Lecture 3: CELLULAR PATHOLOGY Flashcards
It is a phospholipid bilayer with embedded proteins / glycoproteins / glycolipids (eg ion pumps, receptors, adhesion molecules, etc).
Plasma membrane
It is a semipermeable membrane with pumps for ionic/osmotic homeostasis.
Plasma membrane
- Chromatin (euchromatin vs heterochromatin)
- Nucleolus (synthesis of ribosomal RNA/subunits)
- Transcription of genes
Nucleus
- Inner & outer membrane, cristae
- Intermembranous and inner matrix compartments
- Oxidative phosphorylation (main source of ATP)
Mitochondria
Synthesis & packaging of proteins for export. Membranes, lysosomes.
Rough endoplasmic reticulum and Golgi apparatus
- Lipid biosynthesis (eg membranes, steroids)
- Detoxification of harmful compounds (via P450’s)
- Sequestration of Ca 2+ ions
Smooth endoplasmic reticulum
These assist proper folding of proteins and transport across organelle membranes.
Chaperones
These degrade both excess proteins and incorrectly folded (misfolded) proteins.
Proteasomes
- Enzymatic digestion (acid hydrolases) of materials in the cell
- Primary vs secondary lysosomes; residual bodies
- Autophagy vs heterophagy/endocytosis
- Phagocytosis/phagosome; pinocytosis/pinocytic vesicle; receptor-mediated endocytosis
Lysosomes
- Structure and movement of cells/organelles/ granules/ surface molecules/
phagocytosis. - Microfilaments: actin in various forms – cell shape and movement.
- Microtubules: polymers of tubulin – organelle movement/flagella/cilia/ mitotic spindle.
- Intermediate filaments: cytokeratin, vimentin, desmin, GFAP, neurofilament proteins.
Cytoskeleton
Enzymes (eg catalase, oxidases) – metabolism of hydrogen peroxide and fatty acids.
Perixisomes
When cells are able to maintain normal structure and function (e.g. ion balance, pH, energy metabolism) in response to normal physiologic demands.
Homeostasis
It is any stimulus or succession of stimuli of such magnitude that tend to disrupt the homeostasis of the organism.
Stress
- As cells encounter some stresses (eg excessive physiologic demand or some mild pathologic stimuli) they may make functional or structural adaptations to maintain viability/ homeostasis.
- Cells may respond to these stimuli by either increasing or decreasing their content of specific organelles.
Cellular adaptation
These are adaptive processes. They forms of adaptation. (4)
Atrophy, Hypertrophy, Hyperplasia and Metaplasia.
If the limits of adaptive response are exceeded, or in certain instances when adaptation is not possible (e.g. with severe injurious stimulus), a sequence of events called ____________ occurs.
Cell injury
It is the removal of stress / injurious stimulus results in complete restoration of structural and functional integrity.
Reversible cell injury
If stimulus persists (or severe enough from the star) the cell will suffer through these.
Cell injury and cell death
Two principle morphologic patterns that are indicative of cell death: (2)
Necrosis and Apoptosis
It is a type of cell death characterized by sever membrane injury and enzymatic degradation; always a pathologic process.
Necrosis
It is regulated form of cell death; can be a physiologic or pathologic process.
Apoptosis
CAUSES OF CELLULAR INJURY: (9)
Hypoxia
Physical agents
Chemical, Drugs & Toxins
Infectious agents
Immunologic reactions
Genetic abnormalities
Nutritional imbalances
Workload imbalances
Cell aging
It is one of the most important and common causes of cell injury and cell death. It causes impairment of oxidative respiration, it interferes with energy production.
Hypoxia
Severity of a physical injury may be increased by tissue hypoxia due to associated local vascular injury.
a.) Direct mechanical trauma - lacerations or crush injuries.
b.) Temperature extremes - heat (thermal burn), cold (frostbite).
c.) Radiation - radioactive isotope emissions or electromagnetic radiation (e.g. UV light, x-rays).
d.) Electrocution - pets chewing electric cords, faulty wiring in barns, lightning strike, etc.
e.) Sudden changes in atmospheric pressure - marine mammals have mechanisms to mostly avoid the “bends”.
Physical agents
a.) Inorganic poisons - e.g. lead, copper, arsenic, selenium, mercury, etc.
b.) Organic poisons - e.g. nitrate/nitrite, oxalate, hydrocyanic acid, etc.
c.) Manufactured chemicals - e.g. drugs (overdose idiosyncratic), pesticides, herbicides, rodenticides, etc.
d.) Physiologic compounds - e.g. salt, glucose, oxygen, etc.
e.) Plant toxins - e.g. ragwort, sweet clover, braken fern, etc.
f.) Animal toxins - e.g. snake or spider venom, tick toxin, etc.
g.) Bacterial toxins / Mycotoxins - e.g. botulinum toxin, aflatoxin, ergot, etc.
Chemical, drugs & toxins
a. Viruses
b. Bacteria / rickettsiae / chlamydia
c. Fungi
d. Protozoa
e. Metazoan parasite
Infectious agents
a.) Immune response - e.g. cells damaged as “innocent bystanders” in immune/inflammatory response.
b.) Hypersensitivity (allergic) reactions - e.g. anaphylactic reaction to a foreign protein or drug.
c.) Autoimmune diseases - reactions to self-antigens
Immunologic reactions
a.) Cytogenetic disorders / chromosomal aberrations - one cause of congenital anomalies.
b.) Mendelian disorders (mutant genes)
* enzyme defects, e.g. lysosomal storage disease.
* structural / transport protein defects - e.g. collagen dysplasia, cystic fibrosis, sickle cell anemia, etc.
c.) Multifactorial inheritance - combined effects of environmental factors and 2 or more mutated genes (e.g. neoplasia, hypertension, coronary artery disease, etc.)
Genetic abnormalities
a.) Overworked cells - cell injury occurs if stimulus prolonged and/or exceeds ability to adapt.
b.) Underworked cells - prolonged lack of stimulation (e.g. disuse, denervation, lack of trophic hormones) can lead to atrophy and eventually the loss of cells.
Workload imbalances
It is the cumulative effects of a life time of cell damage (chemical, infectious, nutrition, etc.) leads to a diminished capacity of aged cells / tissues to maintain homeostasis and adapt to harmful stimuli.
Cell aging
Mnemonic acronym for agents of disease = “double MINT”
Malformation
Miscellaneous
Infectious
Immune
Nutritional
Neoplastic
Trauma
Toxicity
4 intracellular systems are particularly vulnerable to injury.
- Cell membranes
- Mitochondria
- Protein synthesis, folding and packaging
- Genetic apparatus
These are chemical species with a single unpaired electron in outer orbit (donate or steal electrons, extremely unstable); readily react with organic or inorganic chemicals, avidly attack/degrade membranes, proteins & nuclei acids.
Free radicals
It is an important mechanism of cell damage in many disease processes (chemical, radiation, O2 toxicity, inflammation, reperfusion, etc.)
Free radical-induced injury
It occurs when the free radical generation overwhelms antioxidant defense mechanisms.
Cell injury
Small amounts produced from cell redox reactions, e.g. normal oxidative phosphorylation (leakage from mitochondria), other intracellular oxidases (e.g. peroxisomes), PMN’s in inflammation, excess O2, altered metabolism in cell stress (e.g. reperfusion injury).
Cellular metabolism
Some intermediary metabolites of chemical/drugs are highly reactive free radicals.
Enzymatic metabolism of exogenous chemicals