Epithelial Tissue: junctional complexes and cell cycle Flashcards
name the order of junctions (top to bottom)
zonula occludens
zonula adherens
macula adherens
gap junctions
hemidesomosomes
describe zonula occludens
most apical
tight junctions
membrane proteins
cytoplasmic proteins
describe membrane proteins of zonula occludens
occludin
claudin
forms dimer on each side of plasma membrane
brings membrane together
describe cytoplasmic proteins of zonula occludens
ZO-1
actin
etc…
cytoplasmic proteins link to ZO-1 and it grabs onto actin filaments and forms tight junction
describe zonula adherens
intercellular space - 15nm
gap where transmembrane protein becomes dimer
describe cadherins of zonula adherens
form dimers with each other
links 2 cells
describe actin of zonula adherens
alpha actin
vinculin
these are cross linking proteins and make terminal web of actin
describe macula adherens
demosomes - in stratum spinosum
looks like hair pin
vert big and strong
name the components of macula adherens
desmoplakins I&II
plakoglobin and desmocalmin
intermediate filaments
intracellular space
transmembrane proteins
describe desmoplakins I&II
plakoglobin and desmocalmin of macula adherens
plakoglobin and desmocalmin = makes up plaque inside cell
grouping of proteins bind to pm
what are the 3 types of cytoskeleton
actin
intermediate filaments
microtubules
describe intermediate filaments of macula adherens
makes hair pin in plaque
gives rigidity to inside - hard to pull apart
describe intercellular space of macula adherens
25nm
thick because of the 2 transmembrane proteins
describe transmembrane proteins of macula adherens
desmocollin
desmoglein
form dimers and bind to each other
inside the desmoplakins make plaque and tonofilaments come in and adds to inside where plaque is
describe hemidemosomes
plaque contains BP 200
connects through basement membrane
transmembrane proteins
describe BP 200 (name)
related to bullous phemphigoid
autoimmune disease - body makes antibodies that make up plaque and some transmembrane proteins
disconnects tissue from BM = blisters
describe hemidesmosome plaque
plaque and intermediate filaments
tonofilaments come in and add rigidity to inside and plaque
name hemidesmosome transmembrane proteins
alpha 6 integrin
beta 4 integrin
BP 180
describe gap junctions
2 nm
small space
couple connexon
below zonula adherens
describe coupled connexons of gap junctions
connexon = 6 connexins
channel = 1.5 nm diameter
make tunnels between one cell and another - 6 connexins forms a barrel and matches with another
what does epithelial tissue have very little extracellular space
due to the many junctional complexes = ZO, ZA, desmosomes, hemidesmosomes and gap junctions
what can stem cells do
give rise to all other cells
divide to itself or differentiate to next cell type
describe steady state
number of newly originated cells by stem cells are equal to number of dead cells on surface of epithelium
describe turnover time
time required to change whole population pf epithelial cells - 30 days
describe radioautography
provides a means to study the turnover of epithelial cells and other types of cells
describe mouse and triniated thymidine experiment
take mouse and inject with triniated thymidine
gives dark spot on film - do time study and saw that thymidine came from stem cell layer
what is purpose of cell division
during embryogenesis and post natal development to produce growth
during adulthood - cells and tissues
describe (give ex of places) the 3 ways tissue behaves (cell division)
static - neurons and skeletal muscle
expanding - liver
renewing - epidermis and most epithelia
describe cell cycle (interphase and mitosis) and times
G1 - presynthesis of DNA - 25 hrs, 2n
S - synthesis of DNA - 8 hrs
G2 - post DNA duplication - 3hrs, 4n
mitosis - 2.5 hrs, 2n restored
how many chromosomes in humans
23 pairs of homologous chromosomes - 46 total
name the phases of mitosis
preprophase
prohase
metaphase
early anaphase
late anaphase
telophase
describe preprophase
intranuclear condensation of chromosomes
describe prophase
visualization of chromosomes and mitotic spindle
describe metaphase
chromosomes in equatorial plane
loss of nuclear envelope and nucleolus
describe early anaphase
longitudinal splitting of chromosomes
kinetochores move back
describe late anaphase
migration of chromosomes to poles
DNA moves back
describe telophase
nuclear restitution
nuclear envelope and nucleolar formation
end of cell division
what does dermis do
supports epidermis and binds to hypodermis
describe CT of dermis
2 sublayers = papillary and reticular layer
describe papillary layer of dermis
loose ct
slightly smaller
more cells less fibers
describe reticular layer of dermis
dense irregular ct
more fibers less cells
can you describe loose ct as irregular
no bc not enough fibers
what is difference between regular and irregular ct
regular is uniform
Irregular is no specific pattern
describe ct of hypodermis
loose ct - specialized
usually infiltrated with fat cells - adipocytes
more cells than fibers
what is function of connective tissue
carries nerves and blood vessels - innervation and blood supply to epidermis and other epithelial tissues
provides support and a connecting framework to other tissues of body
what is structural composition of ct
extracellular fibers + amorphous ground susbtance (proteoglycans and glycoproteins) = ECM
population of different types of cells (fibroblasts)
name and describe the varieties of ct
loose - papillary layer of dermis
dense = dense irregular (reticular layer of dermis) or regular (tendons)
supporting - cartilage and bone
special properties - hemopoietic bone marrow
name the 3 layers of embryos
ectoderm
mesoderm
endoderm
where does all ct come from
mesoderm layer = mesenchymal cells
which ate pluripotent stem cells and become all cells of ct
what can ct mesenchymal cells differentiate into
bone
cartilage
fibroblasts
blood cells
describe ct differentiation to lipoblast
gives rise to lipoblast - can divide and become lipcytes
describe ct differentiation to chondroblast
makes cartilage
chondroblast = active cell, divide and makes ecm and becomes trapped and then becomes chondrocytes
describe ct differentiation to osteoblast
bone cell that is making bone
same type of differentiation of a chondroblast
describe how main cells of ct form
mesenchymal cell –> fibrobalst –> fibrocyte (terminal stage)
describe chromatin of mesenchymal cell
pale chromatin - euchromatin
nucleus is pale
describe chromatin of fibroblast
older cell
still some pale chromatin
dark chromatin too (euchromatin and heterochromatin)
describe chromatin of fibrocyte
dark chromatin - heterochromatin
condensed DNA - to divide, can only divide
not an active cell
what can fibrocytes sometimes do
de differentiate to fibroblast
happens when wound healing - causes scars
are the cells of ct directly attached to each other
NOOOOO
not bound
there is space - cells separated by ecm
what is big difference between ct and epithelial tissue
ct derived from mesoderm
most epithelial tissue derived from ectoderm and endoderm
