Disorders of Growth

Question 1

Explain the purpose of the various phases of the cell cycle

Answer 1

Divided into 7 phases
G0 phase- Cells are in a quiescent state(phase outside cell cycle)
G1 phase-Cells grow in size in preparation for DNA replicationit does this by producing protein required for DNA sythesis
G1/S phase- Before DNA replication begins the cell checks for DNA damage and for sufficient cell growth and nutrients
S phase- DNA replication occurs here. If there is any DNA damaged this is where it is repaired.
G2 phase- Cell prepares for mitosis by producing more proteins and grows further in size .
G2/M- DNA is checked by p53 and other tumour-suppressor proteins.
M phase- Chromatin condenses into chromosomes and the cell divides by mitosis

Question 2

Define labile cells

Answer 2

Cells that regularly divide to replenish themselves. e.g. g. stratified squamous epithelium, gastrointestinal lining epithelium,
urothelium, haematopoietic cells, endometrium, ductal cells

Question 3

define stable cells

Answer 3

Cells that do not regularly divide but can divide if stimulated to do so. e.g. fibroblasts, smooth muscle
cells, osteoblasts, endothelial cells, astrocytes

Question 4

Define permanent cells

Answer 4

This are cells that cannot divide . e.g. neurons, cardiac myocytes, skeletal muscle, podocytes, retinal
photoreceptors, lens cells, hair cells of cochlea, osteocytes

Question 5

Define hyperplasia

Answer 5

Increase in cell number

Question 6

Hypertrophy

Answer 6

increase in cell size

Question 7

Cachexia

Answer 7

weakness and wasting of the body due to severe chronic illness.

Question 8

Metaplasia

Answer 8

reversible change of one adult cell type to another adult cell type due to reprogramming of stem cells.

Question 9

define Dysplasia and explain how is it different from neoplasia

Answer 9

Cellular dysplasia (often simply termed “dysplasia”) refers to the pre-malignant / pre-invasive
/ pre-neoplastic stage where genetic mutations lead to increased cell growth that remains
confined by the basement membrane (non-invasive) but is associated with a risk of
progression to invasive malignancy (cancer).

Malignancy neoplasm is when the the dysplasia becomes invasive, it then looses the name dysplasia and becomes neoplasms.

primarily the difference is that dysplasia is confined to the surface lining of the epithelium but neoplasm breaches into the basement membrane to grow into the underlying connective tissue)