الفهرس 
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Abstract
The present study was carried out on sixty four apparently healthy birds of each of the Sudan’s duck, fayomi chicken and pigeon, of native breed of different sexes and ages of one day, one month, three months and six months old forty eight specimens from each species were used for gross anatomical studies of the stomach, intestines and liver. Other sixteen specimens were used for the histological study to confirm some anatomical findings.
The present study revealed that The stomach of the duck, chicken and pigeon consists of two compartments. The proventriculus and the ventriculus The highest ratio of the stomach to total body weight are recorded in pigeon at one day old (8.3%), one month old (4.9%) and at six months old (3.1%) while in duck at three months old (5.5%). The weight of the stomach increased by about 18 time from one day to six month old age in the duck, 17 time in the chicken and 8 time in the pigeon.
The proventriculus appears as a spindle shaped dilatation. The mucosal surface of the proventriculus of the duck and pigeon proventriculus showed four longitudinal folds. These folds were not recognized in chicken proventriculus. The number of the proventricular papillae of six months old duck is about 37/cm2, in the chicken is about 8/cm2 and 47/cm2 in pigeon.
The isthmus is an intermediate zone between two chambers of the stomach. It appears externally as a narrow constriction, its mucous membrane devoid from neither proventricular papillae nor cuticle which covers the internal surface of the muscular stomach.
The muscular part of the stomach is a largest organ in the body cavity. It has a biconvex lens shape. The ventral contour of the ventriculus reaches the floor of the abdominal cavity and the sternum in the studied birds at the studied stages of age however in the chicken and pigeon at 6th months age the ventriculus has a ventral relation with the sternum only. The muscular part of the stomach is related caudally to the remnant of the yolk sac in the studied birds at one day old age. The muscular part of the stomach consists of a body, a craniodorsal blind sac and a caudoventral blind sac .
The ventriculus is lined internally by a thin cuticle , by advancement of age of the birds it become thick and hard. The cuticle is well developed over the blind sacs than in the body of the ventriculus.
The mucosa of the proventriculus is showed plicae and sulci. The lining epithelium is simple columnar. The proventriculus of advanced ages show that the size of the plicae and sulci is increased and the proventicular glands lobulation is more distinct.
The thickness of the cornified layer of the ventriculus of the studied birds is varied in thickness. The cornified layer is ill-developed at one day old bird. The increase in the age accompanied with increase in the cornified layer and the glandular pits become clear. The cornified layer of the Ventriculus of three and six months old birds become hard and thicker with the age advancement.
The intestinal tract of the studied birds is differentiated into small and large, intestines. The small intestine includes duodenum, jejunum and ileum, while the large intestine is composed of paired ceci and rectum.
The weight of the intestine increased by about 20 time from one day to six month old in the duck, 40 time in the chicken and 53 time in the pigeon. The highest length of the intestinal tract of the studied birds recorded in the duck as it reach about 250 cm , in the chicken is about 180 cm but in pigeon about 114.
The duodenum of the duck, chicken and pigeon forms two loop with the descending limb and ascending limb The ascending limb is the longest of the two duodenal limbs in the studied birds. The ascending limb represents about 52.3 % of the total duodenal length in the duck, 52.2 % in the chicken and about 53.5 % in the pigeon.
In the duck the jejunum is arranged in seven parallel loops to each other. In the chicken it is arranged in the form of half circle with 8-10 coils of different sizes and in the pigeon the jejunum take the form of cone with caudoventrally directed apex which consists of two centripetal coils and two centrifugal coils.
The ileum is the terminal and the shortest segment of the small intestine lie between two ceci Along paired ceci present in the duck and chicken. The left one is the longest of the two ceci. In the pigeon the ceci are short bud like projection at the connection of the terminal part of the ileum with the rectum. The rectum is the terminal part of the intestinal tract that continues with the ileum cranially and connect with cloaca caudally .
The villi of the small and large intestine of the studied birds are quite tall tongue like in the duodenum, while finger-like in the jejunum and thick finger like in the ileum. The surface area devoted to goblet cells is considerably less than that of the columnar epithelium. The lining epithelium is simple columnar cells with goblet cells. The age advancement accompanied by increasing in the length of the villi and intestinal glands with the thickening in the muscular wall, also increasing the number of the goblet cells. The cecal tonsils become prominent.
The liver of the studied birds lies in the ventral part of the cranial half of body cavity. The relation of the caudal end of the liver to the end of the sternum differ according to the age of the birds. The study revealed that the liver is composed of right lobe and left lobe. The left hepatic lobe is divided only in the chicken .
The liver represents about 4.4 % of total body weight in duck, 2.68 % in chicken and 3.2 % in pigeon. The weight of the liver increases by about 25 time from one day to six month old age in the duck, 18 time in the chicken and 4 time in the pigeon. Among the two lobes of the liver, the right one is the heavier and largest one.
The gall bladder present in the duck and chicken but absent in pigeon. It lies in fossa for gall bladder in the cranial half of the visceral surface of the right lobe of the liver. The fossa is more deep in the duck than in the chicken.
The gall bladder is dilated sac in duck with cranially directed apex, while in chicken it is tubular sac with caudally directed apex .On the right lobe of the liver in the duck and chicken, ductus hepatocysticus open from the right lobe to the gall bladder and ductus cystoentericus pass from the gall bladder to the distal ascending loop of the duodenum beside the hepatoenteric duct. In the pigeon, the cystoenteric duct is absent so, the right hepatoentric duct which arises from the right hepatic duct open distally in the ascending duodenum, while the left hepatoentric duct open in the proximal part of the descending duodenum.
The liver of one day post-hatching birds is covered by thin layer of capsule and is formed from clusters of hepatocytes arranged in irregular anastomosing cords. With the age advancement the hepatic cords are arranged in regular manner as two cells thick.. The portal triads are clear and more scattered in the parenchyma of the liver.
During the studied stages of the development of the gall bladder. In the duck, the villi are short, lymphocytic infiltration were increased with the age advancement, but in the chicken, it is quite tall villus in comparison with the duck. The thickness of the core was increasing by the age advancement.
The obtained results are compared and discussed with those of the duck, chicken and pigeon and other birds.
The nomenclature used is adopted according to Nomina Anatomica Avium 1979.