Pathology is the study of the causes and effects of a disease/injury. The word pathology also refers
to the study of the disease in general, incorporating a wide range of biology research fields and
medical practices. However, when used in the context of modern medical treatment, the term is
often referred to the diagnosis of diseases, mostly through analysis of organs, tissues, cells and body
fluids.
- Disease: any abnormality that causes lose of health (‘ill health’). it is characterized by a
specific set of features (signs, symptoms, functional and morphological manifestations) that
are not normal.
a. Normal: normal is the most frequent state in a population defined by age distribution,
gender etc.
Pathology is part of the disease’s systematic description; pathology has to do with epidemiology,
causes, pathogenesis, clinical signs and symptoms, morphological, complications and sequelae,
prognosis and mortality.
We use technical terminology because for technical terms, there is only one definition.
a. Prefixes (hyper-, meta-, hypo-, etc) are the beginning parts of a word such as hypertrophia.
Hyper means ‘increased’ and hypo means ‘decreased’. Meta means ‘similar to’
b. Suffixes (-itis, -oma, -oid, etc) are words that are put at the end such as blastoma.
c. Eponyms: when a disease is given the name of the person that for example carries the
disease.
Pathologists take care for the diagnosis from the operation room. For example, a little piece of tissue
is gathered from the surgeon and this piece of tissue that may contain a tumor, is processed by
pathologists under the microscope so that the diagnosis can be made. This costs a lot of work, there
are about 40000 diagnosis/year. Nowadays, we obtain as much information as possible from cells
and tissues (molecular diagnostics). Looking at the tissue under the microscope is not enough to
make a diagnosis; you need to correlate it with the norm of the pathogenic mutation.
- Autoptic pathology: making a diagnosis of the whole body. You not only observe how the
diseased tissue looks, but you also obtain knowledge of the disease mechanisms and you
figure out the effects of the disease treatments which cannot be determined by a biopsies or
CT scan for example. It means providing researchers with tissue of rare disorder.
Another important task of pathologists is to register the tissue that arrives at the department,
because you obviously don’t want to mix the tissue of Sam with the tissue of Noor. After this
registration, specimen grossing takes place in the cutting room (the tissue is dissected/cut). Then,
these little pieces of tissues (specimen selection) are embedded in cassettes that contain paraffin.
Parafilm is a substance that makes the tissue hard so that the tissue can be cut in very thin sections
(3-5 m thick tissue sections).
Tissue processing: fixation (formalin) → dehydration → embedding → paraffin blocks → cutting →
slides → H&E stain (the immutoxilin staining binds to the DNA so it shows the nuclei but also to the
proteins )
The next step is the evaluation by residents and pathology by specialists that make the diagnosis. For
the pathologic diagnosis, these are the source of relevant information:
- Diagnosis: benign vs malignant, type of tumor?
- Prognosis: Radicality and TNM classification?
- Prediction: response to treatment?
,A prognosis refers to how a current condition could be expected to affects someone’s health in the
future. Diagnosis refers to a condition in the present, informed by observation of current symptoms.
In other words, a prognosis is a prediction.
Chapter 2: cell- and tissue adaptation, & damage
What is a disease? → HeLa cells (derived from a cervical cancer) and Nicolo Paganini (Marfan’s
syndrome). Remember that a disease is not always a disadvantage but it is in fact an abnormality.
- A disease is a dysfunction of an organ or tissue, because of damage to the cells.
- The damage can be of many causes, chemical, thermal, radiation, DNA damage, micro
bacterial etc.
- The damaging agent is the etiology,
the influence and the changes in
cellular processes reflect the
pathogenesis (disease mechanisms).
The damage that is causes by this
etiology is called pathogenesis.
Example (radiation on DNA by the
sun): when one nucleotide base is
changed due to this mutation, it can
translate another amino acid and thereby to another protein. An example of such a disease is
called sickel cell anemia; the mutation changes your hemoglobin, this altered hemoglobin is
unattative to malaria and therefore people that have this disease often are not endangered
by malaria.
The etiology of cholera versus the
pathogenesis (biological
mechanisms that account for the
origin and development of a
disease) of diarrhea of cholera: the
infection of cholera is fairly
innocent however, the bacteria
can produce a toxin which
interferes with your fluid balance
and therefore causes massive
diarrhea. You will lose a massive
amount of fluid and if you don’t
replenish that fluid, you will die.
Rudolf Virchow was a professor that
determined that when something goes
wrong with a person, this error can be
tracked back to one of the cells. He laid the
foundation for everything in pathology.
Schwann and Schleiden determined that
different cells have different functions and
that when a cell dysfunctions, it can lead to
an error.
- Community: loads of cells that work
together form a community. A human has many different cells and therefore is a community
themselves as well. Example: Dictyostelium Discoideum; it is a social amoebe (multicellular
by choice organism) that survives periods of food shortage by organising itself in a
, multicellular aggregate so when they have harsh surviving times, they come together to work
together and survive. Every organism is multicellular but some are multicellular by choice
such as dictyostelium discoideum (the circumstances dictate that).
Multicellular organisms work together and form a niche in nature (forming a community) which has
pros and cons:
The pros are that you have a good way of organising cells that are working together (high
organisation) but when certain types of cells aggregate together (work together) they can become
attractive for bacteria and viruses:
- The internal milieu is optimised and thus also attractive for intruders. Effective defence is
required – infectious diseases. If you want to survive, an aggregate must have an effective
defence system to fight the intruder. An example of such an aggregate is our immune
system.
- Organisation and clear division of tasks is mandatory if you have this high organisation
including discipline of cells a.o. with regards to proliferation. We need proliferation but if the
wrong (mutated) cells are proliferated, it can lead to cancer so proliferation needs to take
place under close control– cancer.
Cell damage, stress and stressors:
1. Disease is caused by damage of (part of) a cell or group of cells - etiology.
2. The initial damage can cause further damage – pathogenesis.
3. The cell/organ reacts to minimize the impact of the damage – adaptation.
4. Damage can be reversible, lead to adaptation or, ultimately to death of cell – cell apoptosis.
Adaptation VS cell death
Above you see a normal heart
cell (myocyte). Adaptation: if
you increase the workload of
the heart by getting a higher
blood pressure for instance, a
higher resistance is created
and therefore a higher
workload for the heart cell (+
the heart can increase in size
which is called hypertrophy).
Hypertrophy is an adaption
for higher workload, if all the cells are exposed to this, they
all become bigger in size and thereby the heart itself
becomes bigger as well. If the stressor is permanent and
unable for the cell to bear, the cell will die (cell death) →
myocardial infarction. If a part of your heart dies, the other
functioning part will adapt (hypertrophy) to take over the
role of the dead part.
- Cell- and tissue adaption 1 → Hypertrophy: increase
in the size of cells, NO INCREASE in number of cells.
