2. Anatomy of the Skull Flashcards
Skeleton of the head includes:
-skull
-mandible
-hyoid apparatus
-ossicles of middle ear
-cartilages of external ear, nose and larynx
Skull bones:
-mostly paired
-provide essential landmarks
*different bones are outlined by ‘sutures’
Sutures:
-signify merging ossification centers
Young animals skull:
-bones can be separated and examined individually
Skull bones consist of:
-walls of cranium
-bones of the face
*proportions differ among species
Orbits:
-part of the face
-lie at the boundary of the face and cranium
Cranium: brain case
-dorsolateral wall
-lateroventral wall
-caudal wall
-cranial wall
Dorsolateral wall: cranium
-frontal bones
-parietal bones
Lateroventral wall: cranium
-palatine bones
-sphenoid bones
Caudal wall: cranium
-occipital bone
Cranial wall: cranium
-cribriform plate of ethmoid bone
Ethmoid bone
-separates the cranial cavity from the nasal cavity
-unpaired
Cribriform plate of ethmoid bone:
-spongy-shaped
-perforations (holes) that pass olfactory nerves
Nasal bots in sheep brain:
-larvae of botfly
>migrate through the cribriform plate when still developing
>much smaller when they squeeze through, then when you are dissecting
-occasionally in goats and deer
Nasal cavity:
-dorsal wall
-lateroventral wall
-laterocaudal part
*-filled by conchae (turbinate bones)
Dorsal wall: nasal cavity
-nasal bones (paired)
Lateroventral wall: nasal cavity
-incisive bones (cranial)
-maxilla bones (caudal)
Laterocaudal part: nasal cavity
-lacrimal bones
>’tear shaped’ with small hole in middle
>lacrimal duct goes through it all the way to the nostrils
Nasal septum:
-divides the left and right nasal cavities
-cartilaginous rostrally: parts may become ossified with age
Ventral nasal septum:
-has a trough-shaped vomer bone
Caudal nasal septum:
-perpendicular lamina of ethmoid bone
Conchae (turbinate bones):
-delicate bony scrolls
-warm, moisten , and clean the air
-dorsal, ventral and ethmoid concha/turbinate
*increase SA
Dorsal conchae:
-from nasal bone
-‘shelf’ all the way to the back
Ventral conchae:
-from maxilla
-more complex
-scrolls up and down
-fills the space more
Air through the nasal cavity:
-a portion stays longer to help with the sense of smell
Zygomatic arch originates from:
-zygomatic bones
-squamous temporal bones
Temporal bone parts:
-squamous (flat)
-petrous (dense bone housing internal ear)
-tympanic (housing middle ear)
Temporal process of zygomatic bone:
-points toward the temporal bone
Zygomatic process of temporal bone:
-points toward the zygomatic bone
Mandible:
-two halves meet at the symphysis
-body (horizontal)
-ramus (vertical)
Mandibular symphysis:
-never completely fuses in a dog
>helps them with cracking a bone
Ramus:
-coronoid process
-condylar process
Coronoid process:
-dorsal extremity of the ramus
-attachment for temporal muscle
Condylar process:
-discoidal margin
-articulates with the skull
Lateral ramus:
-has a roughened depression where masseter inserts
Medial ramus:
-gives insertion to pterygoid muscle
-mandibular foramen
Caudo-ventral margin of ramus:
-angular process to extend muscle insertion
Rostro-lateral surface of ramus:
-several mental foramina
>middle one is bigger
Hyoid apparatus:
-series of bony rods joined together
-forms a mean of suspending the tongue and larynx from the skull
Parts of hypoid apparatus:
-basihyoid
-ceratohyoid
-epihyoid
-stylohyoid
-thyrohyoid
Basihyoid:
-across the back
-lingual process in horse and cow
Lingual process:
-rostral prominence of the basihyoid
-dives in the root of the tongue
-gives attachment to several muscles
Ceratohyoid:
-‘horn like’
Epihyoid:
-over
Stylohyoid:
-pointy
Thyrohyoid:
-goes to thyroid cartilage
Dorsal surface of dog skull:
-cranium
-external occipital protuberance
-nuchal crests
-sagittal crest
-zygomatic process of frontal bone
-nasal bones
Cranium:
-ovoid
-occupy middle third of head width
External occipital protuberance:
-caudal extremity of the cranium
Nuchal crests:
-lateral cranium
Sagittal crest:
-center more rostral part
Zygomatic process of frontal bone:
-points toward zygomatic arch
Nasal bones:
-end at wide nasal aperture
-continued by nasal cartilages
Lateral surface of dog skull:
-orbital rim
-temporal fossa
-retroarticular process
-typmanic bulla
-external acoustic meatus
-paracondylar process
-pterygopalatine fossa
-foramina
-infraorbital foramen
Orbital rim:
-not fully bony
-completed by orbital ligament
Temporal fossa:
-behind the orbit
-walls of cranium
Retroarticular process:
-ventrocaudal to zygomatic arch
Tympanic bulla:
-large, smooth dome
External acoustic meatus:
-leads to middle ear
Paracondylar process:
-conspicuous at the caudal limit of the skull
Pterygopalatine fossa;
-ventral to orbit
Foramina of lateral surface of dog skull:
-optic canal
-orbital fissure (middle, bigger)
-rostral alar foramen
Infraorbital foramen:
-important for dentistry
Ventral surface of dog skull:
-base of cranium
-tympanic bulla and paracondylar process
-jugular foramen
-foramen lacerum
-hypoglossal canal
-oval foramen
-choanal region
-hard palate
Base of cranium:
-occipital condyles flank the foramen magnum
Tympanic bulla and paracondylar process:
-occupy each side of the ventral surface
Jugular foramen:
-between bulla and occipital bone
>more caudal
foramen lacerum:
-between bulla and occipital bone
>more rostral
Hypoglossal canal:
-between jugular foramen and condyle
Oval foramen:
-rostral to foramen lacerum
Choanal region:
-where nasal cavities open into pharynx and openings (choanae)
Hard palate:
-lies rostral to choanea
-margined by tooth sockets and rostrally palatine fissures
Cat skull:
-with the mandible, appears globular
-rounded brain-case
-relatively short face
Zygomatic arches: cat
-very convex
Orbits: cats
-large
-face even more rostrally than in dogs
>predators
Hard palate: cat
-short
Tympanic bulla: cat
-very large
Horse skull:
-long face
-narrow cranium
Zygomatic arches: horse
-very strong
-strong zygomatic process connecting it with the frontal bone
*continues rostrally and forms the facial crest
Orbit: horse
-faces almost laterally
-complete bony rim
Nasoincisive notch: horse
-deep
-separates nasal and incisive bones
*allows them to breath better (only breath from nose)
Mandible: horse
-massive
-two halves fuse early in life
-ramus is high (more space for masteur muscle)
Bovine skull:
-relatively short and wide
-generally pyramidal
Cornual process: bovine
-‘horn’
-project from frontal bones
Frontal region: bovine
-consists mostly of frontal bone
-very wide and flat
-overhanging the temporal fossa
Orbital rim: bovine
-raises above its surrounding
-completely bony
-‘security camera’
Facial tuberosity: bovine
-no facial crest
-where rostral part of masseter arise
Choanae: bovine
-separated by caudal prolongation of the nasal septum
‘teeth’: bovine
-no alveoli (teeth sockets) for upper incisors
Mandible: bovine
-weaker than horses
Mandibular symphysis: bovine
-ossifies late, if at all
Head conformations for dog:
-dolichocephalic: long-head
-mesaticephalic: intermediate-head
-brachycephalic: short-head
Head conformations for horse:
-straight profile: common
-dished profile of Arabian
-domed contour of foals
Domed contour of foals:
-cranium just follows the brain
-later on with development of facial bones and sinus, it will flatten out
Head conformations for cats:
-long-headed: oriental
-medium-headed: European
-short-headed: persian
