IVRI Anatomy
A free veterinary anatomy learning platform for B.V.Sc., M.V.Sc., DVM and veterinary medicine students worldwide, developed at the Veterinary Anatomy Section, ICAR-Indian Veterinary Research Institute, Bareilly—covering VCI/MSVE and international university curricula through regional anatomy, histology, embryology, comparative biomechanics, clinical notes, quizzes and revision.
A complex composite bone forming the lateral wall of the cranial cavity and housing the auditory and vestibular apparatus. It results from the fusion of the squamous, petrous, and tympanic parts.
Squamous Part: Forms the lateral wall of the cranium. It features the mandibular fossa for articulation with the mandible (TMJ). In the ox, this fossa is saddle-shaped (convex-concave) to allow for lateral grinding movements. The zygomatic process projects forward to overlap the temporal process of the zygomatic bone, forming the zygomatic arch.
Petrous Part: The hardest bone in the body, housing the cochlea and vestibular apparatus. It projects into the cranial cavity and is not visible externally.
Tympanic Part: Forms the Bulla Tympanica (osseous bulla). In the ox, the bulla is laterally compressed, rough, and less bulbous than in carnivores. It bears the external acoustic meatus, which faces laterally.
Hyoid Process: The styloid process (vagina processus styloidei) is a sheath-like bony projection that encloses the root of the stylohyoid bone of the hyoid apparatus.
| OX (BOS TAURUS) | Tympanic bulla compressed laterally; rough surface. Zygomatic process curved; forms wide arch. Small mastoid process; part of nuchal line. Glenoid fossa (TMJ) concave-convex. External acoustic meatus directed laterally. |
| HORSE (EQUUS CABALLUS) | Tympanic bulla large, bulbous, smooth (shell-like). Zygomatic process short; overlaps zygomatic bone. Small but distinct mastoid process. Convex/Concave; allows lateral grinding. Directed laterally. |
| DOG (CANIS LUPUS) | Tympanic bulla very large; elongated vertically; flask-shaped. Zygomatic process long; overlaps zygomatic bone. Very long and distinct mastoid process. Convex/Concave; allows grinding. Directed dorsolaterally. |
| PIG (SUS SCROFA) | Tympanic bulla distinct; fused with paraoccipital. Zygomatic process short; robust mastoid. Distinct. Deep groove; strictly hinge-like (ginglymus). Directed ventrolaterally. |
| FOWL (GALLUS DOMESTICUS) | Tympanic bulla absent (analogous structures differ). Part of temporal fossa rim (squamosal). Absent. Articulates via Quadrate bone (not TMJ). Not applicable. |
Explore the hidden mechanics of why structures are present, absent or modified across domestic and wildlife species—and how each anatomical design supports movement, function and clinical practice.
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