3. Cellular Reaction to Injury

Prokaryotes

single-celled organisms- including bacteria and archea

Eukaryotes

can be single-celled or multicellular, including plants, animals, fungi and others

3 main parts of a cell

1. cell membrane

2. the nucleus

3. cytoplasm

Biological Hierarchy

cell→ tissue→ organ→ organ system→ organism

Extracellular Space

the part of a multicellular organism outside the plasma membrane of cells, occupied by fluid

Metabolism

the chemical processes that occur within a living organism in order to maintain life, or all the chemical changes that take place in an organism

Catabolic

breaking down compounds; produces energy (katabasis – a downward journey, or journey to the underworld)

Anabolic

building up compounds; consumes energy

Physiological Responses in cells are

normal response to the environment and stimuli

Pathological Responses in cells are

a harmful reaction to stimuli ue to an underlying disease or illness

Homeostasis

the state of steady internal physical and chemical conditions maintained by a living organism; the organism’s state of optimal function

What affects the body’s ability to maintain homeostasis?

body temperature, fluid balance, pH, concentrations of potassium and calcium ionos, blood sugar

Homeostatic Range

narrow set of factors and pre-set limits that need to be regulated despite changes in the environment, diet or activity level

Cells adapt in response to environmental changes in which ways?

Physiologic (normal) or pathologic (abnormal)

if a cell is unable to adapt with changed then what happens?

Cell degeneration or regressive changes

Cell Degeneration

the deterioration of cellular function and structure, which can lead to tissue malfunction; usually a result of disease or injury

Regressive Changes

pathological processes indicating changes in cell metabolism; can alter structure and function and eventually cause tissue death

Necrosis

the pathological death of cells and tissues while still a part of a living organism

What are the causes of cellular injury?

1.Chemical agents – drugs, pollution, etc.

2. Pathogens (infectious agents)

3. The body’s own defense system (autoimmune disorders)

4. Genetic defects

5. Nutritional imbalances

6. Physical agents: trauma, temperature, radiation, electricity

7. Cellular senescence – the natural aging process of cells

Types of Cellular Injury

Deficiency

Intoxication

Trauma

Hypoxia

Deficiency

lack of substance necessary to the cell

Intoxication

presence of substance that interferes with the normal function of a cell

Trauma

Loss of cells’ structural integrity

Hypoxia

Lack of sufficient oxygen (total absence of O2 or excessive amounts of CO2)

What is the first sign of cellular injury?

Swelling

Swelling

when cells are unable to maintain the correct balance and concentration between ioonos and fluid levels

Steatosis (fatty Change)

the abnormal retention of triglycerides in a cell or organ (can be caused by toxins, proteins, malnutrition, diabetes etc..

Amyloid

protein aggregates, or sticky, waxy proteins that may clunmo in certain tissues and organs

Amyloidosis

a group of diseases caused by amyloid buikldup in different parts of the body

Prions

infectious amyloids, which then act as a template and misfold other proteins, specifically affecting the brain and neural tissue in mammals

Infiltration

the process of a substance seeping or diffusing into cells or tissues where it shoould not be

Pigmentation

happens when cells are infiltrated by pigmented substances, either exogenous or endogenous

Exogenous

comes from outside the body (black lung)

Endogenous

comes from within the body (hemoglobin, bilirubin)

Calcification

the depositing of calcium salts, magnesium, iron, or other minerals inside a cell, leading to hardening of tissues

Types of Cell’s adaptive responses

•Atrophy

•Hypertrophy

•Hyperplasia

•Metaplasia

•Dysplasia

Atrophy

decrease in the size of a cell, tissues or an organ due to loss of cellular substance

can by physiological or pathological

Hypertrophy

increase in the size of cell causing an increase in size of the tissue or organ

Reasons for Hypertrophy

Physiological – muscle cells increase in size in response to increased stress, e.g. weightlifting

Pathological – happens in response to cell damage; remaining cells will increase in size to compensate for dead cells, e.g. myocardial infarction

Compensatory – compensation without disease or injury, e.g. a person born with one kidney

Hyperplasia

an increase in size of a tissue or organ caused by an increased number of cells

can be physiological, pathological and compensatory

Metaplasia

a type of cellular regeneration after injury; one cell type is replaced by another type more capable of withstanding environmental change; usually reversible (scabbing)

Dysplasia

abnormal cell growth or development in a tissue or organ. Dysplasia is not cancer, but it may sometimes become cancer

can be micro or macroscopic.

Regeneration

the replacement of damaged cells with identical cells as the body heals; the process of replacing damaged or missing cells, tissues, or organs

What is the difference between Physiological regeneration and Reparative regeneration?

physiological the replacement of cells during homeostatic maintenance, without injury

reparative- occurs in response to injury

Repair

results in the formation of scar tissue