Bones - Dog Anatomy

Great Dane and Chihuahua Skeletons, Sklmsta, March 2010

Introduction

This page is concerned with highlighting the bone anatomy of the domestic dog which will include the major aspects of the anatomy and most of the minor elements of anatomy. Very detailed anatomy of individual bones is not covered below due to space restrictions.

The anatomical information included below is commonly split into three separate areas; head, trunk and the forelimbs / hindlimbs. Therefore the following information will use this concept to facilitate easier understanding of the individual areas of anatomy.

Basic Overview

Dog skeleton, TBjornstad, 2006

Head

Anatomically the head encompasses all bones cranial to the cervical vertebrae of the neck and is shown in yellow in the diagram above. The head consists of a number of complex bones of varying types and size which will be both described in text and where possible will also be shown photographically.

Trunk

The trunk is in broad terms the body of the animal and is what would remain if the head and limbs were removed. It can be seperated in four parts, the cervical vertebrae (pink above), thorax (orange above), lumbar region (dark blue above) and pelvis (red, label 6 and torquiose above). Anatomically these structures are highly distinguishable and each area has a distinctive shape, size and physiological role.

Head

The head is mainly comprised of the skull, mandible, ossicles and hyoid apparatus. Asscessory cartilage is also present within the external ear, larynx and nose.

Skull

Lateral View of a Canine Skull, Cambridge Natural History Mammalia Fig 014. (C.occ - Occipital condyle; F - frontal; F.inf - infra-orbital foramen; Jg - zygomatic arch; Jm - premaxilla; L - lachrymal; M - maxilla; Maud - external auditory meatus; Md - mandible; N - nasal; P - parietal; Pal - palatine; Pt - pterygoid; Sph - sphenoid; Sq - squamosal; Sq.occ - supraoccipital; T - tympanic. (From Wiedersheim's Comparative Anatomy.)

The shape and size of the skull varies widely between different breeds of dog. The skull is divided into three components - the neurocranium, the dermatocranium and the viscerocranium.The skull comprises of many individual bones that are fused together to form a strong single structure. These individual bones in adults are fused via ossification of the cartilage between bones that is found in young animals. The skull protects the brain and head against injury and supports the structures of the face. The neurocranium develops from the neural crest and mesoderm and undergoes endochondral ossification. It lies ventral to the brain. The dermatocranium lies dorsal to the brain and develops from the neural crest and mesoderm. It undergoes intramembranous ossification. The viscerocranium is the pharyngeal skeleton. It is derived only from the neural crest and undergoes endochondral and intramembranous ossification. The various facial muscles attach onto the skull in different places depending on their function. The classification of bones within the skull is based on the traditional views of skull drawings such as the historical drawing shown on the right.