General Pathology: Study of Diseases

General Pathology

• Pathology is derived from the Greek words "pathos" (pain or suffering) and "logos" (the study of).
• Pathology studies diseases, focusing on structural and functional changes in cells, tissues, and organs.
• Pathology is also referred to as pathobiology.
• Rudolf Virchow stated that diseases originate at the cellular level.
• Pathology studies disease origins at both the cellular and molecular levels, including RNA, DNA, and proteins.

Aspects Core to Diseases

• Etiology is the cause or reason for a disease.
• Pathogenesis refers to the mechanism of disease development and progression.
• Morphologic changes are structural alterations forming blebs or protrusions.
• Clinical significance refers to the functional consequences of a disease.

Key Terms

• Pathogenesis is the development, progression, or proliferation of a disease or condition.
• A pathologist is a physician specializing in interpreting disease-related changes in the body.
• A Medical Laboratory Scientist/Medical Technologist prepares tissue and samples for pathologist examination.

Autopsy

• The word origin comes from the the Greek words "auto" (self) and "opsis" (to view).
• Autopsy is also called necropsy (examining the dead) and postmortem exam (PME).
• Autopsy systematically examines a cadaver to study or determine the cause of death.
• Autopsies confirm natural causes of death for grieving families, excluding murder or homicide.

Biopsy

• Biopsy examines cells or tissues from living organisms to diagnose disease or confirm normality.
• Excision involves removing a whole organ, while incision removes part of an organ.

Types of Pathology

General

• General pathology focuses on basic reactions of cells and tissues to abnormal stimuli underlying all diseases.
• It doesn't pinpoint disease origins, encompassing cancer, aging, and inflammation.

Systemic

• Systemic pathology focuses on specific responses of organs/tissues to defined stimuli, such as pneumonia (lungs) or peptic ulcer (GIT).

Divisions of Pathology

Gross Pathology

• Gross pathology recognizes diseases based on macroscopic examination of surgical specimens.
• The examination occurs during surgery or autopsy.

Anatomic Pathology

• Anatomic pathology studies changes in organ/tissue function, structure, or appearance, including postmortem and biopsy specimens.
• Anatomic refers to relationships between gross and microscopic elements.

Branches of Anatomic Pathology

Surgical Pathology

• Surgical pathology studies surgically accessible disease processes for diagnosis.
• Surgical pathology involves living patients through biopsy.

Autopsy Pathology

• Autopsy pathology involves internal and external examination of a body following death.

Exfoliative Cytology

• Exfoliative cytology studies cells shed from epithelium.
• It microscopically examines shed/desquamated cells from body surfaces, harvested by rubbing or brushing tissue.

Clinical Pathology

• Clinical pathology diagnoses/monitors diseases via blood, body fluids, secretions, and tissue biopsies.
• Clinical pathology focuses on chemical, morphological, microbiological, and immunological abnormalities.
• It addresses bacteria, microbes and RBC related diseases, focusing beyond cellular aspects.

Clinical Chemistry Including Toxicology

• Clinical chemistry analyzes biochemicals in human samples (blood, fluids, tissues) outside the body in vitro.
• Clinical chemistry assays substances like sugars, lipids, proteins, antibodies, enzymes, hormones, vitamins, metals, and electrolytes.
• Toxicology analyzes drugs in blood, urine, and fluids to ensure therapeutic levels are adequate.

Hematology

• Hematology assesses cellular elements (red/white blood cells, platelets) in blood samples.
• A hematopathologist specializes in hematology.

Blood Banking

• Blood banking manages collection, storage, compatibility, and safety of blood and its components for transfusion purposes.
• Component preparation separates blood into plasma, platelets, and packed red blood cells.

Microbiology

• Microbiology isolates, cultures, and identifies microorganisms (parasites, fungi, bacteria, and viruses) in biological samples.

Clinical Immunology and Serology

• Clinical immunology and serology diagnoses infectious diseases, detecting antibodies in serum/body fluids.
• As an example, the Anti-Streptolysin O (ASO) tests measures antibodies against streptolysin O produced by Streptococcus pyogenes.

Histotechnology

• Histotechnology: science by histotechnologists/technicians to create good tissue sections for pathologists to diagnose disease presence/absence.

Histopathologic Preparation

• Sequence of histopathologic preparation:
  • Numbering/Accessioning [Accession Number]
  • Fixation to conserve sampes
  • Decalcification to soften is is needed
  • Dehydration, Clearing, Infiltration/Impregnation
  • Embedding/Casting/Blocking
  • Trimming, Sectioning, Staining
  • Mounting, Labelling

Histopathologic Technique

• Histopathologic technique involves different procedures for materials and tissues for microscopic examination.

Histology

• Histology studies microscopic anatomy of biological tissues at the microscopic level.

Four Basic Types of Animal Tissue

Muscle Tissue

• Muscle tissue enables muscles to contract
• It originates during embryonic myogenesis and is classified by striation, movement, and location.

Muscle Tissue Classification

• Smooth Muscle Tissue: No striations, involuntary movement, located in stomach, intestines, etc.
• Skeletal Muscle Tissue: Striated, voluntary movement, located in bones.
• Cardiac Muscle Tissue: Striated, involuntary movement (intercalated discs), located in the heart.

Nervous Tissue

• Nervous tissue, also called neural tissue, is a main component of the nervous system comprising of two components: CNS and PNS

Central nervous system (CNS)

• Consists of The brain and spinal cord

Peripheral nervous system (PNS)

• Consists of nerves consisting of neurons which transmit impulses and neuroglial cells (glia), supporting cells that provide nutrients

Connective Tissue

• Connective tissues consist of three main components including Fibers, elastic, and collagenous, ground substance (mostly liquid), and cells

General Connective Tissues

• Loose Connective: High Ground Substance; Low Fiber content
• Dense Connective:

  • Irregular: between High and Low ground content with High and Low fiber content

  • Regular: low ground substance content with high fiber content

Special Connective Tissues

• Cartilage, Bone, Blood, and Lymph, Hematopoietic, Adipose tissue

Epithelial Tissue

• Epithelium for lining outer and blood vessel surfaces, and inner surfaces to support cavities
• Classified into 3 layers, shape, and locations
• The classifications depend on the layers (1 or many) and the connection to the basal lamina.

Cell Shapes

• Squamous cells are wider than their height, flat, scale-like, and used for covering or protection.
• Cuboidal cells have near-equal height and width, square-like, and used for absorption, secretion, and excretion.
• Columnar cells are taller, ciliated, and glandular for secretion, absorption, or excretion.

Cellular Injury

• Cellular injury is the result of severe cellular stress
• Cells adapt through hyperplasia (cell number increase), and hypertrophy (cell size increase)
• Adaptation: A change in the cell phenotype, called metaplasia; reversible if stress is removed.
• The reversal allows the cell to recover it's normal function
• Abnormal damaging agents or intrinsic abnormalities can also cause this
• Adaptation is a response to both physiologic and pathological stimuli while maintaining steady homeostasis.
• Adaptive responses can be an increase in size, functional activity, cell number; or it can be a decrease in size and activity.

Causes of Injury

• Injury causes mechanical trauma from vehicular accidents, or subtle cellular abnormalities that lack an enzyme
• Injuries include oxygen deprivation called hypoxia
• Results: Lead to adaptation, cell injury, and then cell death
• Hypoxia causes a deficiency in oxygen, which results in reduction of aerobic oxidative respiration, which ends with cell injury and death
• Factors that contribute include reduced oxygen source, inadequate oxygenation, and decreased carrying capacity due to different disorders

Physical, Chemical, and Genetic Agents

• Physical agents also cause cellular injury through temperature extremes, heatstroke, sunlight and trauma.
• Physical:
  • Mechanical accidents
  • Electric shock
  • Atmospheric imbalances
• Chemical:
• Simple chemicals
• Toxins
• Electrolytes
• Pollutants.
• Genetic:
  • Mutations
  • disorders

Nutritional Factors That Effect Cellular Injury

• It's possible for injury to occur when there's to many or two little nutrients
• Enzyme defects play a role

Reversible Injury

• Reversible cell injury is commonly seen in early stages of injury and when there is only mild damage
• Cells can return to normal if damaging stimulus is removed through reduced oxidative phosphorylation, increased fluids in the cell or change in ion concentration
• Reversible Injures is characterized by swelling of the cell and it's organelles through blebbing.

Fatty Changes

• Occurs due to damage such as to much of one substance, or not enough, also toxic or metabolic imbalances
• Manifests in the cytoplasm and seen often in cells related to fat metabolism
• Can commonly effect liver, kidney and heart

Cell Death

• Cell ceases death due to damage
• Happens to the membrane and homeostasis ends causing the death of cells through necrosis

Apoptosis

• Programmed cell death or when a cell dies and is triggered by other cells, can is beneficial to healing process
• Apoptois is a normal healthy system cells need to be removed

Necrosis

• Cell death is triggered by external/internal influence like trauma or disease which is always harmful.
• Is the unregulated or unnatural process of death.

Differences and Similarities to Necrosis and Apoptosis

• Necrosis is triggered from trauma, with the the damage done to outside of the cells.
• Apoptosis cell death takes place on the inside with shrinkage occurring
• Cells are fragmented in both but the fragmentation of the later process is smaller.
• Both result in death though.

Cellular Constituents

• Cellular enzymatic digestion in intact or not is always frequent
• Means of repair of unwanted cells.

Types of Necrosis:

• Coagulative

  • Preserved tissues after death

• Liquefactive

  • Rapid with digestion, or transformation

• Gangrenous

  • Massive or severe dead, often associated with bacteria

-Caseous

• Cheese like

-Fibrinoid - resembles like fiber

• Fat

  • Release of lipase

• Avascular

  • Loss of blood supply

Pathology studies diseases by examining structural and functional changes in cells, tissues, and organs at the molecular level. Key aspects include etiology, pathogenesis, morphologic changes, and clinical significance. Pathologists interpret disease-related changes in the body.