Cell Injury

What are the six major categories of mechanisms by which cells become injured

ATP depletion

mitochondrial damage

intracellular calcium increase

Free radical damage

Defective membrane permeability

Protein misfolding

How does hypoxia cause cellular swelling

Reduced ATP → Na+/K+ pump failure → Sodium accumulates intracellular → water enters → cell swells

What distinguishes ischaemia form general hypoxia

Ischaemia also blocks delivery of metabolic substrates, causing compounded injury

Why can reperfusion worsen tissue injury

Sudden return of oxygen increases ROS formation and inflammation, causing additional cell damage

How do free radicals damage cells

They attack membranes and increase mitochondrial permeability, disrupting cell function

What type of mechanical injury results from freezing

Ice crystal formation perforates membranes and causes osmotic imbalance leading to rupture

How do bacteria cause cellular injury

Via toxic metabolic products, secreted substances and damage from host inflammatory responses

How do caustic chemicals cause cellular death

Extreme pH causes rapid protein digestion and local necrosis

What is the key distinguishing feature of apoptosis compared to necrosis

Apoptosis keeps cell contents contained; necrosis releases them, damaging surrounding tissue

What type of necrosis us most characteristic of myocardial infarction

Coagulation necrosis

What type of necrosis produces a ‘cheese-like’ appearance and is typical in tuberculosis

Caseous necrosis

Why does colliquative necrosis frequently occur in the brain

The brain lacks significant connective tissue, so tissue liquefies completely

What differentiates dry from wet gangrene

Dry: sterile coagulation necrosis

Wet: coagulation necrosis with superimposed infection

What causes fat necrosis

Release of lipases leading to fat breakdown, producing soapy calcium deposits

Define atrophy

Decrease in cell size due to loss of cellular substance

Define hypertrophy

Increase in cell size

Define hyperplasia

Increase in number of cells in a tissue or organ

Define metaplasia

Reversible replacement of one adult cell type by another adult cell type

What distinguishes healing by primary intention form secondary intention

Primary: minimal tissue loss; wound edges brought together; little scarring

Secondary: significant tissue loss; granulation tissue forms; slower healing; more scarring

Which biomarkers indicate myocardial infarction due to necrosis

Troponins, CK-MB, and LDH release from damaged myocytes