Cellular adaptation, tissue regeneration, disordered growth and tumours Flashcards
cellular adaptation
cells changing in some way to become better suited to new environments or conditions
main methods of cellular adaptation
hyperplasia, hypertrophy, atrophy and metaplasia
Hyperplasia
Increase in the number of cells in an organ or tissue resulting in increased volume
Mechanisms of hyperplasia
increased production and expression of growth factors which are excitatory agonists for signalling pathways that activate transcription factors to increase gene expression and hence cell proliferation
Hypertrophy
An increase in the size of cells due to more structural components, resulting in an increase in the size of the organ
causes of hypertrophy
increased functional demand (exercise) or hormonal stimulation (angiotensin, noradrenaline, insulin-like growth factor)
Atrophy
the shrinkage (reduced size) of an organ or tissue from a decrease in cell size and number due to apoptosis
Causes of Atrophy
decreased workload (restriction, bed rest, astronauts in space), loss of innervation (nerve damage), diminished blood supply, lack of nutrition or endocrine stimulation
Healing responses after injury
regeneration (same function), scar formation and fibrosis (loss of function) by the deposition of collagen
what does regeneration and repair depend on?
The ability of the tissue to regenerate, The extent of the injury
terminally differentiated
cells
Differentiated cells incapable of replication
Stem cells
self-renewing cells that are capable of differentiating into a range of cell types
stem cell generation from fertilisation
zygote - divides to form blastocysts. inner cell mass, full of embryonic stem cells, generates the embryo
totipotent
differentiates into any cell type and can proliferate indefinitely
Induced pluripotent stem cells
Differentiated cells of adult tissues can be
reprogrammed to become pluripotent
Impact of stem cell research on
Biology and Medicine
regenerate damaged organs - important to avoid rejection from donors. models for human diseases on knockout mice
Metaplasia
A reversible change in which one adult cell type is replaced by another
Dysplasia
disordered growth - architecture of the tissue may be disordered
Characteristics of dysplasia
Loss in the uniformity and orientation. pleomorphism (strange nuclear size/shape) e.g. hyperchromatic nuclei that are abnormally large. mitotic figures in abnormal locations (not in basal layers)
Anaplasia
Lack of differentiation - marker of malignancy
Morphological changes of
anaplasia
Pleomorphism, Abundance of DNA, Mitoses, Loss of polarity
Neoplasia
process of new growth
tumour
abnormal mass of tissue
Histogenetic classification of tumours
based on cell origin
benign epithelial tumours
papillomas or adenomas
Benign connective tissue tumours
prefix denotes cell of origin
Malignant epithelial tumours
carcinomas
Malignant connective tissue tumours
sarcomas
benign tumours
slow growth rate, regular edges, resemble parent tissue, capsulated by fibrous tissue - readily palpable and early movable surgically
Malignant tumours
rapid growth rate, irregular edges, metastasised, Variable histological resemblance to the parent tissue
Metastases
tumour implants discontinuous with the primary tumour
Pathways of metastasis
direct seeding, lymphatic spread, haematogenous spread and implantation after operations
what are the four classes of regulatory genes that are the principal targets of genetic damage
The growth promoting oncogenes (more cells), The growth inhibiting tumour suppressor genes (less preventing growth), Genes that regulate programmed cell death (less cells killed off), Genes involved in DNA repair (less correction of damaged cells)
