physiology Of Growth > Flashcards

Physiology Of Growth Flashcards

(51 cards)

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1
Q

Intrauterine growth phase is dependent on three factors….

A

Genetics

Nutrition

Placenta

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2
Q

What drives the infancy phase of growth

A

Nutritional factors in the first 2-3 years of postnatal life

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3
Q

Early childhood phase of growth is dependent on…

A

Growth hormones s

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4
Q

What regulates the pubertal growth spurt

A

Combination of GH and sex hormones

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5
Q

Growth is characterised by an increase in …..

A

Hypertrophy

Hyperplasia

Volume of intracellular material

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6
Q

Examples of when apoptosis occurs during foetal development

A

Webs between fingers are removed

Hollow organs such as the heart begin off as solid structures

Apoptosis normal event in fully developed tissues with sites of high cell turnover

Replacement and regeneration of cells in the skin, respiratory and GI tract

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7
Q

What cellular changes are observed with a cell undergoing apoptosis

A

Condensation of the chromatin

Formation of membrane blebs that go on to form apoptotic bodies (cellular fragmentation)

Phagocytosis of bodies and fragments

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8
Q

What triggers the intrinsic and extrinsic pathways of apoptosis

A

Extrinsic = mainly by adjacent cells and immune cells via superfamily of caspases

Intrinsic = stimuli which is lethal such as DNA damage or ER stress, hypoxia and metabolic stress

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9
Q

When is foetal growth at its peak

A

16- 20 weeks

By cell division

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10
Q

When does foetal weight gain peak

A

34 weeks

Due to deposition of fat

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11
Q

Senescent changes occur when

A

Sex hormones decline eg menopause

Reduces capability to initiate homeostatic mechanisms in response to internal or external environmental stresses

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12
Q

What change occurs to the cardiovascular system in senescence

A

Reduced blood flow

Arteriosclerosis

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13
Q

Respiratory system senescence change:

A

Reduced elasticity of lungs

Decreased lung function

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14
Q

Urinary system changes in ageing

A

Decreased muscle tone and decreased GFR

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15
Q

Changes to the skin in senescence

A

Loss of elasticity —> sagging and wrinkling

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16
Q

Immune system senescent changes

A

Reduced sensitivity and responsiveness

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17
Q

What happens to brain in senescence

A

Impaired coordination, memory and intellectual function

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18
Q

Senescent changes to the GI system

A

Decreased GI muscle tone and less peristalsis

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19
Q

Senescent changes to endocrine function

A

Decreased in hormone production and sensitivity

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20
Q

What happens to bones as a person ages

A

Decline in rate of Bone deposition
Decrease in mobility

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21
Q

What happens to muscular system as a person ages

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A

Reduction in muscle mass, strength and ability

22
Q

Why does growth not occur after puberty

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A

Epiphysis and diaphysis of bones fuse so no further increase in length is possible

23
Q

4 zones of bone growth at the epiphyseal plate

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A

Proliferation zone = chondroblasts divide quickly and push the epiphysis away from the diaphysis lengthening the bone

Hypertrophic zone = chondrocytes enlarge and signal surrounding matrix to calcify

Calcification zone (not bone yet) matrix calcifies and chondrocytes die

Ossification zone

24
Q

Which types of hormones required in combination to result in growth

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A

Growth hormones
Thyroid hormones
Sex hormones

25
Effects of growth hormones
Produced by anterior pituitary Direct = fat metabolism Indirect = stimulates liver to produce IGFs which indirectly affect bones
26
Which 5 tissues make IGF-1 and IGF-II
Liver Kidney Bone Muscle Cartilage
27
Which IGF is stimulated by growth factor after birth and which plays a role in foetal development
IGF-I stimulated by GF after birth and is independent previous to birth. Rises during childhood and peaks at puberty and declines to low levels at old age IGF-II = largely independent of GF and role in foetal development
28
Overexpression of IGF-II in foetuses leads to
Disproportionate growth of tongue, other muscles, kidneys, heart and liver
29
Role of thyroid hormones in growth
T3 - triiodothyronine T4 - thyroxine Secretion commences at 15-20 wks of gestation Essential for protein synthesis in brain of foetus and young children Normal differnetaotn and maturation of skeletal and nervous tissue Promotes linear growth of bone until puberty and ossification of bones and maturation of epiphyseal growth regions
30
Deficiencies in thyroid hormones lead to
Mental retardation Insufficient bone and height growth
31
What is cretinism
Inadequate levels of thyroid hormones during foetal period lead to severe mental retardation Due to: - decrease in size and number of cerebral cortical neurons - reduction in degree of branching of dendrites - deficiencies in myelination of nerve fibres - reduced blood supply to the brain
32
Hypothyroidism detected at birth if left untreated leads to what
Permanent neurological and intellectual damage (cretinism)
33
In relation thyroid function what does the Guthrie blood spot detect
High TSH levels in case of hypothyroidism
34
How do corticosteroids affect growth
Cortisol if in excess has inhibitory actions on growth Interfere with cartilage and bone synthesis at growth plates = increased rate of skeletal maturation so potential for further growth is reduced
35
How do sex steroids influence growth
Androgens have anabolic effects Oestradiol and testosterone (leydig cells) positive effect on secretion of GH Results in increase in long bone growth and height
36
Somatotropin/ growth hormone is what kind of hormone
Peptide hormone
37
What is the diurnal variation in secretion of GH
Most secretions occur with slow wave deep sleep (Pursatile bursts)
38
How does GH secretion change over lifetime
Continues to increase from birth until puberty where it peaks. Slight decline in adulthood which remains constant until senescent age (significant reduction but still constant in this period)
39
How does IGF-1 inhibit secretion of GH to regulate levels of growth
1) direct inhibition by suppressing somatotrophs 2) indirectly reducing gnRH release from arcuate nucleus in hypothalamus 3) indirectly via increasing secretion of somatostatin from periventricular region
40
What is achondroplasia
- dwarfism - autosomal dominant inheritance pattern - mutation in gene on C. Four that code for fibroblast growth factor receptor 3 FGFR3 Avg male height 125cm Avg female height 120cm
41
Mutation of gene that produces FGFR3 results in what
Increased function of gene which: Decreased endochondral ossification Inhibited proliferation of chondrocytes in growth plate cartilages Decreased cellular hypertrophy and decreased cartilage matrix production Earlier closure of epiphyseal plates
42
Presentation of achondroplasia
Large forehead Proportionate trunk but limbs are v small compared to rest of body
43
What causes acromegaly
Hypersecretion of GH Adenoma of pituitary somatotroph cells Affects all organs and tissues. Leads to gigantism
44
Those with acromegaly at higher risk of
T2 DM CVD Hypertension Arthritis
45
How is GH secretion pattern diurnally different in those with acromegaly
Constant elevated levels throughout day and night
46
A way to test for acromegaly
Administer glucose Glucose normally suppresses GH secretion but in those with acromegaly there is no change
47
What is pituitary dwarfism
GH deficiency may be accompanied by under secretion of other pituitary hormones. As a result skeleton fails to grow and 120cm height achieved with normal proportions
48
Causes of pituitary dwarfism
Pituitary or hypothalamic tumours Infections such as meningitis or syphilis Pituitary infarction and vascular malformations Head trauma
49
What is panhypopituitarism
Absence of all pituitary hormones
50
What is Laron dwarfism
Mimics GH deficiency but GH levels are high Levels of IGF-I and IGFbinding protein3 are low Caused by mutation in GH receptor - becomes unresponsive —> growth retardation Treated with recombinant IGF-1
51
What is the most common cause of growth failure worldwide
Malnutrition Mainly due to lack of protein and other basic nutrients Shows sign of weakness, frailty and muscle wasting

Block 11 (13 decks)

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