part_of adult proventriculus Fig. 14-17, in Biology of Ticks ISBN:0-19-505910-7. TADS:0000179 TADS:0000179 Valve located at the junction of the esophagus and the antero-ventral region of the stomach portion of the midgut. The proventriculus is surrounded by several layers of smooth muscle fibers. The proventriculus opens when the pharynx contracts, allowing ingested blood to enter the midgut, but closes when the pharynx dilates. The latter is believed to prevent regurgitation of blood from the midgut back into the host. However, this remains a controversial issue since some authors (e.g., Burgdorfer et al. 1989) have argued that regurgitation can occur while others (Riberio et al. 1987) consider it unlikely. Connat (1991, Parasitol. Res. 77: 452 -454) showed compelling evidence of regurgitation using tritiated ecdysteroids). Thus, it appears that there is good evidence that it can occur in argasid ticks. Whether it can also occur in ixodid ticks is uncertain. default_namespace adult foregut simple organ