ANAT241 Lecture 9 - Epithelial Tissue and Defects in the Regulation of Cell Divisions Flashcards
what plays a crucial role in tissue renewal and repair?
stem cells
are different tissue types renewed at the same rate?
different tissues are renewed at different rates and pattern of turnover
what is the relationship between mature skeletal muscle cells + mature neurons and whole cell turnover?
mature skeletal muscle cells and mature neurons largely do not turn over whole cells
what are the 2 causative factors for tissue renewal?
friction and environmental changes
what are the 3 general properties of stem cells regardless of source?
- capable of dividing and renewing themselves for long periods
- they are unspecialised
- can give rise to specialised cell types
what are adult stem cells?
somatic stem cells that are undifferentiated cells found amongst differential cells in tissues/organs
what is multipotent?
adult stem cells that can renew itself and differentiate into major cell types
what is the 2 primary roles of living tissues?
maintenance and repair
what are embryonic stem cells?
defined by their origin of inner cell mass of a blastocyst, they are pluripotent
what is pluripotent?
a stem cell that can differentiate into all cell types in the body
where are skin stem cells found?
found in the bulge under the sebaceous gland
where can skin stem cells translocate to?
can translocate to the basal layer of the epidermis
what do stem cell populations other than skin stem cells contribute to?
contribute to hair growth
what is the turnover timeframe of the epidermis?
approx. 2 months
where are epithelial stem cells in the digestive tract found?
epithelial cells lining the digestive tract occur in deep cysts and give rise to several cell types
what do epithelial cells lining the digestive tract give rise to?
give rise to several cell types such as absorptive cells, goblet cells, paneth cells and enteroendocrine cells
what is the turnover timeframe of intestinal cells?
approx. every few days
what is the chain of events that occurs because of a change in cellular environment to cells that cannot adapt?
if a change occurs in a cellular environment and the cell cannot adapt because the stimulus is severe/lethal. This results in cell injury or death and requires tissue renewal or repair
what is the chain of events that occurs because of a change in cellular environment to cells that can adapt to the change?
if a change occurs in a cellular environment and the cell can adapt then this results in a change in the growth pattern (this is a reversible change if required). This results in either hyperplasia + hypertrophy, tissue atrophy + cell atrophy or metaplasia
what is a cells response to environmental changes dependant on?
dependant on the nature of the stimulus
what are the 3 ways tolerable environmental changes alter the pattern of cell growth?
altered cell size
altered cell division
altered cell differentiation
when does altered cell growth occur?
when there is a high concentration of growth factors/ expression of growth factor receptors
what is hyperplasia?
the increase in the size of tissues/organs by the increased reproduction rate of cells
what is hypertrophy?
the increase in the size of tissues/organs by the increase of cell size
what is the relationship between hyperplasia + hypertrophy and tissue atrophy?
both hyperplasia and hypertrophy are reversible via tissue atrophy
what is tissue atrophy?
the decrease in cell number/size
what is an example of a physiological adaptation of hyperplasia and hypertrophy?
breast epithelial cell increasing in size and number during pregnancy from endocrine stimulation
what is an example of a pathological adaptation of hyperplasia and hypertrophy?
endometrial cells increasing in number under abnormal endocrine stimulation resulting in a tumour
when does metaplasia occur?
occurs when one mature, fully differentiated cell type adopts a totally different fully differentiated cell type
what does cell morphology change in response to?
changes in response to the cellular environment
how does cell morphology provide an adaptive response?
provides an adaptive response as the cell changes to be better equipped to withstand new environments
where is metaplasia common?
common in epithelial tissue
what is dysplasia?
the presence of abnormal cells from an increased rate of cell division coupled with complete maturation of immature cells
what is neoplasia?
uncontrolled growth of cells
when does a neoplasm occur?
occurs from the poorly regulated cell division in which masses of cells form
when does cellular proliferation and growth occur?
occurs in the absense of any continuing external stimulus
when does hyperplasia cease?
the abnormal proliferation of cells will cease with the removal of the stimulus
why do neoplastic cells commonly fail to achieve a highly differentiated state?
because of the failure of mechanisms controlling cellular proliferation and maturation
what is the relationship between genetic material changes and the neoplasm?
changes in the genetic material are transmitted to each new generation of cells within the neoplasm
what is the events of neoplastic formation?
starts with a stimulus causing genetic alteration to a cell. This alters genes for growth factors + receptors, signal transduction, transcription regulation, DNA repair and cell survival. The transformed cell proliferates with poor regulation of growth as a result of genetic changes and develops additional mutations
what is an example of metaplasia?
barretts oesophagus
what is barrett’s oesophagus?
metaplasia (when one mature, fully differentiated cell adopts a totally different fully differentiated cell type) transforms the oesophageal lining that is normally squamous epithelium to columnar cells with goblet cells that replace the squamous epithelium. The columnar cells with goblet cells are supposed to be intestinal epithelium not oesophageal epithelium
what is an example of dysplasia?
repeated sunburn/sun exposure on the epidermis of the skin
how does repeated sunburn/sun exposure cause dysplasia?
dysplasia (the presence of abnormal cells from an increased rate of cell division coupled with complete maturation of immature cells) occurs as sunburn does not allow the skin cells to properly differentiate and mature as they move through the layers. They move too fast through the layers creating nuclei to be present in the keratin layer where they should not be present
what is an example of dysplasia and neoplasia combined?
when dysplasia and neoplasia occurs in the cervix
what occurs when there is dysplasia and neoplasia in the cervix?
normal epithelial layers in the cervix show differentiation of cells from the basal layer to the vagina. Cervical dysplasia can occur with an increased number of the more basal, nucleated cells reaching the vagina. There is a spectrum of neoplastic progression with the stratified layer losing all of its differentation
what are the cellular events required for metastasis?
begins with detachment from the main neoplasm. The neoplastic cell breaks through the basement membrane and connective tissue and uses motility to enter a passage for movement
e.g through the blood and this allows for another tissue type to be entered
what is invasion of tumours?
invasion is when a malignant tumour grows into and at the expense of the surrounding tissue
what are the 3 characterisitics of tumours?
lacks differentiation
erratic growth
locally invasive
what is a primary tumour?
the main neoplasm
what is a secondary tumour?
a detached neoplastic mass which is not in contact with the primary neoplasm
what is metastasis?
a secondary tumour which has spread by metastasis
what are the 4 routes tumours use to spread?
local invasion
trans-coelomic spread
lymphatic spread
blood borne spread
what is the local invasion route of tumour spread?
where the tumour extends into the surrounding tissue
what is the trans-coelomic route of tumour spread?
tumour migrates along the peritoneal and pleural spaces
what is the lymphatic spread route of tumour spread?
tumour spreads through lymphatic vessels
what is the blood borne spread route of tumour spread?
tumour that enters the blood circulation
what is the difference between metastatic cells and tumour cells?
metastatic cells have special cell-surface properties not shared by most other tumour cells . They are less adhesive that other cells to break free from tumour masses and must be able to penetrate numerous barriers such as the ECM of surrounding connective tissues, basement membranes that line blood vessels etc
