part of part of has part has part has_part epithelial cell brush border cell of the proximal tubule kidney proximal straight tubule epithelial cell epithelial cell of proximal tubule segment 3 2022-05-10T13:31:06Z The epithelial cell of proximal tubule segment 3 operates under relatively hypoxic conditions and is particularly susceptible to ischemic injury. A brush border cell that is part of segment 3 (S3) of the proximal tubule epithelium, which extends from the medullary rays of the renal cortex into the outer medulla. epithelial cell of segment 3 of proximal tubule brush border proximal straight tubule