Facet cells (also known as umbrella cells,[1] capping cells, superficial urotheliocytes) are a type of cells located in the
renal pelvis, the
ureters,and the
urethra. Umbrella cells form the outermost layer of the
urothelium, which is a special type of
epithelium found in the
renal pelvis, the
ureters, and the
urethra. Umbrella cells are special in that they can contain
multiple nuclei. Their
apical membrane contains numerous
invaginations, which allows the cells to stretch during
urination. Umbrella cells are linked together with tight
junctions which:
prevents urine from leaking through the
epithelium.
creates an
osmotic barrier. Urine
osmolarity can range from 50 to 1200
mmol/
L while the normal body osmolarity is 290 mmol/L. The difference between the two could lead to fluid entering or exiting the ureter due to the
osmotic pressure.[2]
^Born, Martin; Pahner, Ingrid; Ahnert-Hilger, Gudrun; Jöns, Thomas (July 2003). "The maintenance of the permeability barrier of bladder facet cells requires a continuous fusion of discoid vesicles with the apical plasma membrane". European Journal of Cell Biology. 82 (7): 343–350.
doi:
10.1078/0171-9335-00326.
PMID12924629.
^Lüllman-Rauch (2008). Histologie 1er cycle des études médicales. De Boeck Supérieur.
ISBN9782804156923.