Physiology of Growth Flashcards
Growth is considered to occur in 4 separate but integrated phases: What are they?
- Intrauterine growth phase
- Infancy phase
- Early childhood
- Pubertal growth spurt
Increase in cell size is referred to as..?
Hypertrophy
Increase in cell number is referred to as..?
Hyperplasia
Give examples of cells which do not have regenerative capabilities
Nerve and muscle cells
Why do some cells such as skin, blood and GI epithelium have the ability to replace dead cells with new ones?
They possess a germinative zone
Define the term “development”
An increase in complexity of the organism due to early maturation of the nervous system
Give an example of apoptosis which occurs during foetal development
Webs between fingers and toes are removed to prevent syndactyl
What are the two pathways to which apoptosis occurs?
Intrinsic Pathway
Extrinsic Pathway
For the Intrinsic Pathway, intracellular signals stimulate apoptosis. What kinds of signals might these be?
DNA damage
ER stress
Hypoxia
Metabolic stress
For the Extrinsic Pathway, extracellular signals associate with what receptors on the cell surface membrane? Give 2 examples
Death receptors i.e. TRAILR and FAS
What are the set of enzymes which regulate apoptosis called?
Caspases
Outline the morphological changes which occur during Apoptosis to a cell
- Chromatin condensation
- Membrane bleb formation
- Cellular fragmentation and apoptotic bodies form
- Phagocytosis of apoptotic cells / fragments by a phagocyte
Foetal growth is at its greatest in what weeks of gestation?
Week 16-20
The peak velocity of foetal weight gain occurs in what week of gestation?
Week 34
When does Puberty occur in females and males?
Females: 10-14
Males: 12-16
Ossification of bone occurs by what age?
By 3rd decade
What are the names given to the bone stem cells which give rise to Chondrocytes?
Chondroblasts
When does the average boy and girl stop growing?
Boys: 17.5 yo
Girls: 15.5 yo
From the Epiphysis to the Diaphysis, what are the four distinct morphologies of the Epiphyseal plate?
“Real People Have Career Options”
Resting zone Proliferation zone Hypertrophic zone Calcificaiton zone Ossification zone
Where is Growth Hormone produced and secreted from?
Somatotrophs of the anterior lobe of the Pituitary gland (pulsatile release)
The indirect actions of Growth Hormone are primarily mediated downstream by…?
IGF-I and IGF-II
Describe the secretion pattern of IGF-I before and after birth
Before birth: Independent of GH
After birth: Stimulated by GH
Describe the secretion pattern of IGF-II
Independent of GH
Overexpression of IGF-II in foetuses leads to what?
Disproportion tongue growth, muscles, kidney, heart and liver
Aside from GH and IGFs, what are other mediators for growth? State 5
FGF PDGF NGF T3 and T4 Insulin Prolactin Placental Lactogen PTH Oestrogen Testosterone GCs
Secretion of T3 and T4 commences when?
Week 15-20 gestation
Inadequate levels of thyroid hormone during foetal and early pre-natal periods can lead to..?
Cretinism
Does excess Cortisol production have an increase or decreasing effect on growth?
Decreasing effect on growth
What is Growth Hormone also known as?
Somatotropin
Growth Hormone is released under control of what hormone? Where is this hormone released from?
Growth Hormone Releasing Hormone, from the HypoT
What hormone released from the HypoT has an inhibitory effect on the release of Growth Hormone?
Somatostatin
What is the inheritance pattern of Acrondroplasia?
Autosomal dominant
What is the genetic cause of Acrondroplasia?
Mutation in Gene on chromosome 4 that encodes FGFR3 leading to…
- Decreased endochondral ossification
- Inhibited chondrocyte proliferation
- Decreased cell hypertrophy
- Decreased matrix production
What is the pathophysiology of Acromegaly?
- Hypersecretion of GH
- Due to adenoma of pituitary somatotroph cells
What test can be done to support a diagnosis of Acromegaly?
Glucose intolerance test. GH levels should decrease following oral glucose but in Acromegaly patients will remain unchanged / rise
A GH deficiency can lead to what condition?
Pituitary Drawfism
How might Pituitary Drawfism be caused?
Pituitary / HypoT tumours, inections (meningitis, syphillis), head trauma
What Dwarfism condition mimics Pituitary Dwarfism? What is it caused by?
Laron Dwarfism, caused by low levels of IGF-1
How can Laron Dwarfism be treated?
Recombinant IGF-1
What is the treatment for Hypothyroidism?
T4
