Atrophy, hypertrophy, hyperplasia, metaplasia and dysplasia Flashcards
Under what conditions is hypertrophy the only adaptive option available
In permanent cells
How is DNA effected in permanent cells undergoing hypertrophy
Increase DNA content without undergoing mitosis (stop at G2)
Why is there an increase in cell population during hyperplasia
Because less cells are undergoing apoptosis
More mitosis
Where is hypertrophy commonly seen
Muscle tissues
Where is hyperplasia commonly seen
Bone marrow in individuals at high altitude environments
Breast tissue at puberty when responding to oestrogen
Define autonomous hyperplasias
Cells continue to proliferate rapidly despite no stimulus.
What can hyperplasia’s be confused with and why
Neoplasia - If the cells are monoclonal (a single clone from one cell), this is neoplasia NOT hyperplasia
How is psoriasis a type of hyperplasia
It is hyperplasia of the epidermis
Define angiogenesis
Process by which new blood vessels grow into damaged, ischaemic or necrotic tissues to supply oxygen for cells in repair
How are vascular endothelial cells activated during tissue repair
Growth factors such as VEGF released by macrophages
Describe the role of hyperplasia in tissue repair
- Activated endothelial cells migrate towards stimulus to form a sprout
- Cell migration facilitated by secretion of enzymes
- Adjacent sprouts connect to form vascular loops which canalise to produce blood flow
- Mesenchymal cells stabilise vascular architecture
- Extracellular matrix is remodelled
Role of myofibroblasts in hyperplasia tissue repair
Allow new blood vessels into damaged tissues
What happens to the new blood vessels once they access damaged tissues
Produce matrix proteins such as collagen to strengthen scar.
What happens to the myofibroblasts after they release collagen
They contract and differentiate to fibroblasts
What are two complications of scar contraction that takes place when the myofibroblasts -> fibroblasts
- Deformity and reduced movement of limbs
2. Detachment of the retina
Explain the role of hypertrophy in the heart
- To compensate for less cardiac muscle after an infarction (when it dies it is replaced by scar tissue), cells undergo hypertrophy
Where is hypertrophy in the heart most commonly seen
Right ventricle due to LV failure + pulmonary hypertension
Define atrophy
Decrease in size of an organ or cell by reduction in cell size of cell numbers
What process does atrophy often involve
Apoptosis
Why is atrophy important
To reduce requirement of oxygen and nutrition as the body has less of a need for that organ
How does function effect atrophy
Decreased function -> atrophy
E.g. skeletal muscles
How does innervation effect atrophy
Loss of innervation of muscle causes muscle atrophy
What are five factors that can stimulate atrophy
- Loss of blood
- Pressure atrophy (when tissues are compressed)
- Lack of nutrition
- Loss of endocrine stimulation
- Hormone-induced atrophy
Define hypoplasia
Failure of development of an organ - failure in morphogenesis
What process is hypoplasia often related to
Atrophy
Define metaplasia
The transformation of one type of differentiated cell into another fully differentiated cell type
(the daughter cells replace original cells)
When does metaplasia take place
- Alterations to the cellular environment (e.g. chronic cellular injury)
- Activation and repression of groups of genes involved with maintenance of cellular differentiation
Give examples of squamous metaplasia
- Ciliated respiratory epithelium -> squamous in trachea and bronchi of smokers
- Ducts of salivary glands and pancreas
What is Barrett’s oesophagus
Replacements of normal squamous epithelium in oesophagus by columnar glandular epithelium causes reflux of bile and acid into the oesophagus
What is a congenital disorder
Defects present at birth
When do abortions for kids with congenital disorders tend to happen
Between 6-8 weeks of pregnancy
Define agenesis (aplasia)
The failure of development of an organ
Define atresia
Failure of development of a lumen in a normally tubular epithelial structure
Define hypoplasia
Failure in the development of the normal size of an organ
Define dysplasia
imprecise term for the morphological changes seen in cells in the progression to becoming cancer
