different junctions starting from the topmost type
- zonula occludens
- zonula adherens
- macula adherens (desmosomes)
- gap junction
- hemidesmosomes
what makes up the zonula Occludens?
membrane proteins: Occludins and claudin, which comme together to make homo-dimers that hold the cells together
cytoplasmic proteins: ZO-1, actin
what is another name for zonula occludens?
tight junctions
what makes up Zonula Adherens?
membrane proteins: Cadherins
cytoplasmic: a-actinin, vinculin, actin
what is the intercellular space between cells in zonula adherens?
15 nm
what is another name for macula adherens?
desmosomes
what makes up macula adherens?
intercellular space contains TM proteins Desmocollin and Desmoglein.
Plaque contains desmoplakins I and II, Plakoglobin, and desmocalmin
Intermediate filaments: keratin (no polarity)
what is the intercellular space between cells attached via macula adherens?
25 nm
what makes up hemidesmosomes?
plaque: BP 200
TM proteins: integrins (a6b4) and BP 180
intermediate filaments: tonofilaments
what makes up gap junctions?
6 connexins, which make a connexon, attaches to another connexon from the other cell to make a channel that is 1.5 nm in diameter
intercellular space between gap junction?
2 nm
when talking about stem cells, what does steady state mean?
of newly originated cells by the stem cell are equal to the # of dead cells on the surface of the epithelium
what is turnover time?
the time required to change the whole population of epithelial cells
what is the turnover time of skin
30 days
what is radioautography and how does it work?
- provides a means to study the turnover of epithelial cells and of other cell types
- works by adding radiated Thymidine (H3-T), then using photographic development which will allow us to see a black dot where the DNA is radioactive
what is the purpose of cell division?
During embryogenesis and postnatal development, for growth.
During adulthood, to maintain tissue.
what are the 3 ways cells/tissues behave in adulthood?
static (e.g. neurons and skeletal muscle)
Expanding (e.g. liver)
Renewing (e.g. epidermis)
how many chromosomes (and pairs) do humans have?
23 pairs, so 46 total
what are the phases of the cell cycle? how long is each?
G1: presynthesis of DNA; 25 hours – 2n
S: synthesis of DNA; 8 hours
G2: post DNA duplication; 3 hours – 4n
Mitosis: 2.5 hours – 2n
what are the stages of mitosis?
- preprophase: intranuclear condensation of chromosomes
- prophase: visualization of chromosomes and mitotic spindle
- metaphase: chromosomes in equatorial plane and loss of nuclear envelope/nucleolus
- early anaphase: longitudinal splitting of chromosomes
- late anaphase: migration of chromosomes to the poles
- telophase: nuclear restitution, nuclear envelop and nucleolus formation
