Neoplasia Flashcards
Define Atrophy, Aplasia and hypoplasia
Atrophy: The lack of nourishment
Aplasia: lack of development
Hypoplasia: No development
Is atrophy always Pathological? If not give an example
Atrophy is not always pathological, it can happen in the natural development of the thymus which atrophies as children begin to grow. The process is known as THYMUS INVOLUTION.
Discuss the differences between Aplasia and Hypoplasia
Differences between Aplasia and hypoplasia
In Aplasia, the precursor cells are completely absent
In Hypoplasia, some precursor cells are present but not enough
In aplasia, the Organ never forms such as in people with digeorge syndrome where the thymus never forms, leaving people with a severely impaired immune system.
Hypoplasia is more common and results in less severe side effects, it usually leads to misshapen or smaller organs.
What happens in Metaplasia
In METAPLASIA, a mature and differentiated cell type is replaced by another mature and differentiated cell type. This happens due to environmental stressors, for example going from breathing fresh air to smoking cigarettes. This causes the columnar epithelial cells to differentiate into squamous epithelial cells better suited to deal with the cigarette smoke.
Give another example of metaplasia
example is the esophagus walls which are lined with non keratinizing squamous epithelial cells however in people with acid reflux, acid constantly finds its way up the esophagus damaging the walls. The cells replicate and differentiate into non ciliated columnar mucosin producing epithelial cells. This condition is known as BARRETT’S ESOPHAGUS.
This is usually reversible unless the acid reflux goes untreated for too long and the cells become dysplastic.
explain Dysplasia and what happens in it
In Dysplasia, the cells usually develop a weird shape as well as there being a high number of immature cells.
There are 4 MAJOR pathological changes in dysplasia
Pleomorphism: The cells are of uneven size
Nuclear pleomorphism: Different shapes and sizes of nuclei
Hyperchromatism: Darkly stained nuclei due to increase of chromatin
Increased number of cells with mitotic figures indicating high number of cells undergoing mitosis.
How does atrophy happen
Atrophy, starts with a decrease in nerve or hormonal supply, then there is the ubiquitin proteasome pathway, whereby the cells which are getting less nourishment are tagged with ubiquitin which schedules them for demolition. The ubiquitin proteins bind together in a process known as poly ubiquitination and then a proteasome comes in to destroy all the poly ubiquitinated filaments leading to a decrease in cell size. Organelles can also be ubiquitinated and when this happens, the ubiquitinated cell is trapped in a vesicle, and another vesicle containing lysosomes binds to it releasing the lysosomes to destroy the ubiquitinated organelle.
An example is muscle atrophy which can occur from long disuse of muscles but it can be reversed with exercise.
However in cases such as CACHEXIA also known as whole body wasting syndrome, it is irreversible and is commonly found in people with AIDS or cancer.
Define Hyperplasia and Hypertrophy
HYPERPLASIA is when the cells of a tissue or organ increase in number
HYPERTROPHY is when they increase in size.
Explain the difference between physiological and disease processes that lead to hypertrophy
An example of physiological is heavy lifting, which causes the muscles to grow bigger in order to adapt to the heavy loads
An example of pathological hypertrophy is when the heart increases in size to deal with high blood pressures and hypertension
What kind of organs undergo Hyperplasia
Hyperplasia can only happen in organs with stem cells that can differentiate and mature, like cells in the intestines.
Explain the 2 types of hyperplasia
Compensatory: which happens in organs that regenerate such as the skin, liver, bone marrow and lining of the intestines.
Hormonal: happens in organs regulates by hormones like endocrine and reproductive organs
Give a physiological example of hyperplasia
A physiological example is the increase in breast size of women during pregnancy. To prepare for breastfeeding, Prolactin, progesterone and human placental lactogen stimulate the growth of glandular tissue in the breasts.
Give a pathological example of hyperplasia
A pathological example could be excessive hormonal stimulation, for example, the endometrium during the menstrual cycle, grows and proliferates when exposed to estrogen , however an excess in production of estrogen could lead in overgrowth of the endometrium
