Lecture 2: Cell junctions and Epithelial tissue Flashcards
What is the structure of a tight junction: what proteins are in it
weblike transmembrane proteins made of claudins and occludins fuse together adjacent cell surfaces
What is the structure of an adherens junction; what are its components
Plaque- a dense layer of proteins is the belt. It is connected to the micofilament actin. Catenins link actin to cadherins which are transmembrane glycoproteins forming the finger belt buckle across intercellular space.
What are tight junctions good at
stopping the leakage of fluids.
What are adherins junctions good at
resist separation during contracile activities such as moving food in the intestine
What is the structure of a desmosome; what are its components
Made from a semicircle plaque that connects to intermediate filaments made of keratin across from one side of the cell to the other. Two cells are linked together by glycoprotein cadherins
What is the structure of a hemidesmosome; what are its components
one semi circle plaque that links the transmembrane glycoprotein integrin to intermediate keratin filaments. Integrin attach to protein laminim in the basement membrane.
What are desmosomes good at
preventing epidermal cells from separating under tension and cardiac muscle cells under contraction
What are hemidesmosomes good at
anchoring the cell to the basement membrane
What is the structure of a Gap junction; what are its components
6 conneXINs (membrane protein) form one hemichannel. This hemichannel is called an connexON. 2 connexons are tiny fluid filled tunnels that connect neighbouring cells.
What are gap junctions good for
Allow passage of ions, small molecules, transferring nutrients and wastes, nerve impulses- communication between cells.
What are microfilaments made of
actin
What are intermediate filaments made of
keratin
What are the two parts of the basement membrane and who secretes them
Basal lamina secreted by epithelial cells and reticular lamina secreted by fibroblasts
Does epithelial tissue contain nerves and blood vessels
nerves yes, but it is avascular
What materials does the basal lamina contain
collagen, laminim, proteoglycans/glycoproteins
What materials does the reticular lamina contain
fibrous proteins- fibronectin, collagen.
Simple squamous epithelium has 3 functions and two locations. Tell me
used for filtration, diffusion and slippery surface where secretion is. Found as endothelium (lining cardiovascular/ lymphatic system) and mesothelium (lining peritoneum, pleura, pericardium cavities)
Simple cuboidal epithelium have two functions and 4 locations. Tell me
Involved in secretion and absorption so lines many ducts. Locations are kidney tubules, posterior of retina, thyroid and pancreas
What types of epithelial cells can be cilliated
simple columnar and pseudostratified
What types of epithelial cells can be microvillied and what is another name for this
simple columnar cells can have a ‘brush border’
What epithelial cells have goblet cells
Both types of simple columnar but only cilliated pseudostratified columnar.
Where are non cilliated simple columnar cells found and why are they there?
lining the gastointestinal tract, gall bladder and gland ducts because they have higher rates of absorption, can lubricate linings
Where are cilliated cells found and why are they there
simple columnar are found in spinal cord, bronchioles, fallopian tubes and sinuses.
pseudostratified columnar found lining the upper respiratory tract. This is because cillia can beat in unision to propel foreign stuff out or move eggs.
Where are keratinised and non keratinised stratified squamous epithelium found
Keratinised is the superficial layers of skin, non keratinised is where penises go including the oesophagus.
Where are stratified cuboidal cells found
they are fairly rare, found in male urethra, oesophageal glands and sweat gland ducts.
Where are stratified columnar cells found
large excretory ducts, anal mucous membrane, urethra, eye. squishy and gross
What are the main functions of basic stratified cells
protection - against wear and tear and microbes
with limited secretion and absorption.
What is the structure, function and location of stratified transitional cells
it goes from relaxed rounded cuboidal stratified to stretched flattened squamous allowing urinary organs (mainly bladder) to hold variable amounts of liquid and maintain protective lining without rupturing.
What does pseudo stratified mean
All cells are in contact with the basement membrane but not all of them reach the apical surface of tissue.
What is the function and location of non cilliated pseudostratified columnar cells
absorption and protection; lining larger ducts of many glands, epididymus and male urethra
What are the two main types of glandular epithelium and how are they different
Exocrine secrete their products into ducts that empty onto the surface of a covering and lining epithelium and Endocrine secretes hormones that enter the interstitial fluid and directly diffuse into the bloodstream.
How are multicellular exocrine glands classified and what are the names under each classification
- Whether the duct is branched or not.
Simple is no branches. Compound is branched. - The shape of the duct
tubular, branched tubular = one tear drop, clover tear drops. Coiled is a pig tail. Acinar/alveolar is rounded berry drop. Tubuloacinar is a mix.
What are the three compound glands
compound tubular, acinar and tubuloacinar.
What is holocrine secretion
secretory product is accumulated in the cytosol and then the cell ruptures. eg. sebaceous glands
What is apocrine secretion
secretory product accumulates on the apical surface of the cell and then that part pinches off in exocytosis to release the product.
What is merocrine secretion
secretory product is synthesised in RER, processed and packaged at the Golgi and sent to be released from the cell in secretory vesicles via exocytosis.
