Anatomy of the Head Flashcards
Skeleton of the head
- Skull
- Mandible
- Hyoid apparatus
- Ossicles of middle ear
- Cartilages of external ear, nose, and larynx
Skull
- Mostly paired
- Different bones are outlined by sutures
- Provide essential landmarks
Sutures
Signify merging of ossification centers
- Young animals skull bones can be separated and examined individually
Skull bone components
- Consist of walls of cranium and bones of the face
- Orbits are considered part of the face (they lay at boundary of the face and cranium)
Cranium
Brain case
- Dorsolateral wall: frontal and parietal bones
- Lateroventral wall: palatine and sphenoid bones
- Caudal wall: occipital bone
- Cranial wall: cribriform plate of ethmoid bone
Cribriform plate of ethmoid bone
- Separates the cranial cavity from the nasal cavity
- Spongy-shaped
- unpaired
- Has perforations where olfactory nerves pass through
Bones of the nasal cavity
- Dorsal wall: nasal bones
- Lateroventral wall: incisive and maxilla bones
- Laterocaudal part: lacrimal bones. Lacrimal glands present here and produce tears
Lacrimal
Corner of eye
Nasal cavity divisions
Left and right cavities divided by nasal septum
- Cartilaginous rostrally; can become ossified with age
- Trough-shaped vomer bone ventrally
- Caudally has perpendicular lamina of ethmoid bone
Filled by conchae (turbinate bones)
- Delicate bony scrolls
- Dorsal concha from nasal bone
- Ventral conchae from maxilla
- Ethmoid concha/tubinate
Purpose of conchae
- Increases SA
- Allows for moistening air, trapping pathogens
Zygomatic arch
Originates from zygomatic bone and squamous part of temporal bone
Parts of temporal bone
- Squamous (flat)
- Petrous (dense bone housing internal ear)
- Tympanic parts (housing middle ear)
Temporal and zygomatic processes
- Temporal process of zygomatic bone goes towards the temporal bone
- Zygomatic process of temporal bone goes towards the zygomatic bone
Mandible
- Lower jaw
- Two halves meet at symphysis. Each half has a body (horizontal) and ramus (vertical) part
- Dorsal extremity is the coronoid process
- Dorsocaudal margin has condylar process articulating with skull
Coronoid process of mandible attachment
Attachment for the temporal muscle
Hyoid apparatus
- A series of bony rods joined together
- Forming a means of suspending the tongue and larynx from the skull
- Covered by muscles and mucosa
Parts of the hyoid process
- Basihyoid
- Ceratohyoid
- Linguinal process (attachment to tongue)
- Epihyoid
- Stylohyoid
- Thyrohyoid (towards larynx)
Cranium shape and width
- Ovoid
- Occupies middle third of head width
Dorsal surface of the dog skull
- Caudal extremity starts with external occipital protuberance, then proceeds laterally by nuchal crests
- Extends rostrally down dorsal center by sagittal crest
- Zygomatic process of frontal bone points toward the zygomatic arch
- Nasal bones end at the wide nasal aperture and continue by nasal cartilages
Orbital rim
Orbital rim is not fully bony, and in life completed by the orbital ligament
Bone located behind orbit
Walls of the cranium from temporal fossa
Lateral surface of the dog skull
- Ventrocaudal to zygomatic arch is retroarticular process (prevents mandibles from being pushed back)
- Tympanic bulla is a large, smooth dome
- External acoustic meatus- leads to middle ear
- Paracondylar process- conspicuous at the caudal limit of skull
Pterygopalatine fossa
Located ventral to orbit
Foramina located in lateral skull surface
- Optic canal
- Orbital fissure
- Rostral alar foramen
- Infraorbital foramen
Base of the cranium (ventral)
Occipital condyles flank foramen magnum
Ventral surface of dog skull bulla and process
Tympanic bulla and paracondylar process occupy each side
Jugular foramen
- Between the bulla and occipital bone
- More caudal
Foramen lacernum
- Between the bulla and occipital bone
- More rostral
Hypoglossal canal
Between jugular foramen and condyle
Oval foramen
Rostral to foramen lacernum
Choanal region
Where nasal cavities open into pharynx and openings (choanae) are the main features
Hard palate
- Lies rostral to choanae
- Margined by tooth sockets and rostrally palatine fissures
Dog mandible
- Mandibular symphysis- never completely fuses in dog
- Laterally ramus has a roughened depression where masseter inserts
- Medially ramus gives insertion to pterygoid muscles and has mandibular foramen
- Caudo-ventral margin of ramus has angular process to extend muscle insertion
- Rostro-lateral surface has several mental foramina
Cat skull
- Skull and mandible appear globular
- Rounded brain case
- Very convex zygomatic arches
- Relatively short face
- Large orbits which face even more rostrally than in dogs
- Infraorbital canal very short
- Hard palate short
- Tympanic bulla very large
Horse skull
- Skull has long face and narrow cranium
- zygomatic arches are very strong and have a strong zygomatic process connecting it with the frontal bone
- zygomatic arch continues rostrally and forms the facial crest
- orbit faces almost laterally and has a complete bony rim
- a deep nasoincisive notch separates nasal and incisive bones
- mandible is massive, two halves fuse early in life, ramus is high
Bovine skull
- skull is short, wide and pyramidal
- cornual (horn) processes project from frontal bones (contribute to horns)
- frontal region is mostly frontal bone
- temporal fossa is very wide and flat, smaller than canines
- orbital rim rises above surroundings and is completely bony
- no facial crest, but has facial tuberosity
- choanae are separated by caudal prolongation of the nasal septum
- no alveoli for upper incisors
- mandibular symphysis ossifies late
Temporal fossa in dogs
much larger to allow for room for muscles for chewing power
Head conformations of dogs
- dolichocephalic (long head- whippet)
- mesaticephalic (intermediate head- lab)
- brachycephalic (short-head)
Head conformations of horses
- straight profile
- dished profile (arabian horses)
- Domed contour of foals (will flatten out as facial bones and sinus develop)
Head conformations for cats
- Long-headed (oriental)
- Medium -headed (European)
- Short-headed (persian)
