epithelial cells Flashcards
endothelium
specialised type of simple squamous epithelial cells that lines the blood vessel walls, lymphatics and the heart. lined by a BM and individual cells are connected by tight junctions. presence of many vesicles which are involved in transporting substances from one side to another. have many functions including: transport of molecules into and out of blood; formation of BM; produce factors such as nitric oxide to dilate/constrict blood vessels to control blood pressure; assist in blood coaggulation and breaking dow blood clots; angiogenesis - the creation of new blood vessels from pre-existing ones which is important in wound healing and tumour formation; in the presence of histamine the individual cells lose attachment to each other and allow fluid and proteins to diffuse into local tissues causig swelling called oedema (this is rapid and reversible). at some places there is large gaps between endothelial cells and large molecules can pass through (fenestrated endothelium in the endocrine glands and kidney) and at other places there is no gaps (blood-brain barrier)
goblet cells
goblet cells are modified columnar epithelium cells. they are abundant in the gastro-intestinal and respiratory tracts. the apical portion is goblet shaped as it is filled with mucigen granules and the basal portion contains the nucleus and other cell organelles
eratinized stratified squamous epithelium
the outer layer of skin is composed of teh dermis and teh epidermis. the epidermis is composed of 4/5 layers of cells. the epidermis consists largly of keratinocytes which are cells that are produced by mitosis in the BM of the epidermis. continuos division pushes new cells to the surface where they mature and become filled with keratin. kerstinised epithelium helps skin withstand the constant abrasion and dehydration it is constantly exposed to.
mesothelium
the simple squamous epithelium that lines the body cavities (pericardium, peritoneum and pleura). lined by a basement membrane and has a thin layer of supporting connective tissue beneath. secretes a serous membrane which provides a friction free surface and allows movement.
non-keratinised stratified squamous epithelial cells
Non-keratinized stratified squamous epithelium is found in areas of the skin where abrasion does occur but drying out tends not to happen e.g. cornea, oral cavity, oesophagus, rectum and vagina
pseudostratified columnar epitheliam
pseudostraified columnar epitheliam is a specialised type of epithial cells present in the conductive portion of the airways. composed of 3 cell type: goblet cells, basal cells and ciliated columnar cells). all cells are in contact with the BM but only the basal cells do not make contact with the apical surface. the basal cells are constantly dividing to replace the goblet and ciliated cells.
simple columnar epithelial cells
often involved in secretion and/or absorption, can have surface specialistaions for specific funtions (e.g. cilia) these have exstensive rough ER for secreting proteins or smooth ER for secreting steroids e.g. pancreas, salivary glands and endocrine glands found in the small intestine, stomach, gall bladder and kidney tubules
simple cuboidal epithelial cells
composed of one layer of tightly bound cells often found lining the tubules and ducts and at sites involving active secretion and absorption eg collecting duct of kidney, salivary glands and the pancreas
stratified squamous epithelium
the apical layer is composed of squamous epithelial cells. The basal layer is composed of cuboidal or columnar cells. These cells are mitotically active and are constantly replicating to replace the cells which are damaged on the apical layer. This type of epithelium is not suited to secretion or absorption as there are multiple layers of cells present. the loss of the apical squamous cells by abrasion is known as desquamation.
tight junctions
these seal cells together and control which molecules pass between the cells. Claudin and occludin are the membrane proteins, actin is the cytoskeleton fibre. The number of tight junctions connecting cells depends on the function of the tissue
transitional epithelium
transitional epithelium is stratified layers of epithelial cells. this type of epithelial is exclusive to the urinary system and can undergoe change with change in the environment. the cells are round when the bladder is empty and become flat with distension and stretching. this also forms an impermeable layer through which no urine can pass.
what is the brush border of epithelial cells
the apical surface of epithelia cells covered with microvilli often involved in secretion/absroption
what is the function of a brush border?
to increase the surface area for absorption
what term is used to describe a tumour originating in epithelial cells?
a carcinoma
what type of epithelium cells line the oesophagus?
stratified squamous epithelia
