MoD 7 (Cellular Adaptations) Flashcards
What is meant by intracrine hormone signalling?
A hormone which acts inside the cell it was synthesised, regulating intracellular events
What are the 5 key checkpoints during the cell cycle?
1) Restriction (R) point, towards end of G1
2) G1/S transition
3) S/G2 transition
4) G2/M transition
5) M/G1 transition
Which cell checkpoint can activate p53?
Restriction (R) point
What happens if p53 is activated during a cell cycle?
- Cell cycle stops
- Triggers DNA repair or apoptosis
How do Cyclins regulate the cell cycle?
- Bind to and activate Cyclin Dependent Kinase’s (CDKs)
- CDKs cause phosphorylation cascade, which drives the cell cycle
What is the name of the proteins which drive the cell cycle?
Cyclins
Define regeneration:
The replacement of cell losses with identical cells in order to maintain the size of a tissue or organ
Which tissues can regenerate?
- Bone marrow
- Liver
- Epidermis
Regenerated epithelial cells takes years to mature. What is the advantage of this?
Regenerated epithelial cells of the upper respiratory tract do not express the receptor for uptake of the Influenza virus
What is Hayflick’s number?
The number of times a cell can regenerate (dependant on telomere length)
What is the mean Hayflick number for human cells?
61.3
Define reconstitution:
The replacement of a lost body part
Define hyperplasia:
An increase in tissue or organ size due to increased cell numbers.
Can only occur in labile or stable cell populations
In what type of cell populations can hyperplasia occur?
- Labile
- Stable
Proliferation of endometrial wall due to oestrogen influence is an example of which cellular adaptation?
Hyperplasia
Thyroid goitre formation in response to iodine deficiency is an example of which cellular adaptation?
Hyperplasia
Name the cellular adaptation which increases the number of cells present:
Hyperplasia
Define hypertrophy:
Increase in tissue or organ size, due to an increased cell size
In which cell population type is hypertrophy most important?
Permanent
The growth of skeletal muscle due to bodybuilding is an example of which cellular adaptation?
Hypertrophy
The growth of the smooth muscle in a pregnant uterus is an example of which cellular adaptation?
Hypertrophy
Hyperplasia
Define compensatory hypertrophy:
Increase in tissue or organ size due to damage/removal of tissue, or increased functional demand
What type of cells undergo irreversible hypertrophy?
Adipocytes
Define atrophy:
Shrinkage of a tissue/organ due to an acquired decrease in size of and/or number of cells present
What cellular adaptation does the thenar eminence undergo if median nerve damaged?
Atrophy
What can cause pathological atrophy?
- Disuse
- Denervation
- Inadequate blood supply
- Inadequate nutrition
- Loss of endocrine stimulation
- Pressure
- Occlusion of secretory duct
- Toxic agents/drugs
- X-Rays
- Immunological mechanisms
Define metaplasia:
Reversible change from 1 differentiated cell type to another
In which cell populations can metaplasia occur?
- Labile
- Stable
What can cause pathological metaplasia?
Chronic irritation:
- Smoking
- Liver/Pancreas/Kidney stones
- Persistent acid reflux
Describe the metaplasia that occurs in the airways of smokers:
In bronchi: From ciliated pseudostratified columnar epithelia to stratified squamous epithelia
Which cellular adaptation occurs during traumatic myositis ossificans?
Metaplasia
Define aplasia:
Complete failure of a specific tissue or organ to develop (embryonic disorder)
—> Also used to describe tissues whose cells have ceased to proliferate, ie Aplastic anaemia
What is Aplastic Anaemia?
Bone marrow failure, leading to pancytopenia (deficiency of all components of blood- red and white cells, and platelets)
Define involution:
The normal programmed shrinkage of an organ
What is the name of the cellular adaptation which causes physiological atrophy:
Involution
Define hypoplasia:
Congenital underdevelopment or incomplete development of a tissue/organ.
What is the name of the cellular adaptation which describes the congenital underdevelopment of an organ?
Hypoplasia
What is the name of the cellular adaptation which describes the complete failure of an organ to develop?
Aplasia
Define atresia:
The congenital absence of a normal opening, or failure to develop the lumen of a tubular structure
What is Oesophageal atresia?
The congenital failure of part of the lumen of the oesophagus to form
- Therefore part of oesophagus is not hollow
Define dysplasia:
Enlargement of a tissue/organ via proliferation of abnormal cells
Which cellular adaptation describes the enlargement of an organ via proliferation of abnormal cells?
Dysplasia
List some triggers of chronic eczema:
- Irritants
- Allergens
- Microbes
- Temperature
- Foods
- Stress/hormones
What are the symptoms of chronic eczema?
Dry, patchy, red, itchy skin
List some triggers of psoriasis:
- Stress
- Excessive alcohol
- Foods
- Skin injury
- Smoking
- Hormone changes
- Other immune disorders
- Drugs ie ACEi, lithium, NSAIDS, beta blockers
What are the symptoms of psoriasis?
Red, flaky, crusty plaques with overlying silvery scales
- commonly on scalp, knees and elbows
Which skin condition causes red, flaky, crusty plaques with overlying silvery scales?
Psoriasis
Describe how an iodine deficiency can cause goitre formation:
- Iodine deficiency = less circulating T4
= increased TSH release from anterior pituitary
= TSH stimulates the growth and activity of the thyroid gland
= hyperplasia of thyroid gland
What protein is released by a benign prostatic hypertrophy/plasia?
Prostate Specific Antigen (PSA)
Why does benign prostatic hypertrophy/plasia cause chronic bladder outlet obstruction?
Benign prostatic hypertrophy/plasia occurs at the center of the prostate gland, which surrounds the urethra, increasing the pressure put on the urethra.
Describe the metaplasia that occurs due to Barrett’s Oesophagus:
From non-keratinised stratified squamous epithelia to simple columnar epithelia with goblet cells
- Becomes gastric epithelia
What are the complications of Barrett’s oesophagus?
- Increased risk of oesophageal adenocarcinoma
- Oesophageal ulcers
- Oesophageal strictures
- Bleeding
What can cause myositis ossificans?
- Trauma
- Inherited mutation (Autosomal dominant)
What is Myositis ossificans?
The heterotopic ossification of muscle due to the metaplastic change of fibroblasts to osteoblasts.
- Due to trauma or inherited mutation
What is the name of the disorder caused by the metaplasia of fibroblasts to osteoblasts?
Myositis ossificans
What is the usual cause of endometrial hyperplasia?
Excess oestrogen without progesterone
- Oestogen-only-HRT
- Tamoxifen
What are the complications of endometrial hyperplasia?
- Menorrhagia
- Anaemia
- Increased risk of endometrial carcinoma
