Hyperplasia and Hypertrophy

Question 1

Growth Disorders

Answer 1

• Growth disorders are represented by changes in pattern of growth or differentiation related to single cells, tissues or organs
• Deoends on how many cells are effected whether you will see that change grossly in an organ

Question 2

Malformations

Answer 2

• Disoreders of growth which occur during gestation
• These can result in a congenital defect

Question 3

Congenital Defects

Answer 3

• disorders of growth detected at birth
• Not all congenital defects have a hereditary basis although some do

Question 4

Hereditary Defects

Answer 4

• genetically transmitted diseases

Question 5

8 Causes of Defects

Answer 5

1. Chromosome Defects
2. Viral Disease

3 . Toxins

4. Drugs
5. Ionising Radiation
6. Nutritional deficiency
7. Physical Trauma
8. Anoxia

Question 6

Timing of the Insult

Answer 6

• This is a factor that is VERY important in determining the outcome of that exposure
• If the insult occurs early in gestation and it is sufficiently severe, it will result in foetal death and resorption
• If the insult occurs late in gestation, the malformation will be more limited and the foetus usually survives

Question 7

The Normal Cell

Answer 7

1. It is a membrane closed compartment, subdivided into small compartments (organelles) by membranes
2. Organelle Function is dependent on type and quantity of enzymes which are present in membranes and the cytoplasm
3. These membranes and organelles are targets for damage by environmental agents, microbes, toxins, genetic and metabolic diseases

Question 8

General Mechanisms of Cell Injury

Answer 8

1. Oxygen deficiency (hypoxia): depletes ATP (energy) production
2. Membrane damage
3. DIsturbances in cellular metabolism
4. Genetic Damage: no disease/ deprive cell of enzyme required for normal function/ neoplasia

Question 9

Response of Cell to Chronic Injury

Answer 9

Depends on:

• type of injurious agent
• extent of injury
• duration of injury
• cell type affected

Cell can either adapt to the injury or die

Question 10

Response of Cell to chronic injury in relation to cell type

Answer 10

1. Cells which divide and replicate continuously (epithelium of skin, epithelium of intestine, crypt cells in the intestine (stem cells) )
2. Cells which are capable of cell division in response to demand (liver hepatocytes, osteocytes, lung)
3. Cells which are not capable of cell division (neurons, retina (neural tissue), cardiomyocytes)

Question 11

Atrophy

Answer 11

• decrease in the mass of a tissue or organ due to decreased size and/or number of cells after it has reached its normal size
• different than hypoplasia! (organs that are smaller than normal because they never developed fully)
• The shrinkage of atrophied tissue is caused by decreased size or loss of its principal cells
• sometimes atrophy is a normal physiological response: thymus with age, uterus post-partum (involution)
• ex: the portal vein provides most of the blood supply to the liver, a portosystemic shunt results in hepatic atrophy
• Reversible if the inciting cause can be corrected

Question 12

Hypertrophy

Answer 12

• increase in size and volume of a tissue or organ due to increase in cell size
• the increased tissue mass is due to increased size of the parenchymal cells rahter than stromal cells or leukocytes
• Hypertrophy often accompanies an increase in cell number (hyperplasia) due to cellular proliferation, but as a stand alone phenomenon is observed mainly in organs or tissues such as the heart or skeletal muscle in which the principal cells are postmitotic and incapable of replication
• at cellular level, hypertrophy is an increase in size or number of organelles as distinguished from increased cell size from hydropic swelling (loss of volume control) or from accumulation of endogenous or exogenous substances
• (there are limitations of hypertrophy due to blood supply!)
• Also occurs with increased work load in athletic animals!

Question 13

Hypoplasia

Answer 13

• organ is reduced in size due to never fully developing
• a reduction in the size of cells and tissues due to a failure to grow to normal size
• can range from being mildly hypoplastic to almost complete absence (also called vestigal or rudimentary)
• may also be able to see that there are no cells there at all

Question 14

Hyperplasia

Answer 14

• increase in the number of principal cells of a tissue or organ
• This response can only occur in a cell population that is capable of mitosis
• Many epithelial cells (hepatocytes and epithelia of the epidermis and intestinal mucosae) are quick to undergo hyperplasia in response to hormonal stimulation, inflammation or physical trauma
• hyperplasia differes from neoplastic cellular proliferation in that it generally subsides if the stimulus is removed (e.g. mammary development of pregnancy and lactation)
• but in some cases, such as an inappropriate level of trophic hormones or growth factors can lead to persistent hyperplasia, can be a precursor to neoplastic transformation

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