This functional tissue unit (FTU) illustration includes cell types related to the descending thin limb of loop of Henle FTU in the ASCT+B Table Kidney v1.2. This illustration was inspired by the Kidney Tissue Atlas Explorer created by the Kidney Precision Medicine Project (KPMP). Multiple histology atlases, especially Human Microscopic Anatomy (Krstić 1991) and Histology: A Text and Atlas (Wojciech Pawlina and Michael H. Ross 2019) were referenced. Cell types and metrics were primarily defined by (Hu, McDonough, and Layton 2021; Layton and Layton 2019). Uberon describes this FTU as follows: "The portion of the renal tubule that constitutes the proximal part of the loop of Henle, has low permeability to ions and urea, and is highly permeable to water; it consists of an initial short thick segment lined by low simple cuboidal epithelium and a long thin segment lined by simple squamous epithelium; however, this distinction is not as important physiologically as in the ascending limb, so often the two are treated as one structure."

Bibliography:

• Hu, Rui, Alicia A. McDonough, and Anita T. Layton. 2021. “Sex Differences in Solute and Water Handling in the Human Kidney: Modeling and Functional Implications.” iScience 24 (6): 102667. https://doi.org/10.1016/j.isci.2021.102667.
• Krstić, Radivoj V. 1991. Human Microscopic Anatomy. Berlin, Heidelberg: Springer. https://doi.org/10.1007/978-3-662-02676-2.
• Layton, Anita T., and Harold E. Layton. 2019. “A Computational Model of Epithelial Solute and Water Transport along a Human Nephron.” Edited by Daniel A Beard. PLOS Computational Biology 15 (2): e1006108. https://doi.org/10.1371/journal.pcbi.1006108.
• Wojciech Pawlina and Michael H. Ross. 2019. “Histology: A Text and Atlas: With Correlated Cell and Molecular Biology. Eighth Edition, 2018 Authors: Wojciech Pawlina; Michael H. Ross.” Morphologia 13 (4): 76–89. https://doi.org/10.26641/1997-9665.2019.4.76-89.