Curved long bones forming side walls of thorax.

Ox Standard:
- Number: 13 pairs (= number of T-vertebrae).
- Sternal (true) ribs: 8 pairs — reach sternum directly.
- Asternal (false) ribs: 5 pairs — last 4-5 form COSTAL ARCH; last rib usually FLOATING.
- Each rib has: Head, Neck, Tubercle, Body (shaft), Costal cartilage.
- Costal groove on caudal border (carries Vein-Artery-Nerve = VAN).

THE BARS OF THE RIB CAGE

Ribs are flat, curved bones connecting thoracic vertebrae (dorsally) to sternum (ventrally), forming the side walls of the chest.

PARTS OF A TYPICAL RIB:
• Head: Articulates with 2 vertebrae (its own + the one in front) — a double joint.
• Neck: Constriction below head.
• Tubercle: Articulates with transverse process of its own vertebra.
• Angle: Where the rib bends.
• Shaft (Body): Long curved part. Caudal border has a groove (costal groove) where the intercostal vessels and nerve run.
• Costal Cartilage: Distal end; cartilaginous; joins sternum or the rib in front.

CLASSIFICATION:
• Sternal/True ribs (8 in ox): Cartilage reaches sternum directly.
• Asternal/False ribs (5 in ox): Cartilages join the rib in front to form the costal arch (palpable rim at the side of the abdomen).
• Floating rib: Last rib whose cartilage ends free in the muscle.

FIRST RIB: Shortest, strongest, almost vertical. Forms the bony border of the thoracic inlet.

CLINICAL POINT: When giving an injection or doing paracentesis, the needle is placed along the cranial border of a rib because the vein-artery-nerve bundle runs along the caudal border.