The anatomy, physiology, and diseases of the avian proventriculus and ventriculus  Isabelle Langlois, DMV, Dipl.  Veterinary Clinics: Exotic Animal Practice  Volume 6, Issue 1, Pages 85-111 (January 2003) DOI: 10.1016/S1094-9194(02)00027-0

Fig. 1 (A) Gross and schematic of the proventriculus and ventriculus of an Amazon parrot. The proventriculus (1) is relatively small. The ventriculus (2) is developed and distinct from the proventriculus. Four semiautonomous smooth muscle regions can be identified: the thinner caudoventral (a) and craniodorsal (b) regions and the thicker cranioventral (c) and caudodorsal (d) regions. The muscles attach to the tendinous center (3) present on both lateral walls of the ventriculus. Gross picture is courtesy of Dr. Drury Reavill. (B) Interior of the proventriculus and ventriculus of an Amazon parrot. The proventricular mucosa (1) lacks the longitudinal folds characteristic of the esophagus and has numerous well-developed papillae at the extremity of which open the gastric glands. The intermediate zone (arrow head) separates the proventriculus and ventriculus. The thinner caudoventral (a) and craniodorsal (b) muscles and the thicker cranioventral (c) muscles of the ventriculus (2) are identified. Veterinary Clinics: Exotic Animal Practice 2003 6, 85-111DOI: (10.1016/S1094-9194(02)00027-0)

Fig. 1 (A) Gross and schematic of the proventriculus and ventriculus of an Amazon parrot. The proventriculus (1) is relatively small. The ventriculus (2) is developed and distinct from the proventriculus. Four semiautonomous smooth muscle regions can be identified: the thinner caudoventral (a) and craniodorsal (b) regions and the thicker cranioventral (c) and caudodorsal (d) regions. The muscles attach to the tendinous center (3) present on both lateral walls of the ventriculus. Gross picture is courtesy of Dr. Drury Reavill. (B) Interior of the proventriculus and ventriculus of an Amazon parrot. The proventricular mucosa (1) lacks the longitudinal folds characteristic of the esophagus and has numerous well-developed papillae at the extremity of which open the gastric glands. The intermediate zone (arrow head) separates the proventriculus and ventriculus. The thinner caudoventral (a) and craniodorsal (b) muscles and the thicker cranioventral (c) muscles of the ventriculus (2) are identified. Veterinary Clinics: Exotic Animal Practice 2003 6, 85-111DOI: (10.1016/S1094-9194(02)00027-0)

Fig. 2 (A) Gross and schematic of the proventriculus and ventriculus of a hawk. The proventriculus (1) is relatively large. There is no clear distinction between the proventriculus and the ventriculus (arrow head). The duodenal loop (3) is visible caudal to the ventriculus. (B) Interior of the proventriculus and ventriculus of a hawk. The proventriculus (1) has longitudinal folds. The ventriculus (2) of these species has no cuticle and is involved in the formation of pellets. Note that the pyloric area leading to the duodenum (3) is located in the cranial portion of the ventriculus. Veterinary Clinics: Exotic Animal Practice 2003 6, 85-111DOI: (10.1016/S1094-9194(02)00027-0)

Fig. 2 (A) Gross and schematic of the proventriculus and ventriculus of a hawk. The proventriculus (1) is relatively large. There is no clear distinction between the proventriculus and the ventriculus (arrow head). The duodenal loop (3) is visible caudal to the ventriculus. (B) Interior of the proventriculus and ventriculus of a hawk. The proventriculus (1) has longitudinal folds. The ventriculus (2) of these species has no cuticle and is involved in the formation of pellets. Note that the pyloric area leading to the duodenum (3) is located in the cranial portion of the ventriculus. Veterinary Clinics: Exotic Animal Practice 2003 6, 85-111DOI: (10.1016/S1094-9194(02)00027-0)

Fig. 3 Anatomy of the proventriculus and ventriculus of ratites. The proventriculus of the rhea is much smaller than the ventriculus and gastric glands are limited to a dorsally located area. In the ostrich, the proventriculus passes dorsal to the ventriculus and empties into the ventriculus at its caudal aspect. As in rheas, the gastric glands are limited to a patch at the dorsal aspect of the proventriculus. The opening between the proventriculus and ventriculus is large. The proventriculus of the emu and the cassowary is large and almost the same size as their ventriculus. Veterinary Clinics: Exotic Animal Practice 2003 6, 85-111DOI: (10.1016/S1094-9194(02)00027-0)

Fig. 4 Gross internal surface of the ventriculus of a granivorous bird. The cuticle (c) is a well-developed carbohydrate–protein complex, which acts as an abrasive surface to improve the grinding function of the ventricular muscle (2). The presence of grit (g) provides additional abrasive action. The cuticle separates from the ventricular epithelium with autolysis (arrow head). The proventriculus (1) and intermediate region (arrows) are also identified. Courtesy of Dr. Drury Reavill. Veterinary Clinics: Exotic Animal Practice 2003 6, 85-111DOI: (10.1016/S1094-9194(02)00027-0)

Fig. 5 Schematic of the gastrointestinal cycle in the turkey. (A)Resting proventriculus and ventriculus. (B) The thin muscles of the ventriculus contract while the isthmus is closed (arrow heads). The pylorus then opens leading to propulsion of the ingesta in the duodenum. (C)The duodenum contracts while the isthmus relaxes and the pylorus closes. The contraction of the thick ventricular muscles causes reflux of food from the ventriculus into the proventriculus, which improves digestion by addition of fresh pepsin and HCl. (D) The proventricular muscles contract, propelling the ingesta in the ventriculus, and the isthmus closes. Veterinary Clinics: Exotic Animal Practice 2003 6, 85-111DOI: (10.1016/S1094-9194(02)00027-0)

Fig. 6 Fecal cytology demonstrating an avian gastric yeast, previously known as megabacteria. Note that this organism is much larger than other microorganisms present in the avian gastrointestinal flora. Courtesy of Dr. Cheryl Greenacre. Veterinary Clinics: Exotic Animal Practice 2003 6, 85-111DOI: (10.1016/S1094-9194(02)00027-0)

Fig. 7 Section of the proventriculus of an African Grey (Psittacus erithacus) with proventricular dilatation disease (PDD). A myenteric ganglia encircled by aggregates of lymphocytes mixed with a few plasma cells is visible (arrow). There is marked loss of neuron cell bodies. The muscularis (M) is markedly atrophied and ranges in thickness from 40–60 microns. The ventricular glands are also identified (G). Veterinary Clinics: Exotic Animal Practice 2003 6, 85-111DOI: (10.1016/S1094-9194(02)00027-0)

Fig. 8 Lateral whole-body radiograph of an African Grey (Psittacus erithacus). The proventriculus is markedly dilated (arrows) and the spleen (s) is prominent. Proventricular dilatation disease or other infectious diseases, heavy metal toxicosis, foreign body, and other metabolic disorders can result in this radiographic appearance. Veterinary Clinics: Exotic Animal Practice 2003 6, 85-111DOI: (10.1016/S1094-9194(02)00027-0)

Fig. 9 Ventrodorsal whole body radiograph of the African Grey (Psittacus erithacus) described in Fig. 8. The proventriculus is dilated with its margins (arrows) extending beyond the lateral margins of the liver. Veterinary Clinics: Exotic Animal Practice 2003 6, 85-111DOI: (10.1016/S1094-9194(02)00027-0)

Fig. 10 Proventriculus and ventriculus of an African Grey (Psittacus erithacus). The heart (h), right (rl), and left (ll) liver lobes are retracted to the right. The proventriculus (1) and ventriculus (2) are markedly dilated secondary to proventricular dilatation disease (PDD). Note the granuloma (g) present in the left lung. This bird had a severe necrotizing pneumonia most likely secondary to aspiration of regurgitated ingesta. Veterinary Clinics: Exotic Animal Practice 2003 6, 85-111DOI: (10.1016/S1094-9194(02)00027-0)

Fig. 11 Lateral view whole-body radiograph of a cockatiel (Nymphicus hollandicus). Note the presence of the metallic foreign body within the ventriculus. Gas is present within the proventriculus (arrow). This bird was diagnosed with lead toxicosis. Veterinary Clinics: Exotic Animal Practice 2003 6, 85-111DOI: (10.1016/S1094-9194(02)00027-0)

Fig. 12 Ventrodorsal view of the whole-body radiographs of the cockatiel (Nymphicus hollandicus) described in Fig. 11. The metallic foreign body is clearly visible in the ventriculus. The proventriculus is mildly dilated with gas. Veterinary Clinics: Exotic Animal Practice 2003 6, 85-111DOI: (10.1016/S1094-9194(02)00027-0)