Lecture 12 - Cellular Adaptations Flashcards
What determines the size of a cell population in an a adult?
Rate of cell:
-Proliferation
-Differentiation
-Death by apoptosis
When do cell numbers in a population increase?
Increased cell proliferation
Decreased cell death
Where can receptors be that regulate gene expression stimulating or inhibiting cellular proliferation?
Inside cell
On cell membrane
What genes regulate normal cell proliferation?
Proto-oncogenes
Tumour suppressor genes
What happens to a cell once it has completed a full cell cycle?
Renters G1
Leaves at G0
What is the type of differentiation which makes a cell permanently leave the cell cycle?
Terminal differentiation
What are the 3 parts to Interphase?
G1
S (DNA Synthesis)
G2
What is the protein which suppresses the cell cycle?
P53 protein
What is the point of checkpoints in the cell cycle?
Sense damage to DNA
What are the checkpoints in the interphase stage of the cell cycle?
G1 Checkpoint
G2 Checkpoint
What is the function of the G1 checkpoint?
Checks for DNA damage before replication
What is the function of the G2 checkpoint?
Checks DNA after replication
Checks cell size
What is the name of the proteins which drive cell cycle by phosphorylation of proteins?
Cyclin Dependant Kinases (CDK)
What is the Cyclin Dependant Kinase which allows for DNA replication to take place?
CDK4
How does CDK4 allow for DNA replication to take place?
CDK4 inactivates Rb
Rb inactivates/prevents DNA replication
What is the effect of CDK inhibitors on the cell cycle?
CDK always activated, meaning Rb always inactivated so cell cycle is driven .
Rb not able to inhibit cycle
What is cell adaptation?
The state between a normal unstressed cell and an overstressed injured cell
What are the 4 important types of cell adaptation?
- Hyperplasia
-Hypertrophy
-Atrophy
-Metaplasia
What is Hyperplasia?
Increase in number of cells
What is Hypertrophy?
Increase in cell size WITHOUT increase in cell number
What is Atrophy?
Decrease in cell size and or cell number
What is metaplasia?
Cells are replaced by cells of a different cell type
In hyperplasia, what are the reasons that hyperplasia may take place?
Increased functional demand
External stimuli
What type of tissues can hyperplasia take place?
Labile tissues
Stable tissues
What is neoplasia?
Irreversible hyperplasia that is irreversible
What triggers hyperplasia to take place?
Hormones (hormones that inc functional capacity)
Compensatory (inc in tissue mass after tissue damage)
What 2 hormones lead to the physiological hyperplasia of breast tissue?
Prolcatin
Oxytocin
What excess hormone is linked to psoriasis?
Growth factor hormone
What type of tissue does hypertrophy happen in?
Permanent tissue
When does hypertrophy take place?
When theres on increase in functional demand
Increased hormonal stimulation
What changes happen in the cell in Hypertrophy?
More cytoplasm
More proteins
What are 3 examples of physiological hypertrophy?
Skeletal muscle hypertrophy (gym)
Smooth muscle hypertrophy in pregnancy
Cardiac muscle hypertrophy in athletes
What may be a cause of pathological cardiac hypertrophy?
Hypertension
Heart under constant level of strain
What is Benign Prostatic Hyperplasia?
Prostate under goes hyperplasia.
The smooth muscle of the bladder undergoes hyperplasia due to the urethra narrowing, this means the smooth muscles has to contract harder
What is likely to happen to the remaining kidney following a unilateral nephrectomy?
Compensatory hypertrophy
What levels can atrophy happen at?
Level of cell
Level of organ
Why is atrophy bad for a cell?
Cell contains fewer components so has a reduced function
What type of tissue do atrophic organs have an increased amount of?
Connective tissue
Atrophy is REVERSIBLE, however the longer it goes on for the harder it is for it to be reversed.
Why is this the case?
More and more of the parenchyma cells get replaced by the connective tissue
What are parenchymal cells?
The functional cells that do the specific functions of the tissue
What are 2 examples of physiological atrophy??
Uterine atrophy following birth
Thymic (Thymus) atrophy
What can lead to muscular atrophy?
Atrophy of dissuse
Denervation atrophy (muscle loses innervation and dies)
What is senile atrophy?
Atrophy that happens with age in permanent tissues
How can a brain tumour cause atrophy?
The brain tumour puts pressure on surrounding healthy brain cells causing PRESSURE ATROPHY
How can peripheral vascular disease lead to atrophy?
Inadequate blood supply leads to cells shrinking
What is Metaplasia?
A reversible change where one differentiated cell type is replaced by another cell type
Where does Metaplasia not occur in adults?
Striated muscle cells
Neurones
What is the aim of metaplasia?
An adaptive response where stem cells are programmed to switch to a different cell type more adapted to its environment
What type of tissues does Metaplasia most commonly happen in?
epithelial tissues
In epithelial tissues what epithelial cell type is normally changed from and to in Metaplasia?
Columnar epithelium (fragile) ———> Squamous epithelium (more resilient)
What is the problem with meta plastic epithelium?
My lose functions that the original epithelium performed
What is Dysplasia?
Cells abnormally differentiate into different cell types
Disorganised
Is Dysplasia reversible?
YES (REVERSIBLE)
Is neoplasia reversible?
NO (IRREVERSIBLE)
How is myeloid Metaplasia of the spleen adaptive and useful?
If bone marrow is compromised the spleen can take over as a site of Haematopoiesis
In smokers, what is an example of Metaplasia that takes place?
Squamous metaplasia in bronchiole epithelium
What is the Metaplasia of Barrett’s oesophagus?
Persistent acid reflux causes normal epithelium to replaced by glandular cells
What metaplastic changes happen in Traumatic myositis ossificans?
Fibroblasts change to osteoblasts
Connective tissue changes to bone
New bone forms in soft tissue of leg due to premature return to exercise following trauma
What is Aplasia?
Complete failure of a specific organ or tissue to develop
Also used to describe organs that have stopped proliferating
What is Hypoplasia (NOT opposite of Hyperplasia)?
Congenital underdevelopment or incomplete development of a tissue or organ
Why is hypoplasia NOT the opposite of hyperplasia?
Hypoplasia is congenital
Hyperplasia is not congenital
What is Atresia?
Congenital imperforation of an opening
NO HOLE?ORIFICE
What is Reconstitution?
The replacement of a lost part of the body
(Think of a lizard)
What part of the human body undergoes Reconstitution?
Small blood vessels following injury
What is Involution?
The normal programmed shrinkage of an organ
What is an example of involution in humans?
Shrinkage of the temporary Fetal organs
What are the 3 levels of dysplasia?
Mild
Moderate
Severe
What happens to the level of organisation in the grading of dysplasia?
Becomes more and more disorganised
Why may dysplasia be a cause of concern?
Potentially cancerous
