Physiology of Growth

Question 1

Growth is considered to occur in 4 separate but integrated phases: What are they?

Answer 1

1. Intrauterine growth phase
2. Infancy phase
3. Early childhood
4. Pubertal growth spurt

Question 2

Increase in cell size is referred to as..?

Answer 2

Hypertrophy

Question 3

Increase in cell number is referred to as..?

Answer 3

Hyperplasia

Question 4

Give examples of cells which do not have regenerative capabilities

Answer 4

Nerve and muscle cells

Question 5

Why do some cells such as skin, blood and GI epithelium have the ability to replace dead cells with new ones?

Answer 5

They possess a germinative zone

Question 6

Define the term “development”

Answer 6

An increase in complexity of the organism due to early maturation of the nervous system

Question 7

Give an example of apoptosis which occurs during foetal development

Answer 7

Webs between fingers and toes are removed to prevent syndactyl

Question 8

What are the two pathways to which apoptosis occurs?

Answer 8

Intrinsic Pathway

Extrinsic Pathway

Question 9

For the Intrinsic Pathway, intracellular signals stimulate apoptosis. What kinds of signals might these be?

Answer 9

DNA damage
ER stress
Hypoxia
Metabolic stress

Question 10

For the Extrinsic Pathway, extracellular signals associate with what receptors on the cell surface membrane? Give 2 examples

Answer 10

Death receptors i.e. TRAILR and FAS

Question 11

What are the set of enzymes which regulate apoptosis called?

Answer 11

Caspases

Question 12

Outline the morphological changes which occur during Apoptosis to a cell

Answer 12

• Chromatin condensation
• Membrane bleb formation
• Cellular fragmentation and apoptotic bodies form
• Phagocytosis of apoptotic cells / fragments by a phagocyte

Question 13

Foetal growth is at its greatest in what weeks of gestation?

Answer 13

Week 16-20

Question 14

The peak velocity of foetal weight gain occurs in what week of gestation?

Answer 14

Week 34

Question 15

When does Puberty occur in females and males?

Answer 15

Females: 10-14
Males: 12-16

Question 16

Ossification of bone occurs by what age?

Answer 16

By 3rd decade

Question 17

What are the names given to the bone stem cells which give rise to Chondrocytes?

Answer 17

Chondroblasts

Question 18

When does the average boy and girl stop growing?

Answer 18

Boys: 17.5 yo
Girls: 15.5 yo

Question 19

From the Epiphysis to the Diaphysis, what are the four distinct morphologies of the Epiphyseal plate?

Answer 19

“Real People Have Career Options”

Resting zone
Proliferation zone
Hypertrophic zone
Calcificaiton zone
Ossification zone

Question 20

Where is Growth Hormone produced and secreted from?

Answer 20

Somatotrophs of the anterior lobe of the Pituitary gland (pulsatile release)

Question 21

The indirect actions of Growth Hormone are primarily mediated downstream by…?

Answer 21

IGF-I and IGF-II

Question 22

Describe the secretion pattern of IGF-I before and after birth

Answer 22

Before birth: Independent of GH

After birth: Stimulated by GH

Question 23

Describe the secretion pattern of IGF-II

Answer 23

Independent of GH

Question 24

Overexpression of IGF-II in foetuses leads to what?

Answer 24

Disproportion tongue growth, muscles, kidney, heart and liver

Question 25

Aside from GH and IGFs, what are other mediators for growth? State 5

Answer 25

``` FGF PDGF NGF T3 and T4 Insulin Prolactin Placental Lactogen PTH Oestrogen Testosterone GCs ```

Question 26

Secretion of T3 and T4 commences when?

Answer 26

Week 15-20 gestation

Question 27

Inadequate levels of thyroid hormone during foetal and early pre-natal periods can lead to..?

Answer 27

Cretinism

Question 28

Does excess Cortisol production have an increase or decreasing effect on growth?

Answer 28

Decreasing effect on growth

Question 29

What is Growth Hormone also known as?

Answer 29

Somatotropin

Question 30

Growth Hormone is released under control of what hormone? Where is this hormone released from?

Answer 30

Growth Hormone Releasing Hormone, from the HypoT

Question 31

What hormone released from the HypoT has an inhibitory effect on the release of Growth Hormone?

Answer 31

Somatostatin

Question 32

What is the inheritance pattern of Acrondroplasia?

Answer 32

Autosomal dominant

Question 33

What is the genetic cause of Acrondroplasia?

Answer 33

Mutation in Gene on chromosome 4 that encodes FGFR3 leading to... - Decreased endochondral ossification - Inhibited chondrocyte proliferation - Decreased cell hypertrophy - Decreased matrix production

Question 34

What is the pathophysiology of Acromegaly?

Answer 34

- Hypersecretion of GH | - Due to adenoma of pituitary somatotroph cells

Question 35

What test can be done to support a diagnosis of Acromegaly?

Answer 35

Glucose intolerance test. GH levels should decrease following oral glucose but in Acromegaly patients will remain unchanged / rise

Question 36

A GH deficiency can lead to what condition?

Answer 36

Pituitary Drawfism

Question 37

How might Pituitary Drawfism be caused?

Answer 37

Pituitary / HypoT tumours, inections (meningitis, syphillis), head trauma

Question 38

What Dwarfism condition mimics Pituitary Dwarfism? What is it caused by?

Answer 38

Laron Dwarfism, caused by low levels of IGF-1

Question 39

How can Laron Dwarfism be treated?

Answer 39

Recombinant IGF-1

Question 40

What is the treatment for Hypothyroidism?

Answer 40

T4