LECTURE 2 - Causes of Cell Injury

Oxygen Deprivation, Physical Agents, Electrical Injury, Chemical agents and drugs, Infectious agents, Immunologic reactions, Genetic abnormalities, Nutritional imbalances

Causes of cell injury

Hypoxia, Ischemia

oxygen deprivation

Trauma, Radiation, Temperature extremes

Physical agents

Type, severity, and duration of the injury

the cellular response depends on

Hypoxia

inadequate oxygen availability

Reduced blood flow, respiratory failure, reduced oxygen-carrying capacity, severe blood loss, carbon monoxide poisoning

causes of hypoxia

Ischemia

reduced blood supply to tissue

generally more damaging than hypoxia because it also decreases delivery of nutrients and removal of metabolic waste

Inflammation

protective response of vascularized tissues to infection, tissue injury, or other harmful stimuli

Eliminate the initial cause of injury, removed damaged and dead cells, initiate tissue repair, prevent the spread of infection

Major functions of inflammation

Inflammation

beneficial when appropriately controlled, but excessive or prolonged inflammation can cause tissue damage

Infections, tissue necrosis, foreign bodies, immune reaction

Triggers of inflammation

Infection

bacteria, viruses, fungi, parasites

Tissue necrosis

ischemia, trauma, toxins

Foreign bodies

splinters, dirt, sutures

Immune reactions

autoimmune and allergic disorders

Major components of inflammation

Vascular reaction, cellular reaction

components of inflammation

•Vascular reaction

•Vasodilation

•Increased blood flow

•Increased vascular permeability

•Leakage of plasma proteins

•Formation of inflammatory edema

Rapid

acute onset

Hours to days

acute duration

Neutrophils

acute main cells

Prominent

acute vascular changes

Usually mild/ limited

acute tissue injury

Usually minimal

acute fibrosis

Slow/ prolonged

chronic onset

weeks to years

chronic duration

Macrophages, lymphocytes

chronic main cells

usually less prominent

chronic vascular changes

often significant

chronic tissue injury

common

chronic fibrosis

Acute inflammation

Rapid onset

Short duration

Exudation of fluid and plasma proteins

Predominance of neutrophils

Rubor

redness

Calor

heat

Tumor

swelling

Dolor

pain

Functio laesa

loss of function