W5 Lecture 1: Disorders of Growth

Question 1

What’s the complete failure of growth called?

Answer 1

• agenesis

Question 2

What’s the partial failure of growth called?

Answer 2

• hypoplasia

Question 3

What is hyperplasia?

Answer 3

• Is an increase in the size of tissue due to an increase in the number of its constituent cells

Question 4

When does the hypertrophy or hyperplasia effects cease?

Answer 4

When the stimulus triggering and promoting their action is removed

Question 5

What mechanisms within the body cells lead to hyperplasia?

Answer 5

• Transcription be turning on genes including those responsible for production of growth factor receptors
• Increase in levels of growth factor receptor receptors on cells
• Increase in local production of growth factors
• Activation of intracellular signaling pathways

Question 6

Which organs see hyperplasia as a result of hormones or endocrine system??

Answer 6

• Breasts during puberty and pregnancy(stimulated by hormone estrogen)
• Thyroid gland at puberty and during pregnancy (stimulated by thyroid stimulating hormone from the pituitary gland)

Question 7

What is compensatory hyperplasia, and why do we see it?

Answer 7

• It’s a form of hyperplasia that results from an increased functional demand of a specific tissue or organ.

Question 8

When do we commonly see compensatory hyperplasia?

Answer 8

• On bone marrow:
  -Due to an increased demand of RBC (erythropoiesis) when on high altitude or coz of blood loss;
  -And due to an increased demand for granulocytes if microbial infection is evident.
• On a liver:
  -Following liver hepatectomy

Question 9

A growth disorder resulting from chronic irritation of oral mucosa due to ill fitting denture, or callus on feet due to small shoes

Answer 9

Hyperplasia

Question 10

A growth disorder resulting from chronic inflammation in the bronchi of smokers, also termed chronic bronchitis

Answer 10

• Hyperplasia

Question 11

What is hypertrophy?

Answer 11

Is an increase in size of tissue due to an increase in size of its constituent cells

Question 12

An important growth disorder on permanent cells, cells that cannot divide: skeletal, cardial myocytes, brain…

Answer 12

Hypertrophy

Question 13

When do skeletal muscle hypertrophies?

Answer 13

-When there is an increased functional demand which is through:
- exercise

Question 14

What a condition that forces the left ventricle, supplying oxygenated blood to the body to undergo hypertrophy?

Answer 14

Hypertension.

*Blood be moving with high pressure from the left ventricle to the body

Question 15

Right ventricular hypertrophy is a result of ________

Answer 15

• Pulmonary hypertension
  or pulmonary vulvar disease

*Blood be moving with great pressure from the lung to the right ventricle.

Question 16

When does cardiac failure result from hypertrophy action of the heart ventricles?

Answer 16

• When the heart reaches the limit beyond which enlargement of muscle
  mass is no longer able to compensate for increased burden.

Question 17

Which hollow organs with smooth muscle undergo hypertrophy?

Answer 17

• Urinary Bladder- in urinary outflow obstruction
• Prostate- on elders
• Media of muscular arteries in hypertension

Question 18

What are the 5 disorders of growth?

Answer 18

• Hyperplasia
• Hypertrophy
• Atrophy
• Metaplasia
• Dysplasia
• Neoplasia

Question 19

What abnormal growth is anticipated on thyroid gland and on the breast during puberty/pregnancy?

Answer 19

Hyperplasia

Question 20

A hormonal induced abnormal growth seen on the smooth muscle fibers of a pregnant uterus

Answer 20

hypertrophy

Question 21

What is the normal cellular mechanism which induces atrophy

Answer 21

apoptosis

Question 22

With respect to physiological and pathological atrophy, Which organs see physiological atrophy as we grow from embryonic stage to alders?

Answer 22

• Embryo and foetus:
  *Part of process morphogenesis e.g. branchial clefts, notochord,
  thyroglossal duct, Mullerian duct (males), Wolffian duct (females)
• Infant :
  *Closure of ductus arteriosus, umbilical vessels
• Adolescence:
  *Involution of thymus
• Late adulthood & old age:
  *Uterus, endometrium, testes, bone (particularly females),
  cerebrum, lymphoid tissue

Question 23

With respect to physiological and pathological atrophy, What exposes humans to pathological atrophy? What factors drive or perpetuates it so it happens?

Answer 23

• Malnutrition:
  *Generalised atrophy due to starvation / malabsorption
  *Also wasting from chronic inflammation / malignancy
• Disuse atrophy:
  *E.g. limb immobilised in a plaster cast>muscular atrophy
• Neuropathic atrophy:
  *Denervation- loss of muscle mass and function as a result of damage to the nerves supplying the muscle.
• Ischaemic atrophy:
  *Loss of muscle mass and function due to a decreased blood flow to the muscle
  *E.g. partial limb ischaemia due to atherosclerosis
• Pressure atrophy:
  *Results from continuous pressure
  *Probably due to ischaemia

Question 24

What is metaplasia?

Answer 24

A change from one differentiated cell type to another type of
differentiated cell, which is usually less specialised

*maybe a reversible change

Question 25

What cells are mostly impacted by metaplasia?

Answer 25

• Epithelial cells of mucosal lining
• and Mesenchymal cells (connective tissue cells)

Question 26

What is the significance of metaplasia in human body?

Answer 26

The new group of cells replace original cells; giving rise to a tissue type better able to withstand adverse environmental conditions

Question 27

When should we expect to see metaplasia in the organ/tissue epithelium?

Answer 27

Metaplasia is seen in the setting of chronic cellular injury and repair.

Question 28

What are the 2 common metaplasia seen in the body tissues?

Answer 28

1. Squamous cell metaplasia: Where epithelium layer of a tissue changes from maybe being columnar to being squamous.
2. Columnar metaplasia:
   Where epithelium layer of a tissue changes from maybe being squamous or cuboidal, to being columnar.

Question 29

Which organs see squamous cell metaplasia?

Answer 29

1. Ciliated columnar respiratory epithelium of trachea & bronchi in smokers
2. Ducts of salivary glands, pancreas, bile duct with stones
3. Urothelium of bladder, ureter, renal pelvis in cases of renal stones & Schistosoma haematobium infection
4. Squamocolumnar junction of uterine cervix - puberty &
   pregnancy (physiological phenomenon

Question 30

Which organs see columnar metaplasia?

Answer 30

• The pseudostratified ciliated respiratory epithelium change to simpler mucus-secreting columnar epithelium
• In oesophagus, chronic reflux of gastro-duodenal contents –squamous epithelium is replaced by intestinal-like columnar cells
  = Barrett oesophagus

*Barrett’s esophagus is a condition in which the lining of the lower esophagus undergoes changes that make it more similar to the lining of the intestine.

Question 31

With respect to epithelial and mesenchymal metaplasia, where, like which body organs see mesenchymal hyperplasia?

Answer 31

Bone

Question 32

What is dysplasia?

*also called atypical hyperplasia or intra-epithelial neoplasia

Answer 32

A premalignant condition characterised by increased cellular proliferation with features of atypia

*Atypia: Abnormal number, size, shape & orientation of epithelial cells which fall short of true malignant change

Question 33

What is a potential cause of dysplasia?

Answer 33

• Longstanding irritation & injury of tissue(chronic inflammation)
• Exposure to carcinogenic
  substances

*Severe dysplasia is a reflection of underlying DNA damage

Question 34

What are the features of dysplasia?

Answer 34

• Increased growth:
  -ncreased epithelial thickness &
  -increased numbers of mitoses
• Cellular atypia
• Pleomorphism (variation in size & shape of cells & their nuclei)
• Large, hyperchromatic nuclei, high nuclear:cytoplasmic ratio,
  increased DNA content (more darkly staining nuclei)