Pinacocyte
Pinacocytes are flat cells found on the outside of sponges, as well as the internal canals of a sponge.{{Cite journal|last1=Maldonado|first1=Manuel|last2=Riesgo|first2=Ana|date=2007-06-01|title=Intra-epithelial spicules in a homosclerophorid sponge|url=https://doi.org/10.1007/s00441-007-0385-7|journal=Cell and Tissue Research|language=en|volume=328|issue=3|pages=639–650|doi=10.1007/s00441-007-0385-7|pmid=17340151 |s2cid=9930528 |issn=1432-0878}} Pinacocytes are not specific to the sponge however. It was discovered that pinacocytes do not have as many sponge specific genes. These genes suggest that pinacocytes had evolved before the metazoan time period, which is, before porifera had evolved.{{Cite journal|last1=Sogabe|first1=Shunsuke|last2=Hatleberg|first2=William L.|last3=Kocot|first3=Kevin M.|last4=Say|first4=Tahsha E.|last5=Stoupin|first5=Daniel|last6=Roper|first6=Kathrein E.|last7=Fernandez-Valverde|first7=Selene L.|last8=Degnan|first8=Sandie M.|last9=Degnan|first9=Bernard M.|date=June 2019|title=Pluripotency and the origin of animal multicellularity|url=https://doi-org.webdb.plattsburgh.edu:2443/10.1038/s41586-019-1290-4|journal=Nature|volume=570|issue=7762|pages=519–522|doi=10.1038/s41586-019-1290-4|pmid=31189954 |bibcode=2019Natur.570..519S |issn=0028-0836|hdl=10023/19125|s2cid=92562184 |hdl-access=free}}
Function
Pinacocytes are part of the epithelium in sponges. They play a role in movement (contracting and stretching), cell adhesion, signaling, phagocytosis, and polarity. Pinacocytes are filled with mesohyl which is a gel like substance that helps maintain the shape and structure of the sponge.{{Cite web|date=2015-11-02|title=28.1: Phylum Porifera|url=https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology_(OpenStax)/5%3A_Biological_Diversity/28%3A_Invertebrates/28.1%3A_Phylum_Porifera|access-date=2020-12-03|website=Biology LibreTexts|language=en}}
Types
= Basipinacocytes =
These are the cells in contact with the sponge's substrate (the surface to which it is attached).
= Exopinacocytes =
= Endopinacocytes =
These line the sponge's interior canals.