adaptation, irreversible injury, and ischemia

atrophy as an adapation

conservation effort: minimize energy use/demand and nutrient consumption

what causes atrophy to happen?

disuse, denervation, ischemia, starvation, endocrine changes, injury

hypertrophy as an adaptation

increased cell mass and functional capacity

what causes hypertrophy?

increased workload

hyperplasia as an adaptation

increased number of cells

what causes hyperplasia?

increased functional demand

hormonal stimulation (endocrine structures)

persistent injury

chronic irritation

metaplasia as an adaptation

replacement with cells better suited to conditions

cells change structurally because of a new demand

what causes metaplasia?

persistent injury

is metaplasia reversible?

yes! fully reversible once the injurious stimulus is removed

• ex: GERD

dysplasia as an adaptation

an adaptive effort gone astray → cells become disorganized, with irregular sizes and shapes

what is dysplasia often considered as?

often considered as pre-cancerous tissue

may become cancerous if the stressor is not removed

what is necrosis?

premature cell death

what causes necrosis?

caused by factors external to the cell

why is necrosis most commonly related to ischemia and oxygen deprivation?

lack of good oxygen delivery → ischemia

ischemia is a precursor to necrosis

what is apoptosis?

programmed cell death

what triggers apoptosis?

generally triggered by normal, health processes in the body

what is apoptosis most commonly related to?

the normal aging process

necrosis vs. apoptosis: what happens to the nucleus?

necrosis: nucleus shrinks

apoptosis: nucleus divides

necrosis vs. apoptosis: what happens to the organelles?

necrosis: organelles cease to function

apoptosis: organelles redistribute

necrosis vs. apoptosis: what happens to ATP production?

necrosis: ATP production disrupted

apoptosis: ATP production continues

necrosis vs. apoptosis: what happens to the plasma membrane?

necrosis: plasma membrane dysfunction and rupture

apoptosis: plasma membrane stays intact while dividing into smaller apoptopic bodies

necrosis vs. apoptosis: what happens to the adjacent cells?

necrosis: adjacent cells become inflamed

apoptosis: adjacent cells unaffected

what is ischemia the most common cause of?

cell injury

what is ischemia?

inadequate blood supply to a tissue or organ

tissue is on the brink of cellular dysfunction

ischemia causes of a disruption of what?

oxygen supply plus accumulation of metabolic waste (lactic acidosis)

what happens to the cellular proteins and enzymes during ischemia?

become dysfunctional

is ischemia injury reversible?

yes! if we get more oxygen

when does cell death occur from ischemia?

when plasma, mitochondrial, and lysosomal membranes are critically damaged

🍌common causes of ischemia

thrombosis

embolism

trauma

arterial insufficiency (aneurysm, constriction, hypovolemia, anemia)

🍌general signs and symptoms of ischemia

fever

malaise

tachycardia

increased WBCs

loss of apetite

🍌first step in the ischemia cascade

ischemia:

nutrient deficiency

oxygen deficit

waste accumulation

🍌second step in the ischemic cascade

damage to cellular structures:

plasma membrane, nucleus, mitochondrion, ER and ribosomes, golgi apparatus, lysosomes

🍌third step in the ischemic cascade

necrosis

🍌what is ischemia-reperfusion injury?

tissue damage when blood supply returns to the tissue after a period of lack of oxygen

there is calcium overload and a sudden rush of free radicals leading to inflammation