cell injury and inflammation pathology Flashcards
What is apoptosis?
● Programmed cell death
● A process that removes degraded or unneeded cells, prevents excess growth
● Tightly controlled
● Cells activate degradation enzymes, chromatin is condensed, the cell contents
are degraded within cytoplasmic blebs forming apoptotic bodies, and the cell
shrinks
● Cell membrane remains intact
● Not an inflammatory process
List some important stimuli for apoptosis
Physiological
● Developmental atrophy (embryogenesis)
● Loss of growth stimulation (such as endometrial cells during menstruation)
● Cell death induced by cytotoxic T cells
● Elimination of potentially harmful self reactive lymphocytes
Pathological
● Excessive DNA damage (p53 build up)
● Unfolded protein build up
● Cell death secondary to radiation or cytotoxic injury
● Cells displaying harmful characteristics
● Viral infections such as hepatitis
Describe the cellular changes in necrosis
● Irreversible injury
● Swollen cells
● Myelin figures
● Nucleus may fade, shrink and fragment
● Organelle and cell membrane disruption with release of contents
● Adjacent or surrounding inflammation
What are the patterns of tissue necrosis?
● Coagulative - architecture of tissue preserved
● Liquefactive - digestion of tissue into a viscous liquid mass
● Fibrinoid - a microscopic feature of antigen/antibody complexes in vessel walls
● Caseous - friable white (such as in TB)
● Gangrenous - typically a type of coagulable necrosis applied to a limb, may have
superimposed liquefactive necrosis
● Fat necrosis - focal area of fat destruction
What is atrophy?
Decrease in the size of an organ or tissue resulting from a decrease in cell size and
number. Can be physiological or pathological.
What are the causes of atrophy?
● Decreased workload (such as immobilisation of a limb in plaster)
● Denervation
● Diminished blood supply (such as arterial occlusion)
● Inadequate nutrition (such as marasmus)
● Loss of endocrine stimulation
● Ageing
● Pressure
What are the mechanisms underlying atrophy?
● Decreased protein synthesis
● Increased protein degradation
● May be accompanied by increased autophagy, where a cell consumes its own
components for energy and nutrients
Please describe the 2 different forms of pathological calcification and give an
example of each.
● Dystrophic calcification
○ Normal serum calcium
○ Occurs in necrotic or damages/dying tissue
○ Examples: atherosclerosis, calcific aortic stenosis, tuberculous nodes
● Metastatic calcification
○ Abnormally raised calcium
○ Occurs in normal tissues
○ Examples: nephrocalcinosis, pulmonary calcinosis, gastric mucosal
calcification
What are the different causes of hypercalcaemia?
● Increased parathyroid hormone (PTH) secretion + bone resorption, seen in
hyperparathyroidism
● Destruction of bone tissue - skeletal mets, myeloma, Paget’s disease
● Vitamin D related disorders - sarcoidosis, hypervitaminosis D
● Renal failure causing secondary hyperparathyroidism and phosphate retention
What is hyperplasia?
The increase in the number of cells in an organ or tissue. Usually associated with
increase mass
What are the different types of hyperplasia? Please give some examples.
● Physiologic:
○ Hormonal i.e. breast tissue development during puberty and pregnancy
○ Compensatory: post partial hepatectomy, skeletal muscle with increased
workload
● Pathological:
○ Excess hormones i.e. Benign prostatic hyperplasia or dysfunctional
uterine bleeding
○ Viral infection i.e. papillomavirus
What is hypertrophy?
Increased size of a tissue due to increased cell size. Arises from increased synthesis of
cell structural components
What are the types of hypertrophy?
May be physiological or pathological depending on either increased functional demand
or specific hormonal stimulation.
Cell hypertrophy can occur in dividing or non dividing cells
Give some examples of each type of hypertrophy
Physiological - skeletal muscles with exercise, the uterus during pregnancy, breast
tissue during lactation
Pathological - heart in chronic hypertension
What is metaplasia?
Replacement of one normal cell type with another normal cell type. May be adaptive or
pathological. Can be reversible.
Metaplasia examples
Columnar to squamous due to chronic respiratory irritation i.e. smoking
Squamous to columnar i.e. in Barretts oesophagus
Connective tissue change in myositis ossificans - muscle to bone or cartilage
What are the potential outcomes of metaplasia?
● Malignant transformation
● Reversibility/resolution
● Ongoing change