Cell Death

You have approximately 30 trillion red blood cells.

Nearly 2 million die in the time that it takes to say this. Why aren’t you anemic? Bone marrow replaces them

Cells have a life span Different cells have different life spans Ex. Esophagus maybe live hours, rbc may be 120 days

From a cell point of view, it’s not what caused the cell death, but what’s happening in the cell

Two Types of Cell Death: Apoptosis: programmed cell death, “cell suicide”

Apoptosis

Necrosis: death caused by injury through trauma, virus, bacteria, toxins We are looking at death caused by injurious agents

Cell Injury All injuries have an effect at the molecular level first Cells are damaged long before injury is observed Ex. Heart attacks account for a huge amount of cell death, but you can’t see any structural changes in a cardio cell for approximately 12 hours We cannot tell the moment a cell dies

Cells that undergo traumatic death resulting from acute cellular injury demonstrate a characteristic series of changes including the following:

The cell and its organelles swell Why? Cannot control water and ion regulation Cell contents leak out, leading to Inflammation of surrounding tissue

Swelling Endoplasmic Reticulum: folded membranes swell apart and eventually rupture Ribosomes come off the rough ER Cannot see under a compound microscope Protein synthesis cannot occur even if cell is still alive What happens?

Complete chaos If one chemical pathway is interrupted, all others will be affected

Mitochondria: Swell and rupture Cristae is lost No ATP production Cannot see this under a compound microscope

Nucleus: Nucleus takes on an irregular look (“clumping”) Nuclear envelope begins to break apart Normal nucleus looks smooth and homogenous We can see this under the microscope

They do not kill the cell, they usually make dead cells go away Lysosomes: rupture and release protein digesting enzymes that can destroy cells They do not kill the cell, they usually make dead cells go away Occurs often with infection, cuts

What would happen if you left dead cells/tissue in an area of your body? Fertile ground for massive infection

Necrosis of the Heel

Necrosis can be divided into the following: Necrosis: includes all of the above changes that can be observed following “accidental” cell death Necrosis can be divided into the following: Autolysis Heterolysis

Autolysis Cellular degradation caused by the cell’s own enzymes Occurs when a lysosome allows the digestive enzymes out of its membrane Always occurs before heterolysis

Normal Liver Histology

Normal Liver

Autolysis (Image 2)

Autolysis (Image 3)

Autolysis (Image 4)

Characteristics of autolysis of liver cells Disorganized intercellular material Granular appearance of cytoplasm Orange peel look White spots within the cytoplasm Fat accumulation Clumping of nuclear material

Why do we see fat?

Cell has been damaged and is unable to adequately metabolize fat. Small vacuoles of fat accumulate and become dispersed within cytoplasm.

Heterolysis Digestive enzymes from other cells break down the dead cell Usually leukocytes (white blood cells)