Pathology - The Medical Training Resource Guide

What is Pathology?

Pathology is the branch of medicine which investigates the causes, effects and functioning of a disease to assist physicians in patient treatment. Pathologists examine bodily fluids, such as blood, organs, tissues and post-mortem bodies in their work. The field is divided into two main categories: general and medical. General pathology focuses on disease processes. Medical pathology is further subdivided into two categories: anatomical and clinical. To work as a pathologist, individuals must complete medical school, become licensed to practice medicine and become certified. Some states may require completion of a pathology residency.

  • American Society for Clinical Pathology: This website explains the general practice of pathology and information about pathology certification. The Association also offers educational opportunities for Pathologists.
  • The University of Kansas School of Medicine: This site provides a definition and explanation of pathology. The resource page, accessible through a link on the left side, directs to other pathology associations.
  • NYU Medical Center: This page provides a patient-geared explanation of the practice of pathology.
  • University of Chicago Hospitals: The hospital network’s explanation of the study of pathology. Links at the bottom of the page discuss clinical and anatomical pathology.


Inflammation is caused by the body attempting to protect itself from damage or block off something foreign. Inflammation can be acute or chronic. Acute inflammation appears after the body has been injured to seal off the injury and begin the healing process. This type of inflammation usually occurs when the body is aware of the injury. Chronic inflammation, on the other hand, is the result of a long-term injury. The types of bodily fluids a body releases for chronic inflammation are different than those for acute inflammation

Fluids and Blood

A large percentage of pathology is performed by studying bodily fluids and blood. Disorders of the blood, such as cancer, are sometimes only diagnosed through pathological examination. Other types of fluids tested include urine, phlegm and spinal fluids. Patients can also have a disorder of the blood or fluid that is causing them to feel ill; sometimes, these disorders develop independently, but many times they are attributable to a disorder in an organ or other area of the body.


Pathology is also used to identify genetic diseases and study potential cures. For example, recent pathological testing at Harvard University has identified a potential genetic cause for Sudden Infant Death Syndrome (SIDS). The majority of genetic diseases are present at the moment of fertilization of the egg, but some are due to abnormal changes in genetic material later in life. Because of this, testing may be performed on relatives of the patient as well as the patient. Testing can be performed by gathering bodily fluids, blood or tissue samples.

  • Harvard University: This page provides an explanation of the school’s pathological tissue study of patients. A study of patients afflicted by a genetic intestinal disorder is also described.
  • Stanford University: This site provides information on the University’s study of molecular genetics. Links at the bottom of the page explain the types of testing performed for genetic studies.  


There are several types of immunities in the human body. Pathologists study these immunities to discover if they are harmful, helpful and why they exist. One well-known type of immunity is AIDS, in which a virus grows on the body’s immune system weakening the patient’s immunity. Other types of immunities include immunodeficiency, in which the body’s immune system is weakened or absent and therefore unable to fight disease, and autoimmunity, in which the body’s immune system attacks itself.

  • University of Chicago: This site provides basic information about AIDS, including its origins and early treatment.
  • Johns Hopkins University: The school’s autoimmunity department explains the types, causes and diagnosis of autoimmune disorders.

Infectious Diseases

An infectious disease is one that is transferred to a person, and which is usually contagious. Some infectious diseases are transferred from animal to human; these diseases are referred to as “Zoonotic”. There are hundreds of types of infectious diseases, the most recognizable of which may be the flu. Pathologists study blood, bodily fluids and tissue to identify the presence of infectious diseases in a patient. Some infectious diseases are treatable through antibiotics.

  • This site defines infectious diseases and provides links to numerous types of these diseases.
  • World Health Organization: This page identifies the numerous types of infectious diseases as well as statistical information on infectious disease epidemics.

The Heart

Diseases of the heart and surrounding arteries are commonly called “cardiovascular diseases”. These diseases can be genetic, but can also develop as a patient ages. Common types of cardiovascular diseases include high blood pressure, malfunctioning heart valves and heart disease. Pathological testing for these diseases is usually performed on a patient’s blood or other fluids.

  • This site provides a list of the common types of disorders of the heart.
  • Tulane University College of Medicine: The school’s page lists several types of heart diseases and photos of the appearance of the diseases after testing.

The Liver

Diseases of the liver can be genetic or caused by a disease. As the liver is responsible for making a body’s fluids and breaking food down into metabolic parts for digestion, pathologists often test a patient’s blood to identify any existing disorders. Common types of liver diseases include cirrhosis and hepatitis. Some diseases are curable while others are chronic conditions that must be managed over a lifetime.

The Pancreas

The pancreas is a member of the digestive system responsible for releasing fluids to assist in the digestion of food. Pancreatic diseases can be acute or chronic, and can take the form of the body being unable to release the appropriate types and amounts of fluid to aid digestion. Pancreatic cancer is a prominent type of cancer. Pathological testing of pancreatic functioning can be done through tissue samples, which usually requires surgical removal of the tissue for testing, bodily fluids or blood. 


The kidneys are responsible for processing an individual’s blood and riding it of waste. Malfunctioning kidneys may require a patient to undergo dialysis, the procedure which processes a patient’s blood when his or her kidneys are unable to do so. Sometimes, kidney malfunction and diseases are so serious that a transplant may be required. Common types of kidney disorders include cancer, hepatitis and kidney disease. Pathological diagnosis of kidney disorders is commonly done through blood and urine testing.

Men’s Health Problems

Common men’s health problems include testicular torsion, erectile dysfunction and prostate cancer. Although an extremely serious illness, prostate cancer has a high cure rate if timely diagnosed and treated. The penis is also subject to cancer, but such type is rarer than cancer of the prostate. Diagnosis of men’s sexual organ disorders occurs through tissue testing or medical examination, sometimes using medical equipment.

Women’s Health Problems

Women’s health problems mainly extend to female sexual organs. Breast, uterine or cervical cancer are disorders that are diagnosed through pathological blood or tissue testing. Other types of disorders include hormone imbalances, cysts on the sexual organs and sexually transmitted diseases. These types of disorders are also tested for diagnosis and treatment through tissue or blood analysis.


Skin disorders can take many forms, including a reduction in pigment and cancer. While some skin disorders can be caused by genetics, the majority of them are due to exposure to harsh elements and the sun. Diagnosis of skin disorders is usually done through testing layers of the skin or by using equipment to view the deeper layers of skin. The majority of skin disorders are treatable.


Pathological bone disorders can take the form of weak bones, cancer or tumors. Bones can even become overly large and deformed. Diagnostic testing for bone disorders is commonly performed through the use of medical equipment, such as CAT scans, as well as through X-Rays, needle biopsies and bodily fluid sampling. Except for the use of medical equipment, testing for bone disorders is invasive.

  • Ohio State University Medical Center: This page provides extensive information about bone disorders and includes links to the common types of disorders and their diagnosis.
  • Cedars-Sinai Medical Center: This page describes metabolic bone disorders and their diagnosis. The site also explains how bone marrow transfers are performed.


Muscular disorders can occur throughout an individual’s body and, because they are responsible for maintaining a body’s structure, can affect other parts of the body. Muscular disorders include weakness, degeneration, overly large muscles or genetic muscular rigidity. Muscular Dystrophy and Fibromyalgia are muscular disorders. Diagnosis of muscular disorders is usually performed through a biopsy of the muscle tissue in the affected area.


Located in the neck, the thyroid is a gland. The main job of a thyroid is to produce the thyroid hormone, which is responsible for making energy by regulating the metabolism and also for controlling body temperature. Disorders of the thyroid can appear as hyperthyroidism, in which too many hormones are released, or hypothyroidism, in which the metabolism is slowed. The Thyroid may also become cancerous. Diagnosis of thyroid disorders is typically performed through blood tests.

  • The Hormone Foundation: This page provides an overview of the types of common thyroid disorders.
  • NetWellness: A website created by an association of universities, including the University of Ohio, University of Cincinnati and Case Western University, this page describes the thyroid’s function and common disorders.


Pathologists also study and diagnose diseases of the eyes and the surrounding area. Common disorders include degenerative vision and blindness. Eyes can also become infected and experience temporary or chronic injury. Testing for eye disorders is usually not performed by pathologists unless doing so requires tissue samples. If tissue samples are unnecessary, an optometrist will use external measurement tools to identify any disorders.

  • Merck Manual: This site provides information about the common types of eye disorders and how testing for them is performed.
  • National Institute of Health: This page describes the common types of eye disorders.


Pathological ear disorders usually take the form of a deformed or malfunctioning ear canal. To test for disorders, pathologists may take tissue samples of the inner ear or check for genetic disorders by testing a patient’s blood. Treatments for these disorders are possible, but may not always cure the ailment. Common diseases of the inner ear include malformed cilia and damaged ear canals.

The Nervous System

The body’s nervous system is composed of nerve cells designed to transport information between an individual’s body and brain. Nervous system diseases can affect an individual’s brain and spinal cord. Diagnosis of neurological diseases is usually performed through the use of machinery such as CAT scans and MRIs. The majority of these disorders are not treatable, but can be managed through medication and physician care.

The Respiratory System

Respiratory disorders affect a patient’s ability to breathe normally. Disorders can be genetic, such as asthma, or caused by a virus, as in the case of a common cold. The respiratory system can also be afflicted by cancer, which includes lung and throat cancer. Diagnosis of respiratory ailments is performed through mechanized scans, blood and bodily fluid testing and possibly testing of lung or other tissue.

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