DISORDERS OF GROWTH

what are the major types of disorders of growth

1. too much

2. too little

3. wrong type

4. wrong place

what are the reasons for disorders of growth

• developmental/ congential

  • between life and death

  • congenital: pre natal period

• reactive/ adaptation e.g. to offer more protection

  • short term response

diagram showing cell proliferation and differentiation

how do disorders of growth arise

stress » adaptation » disorders of growth

give examples of disorders of growth

• stress (chronic trauma) on oral epithelial mucosal cells » increase in cell number

• stress (more effort) on skeletal muscle cells » increase in size e.g. going to the gym

what does the prefix hyper mean

hyper = increased

what does the prefix hypo mean 

hypo = decreased

what does the suffix trophos mean

trophos = nutrition/ metabolism (increase/ decrease cell size)

what does the suffix plasis mean

plasis = growth (cell number)

what does the prefix meta mean

meta = changed (different cell type)

what does the prefix dys mean 

dys = bad 

what does the prefix neo mean

neo = new

give an example of a type of developmental/ congenital disorder of growth

hamartoma: benign growths in specific tissues

• tissues are normal for the site but they are excessive

• grows in patient’s growth period then stops growing

what are examples of hamartomas

• congenital pigmented naevi - excessive melanin production

• haemangioma - excessive vascularisation

• odontomes

histology of odontome

give examples of types of reactive/ adaptive disorders of growth

• hyperplasia - increase in cell number

• hypertrophy - increase in cell size

outline hyperplasia

hyperplasia: increase in cell number

• in response to a stimulus

  • can be physiological or pathological

• stops once stimulus is removed

give an example of a physiological VS pathological hyperplasia

• physiological: breast enlargement during puberty

• pathological: thyroid enlargement

give an oral example of pathological hyperplasia

• denture-induced hyperplasia (Epulis fissuratum)

• usually related to ill-fitting complete denture

• benign lump: smooth pink surface lying parallel with the alveolar ridge

what is the management for Epulis fissuratum

• relieve the denture flange and wait for regression

• if it does not regress within 2-3 weeks the lump should be excised

describe this histological image 

• LHS = normal epithelium

• RHS = hyperplasia 

  • thicker granular layer because producing more keratohyaline granules »

  • more keratin at surface 

  • connective tissue is slightly pinker due to overproduction of collagen

outline hypertrophy

hypertrophy: increase in cell size

• often associated with hyperplasia

• in response to a stimulus

  • can be physiological (increase in skeletal muscle size when going to the gym) or pathological

what is pure hypertrophy

increase in the size of skeletal and cardiac muscle

give examples of physiological hypertrophy 

• there is physiological hypertrophy of the uterus during pregnancy

• left ventricular hypertrophy also occurs 

give an example of pathological hypertrophy 

• hypertension - also left ventricular hypertrophy 

diagram showing why left ventricular hypertrophy may occur

hypertrophy and hyperplasia diagram

give another example of compensatory physiological hyperplasia/ hypertrophy 

• compensatory physiological hyperplasia/ hypertrophy is a type of regenerative growth

• usually occurs after organ damage, removal or malfunction

• growth can be a result of increased cell size (compensatory hypertrophy) or increased cell division (compensatory hyperplasia) 

  • or both

what does this image show

• LHS: pig born with both kidneys

• RHS: pig born with one kidney

give another example of pathological hyperplasia 

• benign prostatic hyperplasia (BPH)/ prostate gland enlargement

• common condition in older men

• as the gland enlarges it can squeeze the urethra 

state congenital changes of too little growth

• agenesis: does not develop at all

• aplasia: fails to develop normal structure

• hypoplasia: less tissue is formed

outline tooth agenesis

tooth agenesis: congenital absence of one or more teeth

• 8s > 5s > 2s

• hypodontia - agenesis of one to six teeth (excluding 8s)

• oligodontia - absence of more than 6 teeth (excluding 8s)

• anodontia - complete absence of teeth

outline aplasia (achrondroplasia)

• achondroplasia i.e. dwarfism

  • random event, but the gene change can also be inherited

  • defect in converting cartilage into bone

  • most common type of restricted growth

  • normally occurs in limbs, hence stunted growth

outline dental enamel hypoplasia 

dental enamel hypoplasia

• enamel is deficient in quantity 

• affected region = area of ameloblastic activity at the time of injury 

• areas of coronal discolouration or actual pits and irregularities

• increased risk of caries

what are causes of dental enamel hypoplasia

• nutritional deficiency

• prematurity

• allergic diseases

• trauma

state another term for developmental/ pathological changes of too little growth

• atrophy: decrease in cell size and/ or number

outline atrophy 

• mechanisms:

  • imbalance of cell loss and production

    • reduced proliferation

    • increased cell loss (apoptosis > necrosis)

• reduction in structural components of the cell i.e. cell volume 

• generalised VS localised

outline generalised atrophy

• nutritional e.g. in starvation

• age related (senile)

  • endocrine: release of hormones into the blood produces a dysregulated signalling pathway » systemic atrophy

  • bone: osteoporosis (linked with endocrine dysregulation)

outline localised atrophy

• ischaemia: lack of blood supply can lead to localised atrophy and cell death

• pressure » localised atrophy

• disuse » localised atrophy

• neuropathic changes » localised atrophy

• immune mediated: e.g. atrophic gastritis (own immune system attacks stomach lining)

• idiopathic: unclear cause » localised atrophy

outline atrophic glossitis

• partial or complete absence of filiform papillae on the dorsal surface of tongue

• diabetes is a comorbidity of atrophic glossitis

list causes of atrophic glossitis 

• deficiencies of major nutrients incl.

  • riboflavin, niacin, pyridoxine, vitamin B12, folic acid, iron, zinc, vitamin E

• protein-calorie malnutrition

• can be due to infiltration of various fungi e.g. Helicobacter pylori

• candidiasis

• xerostomia 

outline pressure as a cause of localised atrophy

• most commonly from being bed ridden » bed sores (huge issue for NHS)

• pressure points » ulceration

• pressure stops the delivery of nutrients into that area of tissue

outline metaplasia

metaplasia change in which one adult cell type (epithelial or mesenchymal) is replaced by another adult cell type (wrong type)

• this is an adaptive response

  • sensitive cell type is replaced by another cell type better suited to withstand the adverse environment

• however it often results in the loss of the original tissue’s specialised function

  • can be a precursor to dysplasia and cancer

what is the most common type of metaplasia 

epithelial metaplasia 

table showing types of metaplasia 

outline squamous metaplasia

• occurs in smokers

• normal ciliated columnar epithelial cells of the trachea and bronchi is replaced by stratified squamous epithelial cells

• SSE is more resistant to noxious chemicals in cigarette smoke and vapes

• important protective mechanisms like mucous secretion and ciliary clearance are lost

squamous metaplasia VS epithelial dysplasia diagram

outline intestinal metaplasia

• chronic gastric reflux

  • stomach is producing acid (stressor) which flows into and damages oesophagus

• normal SSE of lower oesophagus undergo metaplastic transformation to gastric or intestinal-type columnar epithelia

what does intestinal metaplasia lead to 

Barrett’s oesophagus 

• premalignant lesion of oesophageal adenocarcinoma

• 10% rate of malignant transformation » oesophageal carcinoma

outline (epithelial) dysplasia

epithelial dysplasia: abnormal growth and differentiation in a tissue, with abnormal cells and tissue architecture

• has the potential to become a malignant tumour (neoplasia)

• ‘dysplasia’ also used to name different pathological conditions e.g. renal dysplasia, bone dysplasia

outline neoplasia

neoplasia: uncontrolled growth which does not stop and persists after the stimulus is removed

outline ectopia

ectopia (wrong place)

• developmental abnormality 

• normal tissue

• abnormal site 

give an example of ectopia in the oral cavity

ectopic sebaceous glands

• i.e. Fordyce spots

• soft yellowish granules seen in upper lip and buccal mucosa

• 80% of population

• rarely evident in infants

• increase during puberty

give an example of ectopia elsewhere in the body

ectopic thyroid tissue

• e.g. lingual thyroid

• lack of descent of thyroid tissue during development - true incidence not known

• 90% of all ectopic thyroid tissue is associated with dorsum of the tongue

• usually not clinically evident

  • when clinically evident it is largely asymptomatic/ associated with hypothyroidism

what leads to adaptation

stress

how does potential carcinogenesis result from stress

chronic stress » metaplasia » dysplasia » potential carcinogenesis