Lecture 25

Question 1

What is morphogenesis?

Answer 1

The formation of shape and organisation of organs involving co-ordinated growth, differentiation and destruction

Question 2

What occurs to growth and differentiation in adult life?

Answer 2

Cells undergo a constant cycle of death replacement and growth impacted by both physiological and pathological stimuli, these can be positive or negative impacts

Question 3

What is multiplicative growth?

Answer 3

Increases in cell number via mitotic division

Question 4

What is auxetic growth?

Answer 4

Increased size of individual cells

Question 5

What is accretionary growth?

Answer 5

Increase in extracellular tissue in-between cells

Question 6

What type of growth occurs in the embryo?

Answer 6

A combination of growth patterns therefore it is termed ‘combined pattern’

Question 7

What determines growth rate? and how does this change with age?

Answer 7

Balance between cell proliferation and cell death
In fetal development growth is rapid with apoptosis playing a key role in morphogenesis
Adult cell replication is slower and usually due to the need to regenerate or replace damaged cells

Question 8

What is an oligopotent stem cell? And what are some examples?

Answer 8

A stem cell able to differentiate into a small number of cell types
examples include skin keratinocytes, bone marrow hematopoietic system and the gastrointestinal epithelium

Question 9

What are liable cells?

Answer 9

Cells that divide and proliferate continuously and are very sensitive to toxic injury

Question 10

What are stable cells?

Answer 10

Cells that divide infrequently under normal conditions as they have been arrested in the G0 phase of the cell cycle

Question 11

What are examples of stable cells?

Answer 11

Fibroblasts of connective tissue
Endothelial cells of blood vessels
Parenchymal cells of most organs
Melanocytes of epithelium

Question 12

What are the adaptive responses of cells with regards to cell growth and differentiation?

Answer 12

Atrophy, Hypertrophy, Hyperplasia, Metaplasia

Question 13

What is atrophy?

Answer 13

Decrease from normal size by either change in cell size or cell number which is associated with a diminished functional ability

Question 14

What are the different types of atrophy?

Answer 14

Physiological atrophy which occurs during aging (reduction of endometrium post-menopause)
Nutritional Atrophy, loss of blood supply or starvation may result in loss of fat and muscle tissue
Disuse atrophy decreased amount of tissue due to loss of use eg muscles during limbe fracture

Question 15

What is the difference between atrophy and hypoplasia?

Answer 15

Hypoplaisa is failur of a tissue to initially develop to a normal size
While Atrophy is a reduction from an initial size

Question 16

What is the difference between hyperplasia and hypertrophy?

Answer 16

Hyperplasia is increase in cell number while hypertrophy is an increase in cell size
Hyperplasia is usually seen in conjunction in hypertrophy, though hypertrophy maybe seen on its own as it is the only option for permanent tissues
Hypertrophy is a more risky option as increasing DNA content without mitosis may cause polyploidy

Question 17

What is an example of hypertrophy seen in disease?

Answer 17

Cadiac hypertrophy where the ventricle wall thickens

Question 18

What are the two methods via which hyperplasia can be produced?

Answer 18

Increase in cell replication or a decrease in the level of cell apoptosis

Question 19

Where does normal hyperplasia occur?

Answer 19

The erythropoietic system where red blood cell number increases with altitude

Question 20

How can hyperplasia contribute to disease processes?

Answer 20

Proliferation of myofibroblasts in scar tissues and regeneration of parenchymal tissue
Or in endometrial hyperplasia where there is an abnormal increase in the amount of endometrial glandular cells

Question 21

What is metaplasia?

Answer 21

When a cell changes its differentiation, this typically occurs in response to either genetically inherited features or interactions of the environment with the genes of the cell
This is a reversible process

Question 22

Why might metaplasia be an advantage?

Answer 22

It allows the cell to adapt to changes in the environment by changing which genes it expresses to deal with the scenario

Question 23

What are the two common types of metaplasia?

Answer 23

Squamous where the cell changes from a complex structure to a more simplistic structure
Glandular where a complex cell structure changes to a another complex cell structure

Question 24

What are examples of altered cell expression as a consequence of addition of chromosomes?

Answer 24

Down's Syndrome where there is mental delay abnormalities of the face, ears, pelvis
Klinefelters syndrome (extra X chromosome) associated with testicular hypoplasia, absence of spermatogenesis, gynaecomastia and mental delay

Question 25

What single gene defects cause altered cell expression?

Answer 25

Many inherited genes, occasionally novel mutations but uncommon
Deficiency of phenylalanine hydroxylase causes mental delay as phenylalanine will accumulate (mutation in PAH)
Mutation in CFTR leads to cystic fibrosis

Question 26

What is the payoff of the metaplasia induced by barretts oesphagus?

Answer 26

While the columnar epithelium is better at coping with the constant acid reflux of the stomach it has lost the protective keratin layer

Question 27

What is trans-differentiation?

Answer 27

Change from one cell type to another, this a reversible process which is adaptive, protective and a normal physiological function

Question 28

What is dysplasia?

Answer 28

abnormal alteration is size, shape and organization of the cellular components of a tissue

Question 29

What are the results of dysplasia?

Answer 29

Premalignant condition which is reversible if the stimulus is removed from early/mild conditions
if the dysplasia is severe however then there will be progression to a neoplasm

Question 30

What are the features of dysplasia?

Answer 30

increased growth, atypical cells and altered differentiation this allows for a window of screening before dysplasia becomes neoplastic

Question 31

What is a neoplasia?

Answer 31

Abnormal tissue mass with excessive growth and disordered differentiation which is unco-ordinated with normal tissue

Question 32

What are the characteristics of neoplasms?

Answer 32

Loss of specialized functions, acquisition of new properties like uncontrolled growth
Lack of feedback mechanisms
Only stop growing due to a lack of nutrients

Question 33

What do neoplasms arise from?

Answer 33

A single cell which has undergone neoplastic transformation