Moss - Tissues and Stem Cells Flashcards
what happened to cells due to the evolution of multicellularity?
cells in the human body have lost the capacity for independent survival, rather they are members of a cohesive and integrated organism
how many cells are there in the human body?
more than 1014
how many distinct varieties of cells are there in the adult human body?
~210, not including subtle differences
what do all cell varieties have?
the same genome
how can similar-looking undifferentiated cells give rise to very different adult organisms?
through development
what cells divide and differentiate into mature cells found in tissues and organs?
stem cells and progenitor cells
what are the three main factors that contribute to the stability of tissue organization?
cell-to-cell communication
selective cell adhesion
molecular cell memory
what contribution does cell-to-cell communication give to the stability of tissue organization?
direct contact and diffusible signals will influence the survival, proliferation, and behavior of cells
what is an example of cell-to-cell communication in tissue stability/organization
tissue growth can induce the formation of blood vessels; nerves die if they don’t find a cell to innervate
what contribution does selective cell adhesion give to the stability of tissue organization?
cells form selective attachment to other cells or to the basement membrane or ECM
loss of attachments can change their cell behavior
what kind of binding do cadherins and other cell adhesion molecules use?
cadherins and other cell adhesion molecules follow certain molecular rules, such as homophilic binding
what contribution does molecular cell memory give to the stability of tissue organization?
gene expression patterns established during development are stabilized, thus maintaining cell identity throughout life
even as cells proliferate and generate new cells, they pass on the inherited pattern to their cellular progeny
in what way would skin be classified?
as a stratified squamous epithelium
what happens to cells in the epithelium?
the basal cell layer is attached to the basal lamina
as cells begin to die they detach from the basal lamina, move up through the different layers until it reaches the surface and flakes off
what are the different layers found in the epithelium (from top to bottom)?
Squame about to flake off
keratinized squames
granular cell layer
prickle cell layer
basal cell layer
basal lamina
connective tissue of dermis
what skin layers are keratinocytes?
basal cell layer
prickle cell layers
granular cell layer
keratinized squames
how would the cell layers in the intestine be classified?
simple columnar epithelium
TRUE or FALSE: Progenitor cells have limited capacity to divide
TRUE
TRUE or FALSE: Stem cells have a lifetime capacity to divide as long as they are in the stem cell niche
TRUE
In the lumen of the gut, how do cells develop?
cells move up from the bottom as they develop from dividing stem cells
once stem cells divide, they become dividing precursor cells
once they reach the top of the crypt, they become nondividing terminally differentiated cells
in the case of the gut lumen, absorptive cells and secretory cells
what do all self-renewing tissues have?
stem cells
what are stem cells?
multi- or pluripotent (maybe totipotent)
practically unlimited division potential
daughters either remain stem cells or become committed to differentiation
what is multipotent?
many cell types
what is pluripotent?
all cell types of the body
what is totipotent?
all cell types, plus extraembryonic tissues
what are the three ways stem cells may divide?
symmetrically
asymmetrically
symmetrically with commitment
why are stem cell divisions slow?
to preserve the genome
what is symmetric division of stem cells without commitment?
stem cells divide and their daughters remain stem cells
what is asymmetric stem cell division?
stem cells divide
one daughter remains a stem cell
the other daughter cell differentiates and divides until it is terminally differentiated
what is symmetrical stem cell division with commitment?
stem cells divide and their daughter cells both commit to differentiation
what creates the stem cell niche?
paneth cells
what surrounds the outside of the crypt?
the basement membrane
what maintains stem cell identity?
Wnt signaling from Paneth cells, and other signals from nearby tissues
what does the Wnt pathway do in the crypt?
it maintains the proliferation zone
What does Wnt signaling do in the crypt?
it helps define the stem cells of the intestinal crypt
what happens without the Wnt signal?
Wnt-responsive genes are off
what happens when the Wnt signal is on?
transcription of Wnt-responsive genes, leading to proliferation of gut stem cells
what kind of pathway is the Wnt pathway?
a signal transduction pathway
what are the two types of non-dividing, differentiated intestinal cells?
absorptive cell
secretory sell (goblet cell)
what does the adsorptive cell in the intestines do?
uses cilia to take in nutrients from the gut
what does the secretory (goblet) cell do in the intestine?
secretes mucous
where are specialized cells derived from?
multipotent stem cells
different numbers of each are produced
how do stem cells divide? what do they produce?
they divide slowly and give rise to rapidly-dividing cells (committed precursor cells or transit-amplifying cells) that are fated to differentiate
what are the rapidly dividing cells that stem cells give rise to?
committed precursor cells
or transit-amplifying cells
TRUE or False: Differentiated cells do not divide
TRUE
what do the differentiated cells do?
they move away from the stem cells
in the intestine, where do the cells of the villus move?
up
in the intestine, where do the differentiated cells of the crypt (Paneth cells) move?
down
what eventually happens to all differentiated cells?
they die via apoptosis and are phagocytosed
how are stem cells and tissues maintained?
- specialized cell types derive from multipotent stem cells
- Different numbers of each type are produced
- stem cells divide slowly and give rise to rapidly-dividing cells (committed precursor cells or transit-amplifying cells) that are fated to differentiate.
- Differentiated cells don’t divide
- The differentiating cells move away from the stem cells.
- cells of the villus move up
- Paneth cells of the crypt move down
- All differentiated cells eventually die via apoptosis and are phagocytosed
what type of stem cell are blood cells derived from?
hematopoietic stem cells
what are the types of blood cells?
- erythrocytes (RBCs)
- leukocytes (WBCs)
- granulocytes
- neutrophils
- eosinophils
- basophils
- lymphocytes
- monocytes
- granulocytes
- platelets (fragments of megakaryocytes)
- osteoclasts
what do granulocytes contain?
many lysosomes and secretory vesicles
what can happen to monocytes?
they can become macrophages
how much blood do people have?
about 5 liters
what is different about the development of blood cells from stem cells vs. other cells?
lineage commitment occurs in steps in blood cells
precursors continue to divide
they are essentially transit amplifying cells
how are embryonic stem (ES) cells made?
cells of the inner cell mass of the blastocyst ae used to make ES cells
what are embryonic stem (ES) cells?
pluripotent or totipotent cells that can be cultured indefinitely
created from inner cell mass of blastocyst or derived from unused human IVF embryos
what do invitro differentiation protocols require?
knowing and administering the specific factors and culture conditions to produce different cell types
what can aggregates of pluripotent cells form?
organoids
what are organoids?
small organ-like structures, like and eye-like structure
formed from aggregates of pluripotent cells
may not be functional but have parts of functional cells
how is a cell reprogrammed/cloned?
somatic cell nuclear transfer (SCNT)
highly variable technique and many attempts are needed for one success
what is required for cloning?
extensive epigenetic reprogramming of differentiated cells
a process that is inefficient and inexact
what is a potential use for SCNT?
to make personalized “ES” cells
where do human ESCs come from?
from embryos from IVF
in what ways besides IVF can ES-like cells be obtained?
Somatic Cell Nuclear Transfer (SCNT)
Co-transfection of a a cocktail of three or four master regulatory factors into a differentiated cell to create an iPS cell
how can SCNT create ES-like stem cells?
the nucleus of a patient’s cell is transferred to the cytoplasm of an ES or ES-like cell
what is an iPS cell?
created when a cocktail of three or four factors are placed into a differentiated cell
the factors becomes expressed in fibroblasts
and the cells revert to an ES-like state
what are the most commonly used regulatory factors to create iPS cells?
Oct¾, Sox2, Myc, Klf4
Oct¾, Sox 2, Nanog, Lin28
why are iPS cells so useful?
they can be derived from an individual’s own fibroblasts with minimal invasiveness
they offer a solution to the immune rejection problem, and provide material for studying patient-specific disease mechanisms
what diseases are within reach of cures when stem cell engineering is achieved?
muscular dystrophy
Parkinson’s disease
Type I diabetes
Heart Attack
Neurodegenerative diseases
Spinal cord Injury, etc.