L13 - cellular adaptations Flashcards
The cell enters the cell cycle which goes __ -> ___ -> ___ -> ___. After cell cycle competion the cell either restarts or exits via G0 until further growth signals occur.
G1/S/G2/M
Which is the only phase visibe under the conventional microscope. What does this consist of?
M phase - Mitosis (nuclear division) and cytokinesis.
Briefly explain what happens in G1, S and G2
G1 - cell and organelle growth
S - DNA synthesis
G2 - cell prepares to divide.
What is the restriction point? What phase is this in?
Towards the end of G1, it is the most important cell checkpoint. The majority of cells that pass this point will go on to divide
NOTE - this is the most commonly altered checkpoint in cancers
What are the other two checkpoints?
G1/S - checks for DNA damage before DNA replication
G2/M - checks for DNA damage after DNA replication
If any of the cell checkpoints are activated, the tumour suppressor gene protein ___ comes into action.
P53
P53 has many effecs including inhibition of angiogenesis/stimulation of DNA repair etc. but mainly ___ ___ ___. If the promblems aren’t fixed it will trigger apoptosis
cell cycle arrest
Progression through the cell cycle and particularly the G1/S transition is regulated by proteins called ___ and their associated enzymes ___ ____ ____.
Cyclins
Cyclin-dependent kinases (Cdk’s)
Activated Cdk’s drive the cell cycle by phosphorylating proteins - an important one is the _______ ___, theey are critical for the cell cycle to move to the next phase
Retinoblastoma protein (RB protein)
Cdk’s are tightly regulated by Cdk ______
inhibitors
Complete G1/S phase = Cyclin _/Cdk 2 S/G2 phase = Cyclin _/Cdk2 G2/M phase = cyclin _/Cdk 1 M/G1 phase = Cyclin D/Cdk _
E
A
B
4
(EABD 2214)
What is the normal function of the Rb protein. Which cyclin/Cdk complex inactivates it thus permeating progression through the cell cycle?
Prevents DNA replication
Cyclin D/Cdk4
Name three factor determining the size of a cell population
Balance of cell proliferation versus cell death/physiological conditions/proto-oncogene activation/growth factors/pathological conditions
Definre hyperplasia
An increase in tissue or organ size by increasing cell NUMBER
What categories of tissues does hyperplasia take place in?
Labile/stable
Hyperplasia is a reversible normal response but can happen secondary to a pathological cause. Why can repeated cell divisions be bad?
Increases the risk of mutations and neoplasia
Give a physiological and pathological example of hyperplasia
Physiological - prolierfation of endometrium in response to oestrogen in the menstrual cycle/Bone marrow produces more erythrocytes in response to hypoxia
Pathological - Eczema/thyroid goitre in iodine deficiency
Define hypertrophy
An increase in tissue or organ size due to increase in cell SIZE
All types of tissue undergo hypertrophy but what tissue category in particular?
Permanent
Give a physiological cause of hypertrophy and a pathological one.
Physiological - Skeletal muscle growth/pregnant uterus/cardiac muscle in athletes
Pathologial - RV hypertrohpy (secondary to pulmonary issues)/inflammatory bowel conditions
Give an example of a ‘compensatory hypertrophy’’
If a kidney is removed the other will hypertrophy to compensate for this
What is atrophy?
A shrinkage of a tissue or organ due to an acquired decrease in size and/or number of cells
Give an example of physiological and 3 of pathological atrophy
Physiological - Ovarian atrophy in post-menopausal women
Pathological - Muscle atrophy after disuse/denervation atrophy (e.g. wasted hand muscles after median nerve damage)
/inadequate blood supply (e.g. thinning of the legs in peripheral vascular disease)/inadequate nutrition (e.g. wasting of muscles with malnutrition)/senile atrophy (brain/heart)/pressure on tissues secondary to tumours/cerebral atrophy in alzheimers
Define metaplasia
A reversible change of one differentiated cell type to another
What tissue categories can metaplasia occur in?
Labile or stable
NOTE - cannot occur across germ layers.
Metaplasia is the result of genetic reprogramming of stem cells in response to stress, it is sometimes a preulde to dysplasia and cancer. Give an example of metaplasia
Bronchial pseudostratified ciliated epithelium becoming stratified squamous epithelium in response to cigarette smok/
Stratified squamous epithelium becoming glandular in the oesophagus (Barrett’s oesophagus) - in response to chronic acid reflux
Give an example of when metaplasia can be a preulde to cancer
Barret’s oesophagus and oesophageal adenocarcinoma/squamous metaplasia in the bronchus and bronchial cancer/intestinal metaplasia of the stomch and gastric adenocarcinoma
Define aplasia and give an example
Complete failure of a specific organ or itssue to develop
Examples - Kidney aplasia/aplastic anaemia/thymic aplasia in autoimmunity
Define hypoplasia and give an example
Underdevelopment of a tissue or organ due to an inadequate NUMBER of cells. It is congenital
Examples - testicular in Klinefelter’s syndrome/renal/breast/heart chambers
What is involution
It is normal programed shrinkage of an organ e.g. the uterus after childbirth (overlaps with atrophy)
Define reconstitution and give an example
Replaement of the lost part of the body. Different to regenerating as it requires several different cell types.
Example - normal angiogenesis in adults
Define atresia and give an example
The congenital imperforation of an opening (fails to open). It is congential
Examples - Anus/vagina/small bowel
What is dysplasia
The abnormal maturation of cells within a tissue - potentially reversible. Often a preulde to cancer
What should be given to a patient who has taken a suspected opioid overdose?
Naloxone (opiate antagonist)
Which cellular afaptation does NOT generally predispose to neoplasia?
hypertrophy
