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The anatomical information included below is commonly split into separate areas; the '''[[Bones_-_Dog_Anatomy|head]]''' (displayed in yellow on the right), the '''neck''' (displayed in pink), the '''[[Bones_-_Dog_Anatomy|trunk]]''' (displayed in dark blue) and the '''[[Bones_-_Dog_Anatomy|forelimbs]]''' / '''[[Bones_-_Dog_Anatomy|hindlimbs]]''' (displayed in light blue). The limbs will be further sub-divided into proximal and distal anatomy. The following information will use this concept to facilitate easier understanding of the individual areas of anatomy.

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The anatomical information included below is commonly split into separate areas; the '''[[Bones_-_Dog_Anatomy|head]]''' (displayed in yellow on the right), the '''neck''' (displayed in pink), the '''[[Bones_-_Dog_Anatomy|trunk]]''' (displayed in orange and dark blue) and the '''[[Bones_-_Dog_Anatomy|forelimbs]]''' / '''[[Bones_-_Dog_Anatomy|hindlimbs]]''' (displayed in light blue). The limbs will be further sub-divided into proximal and distal anatomy. The following information will use this concept to facilitate easier understanding of the individual areas of anatomy.

=Anatomy of the Head=

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Anatomically the head encompasses all bones cranial to the cervical vertebrae of the neck ~~and is shown in yellow in the diagram above~~. The conformation of the canine head is extremely variable due to selective breeding over many generations. The key characteristics of the head that create this variability include the ear shape and size, eye position and the length of the nose.

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Anatomically the head encompasses all bones cranial to the cervical vertebrae of the neck. The conformation of the canine head is extremely variable due to selective breeding over many generations. The key characteristics of the head that create this variability include the ear shape and size, eye position and the length of the nose.

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. 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.

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[[Image:Pug skull.jpg|thumb|right|150px|'''Brachycephalic skull''', nabrown, 2008]]

[[File:Cambridge Natural History Mammalia Fig 014.png|thumb|right|400px|'''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.) ]]

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The shape and size of the skull varies widely between different breeds of dog. Dogs have different skull lengths depending on breed. '''Mesocephalic''' dogs have average conformation whilst '''dolichocephalic''' dogs have longer skull lengths and '''brachycephalic''' dogs have shorter skull lengths. The skull protects the brain and head against injury and supports the structures of the face. The skull is comprised of many individual bones that are normally fused together in adults to form a strong single structure. The process of bone fusion is called endochondral ossification and represents the process where the various plates of cartilage within the skull are converted to bone. In young animals each bone within the head is seperated by narrow fibrous tissues or 'sutures' and it is these sutures that allow provision for growth. The sections below will highlight these major bone structures of the skull.

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=== Occipital Bone (''os occipitale'') ===

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The occipital bone is the most caudal bone of the skull and the '''external occipital protuberance''' is the most caudal element found medially within the bone. This protuberance provides the attachment for the nuchal ligament. The occipital bone has '''nuchal crests''' laterally and a '''sagittal crest''' medially and dorsally to the external occipital protuberance. The '''sagittal crest''' is prominent and can be palpated in most canines unless they are very well muscled. These elements together form the '''nuchal wall''' and the '''foramen magnum'''. The '''pars basilaris''' element is the caudal base of the cranium, although rostral to foramen magnum and joined by a cartilagenous suture to '''basisphenoid bone'''. It has muscular tubercules on ventral surface where the flexors of the head and neck attach and a caudocranial fossa encloses the pons and medulla oblongata. The squamous part '''''(pars squamosa)''''' is dorsal to lateral parts and occipital condyles. The nuchal crest is often used as a landmark for collection of cerebrospinal fluid (CSF). '''Occipital condyles''' are present which articulate with the atlas to form the atlanto-occipital joint. The '''paracondylar process''' ~~provide~~ muscle attachment sites for muscles of the head. The '''hypoglossal canal''' is also within this structure.

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The occipital bone is the most caudal bone of the skull and the '''external occipital protuberance''' is the most caudal element found medially within the bone. This protuberance provides the attachment for the nuchal ligament. The occipital bone has '''nuchal crests''' laterally and a '''sagittal crest''' medially and dorsally to the external occipital protuberance. The '''sagittal crest''' is prominent and can be palpated in most canines unless they are very well muscled. These elements together form the '''nuchal wall''' and the '''foramen magnum'''. The '''pars basilaris''' element is the caudal base of the cranium, although rostral to foramen magnum and joined by a cartilagenous suture to '''basisphenoid bone'''. It has muscular tubercules on ventral surface where the flexors of the head and neck attach and a caudocranial fossa encloses the pons and medulla oblongata. The squamous part '''''(pars squamosa)''''' is dorsal to lateral parts and occipital condyles. The nuchal crest is often used as a landmark for collection of cerebrospinal fluid (CSF). '''Occipital condyles''' are present which articulate with the atlas to form the atlanto-occipital joint. The '''paracondylar process''' provides muscle attachment sites for muscles of the head. The '''hypoglossal canal''' is also within this structure (see foramen section below).

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=== Sphenoid Bone (''os sphenoidale'') ===

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The sphenoid bone forms the base of the neurocranium and is composed of a body and wings. The bones are separated by cartilage which ossifies with age. The '''presphenoid (''os praespenoidale'')''' is rostral and has a caudal fossa which is a hollow body with sphenoid sinuses located inside. Within the sinuses are the '''optic chiasma''' and '''optic canal'''. The '''basisphenoid (''os basispenoidalis'')''' is caudal and has a '''median cranial fossa'''. The wings oppose the temporal bone, maxilla, orbit and the brain. The wings also form the '''oval foramen'''. ~~The pterygoid processes are also present.~~

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The sphenoid bone forms the base of the neurocranium and is composed of a body and wings. The bones are separated by cartilage which ossifies with age. The '''presphenoid (''os praespenoidale'')''' is rostral and has a caudal fossa which is a hollow body with sphenoid sinuses located inside. Within the sinuses are the '''optic chiasma''' and '''optic canal'''. The '''basisphenoid (''os basispenoidalis'')''' is caudal and has a '''median cranial fossa'''. The wings oppose the temporal bone, maxilla, orbit and the brain. The wings also form the '''oval foramen'''.

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=== Temporal Bone (''os temporale'') ===

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[[Image:Zygomatic arch.jpg|thumb|right|300px|'''Canine Zygomatic Arch''', nabrown, 2008]] The temporal bone is composed of '''squamous, petrosal''' and '''tympanic''' parts and forms the lateral wall of the cranial cavity. It articulates with the frontal, parietal and sphenoid bones. The squamous element joins the temporal process of the zygomatic bone to form the '''zygomatic arch''' and forms the articulating surface of the '''[[Mastication#Jaw_Articulation|temporomandibular joint]]'''. An '''articular tubercle''' and '''mandibular fossa''' are present. Occipital process and retrotympanic processes surround the '''external acoustic meatus''' whilst the petrosal part encloses the inner ear internally via the '''internal acoustic meatus'''. Ventrally this structure forms the '''mastoid process'''. The '''styloid process''' attaches the '''[[Hyoid Apparatus - Anatomy & Physiology|hyoid apparatus]]''' and a '''stylomastoid foramen''' is also present. The tympanic part is the ventral section of the temporal bone containing the '''tympanic bulla'''. The '''tympanic membrane''' separates tympanic cavity from '''external acoustic meatus''' and encloses the '''auditory ossicle''' dorsally. The musculotubal canal contains tensors of the [[Soft Palate#Musculature_and_Innervation|soft palate]].

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=== Frontal Bone (''os frontale'') ===

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The frontal bone is a paired structure joined by the '''interfrontal suture''' between the cranium and the face and enclosing the '''frontal sinuses'''. The nasal and lacrimal bones border the frontal squama section and form the zygomatic process laterally and part of the orbit dorsally. The '''temporal line''' extends into the '''external sagittal crest'''. The nasal section is the rostral part of the frontal bone and the orbital part is perforated by the '''ethmoidal foramen'''. Medially the '''dorsal oblique muscle''' of the eyeball attaches. The temporal part provides the muscle attachments for the '''temporalis muscle'''. ~~ ~~

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The frontal bone is a paired structure joined by the '''interfrontal suture''' between the cranium and the face and enclosing the '''frontal sinuses'''. The nasal and lacrimal bones border the frontal squama section and form the zygomatic process laterally and part of the orbit dorsally. The '''temporal line''' extends into the '''external sagittal crest'''. The nasal section is the rostral part of the frontal bone and the orbital part is perforated by the '''ethmoidal foramen'''. Medially the '''dorsal oblique muscle''' of the eyeball attaches. The temporal part provides the muscle attachments for the '''temporalis muscle'''.

=== Parietal Bone (''os parietale'') ===

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[[Image:Pareital Bone.jpg|thumb|right|300px|'''Parietal Bone''', nabrown, 2008]] The parietal bone is a paired structure and forms the dorsolateral wall of the cranium with the occipital bone caudally and the frontal bone rostrally. It is composed of a parietal plane, temporal plane and a nuchal plane (in the ox). Internally the grooves and ridges correspond with the gyri and sulci of the brain. There is also an '''interparietal bone''' between the occipital bone and the parietal bone which fuses with age.

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[[Image:Pareital Bone.jpg|thumb|right|300px|'''Parietal Bone''', nabrown, 2008]] The parietal bone is a paired structure and forms the dorsolateral wall of the cranium with the occipital bone caudally and the frontal bone rostrally. It is composed of a parietal plane, temporal plane and a nuchal plane (in the ox). Internally the grooves and ridges correspond with the gyri and sulci of the brain. There is also an '''interparietal bone''' between the occipital bone and the parietal bone which fuses with age. ~~ ~~

=== Ethmoid Bone (''os ethmoidale'') ===

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[[Image:Nasal Cavities.jpg|thumb|right|150px|'''Nasal Cavities''', David Bainbridge]] The ethmoid bone forms part of the cranial and facial parts of the skull and is located deep in the orbit. External lamina consist of the roof plate, floor plate and paired orbital plates. The ethmoid bone is separated from the cranial cavity by the '''cribiform plate'''. Numerous small foramina exist where the '''olfactory nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN I]]) passes through. The perpendicular plate splits the ethmoid into two halves and the ethmoid larbyrinth protrudes from the ethmoid tubes. The tubes are composed of two rows of '''ethmoturbinates''' and air filled '''ethmoidal meatuses'''. Secondary ethmoturbinates may also be present. Ethmoturbinates are divided into '''endoturbinates''' and '''ectoturbinates'''. The first endoturbinate forms the dorsal nasal conchae and the second endoturbinate froms the middle nasal conchae. The endoturbinates form 3 nasal meatuses; the '''dorsal nasal meatus''', the '''middle nasal meatus''' and the '''ventral nasal meatus'''.

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[[Image:Nasal Cavities.jpg|thumb|right|150px|'''Nasal Cavities''', David Bainbridge]] The ethmoid bone forms part of the cranial and facial parts of the skull and is located deep in the orbit. External lamina consist of the roof plate, floor plate and paired orbital plates. The ethmoid bone is separated from the cranial cavity by the '''cribiform plate'''. Numerous small foramina exist where the '''olfactory nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN I]]) passes through. The perpendicular plate splits the ethmoid into two halves and the ethmoid larbyrinth protrudes from the ethmoid tubes. The tubes are composed of two rows of '''ethmoturbinates''' and air filled '''ethmoidal meatuses'''. Secondary ethmoturbinates may also be present. Ethmoturbinates are divided into '''endoturbinates''' and '''ectoturbinates'''. The first endoturbinate forms the dorsal nasal conchae and the second endoturbinate froms the middle nasal conchae. The endoturbinates form 3 nasal meatuses; the '''dorsal nasal meatus''', the '''middle nasal meatus''' and the '''ventral nasal meatus'''. ~~ ~~

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=== Nasal Bone (''os nasale'') ===

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The nasal bone is a paired structure and forms the roof of the nasal cavity. '''Dorsal nasal conchae''' attach to the '''ethmoidal crest''' on the internal surface. A rostral suture forms the apex and between the nasal and incisive bones is the '''nasoincisive notch'''.

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The nasal bone is a paired structure and forms the roof of the nasal cavity. '''Dorsal nasal conchae''' attach to the '''ethmoidal crest''' on the internal surface. A rostral suture forms the apex and between the nasal and incisive bones is the '''nasoincisive notch'''. ~~ ~~

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=== Lacrimal Bone (''os lacrimale'') ===

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The lacrimal bone forms part of the lateral wall of the face and orbit and is situated near the '''medial canthus'''. It articulates with the '''frontal bone, zygomatic bone''' and '''maxilla'''. It also articulates with the '''palatine bone''' in canines. It is composed of an orbital and facial part separated by supra- and infraorbital margins. The '''nasolacrimal duct''' is present by the margin of the orbital surface. The '''ventral oblique muscle''' attaches caudal to the margin of the orbital surface. The nasal surface forms the boundaries of the '''maxillary and frontal sinuses'''.

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The lacrimal bone forms part of the lateral wall of the face and orbit and is situated near the '''medial canthus'''. It articulates with the '''frontal bone, zygomatic bone''' and '''maxilla'''. It also articulates with the '''palatine bone''' in canines. It is composed of an orbital and facial part separated by supra- and infraorbital margins. The '''nasolacrimal duct''' is present by the margin of the orbital surface. The '''ventral oblique muscle''' attaches caudal to the margin of the orbital surface. The nasal surface forms the boundaries of the '''maxillary and frontal sinuses'''. ~~ ~~

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=== Zygomatic Bone (''os zygomaticum'') ===

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The zygomatic bone is lateral and ventral to the lacrimal bone and forms the orbit and zygomatic arch. The supraorbital margin is formed by the zygomatic process of the temporal bone and the frontal process of the zygomatic bone. The facial crest is present on lateral surface.

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The zygomatic bone is lateral and ventral to the lacrimal bone and forms the orbit and zygomatic arch. The supraorbital margin is formed by the zygomatic process of the temporal bone and the frontal process of the zygomatic bone. The facial crest is present on lateral surface. ~~ ~~

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=== Incisive Bone (''os incisivium'') ===

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The incisive bone is a paired structure composed of body, nasal, palatine and alveolar parts. It joins with the maxilla to form the '''interalveolar margin'''. It also forms the rostral part of the facial section of the skull, the roof of the '''[[Hard Palate|hard palate]]''' and the opening to the nasal cavity. The alveolar process forms conical sockets for the incisor teeth.

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The incisive bone is a paired structure composed of body, nasal, palatine and alveolar parts. It joins with the maxilla to form the '''interalveolar margin'''. It also forms the rostral part of the facial section of the skull, the roof of the '''[[Hard Palate|hard palate]]''' and the opening to the nasal cavity. The alveolar process forms conical sockets for the incisor teeth. ~~ ~~

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=== Palatine Bone (''os palatinum'') ===

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The palatine bone is a paired structure between the maxilla, sphenoid and pterygoid bones. It is composed of a horizontal plate (forms part of the [[Hard Palate|hard palate]]), perpendicular plate (forms the dorsal and lateral walls of the nasopharyngeal meatus) and the choanae. The '''nasal crest''' is present on the horizontal plate. The '''palatine sinus''' is present on horizontal plate.

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The palatine bone is a paired structure between the maxilla, sphenoid and pterygoid bones. It is composed of a horizontal plate (forms part of the [[Hard Palate|hard palate]]), perpendicular plate (forms the dorsal and lateral walls of the nasopharyngeal meatus) and the choanae. The '''nasal crest''' present on the horizontal plate. The '''palatine sinus''' is present on horizontal plate. ~~ ~~

=== Vomer ===

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The vomer is unpaired and extends from the choanae of the palatine bone to the floor of the nasal cavity. It attaches to the median nuchal crest and has a '''septal sulcus''' which surrounds nasal cavity.

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The vomer is unpaired and extends from the choanae of the palatine bone to the floor of the nasal cavity. It attaches to the median nuchal crest and has a '''septal sulcus''' which surrounds nasal cavity. ~~ ~~

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=== Pterygoid Bone (''os pterygoideum'') ===

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The pterygoid bone is a paired structure bordered by the '''palatine''' and '''sphenoid bones'''. It forms the dorsal and lateral walls of the '''nasopharyngeal cavity'''. The '''pterygoid hamulus''' is formed by the pterygoid bone.

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The pterygoid bone is a paired structure bordered by the '''palatine''' and '''sphenoid bones'''. It forms the dorsal and lateral walls of the '''nasopharyngeal cavity'''. The '''pterygoid hamulus''' is formed by the pterygoid bone. ~~ ~~

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=== Maxilla ===

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The maxilla forms most of the facial part of the skull, including the lateral walls of the face, nasal cavity, [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]] and [[Hard Palate|hard palate]]. It also forms the ventral nasal conchae and articulates with all of the facial bones as it is the largest bone of the face. The maxillary body encloses the '''maxillary sinuses''' and forms the external surface of the face. It also forms the '''facial crest'''. The '''infraorbital foramen''' is palpable. The '''conchal crest''' is on nasal surface where the ventral nasal conchae attaches. The '''lacrimal canal''' opens into the '''lacrimal foramen''' on the nasal surface. The '''pterygopalatine surfaces''' are the caudal part of the maxilla which terminate in the '''maxillary tubercle''' where the '''sphenopalatine, maxillary''' and '''caudal palatine foramen''' are present. The '''alveolar processes''' present are separated by '''interalveolar septa'''. The '''palatine process''' forms the '''[[Hard Palate|hard palate]]''' with the palatine bone. The '''palatine fissure''' is formed at the articulation with the incisive bone. The nasal surface of palatine process forms the '''nasal crest''' and encloses part of the palatine sinuses. The oral surface has numerous palatine foramina present.

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The maxilla forms most of the facial part of the skull, including the lateral walls of the face, nasal cavity, [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]] and [[Hard Palate|hard palate]]. It also forms the ventral nasal conchae and articulates with all of the facial bones as it is the largest bone of the face. The maxillary body encloses the '''maxillary sinuses''' and forms the external surface of the face. It also forms the '''facial crest'''. The '''infraorbital foramen''' is palpable. The '''conchal crest''' is on nasal surface where the ventral nasal conchae attaches. The '''lacrimal canal''' opens into the '''lacrimal foramen''' on the nasal surface. The '''pterygopalatine surfaces''' are the caudal part of the maxilla which terminate in the '''maxillary tubercle''' where the '''sphenopalatine, maxillary''' and '''caudal palatine foramen''' are present. The '''alveolar processes''' present are separated by '''interalveolar septa'''. The '''palatine process''' forms the '''[[Hard Palate|hard palate]]''' with the palatine bone. The '''palatine fissure''' is formed at the articulation with the incisive bone. The nasal surface of palatine process forms the '''nasal crest''' and encloses part of the palatine sinuses. The oral surface has numerous palatine foramina present. ~~ ~~

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=== Mandible (''mandibula'') ===

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The mandible can be divided into the '''body''' and the '''ramus'''. The body of the mandible supports the incisor teeth (rostrally) and cheek teeth (caudally). The section of the body which does not support any teeth is called the '''interalveolar margin''' or '''diastema'''. The mandibule also contains the '''mandibular canal''' and the '''mental foramen'''. The '''facial notch''' is on the ventral surface where the facial vessels run. The '''ramus''' extends from the caudal end of the body dorsally towards the zygomatic arch. The '''masseter muscle''' attaches to the lateral surface at the '''masseteric fossa'''. The '''medial pterygoid''' attaches to the medial surface at the '''pterygoid fossa'''. The angle of the mandible terminates dorsally in the '''condylar process''' and the '''coronoid process''' which are separated by the '''mandibular notch'''. The '''temporal muscle''' inserts onto the '''coronoid head'''. The condylar process articulates with the mandibular process of the skull (see [[Mastication#Jaw_Articulation|here]]).

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The mandible can be divided into the '''body''' and the '''ramus'''. The body of the mandible supports the incisor teeth (rostrally) and cheek teeth (caudally). The section of the body which does not support any teeth is called the '''interalveolar margin''' or '''diastema'''. The mandibule also contains the '''mandibular canal''' and the '''mental foramen'''. The '''facial notch''' is on the ventral surface where the ~~'''parotid duct''' (in herbivores) and~~ facial vessels run. The '''ramus''' extends from the caudal end of the body dorsally towards the zygomatic arch. The '''masseter muscle''' attaches to the lateral surface at the '''masseteric fossa'''. The '''medial pterygoid''' attaches to the medial surface at the '''pterygoid fossa'''. The angle of the mandible terminates dorsally in the '''condylar process''' and the '''coronoid process''' which are separated by the '''mandibular notch'''. The '''temporal muscle''' inserts onto the '''coronoid head'''. The condylar process articulates with the mandibular process of the skull (see [[Mastication#Jaw_Articulation|here]]). ~~ ~~

== Major Skull Foramen and Canals ==

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=Trunk=

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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, thorax, lumbar region and pelvis. Anatomically these structures are highly distinguishable and each area has a distinctive shape, size and physiological role. The vertebrae within the trunk consist of a body, which encloses the vertebral foramen (through which the spinal cord and meninges run), a spinous process, and a transverse process, as well as articular processes by which they join together. The form of the spinous process varies with respect to species and region.

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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, thorax, lumbar region and pelvis. Anatomically these structures are highly distinguishable and each area has a distinctive shape, size and physiological role. The vertebrae within the trunk consist of a body, which encloses the vertebral foramen (through which the spinal cord and meninges run), a spinous process, and a transverse process, as well as articular processes by which they join together. The form of the spinous process varies with respect to species and region. The table below indicates the type and number of bones found in canines.

[[Image:Spinal landmarks.jpg|center|500px|Spinal Landmarks - Copyright Becky Pocock 2008]]

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==Thoracic Vertebrae==

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Canines and most mammals have thirteen thoracic vertebrae. Thoracic vertebrae articulate with one another and with the ribs using both cartilaginous and synovial joints ~~(see section above)~~. Thoracic vertebrae are generally very similar throughout the length with only small differences occurring gradually between those vertebrae cranially and caudally. Thoracic vertebrae have short bodies with flattened extremities, short transverse processes and prominent spinous processes. Each body has costal facets which have a synovial joint to articulate with the corresponding rib. These costal facets become more basic the further caudal the vertebrae. The spinous processes reach a maximum height only a few vertebrae behind the cervicothoracic junction and then decline gradually towards the lumbar vertebrae. The orientation of spinous processes shifts from slanting in a general caudal direction for the first eight thoracic vertebrae to slanting in a cranio-dorsal direction for the last few caudal vertebrae.

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Canines and most mammals have thirteen thoracic vertebrae. Thoracic vertebrae articulate with one another and with the ribs using both cartilaginous and synovial joints. Thoracic vertebrae are generally very similar throughout the length with only small differences occurring gradually between those vertebrae cranially and caudally. Thoracic vertebrae have short bodies with flattened extremities, short transverse processes and prominent spinous processes. Each body has costal facets which have a synovial joint to articulate with the corresponding rib. These costal facets become more basic the further caudal the vertebrae. The spinous processes reach a maximum height only a few vertebrae behind the cervicothoracic junction and then decline gradually towards the lumbar vertebrae. The orientation of spinous processes shifts from slanting in a general caudal direction for the first eight thoracic vertebrae to slanting in a cranio-dorsal direction for the last few caudal vertebrae.

===Ribs===

[[File:Dog ribs.JPG|thumb|right|300px|'''Canine ribs & Sternum''' - Kirill Tsukanov, Moscow State University, 12/04/12]]

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The ribs are paired structures that articulate with a two ribs - the corresponding thoracic vertebrae and also partially with the vertebrae directly caudal. It is the caudal vertebrae that has the same numerical designation as the rib. An individual rib is composed of a number of elements. Dorsally the rib has a tubercle, head and neck. The head of the rib is rounded with two facets, each of which represents the surface which articulates with the vertebral body. The area between the two facets is referred to as the ''crest'' and allows the attachment of the intercapital ligament. The tubercle of the dorsal rib can act as a further third articular facet in more caudal ribs with the transverse processes. The main body of the rib is long and curved and the lateral surface of the rib is often flattened. The highest degree of curvature of the rib is just ventral to the dorsal neck of the rib and is known as the ''angle''. The angle allows the attachment of the iliocostalis muscles whilst the cranial and caudal edges of the rib allow attachment of the intercostal muscles. The caudal aspect of the body of the rib also contains a small groove which is designed to afford protection to the neurovascular bundle that runs along the length of each rib. At the ventral third of each rib the bone structure of the rib is replaced with costal cartilage at the costochondral junction. This costal cartilage is more flexible than the bone and progressively ossifies with age. The cartilage is bent in a cranioventral manner before making contact with the sternum which together with the increased flexibility of the cartilage itself provides the thoracic cavity with a wide degree of changes in shape. There are vast differences in the size of rib depending on which number the rib is - the first rib if usually the shortest and articulates with the sternum in a more rigid manner than caudal ribs to act as an anchor on which the other ribs draw for inspiration. Ventrally the cartilaginous element of the rib articulates with the sternum (see section below) in nearly all ribs. The exception are the most caudal ribs in which the cartilaginous ventral element of the rib fails to make contact with the sternum and is referred to as a 'floating' rib.

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The ribs are paired structures that articulate with two ribs - the corresponding thoracic vertebrae and also partially with the vertebrae directly caudal. It is the caudal vertebrae that has the same numerical designation as the rib. An individual rib is composed of a number of elements. Dorsally the rib has a tubercle, head and neck. The head of the rib is rounded with two facets, each of which represents the surface which articulates with the vertebral body. The area between the two facets is referred to as the ''crest'' and allows the attachment of the intercapital ligament. The tubercle of the dorsal rib can act as a further third articular facet in more caudal ribs with the transverse processes. The main body of the rib is long and curved and the lateral surface of the rib is often flattened. The highest degree of curvature of the rib is just ventral to the dorsal neck of the rib and is known as the ''angle''. The angle allows the attachment of the iliocostalis muscles whilst the cranial and caudal edges of the rib allow attachment of the intercostal muscles. The caudal aspect of the body of the rib also contains a small groove which is designed to afford protection to the neurovascular bundle that runs along the length of each rib. At the ventral third of each rib the bone structure of the rib is replaced with costal cartilage at the costochondral junction. This costal cartilage is more flexible than the bone and progressively ossifies with age. The cartilage is bent in a cranioventral manner before making contact with the sternum which together with the increased flexibility of the cartilage itself provides the thoracic cavity with a wide degree of changes in shape. There are vast differences in the size of rib depending on which number the rib is - the first rib if usually the shortest and articulates with the sternum in a more rigid manner than caudal ribs to act as an anchor on which the other ribs draw for inspiration. Ventrally the cartilaginous element of the rib articulates with the sternum (see section below) in nearly all ribs. The exception are the most caudal ribs in which the cartilaginous ventral element of the rib fails to make contact with the sternum and is referred to as a 'floating' rib.

===Sternum===

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The sternum represents the bony structure that runs ventrally along the thoracic cavity and provides attachment for the ribs and an anchor for some of the muscles involved in respiration. The sternum is composed of three elements; the '''manubrium''', the '''body''' and the '''xiphoid'''. The '''manubrium''' in canines is rod-shaped and projects cranially to the first rib and unless the dog is particularly well ~~muscles~~, it can often be palpated at the region of the ventral neck. The body of the sternum is composed of numerous segments interconnected by the costochondral ventral aspects of the ribs (see section above) via small depressions in the segments. These segments are referred to as ''sternebrae'' and are cartilaginous in young canines and ossify with age. The body of the sternum in dogs is generally cylindrical in shape. The '''xiphoid''' cartilage extends caudally in a similar manner to that of the manubrium cranially. It provides attachents for the most cranial aspects of the abdomen and also for the ''linea alba''.

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The sternum represents the bony structure that runs ventrally along the thoracic cavity and provides attachment for the ribs and an anchor for some of the muscles involved in respiration. The sternum is composed of three elements; the '''manubrium''', the '''body''' and the '''xiphoid'''. The '''manubrium''' in canines is rod-shaped and projects cranially to the first rib and unless the dog is particularly well muscled, it can often be palpated at the region of the ventral neck. The body of the sternum is composed of numerous segments interconnected by the costochondral ventral aspects of the ribs (see section above) via small depressions in the segments. These segments are referred to as ''sternebrae'' and are cartilaginous in young canines and ossify with age. The body of the sternum in dogs is generally cylindrical in shape. The '''xiphoid''' cartilage extends caudally in a similar manner to that of the manubrium cranially. It provides attachents for the most cranial aspects of the abdomen and also for the ''linea alba''.

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==Caudal Vertebrae==

These vertebrae originate from the caudal vertebrae of the sacrum and they become progressively simplified in a caudal direction. Initially the caudal vertebrae have a similar conformation to lumbar vertebrae, although they are smaller in overall size. The most caudal of these vertebrae are almost reduced to a rod shape. The total number of caudal vertebrae vary widely amongst individuals, breeds and species.

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~~==Joints of the Spinal Column==~~

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Within the spinal column there are two types of joints: '''cartilaginous''' and '''synovial'''. '''Cartilaginous''' joints provide direct connections between vertebral bodies. The bodies of adjacent vertebrae are connected by thick, flexible intervertebral discs, consisting of two parts; the ''nucleus pulposus'' and the ''annulus fibrosis''. The '''nucleus pulposus''' has a slightly eccentric shape and is a notochord derivative. It is contained under pressure and prone to escape during spinal trauma. The '''annulus fibrosis''' has encircling bundles of fibrous tissue surrounding the nucleus pulposus that pass obliquely from one vertebra to another with changing orientation. These are not prone to damage. The second type of spinal column joint is the '''synovial''' joint. These are found between facets on vertebral arches and there are various conformational differences between the regions of the head and pelvis.

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The acetabulum is contributed to by all of the above bones. The acetabulum is surrounded by an ''acetabular rim'' and the depth of the acetabulum varies depending on breed, shape of pelvis and hip conformation.

===Pelvic Girdle===

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In canines the wings of the ilium ~~are~~ much more oblique conformation when compared to large animals and this allows the muscles of the pelvis floor to be displaced laterally over a wider area when compared to the vertebral column. This increases the efficiency and therefore power of the abdominal muscles which allows a greater degree of flexibility of the vertebral column which is essential for faster locomotion and agility. Canines also have relatively ~~caudal~~ displaced ''ishial tuber'' which ~~increases~~ the leverage of the hamstring muscles onto the hindlimbs providing further efficiency improvements for locomotion.

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In canines the wings of the ilium have a much more oblique conformation when compared to large animals and this allows the muscles of the pelvis floor to be displaced laterally over a wider area when compared to the vertebral column. This increases the efficiency and therefore power of the abdominal muscles which allows a greater degree of flexibility of the vertebral column which is essential for faster locomotion and agility. Canines also have relatively caudally displaced ''ishial tuber'' which increase the leverage of the hamstring muscles onto the hindlimbs providing further efficiency improvements for locomotion.

=Forelimb=

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[[File:Dog fore limb 1.JPG|thumb|centre|~~350px~~|Canine Forelimb, Moscow State University Department of Biology, Kirill Tsukanov, 2012]]

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[[File:Dog fore limb 1.JPG|thumb|centre|450px|Canine Forelimb, Moscow State University Department of Biology, Kirill Tsukanov, 2012]]

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==~~Structures of the~~ Proximal Forelimb ~~and~~ Shoulder==

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==Proximal Forelimb & Shoulder==

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===Scapula===

[[File:Cambridge Natural History Mammalia Fig 025.png|thumb|right|150px|Canine Scapula, Cambridge Natural History Mammalia Fig 025, Frank E. Beddard, 1902]]

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The proximal part of the ulna extends beyond the articulation with the humerus forming the ''olecranon process''; known anatomically as the point of the elbow. The olecranon allows the bony attachment of the triceps. Slightly distal to the olecranon the cranial margin articulates with the ''anconeal process'' (see above) which fits into the olecranon fossa of the distal humerus. Slightly distal to the anconeal process and trochlear notch of the humerus are the lateral and medial coronoid processes which also facilitate muscular attachments and collateral ligaments of the elbow. The ulna runs the full length of the radius and is seperated from the radius by an interosseous space that in canines is filled with a membrane.

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==~~Structures of the~~ Distal Forelimb==

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==Distal Forelimb==

[[File:Dog hand.JPG|thumb|centre|350px|Canine Carpus, Metacapus and Phalanges, Moscow State University Department of Biology, Kirill Tsukanov, 2012]]

===Carpal Bones===

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====Femur====

The shaft of the canine femur is essentially cylindrical in shape with a slightly flattened shape distally. The distal aspect of the femur articulates with the '''tibia''' and '''patella''' of the stifle joint. The articulation with the tibia is via two femoral condyles which project caudally and slightly medially and laterally from the shaft. Each condyle is seperated by a deep intercondylar fossa. The abaxial surfaces of each condyle provide attachment sites for the collateral ligaments of the stifle and the lateral condyle specifically provides attachments for the ''long digital extensor'' and ''peroneus tertius'' muscles. In canines there are also two small sesamoid bones also called ''fabellae'' which are situated within the origin of the ''gastrocnemius muscle''. On the cranial aspect of the femur there is a '''cranial trochlea''' that provides a groove within the bone to articulate with the patella. The '''patella''' is essentially a sesamoid bone that is involved within the insertion of the ''quadriceps femoris'' which is the main extensor of the stifle. The patella is oval in shape in canines and the influence of the patella is spread medially and laterally via ''parapatellar cartilages''.

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Moving distally the stifle allows articulation between the '''tibia'''. The tibia has intimately related to the fibula which is a much smaller bone that runs parallel to the tibia. The tibia is medial to the fibula and effectively excludes the fibula from articulating with the femur. Proximally the tibia has two condyles to facilitate articulation ~~wioth~~ the femur. These condyles are seperated by a ''caudal popliteal notch'' that allows insertion of the popliteal muscle. The articular surfaces of the tibial condyles correspond to the condyles of the distal femur. The articular surface of the tibia also has small depressions and ridges that allow cruciate ligament attachment within the joint. Slightly distal to the tibial condyles and on the cranial aspect is the large and prominent ''tibial tuberosity'' which is continued distally on the cranial aspect of the tibia via the ''tibial crest'' which gradually reduces distally. Proximally and caudally, the articular surface of the tibia also ~~proves~~ a small facet for articulation with the fibula. The shape of the tibia proximally is triangular in cross-section but distally the tibia becomes more craniocaudally compressed. The distal point of the tibia has an articular surface called the ''cochlea'' which facilitates movement with the ''trochlea'' of the '''talus'''. The cochlea has a central bony prominence which is flanked medially and laterally with grooves. ~~The medial~~ cochlea has a bony salience called the ''medial malleolus''.

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====Tibia & Fibula====

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Moving distally the stifle allows articulation between the '''tibia'''. The tibia has intimately related to the fibula which is a much smaller bone that runs parallel to the tibia. The tibia is medial to the fibula and effectively excludes the fibula from articulating with the femur. Proximally the tibia has two condyles to facilitate articulation with the femur. These condyles are seperated by a ''caudal popliteal notch'' that allows insertion of the popliteal muscle. The articular surfaces of the tibial condyles correspond to the condyles of the distal femur. The articular surface of the tibia also has small depressions and ridges that allow cruciate ligament attachment within the joint. Slightly distal to the tibial condyles and on the cranial aspect is the large and prominent ''tibial tuberosity'' which is continued distally on the cranial aspect of the tibia via the ''tibial crest'' which gradually reduces distally. Proximally and caudally, the articular surface of the tibia also provides a small facet for articulation with the fibula. The shape of the tibia proximally is triangular in cross-section but distally the tibia becomes more craniocaudally compressed. The distal point of the tibia has an articular surface called the ''cochlea'' which facilitates movement with the ''trochlea'' of the '''talus'''. The cochlea has a central bony prominence which is flanked medially and laterally with grooves. Medially the cochlea has a bony salience called the ''medial malleolus''.

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===Distal Hindlimb===

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===Tarsus===

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====Tarsus====

The tarsal bones are arranged in three rows moving proximally to distally and seven bones comprise the tarsus. The proximal row of tarsal bones is made up of the two largest bones; the '''talus''' medially and the '''calcaneus''' laterally. In canines the talus articulates with the tibia and fibula proximally and the calcaneus laterally. The calcaneus only has a slight articulation with the fibula. The middle row of tarsal bones is made up of a single bone; the '''central tarsal bone'''. This bone articulates with the tarsal bone proximally and the individual distal tarsal bones. The distal row of tarsal bones is made up of four bones in canines and are numbered one to four in a medial to lateral direction. Each tarsal bone corresponds to a metatarsal except for the most lateral (bone four) which articulates with the calcaneus proximally and the fourth and fifth metatarsals. The fourth tarsal bone is much larger than the others in canines and and protrudes much deeper into the central space of the tarsus than the other tarsal bones.

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===Metatarsals===

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====Metatarsals====

The arrangement of the metatarsals are similar to those of the metacarpals in that they are rod shaped bones (although slightly more rounded), numbered from I to V. The 1st is the most medial and is very small, the 3rd and 4th are the longest. Overall the length of the metatarsals is 20% longer than the metacarpals. The first metatarsal is not found in every canine as it is a very simplified bone making the ''dew claw'' and it is often not found on many dogs. The proximal base of each articulates with it's corresponding carpal bone and the adjacent metacarpal. The distal end is its head, which is transversely cylindrical and articulates with the proximal phalanx. Metacarpals II - V possess a sagittal ridge on their palmar aspects.

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====Phalanges====

The bone anatomy of the hindlimb phalanges is identical to that of the forelimbs and therefore has not been repeated here. For more detailed anatomy of the phalanges, please see the forelimb distal limb section above.

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[[Category:A%26P_Done_CB]]

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Bones - Dog Anatomy (view source)

Revision as of 13:25, 10 January 2013

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