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.
The parietal bones in the ox are a remarkable example of osteological displacement. Due to the massive caudal expansion of the frontal bones, the parietals are relegated to the lateral and nuchal aspects of the skull.
Location: They form the upper part of the lateral wall of the cranium, situated below the frontal bone and above the occipital bone. They do not form the skull roof (calvaria) as they do in the horse, dog, or human.
Structure: In the adult ox, they are fused with the interparietal and supraoccipital bones. The line of fusion is often indistinct.
Temporal Line: The parietal bone contributes to the temporal line, forming the upper boundary of the temporal fossa.
Situated centrally between the parietal bones and the supraoccipital. In the ox, this bone is distinct in the fetus but undergoes rapid fusion.
Ossification: It ossifies from two centers but fuses quickly with the parietals and occipital in the calf.
Internal Occipital Protuberance: The internal surface bears this projection, which is located on the interparietal bone in the ox, serving as a landmark for the tentorium cerebelli.
| OX (BOS TAURUS) | Parietals: Nuchal/Lateral aspect only; not dorsal. Fuses early with occipital/interparietal. Interparietal: Fuses internally with supraoccipital; rarely distinct in adults. |
| HORSE (EQUUS CABALLUS) | Parietals: Dorsal; forms cranial roof. Fuses late; distinct sutures visible. Interparietal: Distinct in foals; fuses in adults but remains centrally located. |
| DOG (CANIS LUPUS) | Parietals: Dorsal; forms cranial roof. Fuses late; distinct sagittal suture. Interparietal: Often fuses with supraoccipital to form large triangular nuchal crest. |
| PIG (SUS SCROFA) | Parietals: Lateral/Nuchal; vertical orientation. Fuses early. Interparietal: Fuses early; indistinguishable. |
| FOWL (GALLUS DOMESTICUS) | Parietals: Fused with frontal/occipital. Fuses very early; sutures invisible. Interparietal: Absent or completely fused in embryo; no sutural trace. |
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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