epithelia Flashcards
key functions of the basement membrane (+ one random function)
supports the overlying epithelia, gives epithelial cells a surface for migration (e.g during wound healing), is a physical barrier. important for kidney function/filtration (selectively permeable for kindyes to filter in/out specific things)
explain how a tight junction works, incl proteins
strings of proteins- claudins and occludins- ‘sew’ up the gap between cell membranes,
nicknames/shapes for different lateral cell junctions
tight= sewing, gap = pizza, adherens= belt, desmosomes=button.
explain the purpose of tight junctions
at the top of the cells to protect the inner environment; protect from things outside coming in, and prevent things inside leaking out
proteins involved in adherens belts/how they work
plaque of proteins forms a belt, cadherins span the gap between membranes and link to catenins, which link to the microfilaments (actin) of the cytoskeleton
what do adherens junctions prevent
cells from separating due to tension
how do desmosomes work
plaque of proteins on membranes, catherine span the gap between cells and link to desmoplakins, linked to intermediate filament; keratin, of the other cell
what do desmosomes prevent
separation due to shearing forces
how do gap junctions work (proteins)
6 connexin proteins join to form a connexon/hemichannel, which dock to one another and open a channel
what do gap junctions do
provide a communication channel for controlled exchange between two cells, e.g of RNA, calcium, iron.
name and explain the function and purpose of the only basal cell junction
hemidesmosome. keratin of the basal epithelial cell is linked by integrin protein to the laminin of the basement membrane. secures the epithelia down to the BM to prevent it sliding around.
explain the two parts of the BM; where they came from
the top (basal) lamina is made of proteins produced and secreted by the overlying epithelia. the lower reticular lamina is made by the fibroblasts of the connective tissue.
which part of the basement membrane is secreted by the epithelia
basal lamina
where might you find ciliated cells in the body- why?
areas of tissue where movement across the surface is needed; e.g in the upper respiratory system, or uterine tubes. (for mucus and eggs respectively)
do simple, stratified, and pseudo stratified refer to the arrangement or shape of epithelial cells?
arrangement
what do squamous cell shapes looks like
paving stones, fried eggs
what does a transitional cell shape refer to, where are they found
it can change from cuboidal to flat shape to allow stretch- in the bladder
function of a simple squamous epithelium
filtration, diffusion, secretion
what is the mesothelium; where is it found?
a type of simple squamous epithelium that lines visceral cavities/’big sacs:
the peritoneum (abdomen), pleural (lungs), pericardium (heart).
what is the endothelium; where is it found?
a type of simple squamous epithelium that lines the circulatory system; heart, blood/lymph vessels
what is meant by serosa
a secretory tissue layer surrounding certain visceral cavities, consisting of a layer of mesothelium and connective tissue.
what are goblet cells
specialised columnar cells which squirt out mucus
why do goblet cells have more cytoplasm
they’re more metabolically active
what type of columnar cell doesn’t have goblet cells?
non-ciliated pseudostratified columnar epithelium
stratified cuboidal epithelium function and location:
protection and secretion. ducts of exocrine glands, (e.g eccrine sweat glands), male urethra.
stratified columnar epithelium function and location
protection and secretion. conjunctiva of the eye, urethra, ducts of large glands.
what aspects of the epithelium in the bladder are important to consider for its function?
transitional, to allow for stretch during volume fluctuation. stratified to support this, and provide protection against toxic urine for tissues.
what is the ‘lumen’
inside portion of a tubular space, e.g duct
non-ciliated pseudostratified columnar epithelium function and location
absroption and secretion. epididymus, male urethra, larger ducts of glands
what is the name of the sac that surrounds the heart
pericardium
what is the name of the sac surrounding the abdominal cavity
peritoneum
what is the name of the sac surrounding the lungs
pleural
eccrine sweat glands are an example of: and are lined with:
an exocrine gland. stratified cuboidal epithelium.
simple ciliated columnar epithelium function and location:
secretion and movement: upper respiratory tubes e.g bronchioles (move mucus), uterine tube (move eggs into uterus), brain ventricles (move CSF) and sinuses (mucus)
simple non-ciliated columnar epithelium function and location
absorption and secretion. gastrointestinal tract from stomach to anus. for absorption of nutrients (with microvilli) and secretion of digestive enzymes and mucus (goblet cells)
simple cuboidal epithelium location and function
secretion and absorption. found in many places like organs and parts of eye.
stratified squamous epithelium function and location
protection. found in areas of stress. keratinised variation is found in dry trauma areas; skin. non-keratinised is in wet trauma areas; mouth, tongue, throat, oesophagus, anus, vagina.
ciliated pseudostratified columnar epithelium function and location
secretion and movement. most of upper airways, e.g trachea.
transitional stratified epithelium function and location
flexibility. bladder, for stretch during volume fluctuation. and some in ureters and urethra.
what types of cells/tissues have cell junctions. where aren’t they found?
mainly in tightly packed tissues like epithelia, muscle, and nervous tissue.
free-moving cells like blood our immune cells may not have any.
