Avian Anatomy 1 (1) PDF

‫المحاضرة االولى‬  Digestive System The avian digestive system consists of: 1-Oral cavity and pharynx. 2-Alimentary tract which comprises: a) Esophagus b) Stomach c) Small intestine -Duodenum -Jejunum -Ileum d) Lar...

‫المحاضرة االولى‬  Digestive System The avian digestive system consists of: 1-Oral cavity and pharynx. 2-Alimentary tract which comprises: a) Esophagus b) Stomach c) Small intestine -Duodenum -Jejunum -Ileum d) Large intestine -Paired ceca -Colon or rectum 3-Accessory glands which include: - Salivary glands. - Liver. - Pancreas.  Oral cavity -Absence of glossoplatine arch and so oral cavity and pharynx form one cavity called oropharynx. -Absence of soft palate and so pharynx not divided to nasal and oral parts. -Absence of lips and teeth, they replaced by upper and lower beaks. -Oral opening is the entrance of oral cavity. * Beak appearance varies in different birds: 1-Fowl & pigeon: -Pointed beak, sharp tomia, and rigid horny sheath. -Upper beak project give hook like manner beyond lower one. 2-Duck &goose: -Blunt and sharp like spoon beak. -Covered by soft yellow waxy skin called ceroma. -Soft, flexible horny sheath forming horny plate like a finger nails. -Honey lamellae along upper &lower beak. *Roof of oral cavity: 1-Formed of incomplete hard palate. 2-It communicates with the nasal cavity through the choana (coanal cleft or slit). 3-Choana (choanal cleft): - Lies in midline in caudal half of palate. -Connects oropharynx with nasal cavity. -Consists of narrow rostral and wide caudal parts. 4-mucous membrane of hard palate has palatine ridges & papillae. *Palatine ridges: 3 in number 1-Median palatine ridge: on rostral part of palate. 2-Two lateral palatine ridges: laterally from median ridge. *Palatine papillae: -They directed caudally , arranged in five transverse rows , close to midline: 1-Two rows rostral to choana. 2-Two rows on each side of narrow part of choana. 3-Caudal row at junction of narrow &wide parts of choana. 4-Small few papillae are irregularly distributed on palate. *Palate submucosa: Contains paired maxillary & medial palatine and lateral palatine salivary glands. *Cheeks: -It is the lateral wall of oral cavity. -submucosa has salivary glands. *Floor of oral cavity: -Covered by free part of tongue. -Submucosa has paired rostral mandibular salivary glands.  Tongue -Type and Function: 1-long and protrusible for collecting food. 2-Thicker and non-protrusible for moving (swallowing) food. -Shape: vary according to lower beak. -Fixation: fixed by 1-hyobranchial apparatus apex 2-Fraenulum linguae. body -Structure: -apex, body and root. -Median groove on dorsal surface. -Transverse row of lingual papillae present between the body &root. -Extrinsic muscles on all tongue except apex. Microscopically: - No internal muscle. - Consists of connective tissue, adipose tissue and glands. -Lamina propria contains lingual salivary glands. -Birds have far fewer taste buds than mammals. (2)Pharynx: *Roof of pharynx: -Divided by infundibular slit. -Mucous membrane has papillae. -Submucosa contains sphenopterygoid salivary glands. *Floor of pharynx: -Rostral part formed by root of tongue. -Caudal part carries laryngeal mound. -Submucosa has caudal submandibular and cricoarytenoid glands. Laryngeal mound  Salivary glands Occurrence: -Well developed in birds have dry diet. -ill developed in birds have lubricated diet. -Absent in few birds. -Secretion: mucous -Function: secret saliva act as a lubricant in swallowing. -Classification: A- According to site of their openings: (1) Into mouth cavity: Maxillary, palatine, rostral lingual, rostral submandibular &mouth angle gland. (2) Into pharyngeal cavity : Sphenoptrygoid, caudal lingual, caudal mandibular &cricoarytenoid glands. B- According to number of their openings: (1) Monostomatic S. G.: - Which are the maxillary and the glands at the angle of the mouth. (2) Polystomatic S.G.: -All polystomatic except maxillary & gland at angle of mouth are monostomatic. C- According to their situation: -All in submucosa except lingual salivary gland in tongue lamina propria.  Esophagus: -Thin walled & extendible tube with large diameter. -Connects pharyngeal cavity to stomach. -Divided to longer cervical &short thoracic parts. 1)Cervical part: - lies in the midline dorsal to the larynx and trachea. - - Caudal to the fifth cervical vertebra it inclines to become in the right side of the neck (the opposite side to the mammals) -cranial to the thoracic inlet it returns to the midline and enlarges ventrally to form the crop. Crop: -It is distensible diverticulum of the esophagus for storing food for a short time -The shape of the crop differs in various species: -In domestic fowl: is a thin-walled sac. attached to the skin. -In pigeon: 2 large lateral sacs -In aquatic birds (duck &goose): simple spindle shape ( no true crop). 2)Thoracic part: -It is shorter than the cervical part. -It extends caudally in the thorax dorsal to the trachea and the base of the heart. - It ends in the glandular stomach. -Surrounded by cervical and clavicular air sacs. Esophagus function: 1-Transport food. 2-Site of physical digestion. 3-Crop milk formation. Crop milk: -Fed by pigeon &doves to their young. -Both sexes. -Produced by desquamation of fat-laden cells. -Its epithelium proliferation: at 6th day of incubation. -Its secretion: at 16th day of incubation extending to 2 weeks after hatching. -Its composition similar to mammalian milk. -Very rich in fat &protein. -Lack in carbohydrate &calcium.  Stomach It cosists of 2 parts: 1 - Glandular stomach (proventriculus). 2 - Muscular stomach (ventriculus or gizzard). Glandular stomach A) Glandular stomach: Function: production of an acid (HCL) and proteolytic gastric juice. - Shape: - Elongated spindle shape, 5 cm long. - It continues cranially with the esophagus without any distinct demarcation, - However, there is a distinct constriction (isthmus) at the junction with muscular stomach. -Position: -Lower left quadrant of body cavity. -Cause depression on dorsal surface of liver. -Relation: -Related to left abdominal& caudal thoracic air sacs. -Structure: -Its wall is thicker than that of esophagus. - It is lined Simple columnar epithelium. -Has compound tubular glands open on raised papilla on the mucous membrane. B)Muscular stomach "gizzard”: Function: -The muscular stomach is a “masticatory” organ. - It triturates the food by: 1-Powerful contractions of the muscle 2-Tough internal tunica cuticula 3-Presence of folds 4-Presence of stones in the lumen. Shape: - likes large biconvex lens, red &firm. - Craniocaudal diameter is greater than dorsoventral one. Position& relation: -It fills the left lower guadrant of the body cavity. -It has contact with the sternum and The left lateral abdominal wall, thus exposed when the sternum and the abdominal muscles are removed. Description: -The muscular stomach is formed of: 1-Body: It is the main part of the muscular stomach. It has thick wall. 2-Two blind sacs: They are small thin walled sacs They are: a) Craniodorsal blind sac. B) Caudoventral blind sac. -The craniodorsal blind sac opens in the glandular stomach cranially and with the duodenum on the right side. Structure: A) Internal surface -On the surface of the epithelium is a hardened membrane called cuticule. -It is produced by the glands and the surface epithelium - Over the body the cuticle is thick and has longitudinal parallel folds, but over the blind sacs the cuticle is thinner and has longitudinal and transverse folds which form a network. -It is usually brown, green or yellow in colour due to regurgitation of bile pigment from the duodenum. -The cuticle is being worm away by grinding movements. B)Muscles: - The gizzard is formed of 4 smooth muscles which attached to glistening right and left tendinous aponeurosis (tendinous center). -These muscles are: 1-Two thick lateral muscles (dorsal and ventral) of the body. 2-Two thin intermediate muscles (craniodorsal and caudoventral) of the blind sacs.  The intestinal tract Small intestine Large intestine Two ceca Duodenum Short colon (Rectum) Jejunum Ileum Jejunum Ileum colon  Duodenum -The duodenum passes caudally from the right surface of the gizzard. -It forms U shaped loop with descending & - ascending limbs. -The pancreas lies between the two limbs of the - duodenum Ascending limb Descending limb pancreas duodenum Fixation of the duodenum: 1-Both limbs of the duodenum are held together by narrow fold of mesentery; pancreaticoduodenal fold 2-The duodenum is held to the gizzard and liver by two ligaments: a) Suspensory ligament of the duodenum. b) Hepatoduodenal ligament Bile and pancreatic ducts: -They open into the ascending duodenum. - In fowl there are two ducts from the liver and two or three ducts from the pancreas. #The lumen of the duodenum is wider than that of other parts of the small intestine. Jejunum -The jejunum is the longest intestinal segment. -It is so thin-walled that its content causes it to appear greenish in colour. -It forms loose coils along the edge of the long mesentery. -Proximal & distal parts of the jejunum are nearly straight while most of the jejunum form : 1-in fowl short garland-like coils. 2-In duck and goose several U-shaped loops. 3-in pigeon a cone-shaped mass. -Vitelline diverticulum or Meckel’s diverticulum is small outgrowth represents the reminent of the yolk sac found on the convexity of the jejunum. Ileum - Yellowish to reddish gray in color - Is flanked by right & left ceca The ileum is flanked on both sides by the ceca, to which it is joined by the ilioceal ligament. - It is continuous with the rectum caudally where there is a small constriction -It begins at the vitelline diverticulum or opposite the apices of the ceca. colon Cecum -In most birds there are two ceca arise at the junction between ileum & rectum. - In some birds only one cecum is present. - It is absent in carnivores birds & parrots - -The ceca in fowl, duck and goose are well developed, - while that of the pigeon is very short and appears as bud- like appendages to the colon. -Each ceca has base ( proximal part ) , body (middle part ) & apex (distal part ). - Base & apex are light red in color while the body is bluish green to grayish green. -The base is very thick wall due to the presence of heavy muscle coat (cecal sphincter) and much lymphoid tissue (cecal tonsil). Colon or rectum: - Is the direct continuation of the ileum. - Light gray to green in color. -It lies below the vertebral - column and ends at the coprodeum of the cloaca. - It is suspended by a short mesentery from the dorsal wall of the abdominal cavity which continuous with that of the ileum. Accessory glands : Liver The size ,weight , consistancy & color of the liver depend on the breed , age , & nutritional state of the individual bird. Color: 1-From hatching untill the 15 th days: liver has yellow colour due to pigments carried with the lipid from the yolk to the liver in the late stages of incubation. 2-In old bird: the liver is dark brown Lobation: Left lobe It cosists of right & left lobe : a- Right lobe : - it is heart shape - It is larger than the left lobe. -It carries gall bladder in its visceral surface and is perforated by caudal vena cava. b- left lobe : Right lobe - it is smaller in size & prismatic in shape. - it is divided caudally by fissure into caudo dorsal & caudoventral parts. **The two lobes are separated caudally by deep caudal notch and cranially by shallow cranial notch. ** The two lobes are connected by a parenchymatous bridge on dorsal surface of which there is transverse fossa which resembles the hepatic porta in mammals. *** The gall bladder : lies on the dorsal aspect of the right lobe - In fowl it is pear-shaped - In aquatic birds it is more tubular in shape. - it is absent in pigeon & parrots. G.b Right lobe EXTERNAL ANATOMY OF THE LIVER : A- surfaces : parietal & visceral surfaces 1-Parietal (ventral ) surface : - smooth & convex but its cranioventral part is concave in both lobes to lodge the apex of the heart. - it is close to the ventral & lateral body wall. 2- Visceral ( dorsal) surface it is irregularly concave & has many impressions. B- Border : 3 borders 1- sharp lateral border 2-sharp caudal border 3- blunt medial border  Bile duct system : In domestic fowl each lobe is drained by a separate bile duct Right lobe Ascending Hepatocystic duct G.B Cysticoenteric duct duodenum directly Left lobe Hepatoenteric duct Ascending duodenum Pancreas: Colour: - It is a pinkish, ribbon-like structure. - it lies between the two limbs of duodenum & enclosed with in the pancreaticoduodenal ligament. Lobation : - Dorsal , ventral & splenic lobes. -The splenic lobe is the smallest. pancreas Structure: -The pancreas has exocrine and endocrine portions. 1-The exocrine portion : pour their secretion into the ascending duodenum through the pancreatic ducts. 2-The endocrine portion : consists of islets of Langerhans which secret glucagon & insulin. Duct system: -In all species pancreatic ducts drain into ascending duodenu -There are three ducts in fowl and pigeon, and two ducts in duck and goose. Spleen - it is belongs to blood forming organs. - it lies on the right surface of the junction of the proventriculus and gizzard In the fowl: it is brownish red in colour rounded or egg shaped. In duck & goose : it is triangular with flat dorsal & convex ventral surface. In pigeon : it is oval & elongated. In duck