Educational resource developed at the Veterinary Anatomy Section, ICAR-Indian Veterinary Research Institute (ICAR-IVRI), Bareilly.
📝 STANDARD DESCRIPTION:
Avian Wing (Fowl):
- Pectoral girdle = Scapula + Coracoid + Clavicle.
- Clavicles fuse ventrally to form the Furcula (wishbone).
- Humerus is pneumatic (air-filled).
- Distal carpals + metacarpals fuse into a single Carpometacarpus.
📚 DETAILED DESCRIPTION:
FORELIMB OF THE FOWL — THE WING
The wing keeps the same basic segments as the mammalian forelimb (girdle, brachium, antebrachium, manus), but the bones of the girdle and the manus are reduced in number and fused for rigidity.
PECTORAL (SHOULDER) GIRDLE — THREE BONES:
• Scapula: long, narrow and sabre-like; lies almost horizontally along the dorsal thorax, parallel to the vertebral column.
• Coracoid: short, stout and the strongest bone of the girdle; forms a rigid strut from the shoulder to the sternum.
• Clavicles: the two clavicles fuse at the midline to form the furcula ('wishbone'). Its ventral median projection is the hypocleidium.
TRIOSSEAL CANAL:
Where the scapula, coracoid and clavicle meet, a foramen called the triosseal canal is formed. The tendon of the supracoracoideus muscle passes through it and turns over the shoulder to insert on the dorsal humerus, so this ventral muscle raises (elevates) the wing.
SHOULDER JOINT:
The glenoid cavity is formed jointly by the scapula and the coracoid.
BRACHIUM — HUMERUS:
• A pneumatic bone: a pneumatic foramen in the pneumatic fossa on the proximal caudal aspect admits a diverticulum of the clavicular air sac.
• Proximal end carries the head and prominent deltoid and ventral tubercles for the powerful flight muscles.
ANTEBRACHIUM — RADIUS & ULNA:
• Radius: the slender, straighter of the two, lying cranially.
• Ulna: stouter and bowed (caudal). Its caudal border bears small papillae (quill knobs) for the secondary flight feathers.
• The two bones remain separate, allowing the wing to fold and extend.
MANUS — CARPUS, CARPOMETACARPUS AND DIGITS:
• Only two free carpal bones remain — the radiale and the ulnare.
• The distal carpals fuse with the metacarpals to form the single carpometacarpus.
• Three reduced digits are present: the alular digit (carries the alula or 'bastard wing'), the major digit and the minor digit.
STERNUM (associated):
The sternum bears a deep median keel (carina) that greatly enlarges the area of attachment for the pectoralis and supracoracoideus muscles.
UG MEMORY: 'Girdle = 3 (scapula, coracoid, clavicle/furcula); Carpals free = 2 (radiale, ulnare); Digits = 3 (alular, major, minor).'
// COMPARATIVE ANALYSIS
| OX / HORSE / DOG |
Girdle is reduced to the scapula alone (clavicle absent or vestigial); the limb is slung to the trunk by muscle. No coracoid strut and no furcula. |
| FOWL |
Girdle has three bones. The coracoid braces the shoulder against the sternum and the fused clavicles (furcula) act as a spring between the shoulders during wing beats. |
| FOWL |
Carpus has only two free bones (radiale, ulnare) and the manus is fused into a carpometacarpus, whereas the ox has six and the horse seven or eight carpal bones. |
CLINICAL RELEVANCE
Intraosseous fluid therapy: Use the distal ulna or the proximal tibiotarsus. Never use the humerus or femur — they are pneumatic and communicate with the air sacs, so injected fluid would enter the respiratory system.
Wing fractures: The radius and ulna are commonly fractured; because the ulna carries the secondary feathers, callus or malunion here affects flight.
Furcula and keel: The keel is used for body-condition scoring in poultry; a prominent keel indicates loss of pectoral muscle mass.
