Cell Adaptation Flashcards
Define cellular adaptation
In response to physiological or pathological stimuli, cells adapt by modifying metabolism (show new steady state) or growth pattern (show structural changes) to better equip them for survival
What are the three classes of cells once maturity is attained?
- Labile cells
- Stable cells
- Permanent cells
Define labile cells
Constantly divide to replenish those that are constantly lost
Short lifespan
High mitotic rate
Examples of labile cells
skin, mucous membranes, bone marrow, lymph nodes
Define stable cells
Able to divide, but will only do so occasionally
Long Lifespan
Low mitotic rate
These cells need to be specially stimulated to divide
Examples of stable cells
liver, kidney, glands, smooth muscle
Define permanent cells
Have lost the ability to divide Cells need to be maintained for life Cells are lost progressively Not replaced by regeneration No/Little mitotic activity
Examples of permanent cells
Neurones, cardiac muscle, skeletal muscle
Striated muscle in an adult is an example of which cell type?
Permanent cells
What does increased cellular activity mean in terms of cellular adaptations?
Increase in size or number of cells
What does decreased cellular activity mean in terms of cellular adaptations?
Decrease in size or number of cells
What does alteration of cell morphology mean in terms of cellular adaptations?
Change in cell differentiation
What are the 11 types of growth variation?
- Hyperplasia
- Hypertrophy
- Atrophy
- Agenesis
- Aplasia
- Hypoplasia
- Metaplasia
- Dysplasia
- Hamartoma
- Choristoma
- Neoplasia
Define Hyperplasia
Hyperplasia is the increase in mass of an organ due to an increase in the number of its specialised constituent cells
Define physiological hyperplasia
Physiological: endometrium; pubertal/lactating breast
- Hormonal: Growth factor dependent enlargement of striated muscle
- Compensatory: remaining kidney after nephrectomy
Define pathological hyperplasia
Mainly due to altered hormones or growth factors
e. g. fibroadenosis of breast; prostate hyperplasia; thyroid hyperplasia
- Reactive: skin callous, lymph nodes/spleen after infection
Define Hypertrophy
Hypertrophy is the increase in mass of an organ due to an increase in the size of its specialised cells
- Skeletal muscle of athletes (physiological)
- Heart muscle of hypertensive patients (pathological)
Does smooth muscle undergo hyperplasia or hypertrophy?
It undergoes a mixture of both
Define atrophy
Atrophy is the decrease in mass of an organ due to a decrease in the size and/or number of its specialised constituent cells
What is the mechanism of atrophy?
APOPTOSIS
- Increase in catabolism of cytoplasmic structural proteins (proteins link with ubiquitin and then degraded by a protease complex)
- Removal of organelles by autophagy
Define physiological atrophy and give some examples
INVOLUTION
- Uterus after menopause/childbirth
- Testes in old age
- Thymus gland after childhood
What are the 4 generalised pathological atrophy means and some examples?
MALNUTRITION/STARVATION - Kwashiorkor - protein deficiency - Anorexia nervosa MALIGNANT CACHEXIA - Malignancy - tumours spread all over body HYPOPITUITARISM - Decreased growth hormone secretion PROGERIA - Increased ageing rate
Define agenesis
Agenesis is the failure of an organ to develop at all from its primordia
- Complete failure to produce the embryonic cell mass destined to form an organ
3 examples of agenesis
ANENCEPHALY - Lack of a cerebrum - fatal defect AGENESIS OF KIDNEY - unilateral or bilateral AMELIA - no limbs - thalidomide
Define aplasia
Aplasia is a sudden cessation of growth leading to decreased mass of tissue and defective development of an organ
- Correctly formed embryonic mass fails to differentiate into a well developed organ
Causes of aplasia
- Drug therapy (chemotherapy)
- Radiotherapy
- Nuclear accidents
- Nuclear bomb blasts
What is thymus gland aplasia?
Occurs during childhood, depleted T-cells leading to immunodeficiency
What is bone marrow aplasia?
Depleted blood cells, leading to aplastic anaemia
Define hypoplasia
Hypoplasia is where tissues fail to attain full size (deficient growth) leading to decreased mass of tissue and incomplete development of an organ
- Organ-specific structures develop correctly, but are abnormally small and not fully functional
What are 2 examples of hypoplasia
CRYPTOCHIDISM
- Maldescended testes causing sterility
MICROCEPHALY
- Hypoplasia of the brain - neurological deficit
Define metaplasia
Metaplasia is where a fully differentiated adult cell changes into another more resilient, but less specialised, fully differentiated adult cell type in response to chronic injury
What are 3 examples of metaplasia
SMOKERS AIRWAY - CIGARETTES
- Normal respiratory epithelium changes to stratified squamous epithelium
GALL BLADDER - GALL STONES
- Normal columnar epithelium changes to stratified squamous epithelium
URINARY BLADDER - URINARY CALCULI
- Normal transitional epithelium changes to stratified squamous epithelium
Define dysplasia
Dysplasia is abnormal growth and differentiation with loss of regularity of cells, loss of normal orientation and relationship to one another, i.e. abnormal tissue organisation
- Dysplasia leads to a disordered, atypical, defective growth with a compromised function
What are 3 causes of dysplasia
ORAL CAVITY - Smoking, ill-fitting dentures, diet SMOKERS AIRWAY - cigarettes CERVIS OF UTERUS - HPV and HSV II infection
Define hamartoma
A hamartoma is a focal overgrowth of normal cells in a tissue in which these cells are usually present
Define choristoma (ectopia)
A choristoma is a focal overgrowth of normal cells found in a tissue in which these cells are NOT usually present
What is Meckel’s diverticulum?
It is a choristoma
It occurs in 2-3% of the population
2-3 cm blind pouch in the ileum; 20-30 cm from the ileocaecal valve
A persistence of the omphalomesenteric duct
Wall has gastric and pancreatic choristoma
Define neoplasia
Neoplasia is the process which leads to the formation of an abnormal, uncontrolled new growth of tissue, which has no coordinated useful function in the body
- The abnormal mass is called a neoplasm (tumour)
- The study of neoplasia is termed oncology
