Lecture 6 - Reversible Cell Injury and Accumulations

What is reversible injury?

The injured cell can regain homeostasis and return to a morphologically and functionally normal state

What is cellular adaptation?

Cell changes its morphology and function to accommodate for cell injury/stress to achieve homeostasis

What is one consistent feature of reversible cell injury?

Cell swelling

What is seen grossly in reversible cell injury?

Pallor

Organ swelling (organomegaly), increased weight

Decreased specific gravity, increased water

What is seen on histopathology in reversible cell injury?

Increased cell size with rounding

If lining a tubule or vessel, will impinge on/constrict the lumen

Pale, finely vacuolated to granular appearance (cloudy swelling)

Nuclei are not displaced and may be swollen

Vacuoles in reversible cell injury are attributed to...

Increased water in cell and distended organelles

What is a good general description for reversible cell injury seen on histopathology?

Vacuolar degeneration

What is hydropic degeneration specific to?

Used in most tissues

In haired skin, refers to vacuolation of basal keratinocytes

What is ballooning degeneration specific to?

Specific to keratinocytes

What is cytotoxic edema specific to?

CNS cells

General features of hypertrophy

Cell swelling

Organomegaly (heavier)

Underlying cause is increased workload on the cell

Increased size from increased numbers and sizes of organelles

No difference in water amount

General features of acute degeneration

Cell swelling

Organomegaly (heavier)

Underlying cause is cell injury and damage

Increased size from increased water in the cells, organelle swelling

Increased water amount

May see concurrent necrosis or other findings associated with cell injury and damage

How is normal cell volume maintained?

Water moves passively across cell membranes in response to the osmotic pressure gradient generated by Na and proteins

Na/K ATPase pump drives Na out of the cell in exchange for K, and water follows Na

What are susceptible players in maintaining normal cell volume?

Physical barrier function of membranes (phospholipid bilayer)

The pump requires energy, ATP, which requires oxygen

The membrane proteins/enzymes maintaining ion concentrations and membrane function

What mechanisms are responsible for acute cell swelling?

Damage to cellular membranes (reactive oxygen species)

Injury to enzymes regulating ion channels on membranes (pH, elevated enzymes)

Failure of energy (ATP) production (disrupt pump)

What are some potential causes of cell swelling?

Mechanical injury (trauma)

Hypoxia

Toxicity

Free radicals

Infectious (viral and bacterial)

Immune-mediated

Explain the cascade of hypoxia leading to cell swelling.

Hypoxia

ATP production decreases

Na and water move into cell, K out from lagging pump

Osmotic pressure increases

More water moves into cell

Cisternae of ER distend, rupture, and form vacuoles

Extensive vacuolation

What do we call cell swelling from hypoxia?

Hydropic degeneration

What is the significance of cell swelling in the skin?

Decreased barrier function (ulcers, erosions)

What is the significance of cell swelling in the liver?

Decreased hepatic function (detox, protein production)

What is the significance of cell swelling in the nervous and cardiac conduction systems?

Decreased nerve impulse condition (stupor, coma, arrhythmias)

When will we see clinical signs of cell swelling?

If only a few cells are affected, may be subclinical (besides the brain and heart)

If most cells are affected, clinical signs will arise