The Human Body's four basic tissue types Flashcards
What are the major functions of Epithelial cells/tissue?
Protection; filtration; secretion; absorption; excretion (F.A.P.E.S)
What does the epithelial cells/tissue do?
they cover the body’s surfaces, lines hollow organs, tubes, cavities, ducts and forms glands.
The cells of the epithelium are held together by what and in what formation?
The cells are held together by a variety of cell junctions and are arranged in single or multiple layers of continuous sheets.
What are these cell junctions which hold the epithelial cells together?
Tight Junction, Adherens Junctions, Gap junctions, Desmosomes and Hemidesmosomes
What cell junctions are found on the Lateral?
Tight junction, Adherens junctions, Gap junction, Desmosomes
What cell junction is found on the basal junction?
Hemidesmosomes
What is the apical / free surface?
the top, its may be open to the outside world or the lumen inside the gut.
What is the lateral surface?
where two cells are adjacent to each other.
What is the basal or attached surface?
attaches the cell to the basement membrane
What is the protein skeleton of cells called?
Cytoskeleton
What are two key proteins that make up the cytoskeleton?
Microfilaments and Intermediate filaments
What protein are microfilaments primarily made up of?
ACTIN
Where are microfilaments in the cell and what do they do?
They are bundles under the cell membrane and cytoplasm. Microfilaments provide strength and give the shape to the cell, causes movement within the cell, links the cytoplasm to the membrane, tie cells together and muscles contractions.
What protein are Intermediate filaments primarily made up of?
KERATIN
What does the intermediate filament do within the cell?
it provides strength and moves materials through the cells’ cytoplasm
Where about is the tight junction located and how would you describe the tight junctions?
Near the apical surface of the cell, the tight junction has a knitted like appearance
In the tight junctions how are adjacent membranes held together?
transmembrane proteins pass back and forth around the two adjacent cell membrane holding and fusing them together. Tight junctions removes the gap between the two cell membranes.
When tight junctions removes the gap between the two cell membranes, what is this called and why is it called that?
It makes the cells electrically tight. This means that ions and other proteins can’t pass easily down between the cells. This means the environment lower down can be different from what is above the apical surface thereby keeping cell polarity.
What are the two key proteins that make up the knitting (transmembrane proteins) together in tight membrane is called?
Claudins and occludins
What do the protein claudin and occludin do to membrane and in what cell junction?
They bind into the membrane. They are the two key proteins for tight junctions.
What would increase the tightness of the tight jucntion?
more strands
Where are a large quantity of Tight junctions found? And what do tight junctions prevent?
stomach, intestines and bladder. stops the passage of substances between cells and prevents the contents within the organ from leaking out (into blood or surrounding tissue)
Where about is the adherens junction? and how would you describe the Adherens junction?
Generally near the apical surface but more basal that tight junctions. Plaque-like structure with a Belt-like appearance which encompasses the cell.
Why is there a gap in the Adherens junction?
This gap is extended by a transmembrane glycoprotein called cadherin.
What happens to cadherin in the Adheren junctions?
The cadherin extends across the from one membrane and then through the other cells membrane and interacts with another protein called Catenins. Catenins helps the cadherin bind to the microfilaments of the cytosketeons of the two cells (ACTIN). This links the cells at a skeleton level.
What are the two proteins in the adheren Junctions
Cadherin and catenin
What is the advantage of Adheren junctions linking cells together in the skeleton level?
It stops cells from moving around, and so that the cells can move in unison. This is beneficial when epithelial surfaces are contracting as it prevent the cells separating.
Where about is the Desmosome junctions? and how would you describe them?
Found in the lateral wall, and has a button-like appearance.
Why is there a gap in the desmosome junctions?
The gap is held open by transmembrane glycoprotein called cadherin.
What two junctions having the same spanning protein cadherin?
Adheren junction and desmosome junction.
What does the Desmosomes help to do between the cells?
it helps the link the intermediate filaments between the different cells.
How does the Desmosomes junction interact with the intermediate filaments and cadherin?
The keratin protein which are intermediate filaments become attached to the desmosome plaque and those attach to the keratin protein in the other cell.
Where is desmosomes junctions common in? and what are the benefits
Muscle cells. it increases the structural integrity of the cells.
How are the Gap junctions held together? How are the proteins in Gap junctions arranged in?
They are held together by proteins. Gap jucntions are formed by 2 six proteined cells called connexOn or Hemichannel.
How are ConnexOn or Hemichannel formed?
They are formed when ConnexIn proteins molecules are together.
What does a ConnexOn look like?
a donut
What does the ConnexOn look like and do when its first made?
When it is first made it has no hole in the middle. It enters and moves around in the cell membrane until it find a donut in the adjacent cell.
What happens to the ConnexOn when two ConnexOns of adjacent cells in Gap junctions find each other?
The two donuts dock together and then the channel between them opens (the donut hole - conformation change ). This forms a tunnel from the cytosol of one cell to another.
How big can the molecules flowing through the tunnel in Gap Junctions be?
The molecules can be up to
approximately 1kDa.
What kind of molecules can travel through the tunnel in Gap junctions?
ATP, Calcium and ions.
What is it called when several gap junction come together?
to form large communication plaques.
What kind of appearance does Hemidesmosome have, and where are they located?
Button-like appearance, found in the basal surface
What are the advantages of Gap junctions?
enables nerve and muscle impulses to spread rapidly among cells, it also allows cells to communicate with each other and allows the transfer of nutrients and sometimes waste.
Hemidesmosomes are similar to Desmosomes in what way?
Both junctions binds the intermediate filaments (Keratin)
Where does the Hemidesmosome junctions bind the cell to and what is the advantage of this?
it binds the cell down to the basement membrane, this prevents the cells from sliding all over the place.
Since Hemidesmosomes don’t join to another cell but rather the basement membrane, what is its linking transmembrane glycoprotein? and what protein does the transmembrane glycoprotein bind into?
INTEGRIN, binds to LAMININ in the basement membrane.
Describe the relationship belween Keratin, Integrin and Laminin in Hemidesosome junctions.
The keratin protein in the cytoplasm of the cell is linked to the Laminin protein via the Integrin.
What is the combination of Tight junction, adheren junction and desmosome called?
Junctional complex
Where is the Epithelia always located? and why?
It always overlays a basement membrane. so that the epithelia cells can anchor themselves to.
what are the two parts of the basement membrane.
Basal Lamina and Reticular Lamina
Where is the basement membrane found between?
it is found between the epithelium and connective tissue.
What is the basal lamina made up of, and where is those proteins from? give examples of the proteins.
Made by proteins which are largely secreted by the epithelial cells above. Proteins such as collagen, Laminin, glycoproteins.
What is the reticular Lamina made up of? and where are those proteins from? give examples of the proteins.
Made up of proteins which are largely secreted by the the connective tissue called fibroblasts below. Proteins such as fibronectin and collagen.
Epithelia contains nerves but does not contain what? And what does that mean for the epithelia cells?
Epithelia cells are avascular, so the Epithelia cells cant get nutrition. In response to this by nutrients being diffused into the epithelial cells through the basement membrane from the connective tissue. similarly waste material is diffused out of the epithelial cells into the basement membrane into the connective tissue.
what does avascular mean?
contain no blood vessels
What are the functions of the basement membrane?
supports the overlying epithelium cells (especially in the cases of wounds). it also acts as a physical barrier. As well as helps out in the filtration of substances in the kidneys.
How does the basement membrane aid in the cases of wounds?
when cut, the epithelium and basement membrane are both divided. The process to heal includes reform the basement membrane so that the cells can migrate in from the sides so that the epithelial cells can migrate over the basement cells and reform.
Basement Membrane in relation to Malignant melanoma
The basement membrane acts as a barrier from the invasion of tumors such as melanoma, if the tumor depth is above the basement membrane the chances of survival are high but as the depth increases and penetrates the basement membrane the chances of spread increases significantly and therefore survival decreases.
What are the ABCD of melanoma warning signs?
A - asymmetry - if the half of the mole doesn’t match the other half.
B - Border irregularity - the edges of the mole is ragged, notched or blurred
C - Colour - mix of brown, black, red, white or blue
D - Diameter - if the mole has a greater that 6mm diameter.
What are the two major types of Epithelial tissue?
Covering and lining Epithelia. Glandular Epithelia
Where is the Covering a lining Epithelia found?
they line either the outer covering (skin and some internal organs) or the inner lining (blood vessels, ducts and body cavities and interiors of systems)
Where is the glandular epithelia found?
Is the whole secretory portion of glands ( thyroid gland, adrenal gland and sweat glands)
What are the two types of Glandular epithelia?
Exocrine and Endocrine
What are the two aspects used to classify Covering and lining Epithelia?
The arrangement of cells and the shapes of the cell.
What are the three arrangements for Covering and lining epithelia?
Simple, Stratified and Pseudostratified
What does the simple arrangement for covering and lining epithelial look like? and what is its purpose?
it is a single layer, its functions are diffusion, osmosis, secretion, absorption and filtration
What does the stratified arrangement for covering and lining epithelial look like? and what is its purpose?
it is two or more layers, its function is protection in areas where there is alot of wear and tear.
What does the Pseudostratified arrangement for covering and lining epithelial look like? and what is its purpose?
looks like it has multiple layers by where the nuclei positions, but all cells in this arrangement are in contact with the basement membrane, while not all cells reach the apical membrane. It therefore is actually simple epithelial and have the function of secretion.
What are the four shapes in classifying covering and lining epithelial?
Squamous, Cuboidal, Columnar and Transitional.