The Tissue Level of Organization Flashcards
What is a tissue?
a group of cells that usually have a common embryonic origin and function together to carry out specialized activities
how many basic types of cells are there?
Epithelial
connective
muscular
nervous
what are cell junctions?
hold cells together
what are tight junctions?
consist of weblike strands of transmembrane proteins that fuse together the outer surfaces of adjacent plasma membranes to seal off passageways between adjacent cells
what cells have tight junctions?
Cells of epithelial tissue that lines the stomach, intestines, and urinary bladder have many tight junctions
what do tight junctions do?
They inhibit the passage of substances between cells and prevent the contents of these organs from leaking into the blood or surrounding tissues.
what are Adherens Junctions?
contain plaque,a dense layer of proteins on the inside of the plasma membrane that attaches both to membrane proteins and to microfilaments of the cytoskeleton
what are cadherins?
Transmembrane glycoproteins
what do cadherins do?
join the cells. Each cadherin inserts into the plaque from the opposite side of the plasma membrane, partially crosses the intercellular space and connects to cadherins of an adjacent cell.
what do adherents junctions often form?
adhesion belts
what are the structures of the adherent junction?
Adjacent plasma membranes
microfilaments
plaque
transmembrane glycoprotein
intercellular space
What are desmosomes?
contain plaque and have transmembrane glycoproteins (cadherins) that extend into the intercellular space between adjacent cell membranes and attach cells to one another
what is the difference between adheren junctions and desmosomes?
the plaque of desmosomes does not attach to microfilaments
what does the plaque do in desmosomes?
attaches to elements of the cytoskeleton known as intermediate filaments, which consist of the protein keratin.
where are desmosomes commonly found?
These spot weld–like junctions are common among the cells that make up the epidermis and the cardiac muscles
what is the function of desmosomes?
prevent epidermal cells from separating under tension and cardiac muscle cells from pulling apart during contraction.
what are the structures of desmosomes?
Adjacent plasma membranes
intercellular space
plaque
cadherin
keratin
what are the types of cell junctions
Tight
Adheren
Desomosomes
Hemmidesmosomes
Gap
What is the difference between hemidesmosomes and desmosomes?
hemidesmosomes don’t link to adjacent cells
what happens on the inside of hemidesmosomes?
On the inside of the plasma membrane, integrins attach to intermediate filaments made of the protein keratin.
what happens on the outside of the hemidesmosomes?
On the outside of the plasma membrane, the integrins attach to the protein laminin, which is present in the basement membrane
where do hemidesmosomes attach?
the basement membrane
what are the structures of hemidesmosomes?
Keratin
plaque
Integrin
Plasma membrane
Basement membrane
what happens at gap junctions?
membrane proteins called connexins form tiny fluid-filled tunnels called connexons that connect neighboring cells
what does the connexons allow in gap junctions?
ions and small molecules can diffuse from the cytosol of one cell to another, but the passage of large molecules such as vital intracellular proteins is prevented.
what junction allowshe cells in a tissue to communicate with one another?
gap junctions
what junction allows nerve impulses to be transferred quickly?
Gap junctions
what are the structures of gap junctions?
adjacent plasm membranes
connexions
gap between cells
what is the difference between connective tissue and epithelial tissue?
Connective = large amount of extracellular matrix and few cells
Epithelial = little to no extracellular matrix and cells packed together
where do epithelial cells attach?
basement membrane
is epithelial tissue vascular?
no but does have nerve supply
how is epithelial tissue arranged?
in sheets and densely packed
what are the different arrangements epithelial cells can have?
simple
Pseudostratified
Stratified
what are the cells shapes epithelial cells can have?
squamous
cuboidal
columnar
what are the 2 types of epithelial tissue?
surface
glandular
define surface epithelium
forms the outer covering of the skin and some internal organs and the inner lining of structures such as blood vessels, ducts, body cavities, and the lining of the respiratory, digestive, urinary, and genital systems. In other words, it covers or lines a surface.
define glandular epithelium
makes up the secreting portion of glands, such as the thyroid gland, suprarenal (adrenal) glands, sweat glands, and digestive glands.
what is the unicellular cell of glandular epithelium?
goblet cells
What are the multicellular cells of glandular epithelium?
sweat glands
oil glands
salivary galnd
what are the surfaces of epithelial tissue?
apical
basal
lateral
what are apical surfaces
faces the body surface, a body cavity, the lumen (interior space) of an internal organ, or a tubular duct that receives cell secretions
what are lateral surfaces?
face the adjacent cells on either side, may contain tight junctions, adhering junctions, desmosomes, and/or gap junctions.
what are basal surfaces?
is opposite the apical surface. The basal surfaces of the deepest layer of epithelial cells adhere to extracellular materials such as the basement membrane.
what are the 2 layers of the basement membrane
the basal lamina and reticular lamina.
what is the basal lamina?
thin layer,is closer to and secreted by the epithelial cells. It contains proteins such as laminin and collagen, as well as glycoproteins and proteoglycans
what is the reticular lamina?
thin layer,is closer to the underlying connective tissue and contains proteins such as collagen produced by connective tissue cells called fibroblasts
what is simple epithelium?
single layer of cells that function in diffusion, osmosis, filtration, secretion and absorption