Avian Anatomy Final (PDF)

 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...

 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 Both limbs of the duodenum are held together by-1 narrow fold of mesentery; pancreaticoduodenal fold The duodenum is held to the gizzard and liver by -2 :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 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.in fowl short garland-like coils-1.In duck and goose several U-shaped loops-2.in pigeon a cone-shaped mass-3 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 :From hatching untill the 15 th days-1 liver has yellow colour due to pigments carried with the lipid from the yolk to the liver in the.late stages of incubation In old bird: the liver is dark brown-2 :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 - 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 : Parietal (ventral ) surface-1 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 Visceral ( dorsal) surface -2 it is irregularly concave & has many. impressions B- Border : 3 borders sharp lateral border -1 sharp caudal border-2 blunt medial border -3  : Bile duct system In domestic fowl each lobe is drained by a separate bile duct Right Ascending lobe 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- : The exocrine portion-1 pour their secretion into the ascending. duodenum through the pancreatic ducts : The endocrine portion-2 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 Respiratory System ‫أولم يروا الى الطير فوقهم صافات و يقبضن‬ ‫ما يمسكهن اال الرحمن‬  Respiratory system Functions: -provide oxygen to the blood. -Remove carbon dioxide from the blood. -Eliminate heat from the body. Parts of respiratory system: 1-Nasal cavity. 2-Larynx. 3-Trachea. 4-Syrinx.  Nasal cavity. -Cone shaped. -It opens ventrally to oropharynx through choanal slit and rostrally to exterior through nostrils. General function of nasal cavity: -Olfaction. -Filtration of airborne particles. -Humidification of inspired air. Nostrils: -Are elongated narrow slit at base of upper beak. -They are overlaped dorsally by a sheet of horny skin called operculum in fowl and turkey. -They may be screened by feather as in crown. -They may be entirely closed by secondary overgrowth of cornified cells as in gannets. Regions of nasal cavity: 1-Rostral vestibular region: -Lined by stratified squamous epithelium. -It contains the rostral (ventral) concha 2-Respiratory region: -Lined by mucocilliary respiratory epithelium. -It contains the middle (maxillary) concha 3-Olfactory region: -Lined by olfactory epithelium. -It contains the caudal (dorsal or olfactory) concha Nasal septum: -Divide nasal cavity completely into right and left nasal cavities. -Partially bony and partially cartilaginous. -In the aquatic birds the nasal septum is perforated rostrally. Nasal concha: -It is cartilaginous, may be partly or entirely bony. -It increases surface area of nasal cavity. -There are three conchae: rostral ,middle and caudal. A)Rostral nasal concha: -C- shaped. -Absent in some birds. - lined by stratified squamous epithelium. B) Middle nasal concha: -The largest concha. -Scroll like. -Present in birds generally. -Continuous with the nasal cavity. -lined by mucociliary respiratory epithelium. C) Caudal nasal concha: -Hollow mound. -Absent in some birds. -Connects to the infraorbital sinus but not to the nasal cavity. -Lined by olfactory epithelium. Infraorbital sinus: -Wide triangular cavity under skin. -It lies rostroventral to eye. - Its wall is formed from soft tissue. -Its lumen has two exits, both situated in its dorsal wall. -It is lined by stratified squamous epithelium rostrally and by mucociliary respiratory epithelium caudally. -Absent in a few species. Nasal (salt) gland : -Two lobes (medial & lateral). -Each lobe opens in vestibule of nasal cavity. -In some species as fowl only medial lobe present. -Functions of nasal gland: 1-Secrete 5% solution of Nacl in marine birds. 2-Osmoregulatory function in some desert species.  Larynx Position: -The larynx (cranial larynx) is situated on floor of pharyngeal cavity. -It enclosed within laryngeal mound. Function: 1-Modulate voice. 2-Prevent foreign bodies entrance. The inlet of the larynx: -The inlet (glottis) is a narrow slit. -Supported by arytenoid cartilages. The laryngeal skeleton: -Consists of 4 cartilages: -Two single (cricoid, procricoid). -One paired (arytenoid). Thyroid and epiglottic cartilages are absent. (1) Cricoid cartilage: -like a sugar scoop. -Consists of 3 components body and two wings. -Each wing articulates with procricoid cartilage. (2) Procricoid cartilage: -Comma shape. - Consists of rostral body and caudal tail. a) Body articulates with the bodies of right and left arytenoid cartilages. b) Tail articulate with right and left cricoid cartilages. (3)Arytenoid cartilages: - Tunning fork like. -Ventral limb of fork is body articulates with procricoid. - Dorsal limb of the fork is the caudal process. - The hand of the fork is rostral process. - Glottis is narrow slit between the two arytenoids. Laryngeal mound: - carrying the inlet of the larynx. - It is heart-shaped elevation. -Each side of the mound bears four rows of caudally directed papillae : 1-A rostral transverse row. 2-A caudal transverse row. 3-Two sagittal rows of small papillae.  Trachea Tracheal cartilages: - The trachea consists of cartilagenous rings. - Each ring is complete and not C-shaped as in mammals. -First and the last four rings are simple while the remainder are like a signet ring. -The broad part forming left and right halves alternated with successive rings. - Each broad part overlapes externally the narrow parts of two adjacent rings. -The rings are connected by anular ligaments. :Course of trachea.Its cranial end lies in midline ventral to esophagus- After 3-5 cm it passes to right side of neck ventral to -. esophagus.As it approaches thoracic inlet it returns to midline-.In the body cavity it lies ventral to esophagus -.Above base of heart it divides into two main bronchi- The terminal part of the trachea and the first part of the -.main bronchi are modified to form syrinx  Syrinx Function and position: -The syrinx or caudal larynx is the organ of voice. -It lies at bifurication of trachea. Types of syrinx: According to origin of its cartilages, it can be classified into three types: 1-Tracheal. 2-Tracheobronchial (majority of birds). 3-Bronchial. - Structure of syrinx: -The syrinx is composed of hard and soft structures. -Hard structure: consists of four cartilages. -Soft structure : consists of 2 pairs of vibrating membranes. A-Cartilages of the syrinx: 1-Cranial cartilages or tympanum: - Four tracheal cartilages. - It is absent in bronchial type. 2- Pessulus: - Wedge shape cartilage. - lies at bifurication of trachea. - In pigeon it is represented by a connective tissue. 3-Intermediate cartilages: - Four in number. -C-shaped attached to the pessulus at its ventral end and free at its dorsal end. 4- Caudal or bronchial cartilages: -Three in each side. -C-shaped. (B)Vibrating membranes: Voice is produced by two pairs of thin membranes. 1-Lateral 1-L or external tympanic membrane: - It is attached dorsally and ventrally to pessulus. 2-Medial 2-Me or internal tympanic membrane : -It forms medial wall of divided part of syrinx. -It is held between the free ends of the three caudal cartilages of the syrinx.  Lungs -There are no lobes as in mammals. Position: -They are dorsal in position, lying in roof of cranial part of body cavity. -The liver, not lung as in mammals, lies on each side of heart. Description: A-Two borders: 1-Dorsal border parallel to the vertebral column. 2-Ventral border is sharp. B- Three surfaces: A-Dorsolateral or costal surface. B-Dorsomedial or vertebral v l surface. C-Ventromedial or septal surface. Bronchial distributions 1-Primary (main) bronchi: - Each bronchus enters hilus then it runs within lung to reach its caudal extremity where it continues with abdominal air sac. 2-Secondary bronchi: - Four groups arise from primary bronchus. - They named according to region they supply. 1-Medioventral secondary bronchi: 4 in number. 2-Mediodorsal secondary bronchi: 8 in number, 3-Lateroventral secondary bronchi: 8 in number. 4-Laterodorsal secondary bronchi: 25-30 numbe -The first group arises from dorsomedial wall of cranial third of primary bronchus. -The other three groups arise from opposite surfaces of caudal two thirds of primary bronchus. -The fourth group has scattered origin instead of arising in a linear manner as other groups. 3-Parabronchi (tertiary bronchi ): -Large numbers of small & uniform tubes. -Arise from mediodorsal secondary bronchi. -Anastomse freely with each other. -Have a constant diameter. 4-Atria: -Pocket like polygonal dilated cavities. -Open into parabronchi. 5-Infundibula: - Small funnel-shaped cavities. -Open into atria. -They lead into air capillaries. 6- Air capillaries: -Narrow tubes, anastome with each other forming network. -They are surrounded by blood capillaries. - Here gases exchange take place.  Air sacs -They are very thin walled structures. -Joined to the lungs. Function of air sacs: -They reduce the specific gravity of body. -They componsate the small total capacity of lung. -They also play a role = in regulating the body tempature = in the even distribution of body weight during flight. = in voice production. Number of air sacs: In embryo: there are six pair (12) of air sacs. Two pair are fused forming clavicular air sac. Another pair are fused forming cervical air sac. In adult: there are eight ( 8 ) air sacs which are: - One cervical air sac. - One clavicular air sac. - Two cranial thoracic air sacs. - Two caudal thoracic air sacs. - Two abdominal air sac. Classification: 1-Cranial group: -They are four : cervical, clavicular and two cranial thoracic. -They arise from the medioventral secondary bronchi. 2-Caudal group: -They are also four : two caudal thoracic and two abdominal. -They arise from the lateroventral secondary bronchi. 1-Cervical air sac: Consists of main chamber and 2 diverticula. 1-The main or median chamber lying between the lungs and dorsal to esophagus. 2-Two diverticula : on each side of vertebral column, one inside the neural canal and one outside. 2-Clavicular air sac: -Large sac occupying thoracic inlet. -It consists of 2 diverticula : 1-Intrathoracic diverticula: extend around heart and along sternum. 2-Extrathoracic diverticula: spread between bones and muscles of pectoral girdle and shoulder joint. 3- Cranial thoracic air sca: -Each consists of simple cushion-like cavity. -Has no diverticulae. 4- caudal thoracic air sac: -very small. -Has no diverticulae. 5- Abdominal air sac: -It is larger than the other air sacs -They like a thin walled ballon extending from the lung into the pelvic cavity. -They have 3 paired perirenal diverticulae.