Lecture 10 Flashcards
What is the protein best associated with waterproofing of the skin?
Claudin - 1
What is the protein best associated with magnesium reabsorbtion in the kidney ?
Claudin-16
What is the protein best associated with gap junction channels?
Connexins
Stem cells play a crucial role in tissue ______ and ______
Renewal and repair
Are tissues renewed at different rates?
Yes
Is there a variation in rate and pattern turnover?
Yes
Cells in epithelial tissues have _____ regenerative capacity
High
With adequate nutrition canrepleace cells ____ by ____ _____
Lost
Cell division
Why do we need different rates of regeneration in different areas?
Some area will need regeneration more then others - some get damaged more
Causative factors of tissue renewal
Friction
Envisronmaental factors (sunburn)
What kindas of cells repair damages tissue?
Stem cells?
3 general properties of stem cells
- capable of dividing and renewing themselves for long periods
- unspecialised
- can give rise to specialised cell types
4 main stem cell types
- cord blood stem cells
- adult stem cells
- emnryonic stem cells
- bone marrow
Adult stem cells features
- undifferentiated cell sound amoungst differentiated cells in tissue/organ
- can renew itself and can differentiate to major cell types of tissue/organ (multipotent)
- primary roles of adult stem cells in living tissue is maintancece and repair
Embryonic stem cells features
- defined by origin - inner cell mass of blastocyst
- can become all types of cells in body (pluripotent)
Multipotent definition
Able to generate many types of cells within a restricted tissue family (adult stem cells)
Pluripotent definition
Able to generate all tissue types (embryonic stem cells)
Induced pluripotent stem cells
Induced expression of four genes within a cell to create this reversal to a stem cell
Where are skin stem cells found and where can they translocate to?
- skin stem cells are found in a bulge under sebaceous glands
- can translocate to basal layer of epidermis
- epidermis turnover ~2 months
Where are epithelial stem cells lining the digestive tract found? What cell types to they give rise to?
- epithelial stem cells lining digestive tract occur in deep crypts and give rise to several cell types:
- absrobativce cells, goblet cells, planets cells, enteroendocrine cells
- intestine cell turn over~few days
What does having homeostatic mechanisms mean?
Cells are capable of adapting to changes in their environment
2 situations homeostatic mechanisms account for
Physiological conditions: to adapt to normal changes
Pathological conditions: to limit damage in response to disease processes
When there is a change in cellular environment two things can happen:
- the change in growth pattern is usually reversable if you remove the stimulus
Hyperplasia
Increase in size of tissue/organ by increased cell reproduction rate
Hypertrophy
- increase in size of tissue/organ by increase of cell size
Tissue/cell atrophy
- decrease in size
Metaplasia
- reversible transition of one cell type to another
Dysplasia
- presence of abnormal types of cells
Neoplasia
- new, uncontrolled growth of cells
How a cell responds to an evironmantal change is dependednt on…
… nature of stimulus
A TOLERABLE environmental change =
Alter pattern of growth in 3 ways:
- cell size
- cell division
- cell differentiation
Often these changes can occur in response to normal physiological/endocrine responses over life
E.g concentaison of growth factors/expression of growth factor receptors = altered cell growth
Is hyperplasia and hypertrophic revesible?
Yes,
Revesible via tissue atrophy (decrease in cell number/size) and cell atrophy (decrease in cell size)
What do you call atrophy due to physiological events ?
Involution
Physiological adaptation of breast epithelial cells in terms of hyperplasia and hypertrophy
Breast epithelial cells increase in size and number during pregnancy under endocrine stimulation
- will atrophy after finished breast feeding
Pathological adaption of endometrial cells in terms of hyperplasia and hypertophy
- endometrial cells increase in number under abnormal endocrine stimulation from oestrogen-secreting ovarian tumor
Features of metaplasia - ALL THE PLASIAS WILL BE IN EXAM
- one mature, fully differentiated cell type adopts a totally different full differentiated cell type
- morphology changed in response to cellular environment
- adaptive response - cells betweer equipped to withstand new environment
- common in epithelial cells
Examples of metaplasia
Mataplasia: Barrett’s oesophagus
- metaplastic transformation of the eosophageal lining
- squamous epithelium typical of normal oesophagous
- columnar cells with goblet cells - typical of intestinal type epithelium - appear in its place (mucus good for protection)
Features and example of dysplasia
- presence of abnormal cells
- increased rate of cell division coupled with incomplete maturairton of immature cells
E.g
- epidermis of sun-exposed skin
- squamous epithelium at columnar junction of cervix
Dysplasia effects on skin
Normal skin:
- stratified squamous epithelium
- keratin layer
Dysplastic skin:
- caused by sun exposure
- loss of maturation
- lucked present in keratin layer
Cerival dysplasia and neoplasia
- normal epithelial layers in the cervix show differentiation of cells from the basal layer of the vagina
- cervical dysplasia can occur when an increases number of the more basal, nucleated cells are reaching the vagina
- there is a separation of the progression, with the stratified layer losing its differentiation (becoming neoplastic)
The neoplastic state
- poorly regulated cell division in which mass of cells form = neoplasm
- cellular proliferation and growth occur in absence of any continuing external stimulus
- contrasts with hyperplasia - where abnormal proliferation of cells ceases on removal of stimulus
- thus contrasts with hyperplasia - where abnormal proliferation of cells ceases on removal of stimulus
- neoplastic cells exhibit various states of differentiation and commonly fail to achieve highly differentiated state
- failure of mechanisms controlling cellular proliferation and growth
- changes in the genetic material are transmitted to each new generation of cells within the neoplasm
How does the neoplastic state contrast with hyperplasia
In hyperplasia abnormal proliferation of cells ceases on removal of stimulus
Events in neoplastic formation
Events in neoplastic formation - cervical cancer
Tuomors of epithelial origin
Features of benign tumors
- well defined - similar structure to tissue of origin
- progress slowly
Features of malignant tumor
- can lack differentiation
- erratic growth
- locally invasive
- metastatic
Progression of dysplasia to neoplasia
Cellular events needed for metastasis
- detachment from the main neoplasm
- breaking through the basement membrane and connective tissue
- motility
- enter passage for movement
- enter another tissue type
4 main routes of how tumors spread
- local
- trans-coelomic
- peritoneal
- pleural
- lymphatic
- blood borne
Adaptions specific to metastatic cells
- have special cell-surface properties not shared by most other cells in the tumor
- must be less adhesive than other cells to break free of tumor mass
- must be able to penetrate numerous barriers
- ECM of surrounding connective tissues, basement membranes that line blood vessels etc
- must be able to invade normal tissues if they are to form secondary colonies
