Growth disorders Flashcards
What do agenesis, aplasia and hypoplasia have in common?
All developmental disorders that involve too little growth
Definition of agenesis
An organ does not develop at all
Causes of agenesis
genetic defect / mechanical cause (e.g. obstruction) that prevents stem cell development (no primitive precursor for cell)
Aplasia definition
An organ fails to develop its normal structure from primitive embryonic structure (stem cell/embryonic/precursor fails to develop normally)
Hypoplasia definition
Less tissue is formed but it has a normal structure
Example of hypoplasia oral defect
enamel hypoplasia
Potential cause of enamel hypoplasia
high level of fluoride in drinking water
What is the name of developmental disorders that involve too much growth?
hamartoma
What is a hamartoma?
tumour-like growth (but different to a benign tumour)
When does a hamartoma arise?
during the patient’s growth period (childhood) and stops when growth ceases
Examples of hamartomas
pigmented naevi (moles), haemangioma, lymphangioma
What is the clinical name for a mole?
pigmented naevus
What are pigmented naevi made up of?
large collection of melanocytes that are benign but larger than normal
What is a haemangioma?
A lesion made up of lots of blood vessels / blood filled spaces
What is a lymphangioma?
an abnormal collection of lymphatic vessels / large lymph-filled fluid spaces
What is the name of a dental hamartoma?
odontoma
What is an odontoma?
dental tissue that resembles abnormal teeth or a calcified mass found in an abnormal location e.g. lots of small teeth found in a collection around the mandible
When do haematomas occur?
from birth (lesion regresses in size during first 6 months to become a red patch / birthmark)
Why may (cavernous) haemangiomas cause epilepsy?
Haemangiomas may affect meninges of the brain
What is the name of the syndrome that may be associated with haemangiomas?
Sturge Weber syndrome
Describe the haemangiomas associated with Sturge Weber syndrome
large haemangiomas that follow the course of a particular nerve (e.g. CN Vb)
What is the correct term to refer to haemangiomas that form later in life?
vascular malformations
What are vascular malformations?
collection of blood vessels that become more apparent in adult life
Why are vascular malformations more common in older age?
mucosa atrophies (becomes thinner) / trauma which makes the vasculature more apparent
What are the 2 types of haemangiomas?
capillary and cavernous haemangiomas
What is the difference between capillary and cavernous haemangiomas?
capillary haemangiomas are composed of a collection of several capillaries whereas cavernous haemangiomas are larger larger blood filled spaces
Where may cavernous haemangiomas occasionally be located?
in the mandible
What is a difference between the structure of a benign tumour and a hamartoma?
Hamartomas do not have a fibrous capsule separating growth from normal tissue, unlike benign tumours which are often encapsulated
What is the most common type of lymphangioma?
cavernous lymphangioma
Common locations of lymphangioma
tongue (ventral surface), side of neck
What is the name of a lymphangioma that develops on the side of a newborn’s neck?
cystic hygroma
What is the name of developmental disorders that involve normal tissue in an abnormal site?
ectopia
Examples of ectopia
Meckel’s diverticulum, ectopic tooth, ectopic pregnancy
What is Meckel’s diverticulum?
an outpouching of the small intestine that can contain gastric type mucosa (therefore can produce gastric acid)
What is an ectopic tooth?
A normal tooth in the wrong position
Which tooth is most commonly ectopic?
Canine (but also can be central incisors, premolars)
What is an ectopic pregnancy?
fertilised ovum growing in the fallopian tube instead of descending into the uterus
Why do acquired disorders of growth occur?
cells adapt when they are exposed to environmental stresses
What are the different types of acquired growth disorders?
atrophy, hypertrophy, hyperplasia, metaplasia, dysplasia
What is atrophy?
an acquired growth disorder that involves a reduction in size and number of cells
What are the 2 types of atrophy?
physiological and pathological atrophy
What is physiological atrophy?
Part of normal growth and development and is under hormonal influence
Example of physiological atrophy
thymus (needed during childhood then shrinks)
What are the mechanisms by which atrophy occurs?
reduction in organelles reduces cell size, imbalance of cell loss > production, apoptosis (for atrophy of organ)
What are the possible causes of localised atrophy?
ischaemia, pressure (from tumour), disuse/denervation autoimmune, idiopathic
What is ischaemia?
insufficient blood flow to a part of the body (often due to artery blockage)
When may localised atrophy due to disuse occur?
for bedridden patients
What does idiopathic mean?
there is no identifiable cause
What are the possible causes of generalised atrophy?
nutritional deficiencies (e.g. EDs), senile, endocrine
What is senile atrophy?
generalised atrophy in which organs decrease in size with age
What is an atrophic mandible?
reduction in height of alveolar bone of mandible
Cause of atrophic mandible
loss of lower teeth
Why does the loss of lower teeth cause an atrophic mandible?
PDL is lost including mechanoreceptors. Therefore, during pressure (chewing) no stimuli is sent to bone. So mechanical loading of bone is lost leading to gradual bone resorption.
What is the name of the structure that allows the passage of the mental nerve and artery into the mandible?
mental foramen
What must be considered when making a denture for a patient who has an atrophic mandible (10-15 years)?
the alveolar ridge may now be in line with the mental foramen so the mental nerve may be sat on the ridge. Relief around this area must be provided to avoid pain from pressing on the nerve
What is the name of the disorder that involves a reduced bone density and an increased risk of fracture?
Osteoporosis
Where are the common sites for osteoporosis?
Vertebrae (and hip and wrist)
What factors affect the risk of developing osteoporosis?
physical activity, age, hormones
Why are post-menopausal women at an increased risk of developing osteoporosis?
oestrogen has an inhibitory effect on osteoclasts therefore reduced oestrogen increases osteoclast activity. There is increased bone resorption which is imbalanced with bone formation.
What 3 groups can cells be divided into according to their mitotic ability?
labile cells, stable cells, permanent cells
What are labile cells?
cells that divide rapidly to replace lost cells
Example of labile cells
epithelial cells, hepatocytes
What are stable cells?
cells that are able to divide when necessary but spend most time in G0
Example of stable cells
muscle cells (myocytes)
What are permanent cells?
cells that are incapable of dividing e.g. neurons
Hyperplasia definition
increase in cell numbers
What is the effect of hyperplasia?
Increased tissue size and function
What is the effect of hyperplasia of an endocrine gland?
increased hormone production which can lead to clinical symptoms
What happens when the stimulus that causes hyperplasia is removed?
regression of the tissue occurs
Which cells can undergo hyperplasia?
Labile cells (capable of dividing to form new cells)
Why may physiological/pathological hypoplasia occur?
due to hormonal stimulation (e.g. breast development/endometrial thickening) or compensatory (e.g. to make up for lost tissue or function after partial hepatectomy)
Example of hyperplasia
gingival hyperplasia
What is gingival hyperplasia?
Increased thickness of gingival around all teeth
Cause of gingival hyperplasia
Can be a side effect for a drug that is triggered by poor oral hygiene being the stimulus
Which drugs may cause drug-induced gingival hyperplasia?
Anti-epileptic drugs (e.g. Epaneutin), Ca2+ blockers (anti-hypertensive)
What happens when the stimulus for gingival hyperplasia is removed?
Gingiva is remodelled back to normal or periodontal surgery
What are the causes of pathologic hyperplasia?
endocrine stimulation, chronic injury and inflammation, virus
Example of pathologic hyperplasia due to endocrine stimulation by hormone producing organs
benign prostatic hyperplasia (hyperplasia of target organs)
How may chronic injury and inflammation lead to hyperplasia?
cytokines and growth factors stimulate hyperplasia of bone marrow and lymphoid tissue to fight infection
What is the name of the virus that can induce hyperplasia of epithelium?
Human papillomavirus (HPV)
What may human papillomavirus cause?
warts/verrucas and squamous cell papilloma in the oral cavity
What is the name of hyperplasia that is able to regress?
controlled hyperplasia
What are the different mechanisms of hyperplasia?
growth factor-driven proliferation of cells, increased stem cell division leading to increased output, liver regeneration
What is an example of hyperplasia to replace damaged/lost tissue?
liver regeneration
Which cells divide during liver regeneration?
hepatocytes (but typically only stem cells are capable of regeneration)
Hypertrophy definition
increase in cell size
How do cells increase in size during hypertrophy?
increased production of cellular proteins
Which 2 acquired growth disorders usually occur together?
Hyperplasia and hypertrophy
Which cells undergo pure hypertrophy (without hyperplasia)?
stable cells (e.g. myocytes) - limited mitotic ability
What stimulus causes muscular hypertrophy?
mechanical stimulus - in response to increased load
What stimulus causes hypertrophy of skeletal muscle?
exercise (physiological stimulus)
What stimulus causes smooth muscle hypertrophy?
pregnancy (uterus muscles) - physiological.
What stimulus causes cardiac muscle hypertrophy?
Hypertension - left ventricular hypertrophy, LVH (pathologic). Heart must increase workload to overcome resistance from blood vessels
Name of condition in which left ventricle wall thickens due to hypertension
left ventricular hypertrophy (LVH)
What may result if a myocyte does not adapt to increased load?
Cell injury (cloudy swellings or fatty changes - reversible) which may progress to cell death (infarct / coagulative necrosis)
What is the name of an enlargement of the thyroid gland?
goitre
Causes of goitre
dietary iodine deficiency
How does a dietary iodine deficiency lead to goitre?
there is a decreased synthesis of thyroid hormone so thyroid follicular cell hypertrophy and hyperplasia occur together to increase thyroid hormone
Why hormone has an increased production due to goitre?
Thyroid stimulatory hormone (TSH)
Which cell produces thyroid hormone (T3 and T4)?
thyroid follicular cell
Which acquired growth disorders occur during goitre?
both hypertrophy and hyperplasia
Metaplasia definition
change from one differentiated form of a tissue to another (stem cells reprogrammed)
What is the cause of metaplasia?
Adaptive response due to a change in environmental demand (e.g. increased protection required)
What are the 2 types of metaplasia involving the epithelium?
squamous metaplasia and mucous metaplasia
What happens during squamous metaplasia?
epithelium changes into squamous type (tougher, can withstand stress, protects underlying tissues)
What happens during mucous metaplasia?
epithelium changes into mucous producing cells
What happens during mesenchymal metaplasia?
Formation of bone within fibrous / muscular tissue
What are the 2 types of mesenchymal metaplasia?
osseous and cartilaginous (during fracture healing) metaplasia
How does metaplasia occur?
Stem cells or undifferentiated mesenchymal cells are reprogrammed
Examples of patients in which metaplasia will occur
smokers and patients with Barrett’s oesophagus
What is the metaplasia that occurs in smokers?
ciliated columnar pseudostratified epithelium changes into stratified squamous epithelium (squamous metaplasia)
What is the stimulus that leads to Barrett’s oesophagus?
gastric-oesophageal reflux (gastric acid enters the lower oesophagus) which induces epithelium change
What is the metaplasia that occurs in Barrett’s oesophagus?
columnar metaplasia - stratified squamous epithelium changes to columnar epithelium (like stomach)
Dysplasia definition
disordered growth (each cell develops own growth pattern and becomes autonomous)
Which type of tissue may be predisposed to dysplastic changes?
metaplastic tissue
What is the grading system for displasia?
mild to moderate to severe
Why is severe dysplasia more dangerous?
the more severe, the higher the likelihood of a malignant change
What is neoplasia?
An excessive new growth that results in an abnormal mass of tissue
What happens in neoplasia when the stimulus is removed?
the growth persists (unlike hyperplasia where regression occurs)
What are the 2 types of neoplastic tumours?
benign and malignant
Example of benign neoplastic tumour
squamous cell papilloma
Example of neoplastic malignant tumour
squamous cell carcinoma
Which part of the oral cavity is a high risk area for oral cancer?
tongue
