Week 3: Cellular Stress Flashcards
Define adaptation
cells attempt to maintain an internal steady-state (homeostasis), but when exposed to an adverse stimulus undergo various adaptations to establish a new “steady-state”.
Define stem cell
defined as an undifferentiated cell of a multicellular organism which can give rise to indefinitely more cells of the same type, and from which certain other kinds of cells arise by differentiation
List and describe the different types of stem cells
-Embryonic stem cells – totipotent – can give rise to any cell type in the body
-Tissue stem cells – in adults, stem cells replace damaged cells and maintain tissue populations
Define proliferation
defined as a rapid increase in the number or amount of something
Define atrophy
a decrease in tissue mass due to shrinkage of cells
-can be both physiological and pathological
Define hypertrophy
an increase in the size of existing cells resulting in an increase in the size of the organ; often in response to increased workload
-can be both physiologic and pathologic
_____ and _____ also can occur together, and obviously both result in an enlarged organ
hypertrophy and hyperplasia
What is a physiological example of hypertrophy?
hypertrophy of skeletal muscle occurs as a normal physiological response in weight training
What is a pathological example of hypertrophy?
the cardiac enlargement that occurs with hypertension or aortic valve disease
Define hyperplasia
an increase in the number of cells (caused by cell division)
-can be both physiologic and pathologic
What is a physiological example of hyperplasia?
when part of a liver is resected, mitotic activity in the remaining cells beings as early as 12 hours later, eventually restoring the liver to its normal size
What is a pathologic example of hyperplasia?
excessive hormonal or growth factor stimulation (abnormal menstrual bleeding)
Define metaplasia
the substitution of one type of cell for another cell type
What is an example of metaplasia?
cells in the bronchi of smokers change from ciliated columnar epithelial cells to squamous cells
Define dysplasia
an alteration in the size, shape, and/or organization of the cells in a tissue
What are the causes of cell injury?
-Hypoxia
-Physical agents
-Chemical agents
-Biological/infectious agents
-Immunologic reactions
-Genetic alterations
-Nutritional imbalances
_____ _____ can also lead to cell injury.
Cellular aging
What four components are particularly vulnerable to cell injury?
- Cell membranes critical for ionic and osmotic homeostasis
- Mitochondria and the generation of energy via ATP
- Protein synthetic machinery
- Cellular DNA
What are the 4 major mechanisms of cell injury?
- Damage to mitochondria results in a reduction in ATP and an increase in reactive oxygen species»_space; damage to lipids, proteins, and DNA.
- Entry of calcium into the cell results in increased mitochondrial permeability and activation of multiple cellular enzymes.
- If the plasma membrane is damaged there can be a loss of cellular components, and if the lysosomal membrane is damaged, leaked lysosomal enzymes can inadvertently digest cellular components.
- Protein misfolding and DNA damage should trigger pro-apoptotic proteins to initiate programmed cell death. If the checkpoint or repair mechanism is faulty, damaged cells can avoid apoptosis which may result in cancer development.
What are two types of reversible cell injury?
Hydropic swelling and Fatty change
Describe hypropic swelling
injury caused by a variety of agents; produces a characteristic cellular or hydropic swelling when seen under the microscope.
What is another name for fatty change?
Steatosis
Describe fatty change
the abnormal accumulation of triglycerides within cells.
-Is linked to the intracellular accumulation of triglyceride fat either because of increased delivery of fat to the cell (e.g., in starvation, diabetes); an impairment of fat metabolism within the cell (e.g., in liver cells in alcoholism); or decreased synthesis of apolipoproteins for transport out of the cell (e.g., in protein malnutrition, CCl4 (carbon tetrachloride) toxicity).
Define necrosis
is an uncontrolled process of cell death in response to overwhelming injury and is characterized by certain structural changes
What are the structural changes that necrosis is characterized by?
a. eosinophilia (pinkness) of the cytoplasm
b. pyknosis (shrinkage)
c. karyorrhexis (the pyknotic nucleus fragments or breaks up)
d. karyolysis (dissolution) of the nucleus
What are the different types of necrosis?
- coagulative
- liquefactive
- fat
- caseous
Describe coagulative necrosis and provide an example
the most common form of necrosis – microscopically all the changes described above are seen. Typical of ischemia e.g., in heart (myocardial) cells (heart attack)
Describe liquefactive necrosis and provide an example
rapid loss of tissue architecture and digestion of the dead cells. Most often seen in CNS. Typical of bacterial infection or death of brain tissue (following infarction or stroke)
Describe fat necrosis and provide an example
specific to fat (adipose) tissue. Released enzymes digest fat that complexes with calcium to form chalky-white deposits, e.g., pancreatitis; damage to breast tissue
Describe caseous necrosis and provide an example
soft, friable, “cheesy” material. Characteristic of tuberculosis
Describe apoptosis
the morphologic manifestation of programmed cell death and is distinct from necrosis
Apoptosis is an _____-dependent process specifically designed to switch off unneeded or damaged cells and _____ them.
energy; eliminate
Apoptosis can occur under either
physiological or pathological circumstances
Give two pathological examples of apoptosis
-Following radiation injury
-some cancers
Describe the process of apoptosis
Apoptotic cells initiate their own death by the activation of proteases that breakdown the cell nucleus and cytoskeleton. In the initial stages, the cell nucleus collapses due to chromatic condensation and fragmentation. Then the cells shrink and is cleaved into cytoplasmic buds enclosing organelles (apoptotic bodies). Finally, there is phagocytosis of the extruded apoptotic bodies.
List the differences between apoptosis and necrosis
Apoptosis:
-Programmed cell death following a tightly regulated programme
-Cells degrade their own DNA and proteins via intrinsic enzymes
-May be physiologic or pathologic
-Cell shrinks
Necrosis:
-Characterized by loss of membrane integrity and leakage of cellular contents
-Results in host inflammatory reaction in surrounding tissue
-Always pathologic
-Cell swells
Define anoxia
absence or almost complete absence of oxygen from inspired gases, arterial blood, or tissues
Define hypoxia
decrease below normal levels of oxygen in inspired gases, arterial blood, or tissues
