Cellular Pathology

“All organ injuries start with structural or molecular alterations in cells” concept

began by Virchow in 1800's.

NORMAL CELL

NORMAL CELL

• present day study of disease attempts to understand how cells react to injury.

• at the subcellular or molecular level.

NORMAL CELL

• all cells share the basic organelles for the synthesis of proteins, lipids, carbohydrates; energy production.

• transport of ions and other substances.• to understand pathology, review normal

structure and function of cells.• “you cannot appreciate the abnormal before you understand

the normal”

Plasma membrane

• phospholipid bilayer with embedded proteins / glycoproteins / glycolipids.

• semipermeable membrane with pumps for ionic / osmotic homeostasis

Nucleus

• nuclear envelope / nuclear pores• chromatin (euchromatin vs heterochromatin)• nucleolus (synthesis of ribosomal RNA)

Mitochondria

• inner & outer membranes, cristae• intermembranous and inner matrix

compartments• oxidative phosphorylation (main source of

ATP)

Endoplasmic reticulum (ER), Ribosomes & Golgi Apparatus

• rough (RER) vs smooth (SER) endoplasmic reticulum

• ribosomes (free in cytosol or attached to RER)• polysomes (threaded by mRNA).• condensing vacuoles / secretory vesicles

Lysosome• enzymatic (acid hydrolases) digestion of

materials in the cell• endocytosis• phagocytosis / phagosome; pinocytosis /

pinocytotic vesicle; receptor-mediated endocytosis

Peroxisome

• enzymes (eg catalase, oxidases) ! metabolism of hydrogen peroxide & fatty acid

CELL ADAPTATION, CELL INJURY and CELL DEATH

• DEFINITIONS AND TERMINOLOGY

• Homeostasis : cells are able to maintain normal structure and function (eg ion balance, pH, energy metabolism) in response to normal physiologic demands.

Cellular Adaptation

• as cells encounter stresses, either excessive physiologic demand or some pathologic stimuli, they may make functional or structural adaptations to maintain viability / homeostasis.

Cellular Adaptation

• cells may respond to these stimuli by either increasing or decreasing their content of specific organelles.

• adaptive processes: atrophy, hypertrophy, hyperplasia and metaplasia are forms of adaptation.

Cell Injury

• if the limits of adaptive response are exceeded, or in certain instances when adaptation is not possible, a sequence of events called cell injury occurs.

Cell Injury

• a) Reversible Cell Injury• removal of stress will result in complete

structural and functional integrity to be restored.

Cell Injury → Cell Death

• Irreversible Cell Injury / Cell Death• if stimulus persists (or severe enough from the

start) the cell will suffer irreversible cell injury and death.

• cell death is one of the most crucial events in pathology and can affect any type of cell.

Cell Death

• Necrosis: type of cell death characterized by severe membrane injury and enzymatic degradation; always a pathologic process.

• Apoptosis: regulated form of cell death; can be physiologic or pathologic process.