Cellular Adaptations

Question 1

What is the restriction point of the cell cycle?

Answer 1

Critical check point for cell replication

Triggers DNA repair or apoptosis

Question 2

How is the cell cycle controlled?

Answer 2

Cyclins + CDKs (cyclin dependent kinases)

CDKs activated by binding with cyclins

Question 3

What is hyperplasia?

Answer 3

Cells increase in number above normal

Question 4

What is hypertrophy?

Answer 4

Cells increase in size

Question 5

What is atrophy?

Answer 5

Cells become smaller

Question 6

What is metaplasia?

Answer 6

Cells are replaced by cells of a different type

Question 7

In what tissues does hyperplasia occur?

Answer 7

Labile or stable tissues

Caused by increased functional demand or hormonal stimulation

Question 8

In which tissues does hypertrophy occur?

Answer 8

Labile, stable and permanent tissues

Caused by increased functional demand or hormonal stimulation

Cells contain more structural components

Question 9

What are examples of physiological hyperplasia?

Answer 9

Endometrium under influence of oestrogen

Bone marrow produces RBCs in hypoxia

Question 10

What are examples of pathological hyperplasia?

Answer 10

Eczema

Thyroid goitre

Question 11

What are examples of physiological hypertrophy?

Answer 11

Skeletal muscle

Pregnant uterus

Question 12

What are examples of pathological hypertrophy?

Answer 12

RV hypertrophy in hypertension

Bladder hypertrophy as a result of an enlarged prostrate

Question 13

What is compensatory hypertrophy?

Answer 13

Usually occurs in paired organs

One organ is underperforming so other hypertrophies to compensate

Question 14

What happens in cell atrophy?

Answer 14

Cell shrinks to a size where survival is still possible

Reduced structural components

Question 15

What happens in tissue atrophy?

Answer 15

Combination of cellular atrophy and apoptosis

Parenchymal cells apoptose - replaced by fibrous tissue

Reversible up to a point

Question 16

What are examples of physiological atrophy?

Answer 16

Ovarian atrophy in post menopausal women

Uterus after birth

Question 17

What are examples of pathological atrophy?

Answer 17

Atrophy of disuse
- muscle atrophy

Loss of innervation
- wasted hand muscles after median nerve damage

Inadequate blood supply
- skin thinning with PVD

Inadequate nutrition
- malnutrition

Loss of hormonal stimuli

• breast
• ovarian tissue

Persistent injury

Question 18

What happens in metaplasia?

Answer 18

Due to altered stem cell differentiation

Adaptive substitution of cells that are sensitive to stress

Occurs in labile or stable tissues

Reversible

Question 19

Examples of metaplasia

Answer 19

Barrett’s oesophagus

Spleen taking on role of bone marrow

Question 20

What is aplasia?

Answer 20

Complete failure of a specific tissue or organ to develop

Question 21

What is hypoplasia?

Answer 21

Underdevelopment or incomplete development of tissue or organ at embryonic stage

Congenital condition

Question 22

What is involution?

Answer 22

Normal programmed shrinkage of an organ

E.g. uterus after childbirth

Question 23

What is reconstitution?

Answer 23

Replacement of a lost part of the body

Question 24

What is atresia?

Answer 24

Congential imperforation of an opening

Question 25

What is dysplasia?

Answer 25

Abnormal maturation of cells within a tissue

Potentially reversible - often pre-cancerous