Necrosis and Programmed Cell Death

Cell death

when individual cells die by necrosis or apoptosis

Necrosis

is involuntary, toxic, inflammatory and can release harmful chemicals into extracellular fluid

apoptosis

occurs in careful, coordinated manner that minimises damage to surrounding tissue

careful digestion of cellular contents prevents harmful damage to surrounding tissues and minimizes infammation

leaves no trace or damage

when does necrosis occur

when celll death occurs as a result of injury or disease

necrosis leads to__

uncontrolled release of antigens that trigger an inflammatory response

ex: frostbite, infection, lack of blood supply

how does apoptosis happen

when molecular pathways are triggered that induce the cell to undergo a careful and deliberate breakdown

when does apoptosis occur

during viral infection, developement, lack of blood supply, damage or when cell has reached end of lifespan

apoptosis during development examples

• formation of many physical features as well as our brain development occur via apoptosis

• the webbing/space between fingers in apoptosis → ducks dont go through that process to swim better

apoptosis cytological changes

• leads to coordinated destruction of cellular structures

• DNA is digested by nucleases, organelles are broken down and digested, polymers are broken into monomers

• the cell shrinks and becomes lobed (blebbing)

• as cell fragmentation occurs, the cell contents (monomer, metabolised cell components) are sealed into small sacs called apoptic bodies

• those bodies can be further broken down, recycled and used to communicate with neighbouring cells

• apoptic bodies

• as cell fragmentation occurs, the cell contents (monomer, metabolized cell components) are sealed into small sacs

extracellular signal

• the signal to induce apoptosis can occur from external source triggering apoptosis

• caspases proteins

to activate signal for apoptosis

• intracellular signal

the signal can come from damage within the cell