Histomorphological studies
Proventriculus was observed as the typical tubular component with four tunics from inside to outside as tunica mucosa, tunica sub mucosa, tunica muscularis and tunica serosa. Whereas, proventriculus wall is consisted with only three layers
viz. tunica mucosa, tunica muscularis and tunica serosa were observed in Yellow billed grosbeak
(Zhu et al., 2013).
The tunica mucosal layer was encompassing by elastic and collagen fibers. The lining epithelium of mucosa was tall columnar epithelium. Its mucosal layer was thrown into plicae, the folds which were encountered in different heights. These plicae provide the structure to lumen of the proventriculus at one side while at another it was connecting to the proprial glandular structure as the areolar connective tissue between mucosal and submucosal layer. The lamina propria had an existence of blood vessels and the collagen fibers (Fig 1) and this is similar to the findings of other studies Common moorhen (
Gallinula chloropus)
(Jassem et al., 2016).
The submucosal layer was consisting of the submucosal glands, which had several secretory tubules within one submucosal gland encapsulated by elastic fibers. This finding similar to reports in turkey (
Beheiry, 2018), whereas (
Sayrafi and Aghagolzadeh, 2020) reported these glands in the located within the lamina propria of the mucosa of the proventriculus of common starling (
Sturnus vulgaris).
Proventricular submucosal glands observed commensing from abluminal to luminal ends. The stratified epithelium of these glands doesn’t shown a layer with more than three numbers of cells. It was also observed that, the luminal size of these glands decreses when the number of glands are increases. Frequently only single proventricular submucosal gland was observed with maximize luminal diameter which was surrounded by numerous secretory tubules. Sometime there were two to three submucosal gland were occupying the complete submucosal layer, at the instance sometime no lumen was there among radiating secretory tubules (Fig 2).
The numerous submucosal glands had outer elastic fibers and the inside collagen fibers, blood vessels. As the lobe of submucosal glands it has shown interlobular and intralobular ducts. Even the intralobular duct was also seen.
The parenchyma of each submucosal gland had number of secretory rod in anastomosing way with simple acinar glandular structure which opens into central cavity of these glandular lobules. Simple columnar epithelium was observed at the luminal end.
Tunica muscularis had inner longitudinal and outer thick circular layer, while the tunica serosa was observed with surrounding adipose tissue as the connective tissue constituent to endow the access of nutritional supply in the form of blood vessels. The present findings were completely supporting the observations mentioned by
(Das et al., 2017) who has revealed the histomorphological studies on proventriculus in kadaknath fowl but the ducts what they found in the name after primary, secondary and tertiary may be replaced with intercalated, intralobular and interlobular. But the lymphoid infiltration in the lamina propria was not recorded in the present findings.
Histochemical studies
The mild rose to purplish red
i.e. magenta color activity was observed at the luminal surface of submucosal glands. Intercalated, intralobular and interlobular ducts have also exhibited the weak activity towards PAS (Fig 3). These observations were analogous to the results of (
Attia, 2008) in quails, (
Al-Saffar and Al-Samawy, 2015) in the mallard and
(Hamdi et al., 2013) in Black wing kite (
Elanus caeruleus) birds. The present findings were encouragingly implied towards the secretion carrying components of proventricular submucosal glands which has higher functional aspect and thereby the proportionate source of energy in the form of carbohydrate macromolecules there.
Intensified weak alkaline phosphatases activity has shown by the glandular cell rods, serosal layer and adjoining connective tissue and the blood vessels in the present studies. Simultaneously a weak acidic phosphatase activity was also noticed in mucosal folds and lumen of proventricular submucosal glands with a very weak activity at serosal limiting membrane. These outcomes were not different than
(Selvan et al., 2008) in post hatched Guinea Fowl where they had noticed weak activity in younger and stronger in aged birds. The intensity of activity exhibited in present studies against alkaline and acidic phosphatase might be considered inversely proportional to the functional performance of the activity being shown by those structural components, which were cheering the vigorness of performance being carried out to maintain the uneventful functioning of proventriculus.
Mild SDH activity was observed in connective tissue septa of proventricular submucosal glandular cellular rods while intense in tunica muscularis (Fig 4). However,
(Selvan et al., 2008) had not found any reaction against succinic dehydrogenase in the post hatched Guinea fowl. The present findings were emerging as very promising to the function of proventricular submucosal glands as it has to be involved not only into mitochondrial cell respiration and energy generation but also has to perform for oxygen sensing of the tissue.
