Pathophysiology is the study of the changes of normal mechanical

Mechanics

Mechanics is the branch of physics concerned with the behavior of physical bodies when subjected to forces or displacements, and the subsequent effects of the bodies on their environment....

, physical

Physical

Physical may refer to:*Body, the physical structure of an organism**Human body, the physical structure of a human*Physical abuse, abuse involving contact intended to cause feelings of intimidation, injury, or other physical suffering or bodily harm...

, and biochemical functions, either caused by a disease

Disease

A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...

, or resulting from an abnormal syndrome. More formally, it is the branch of medicine which deals with any disturbances of body functions, caused by disease or prodromal symptoms.

An alternative definition is "the study of the biological and physical manifestations of disease as they correlate with the underlying abnormalities and physiological disturbances."

The study of pathology and the study of pathophysiology often involves substantial overlap in diseases and processes, but pathology emphasizes direct observations, while pathophysiology emphasizes quantifiable measurements.

Examples

An example from the field of infectious disease

Infectious disease

Infectious diseases, also known as communicable diseases, contagious diseases or transmissible diseases comprise clinically evident illness resulting from the infection, presence and growth of pathogenic biological agents in an individual host organism...

 would be the study of a toxin

Toxin

A toxin is a poisonous substance produced within living cells or organisms; man-made substances created by artificial processes are thus excluded...

 released by a bacterium, and what that toxin does to the body to cause harm, one possible result being sepsis

Sepsis

Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...

.

Another example is the study of the chemical changes that take place in body tissue due to inflammation

Inflammation

Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...

.
the intersection of two older, related disciplines: (normal) physiology

Physiology

Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...

 and pathology

Pathology

Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....

.

• Physiology
  Physiology
  Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...
  
   is the study of normal, healthy bodily function (as opposed to anatomy
  Anatomy
  Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...
  
  , which is the study of normal structure
  Structure
  Structure is a fundamental, tangible or intangible notion referring to the recognition, observation, nature, and permanence of patterns and relationships of entities. This notion may itself be an object, such as a built structure, or an attribute, such as the structure of society...
  
  ). When something disrupts normal physiological processes, it enters the realm of pathophysiology.
• Pathology
  Pathology
  Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....
  
  , broadly speaking, is the "study of the nature and cause of disease." or the results of disease in the body.

Pathophysiology looks at the specific malfunctioning that comes from or - alternately - causes disease.

One caution in this approach is that "healthy" structure

Structure

Structure is a fundamental, tangible or intangible notion referring to the recognition, observation, nature, and permanence of patterns and relationships of entities. This notion may itself be an object, such as a built structure, or an attribute, such as the structure of society...

 and function is not precisely the same in any two individuals...

Uses

Pathophysiology is a required area of study for nearly all healthcare professional school programs (medical, dental, physician assistant, occupational therapy, physical therapy, nurse practitioner, pharmacy, nursing, and paramedic programs) in the United States and other countries.