Growth and development Flashcards
What continues to grow after puberty?
Hair, skin, nails
How do tissues differ in their growth pattern?
- Do not generate new cells
- Germinative zone, tissues replace dead cells
- Long-lived and stable, can regenerate
4 separate phases of growth:
- Intrauterine phase
- Infancy
- Early childhood phase
- Pubertal growth spurt
Factors in the intrauterine phase =
Genetic constitution
Nutrition
Placental function
Factors in the infancy phase =
Nutrition
Factors in the childhood phase =
GH
Factors in puberty =
GH
Sex hormones
Development =
Increase in the complexity of the organism
Development is due to =
Maturation of the nervous system
2 pathways of apoptosis =
Intrinsic and extrinsic pathway
Intrinsic apoptosis pathways =
Biochemical stress
DNA damage
Lack of growth factors
Modulated by Bax and Blc
Extrinsic apoptosis pathways =
Trigger by TNFR or FAS
Common pathway of apoptosis aka ‘executioner’ is regulated by:
Caspases
Foetal growth is greatest at what weeks gestation?
16-20
Morphogenesis =
differentiation and specialisation of cells into tissues and organs
Max height for girls is reached at =
13.5 years
Max height for boys is reached at =
15.5 years
Aging is also known as
Senescence
Aging changes occur when
Sex hormones decline
Elderly are less able to…
Make homeostatic adjustments in response to internal or external environmental stresses
Why does the growth of the skeleton not end at puberty?
Vertebral column continues to grow until about 30
2 Principle mediators of growth =
Growth hormone
Insulin-like growth factors
Growth hormone is also known as
Somatotrophin
Growth hormone is produced by, where
Stomatotroph cells in the anterior pituitary gland
Direct actions of GH =
Liver: glycolysis, gluconeogenesis
Increase insulin resistance in tissues
etc
Fat metabolism
IGFs are synthesised in
Liver, bone etc.
IGF-II =
Largely independent of GH. Important role in fetus
IGF-I =
Independent of GH before birth, stimulated by GH after. Rises in childhood
IGF-1 peaks when?
Puberty
Other mediators of growth:
- Thyroid hormones
- Growth factors
- insulin
- prolactin
- hPL
- vitamin D, PTH
- sex hormones
- glucocorticoids
What are T3 and T4 essential for?
Protein synthesis in brain of fetus and young child
Normal differentiation and maturation of skeletal and nervous tissue
Linear growth of bone
Inadequate levels of thyroid hormones during late fetal/early prenatal period leads to:
Severe mental retardation
- decrease size and number of cerebral cortex neurones
- reduced myelination
- reduction of branching of dendrities
- reduced blood supply to brain
Ex of condition that leads to inadequate levels of thyroid hormone and severe mental retardation =
Congenital iodine deficiency
Causes of hypothyroidism =
Primary - in thyroid
Secondary - TSH,TRH
Iodine deficiency
Hypothyroidism is tested in the
Gurthrine test
Classic features of hypothyroidism -
Puffy face Dry hair Low hair line Jaundice Constipation Sleep a lot Slow growth Poor school performance
Treating hypothyrodism at birth =
T4
What, if present in excess, can have an inhibitor effect on growth?
Cortisol
Ex of glucocorticoid =
Cortisol
How do glucocortcoids slow growth =
Interfere with cartilage and bone synthesis. Increased rate of skeletal maturation so potential for further growth reduced (not anything to do with GH)
What do sex steroids promote?
GHRH
Oestradiol-17b stimualtes =
Development of: breast, uterus, vagina
Testosterone stimulates =
Deveopment: lean body mass, secondary sexual characteristics
GH is structurally similar to
Prolactin
hPL
GH is stimulated by
GHRH from hypothalamus
GH is inhibited by
Somatostatin
when does secretion of GH peak?
during deep/slow wave sleep
GH has a … variation
Diurnal
What stimulated GHRH
Sex steroids
Adrenaline
Low glucose
What stimulated somatostatin?
High glucose
Glucocorticoids
WHat inhibits somatostatin
Dopamine
Serotonin
What does IGF-1 do in terms of negative feedback?
Inhibits GH
Inhibits GHRH
Stimulated somatostatin
Ex of dwarfism
Achondroplasia
Hypopituitary
Laron
Achondroplasia has what genetic link?
Autosomal dominant
Achondroplasia
Up regulation of fibroblast growth factor receptor 3
What does a patient with achondroplasia look like?
Short limbs
Large head, prominent forehead
Flattened nose
Short hands, stubby fingers
Pituitary dwarfism =
GH deficiency
Treatment for pituitary dwarfism =
Recombinant GH therapy
Causes of pituitary dwarfism =
Pituitary or hypothalamic tumors
Infections
Infarction
Head trauma
Larons dwarfism mimics
GH deficiency
How to test for larons dwarfism?
GH high
IGF-1 low
Treatment for larons dwarfism =
Recombinant IGF-1
Acromegaly is due to
Hypersecretion of GH
Difference between acromegaly and giantism
Acromegaly = adult GIantisms = children, growth plates not closed
Signs and symptoms of acromegaly
Large head, hands, jaw
Increased: CVD, diabetes, carpal tunnel, colorectal cancer
How to be sure of acromegaly diagnosis =
Give oral glucose, in normal individual GH should drop.
Most common cause of growth failure worldwide =
Nutritional failure
