The buccopharyngeal membrane (Latin, bucca = cheek) or oral membrane, forms the external upper membrane limit (cranial end) of the early gastrointestinal tract (GIT). This membrane region first develops in the trilaminar embryo (week 3) during gastrulation. The "membrane" quality comes from being composed of only ectoderm and endoderm, without a middle (intervening) layer of mesoderm.
The membrane lies at the floor of the ventral depression (stomadeum) where the oral cavity will open and will breakdown to form the initial "oral opening" of the gastrointestinal tract. At the lower end of the gastrointestinal tract the membrane region that forms is the cloacal membrane.
Stage 11 Embryo
A ventral view scanning EM embryo head region (Carnegie stage 11, week 4, 25 days, 20 somite pairs) showing the buccopharyngeal membrane breaking down and opening the gastrointestinal tract to the amnion.
Note the position at the "floor" of the stomedeum and relative to the first pharyngeal arch and triangular shape. Midline crack in head is an artefact.
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Cite this page: Hill, M.A. (2019, January 15) Embryology Buccopharyngeal membrane. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Buccopharyngeal_membrane
- © Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G