Lecture 12 - Cellular Adaptations Flashcards by Callum Donoher

What determines the size of a cell population in an a adult?

Rate of cell:
-Proliferation
-Differentiation
-Death by apoptosis

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When do cell numbers in a population increase?

Increased cell proliferation
Decreased cell death

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Where can receptors be that regulate gene expression stimulating or inhibiting cellular proliferation?

Inside cell
On cell membrane

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What genes regulate normal cell proliferation?

Proto-oncogenes
Tumour suppressor genes

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What happens to a cell once it has completed a full cell cycle?

Renters G1
Leaves at G0

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What is the type of differentiation which makes a cell permanently leave the cell cycle?

Terminal differentiation

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What are the 3 parts to Interphase?

G1
S (DNA Synthesis)
G2

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What is the protein which suppresses the cell cycle?

P53 protein

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What is the point of checkpoints in the cell cycle?

Sense damage to DNA

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What are the checkpoints in the interphase stage of the cell cycle?

G1 Checkpoint
G2 Checkpoint

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What is the function of the G1 checkpoint?

Checks for DNA damage before replication

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What is the function of the G2 checkpoint?

Checks DNA after replication
Checks cell size

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What is the name of the proteins which drive cell cycle by phosphorylation of proteins?

Cyclin Dependant Kinases (CDK)

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What is the Cyclin Dependant Kinase which allows for DNA replication to take place?

CDK4

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How does CDK4 allow for DNA replication to take place?

CDK4 inactivates Rb
Rb inactivates/prevents DNA replication

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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

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What is cell adaptation?

The state between a normal unstressed cell and an overstressed injured cell

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What are the 4 important types of cell adaptation?

Hyperplasia
-Hypertrophy
-Atrophy
-Metaplasia

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What is Hyperplasia?

Increase in number of cells

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What is Hypertrophy?

Increase in cell size WITHOUT increase in cell number

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What is Atrophy?

Decrease in cell size and or cell number

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What is metaplasia?

Cells are replaced by cells of a different cell type

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In hyperplasia, what are the reasons that hyperplasia may take place?

Increased functional demand
External stimuli

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What type of tissues can hyperplasia take place?

Labile tissues
Stable tissues

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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