Head

Page 1

Skull

Skeleton of the head

Skull

Mandible

Hyoid apparatus

Ossicles of ear

Cartilages of ear and nose

Skull

Cranium

Protect brain

Boney box

Mandible?

Bony extension ?

Frontal bone

Frontal sinus

Parietal

Temporal

Zygomatic

Lacrimal

Nasal

Maxilla

Maxilla sinus

Incisive

Nasal

External nares

Horse

Much smaller cranium

Parietal frontal such cmaller

Much bigger nasal +maxilla

Much wider mandible

Complete boney orbit

Bulla

Pterygoid

Hard pallet

Palletine

Maxilla

Incisive

Clinical significance

Separates oral + nasal cavity

Unfused hard plate

Cleft lip

Inscisors + maxilla fail to close

Cleft palate

Left + right max +pal bones

Life threatening ?

Inhale milk

Pn

Slide 13

?slide 11

Foramen magnum

Occipital bone

Exoccipitals

Basioccipital

Supraoccipital

Clinical significance

Syringomyelia

Congential condition

Undersized occipital cone

Cerebellum becomes compressed against foramen interrupting flow of CSF

Pockets CSF build up causing neurological conditions

Internal nares or choanae

Occipital condyles

Horse

External occipital protuberance

Paramastoid process

Inferior alveolar foramen

Front of skull

Frontal

Maxilla

Infraorbital foramen

Maxilla

Incisive

Nasal

Horse

Temporal

Occipital

Parietal

zygomatic

Lacimal

Ox

Horn comes of frontal bone

?

Mandible

Inferior alveolar foramen

Coronoid process

Condyloid process

Angular process

Mental foramen

Genu

Horse

Angle of mandible

Horse palpable

Nasoincisive notch

Infraorbital foramen

Facial crest

Genu

Mental foramen

Young animals

Immature dentition

Sutures of skull easy to see

NB ? remains unfused - radiographically visible

Tympanic bulla

Part of temporal bone

Filled with air in healthy animals

Contains middle ear

Bounded laterally by tympanic membrane core????

Hyoid apparatus

Series of small bones + cartilages that form a suspensory mechanism for the tongue + larynx

Radiographically visible

??

Horse

Stylohyoid fused with epihyoid

Lingual process of basihyoid

Foramina

Ethmoidal foramina

Optic canal

Orbital fissure

Rostral alar foramina

Caudal alar foramina

Oval foramina

Jugular foramen

Stylomastoid foramen

Hypoglossal formate

?

Palpable

Inorbiatal

Inferior alveolar

Mental foramen

Horse + ox

Supraorbital foramen

Head shapes

Dolichocephalic

Mesaticephalic

Brachycephalic

Stenotic nares

Too much cartilage + soft tissue for nasal bones to support

Difficulty breathing through nose

Long soft palate

Too much soft tissue

Not reduced in accordance with skeletal support

Soft palate occludes larynx = difficulty breathing

Often have normals number of teeth

Crowded into smaller space

Unusual orientations

Difficulty eating

Increased dental disease

Maloclusion ????

Expothalmic eyes

??

Wrinkly skin

???

Entropian

Skin fold dermariris

Cat head shapes

Dolichcephalic

Mesaticephalic

Brachycephalic

Adapt better

Horse head shapes

?

Page 2

Nasal cavity

Functions

Warms. + humidifies air

Filters particles of air going to lungs

Detecting odour molecules in air

How?

Air brought into contact with large surface area for water + heat ?

?

Turbinate bones

?

Stream

Transverse

Ethnoturbinates

Nasal septum

?

Middle

Doral meatus

Dorsal turbinate

Middle meatus

Common meatus

Ventral turbinate

Palatine sinus

Mxillary sinus

Maxilla

Nasal bone

Ventral turbinate

Basic plan

Dog

Extensive

Inc SA

V good sense

Difficult to stick something up

Horse

Loses ventral scrol

Large ventral space

Paranasal sinuses

Air filled diverticula of nasal cavity

Invaginate several bones of skull

Between inner and outer tables of bone

Retain connection with nasal cavity via narrow openings

Prone to blockages by inflammation/ congestion

Lined with nasal epithelium

Share same innervation

Functions?

Not sure

Mechanical + thermal protection ?

Enlarge skull without adding weight

Greater SA for muscle attachment

Allows for larger oral cavity

Frontal

Lies in frontal bone

Has up to 5 compartments

???

Brachycephalic

Not present / Very tiny

Maxillary sinus

?

Dog and cat

Communicates very freely

Horse

Frontal sinus drains into maxillary sinus

Rostral + caudal

?

Dont communicate

Excluding donkeys

Infraorbital canal?? slide26

Trepining

Flush

Points ? slide 30

Young horse

Clinical significance

Lateral parts quite small due to unerupted cheek teeth occupying space

Trepinning

Horns + dehorning

Horns are per

Polled breeds = no horns

??

5 potential nerves to horn

Euthanasia by shooting

Aim for medulla oblongata

Avoid midline on species with strong bony midline septum

Pigs

Large frontal sinus

Page 3

Dentition

Structure

Sits in alveolus

Dentineis bulk of tooth

Outside above gum line is enamel

Outide below is cementum

Apical foramen innermost - communication with bv

Periodontal ligament holds teeth into ?

?

Enamel

??

Dentine

Mesodermal

Formed by odontoblasts

Forms bulk of tooth

2nd hardest

Structure similar to bone

Bone osteoblasts stay in bone matrix

Odontoblasts raced from newly formed dentine and remain as a continuous layer on the surface of the pulp caved ???

Cementum

Mesodermal

Calcified CT

Outer lining of tooth in socket in brachydont teeth

??

Pulp cavity

??

Rough guide ti age of animal

Periodontium

Consists of

Gingiva

Periodontal ligament

Cementum

Alveolar bone

Role is to anchor tooth

Gingiva

Gums

Oral mucosa that covers alveolar processes of jaws and neck of teeth

Gingival sulcus

?

?

PDL

Collagenous

Attaches cementum t line of alveolus

Sling formation

Allows small movements during mastication

Shock absorbers

Alveolar bone

Thin white line radiographically - lamina dura

May be superimposed on tooth

Innervation

Innervated by branches of trigeminal nerve

Upper teeth supplied by maxillary alveolar nerve

Lower teeth supplied by mandibular alveolar nerve

Mental nerve is branch of mandibular nerve

Generic dentition

Diphyodont - deciduous and permanent teeth

Mammals

Heterodont - different types of specialised teeth

Dental formulae

Standerd mammal has 44 teeth

I 3/3 C 1/1 ???

Deciduous = no molars

All deciduous =?

All permanent?

Hypsodont

Brachydont

Aradicular/elodnont

Radicular/anelodont

Clinical crown

Anatomical crown

Labial

Buccal

Lingual

Mesial

Distal

Occlusal

Carnivore

Radicular

Brachydont

Roots longer + wider than crown

Missed this bit

More than one root? Roots diverge

Easiest to section then treat as two diff teeth when removing

Heterodont

Incisors

Canines

Premolars/molars -carnassials

Molars

Carnassials

Pointy + sharp

Biggest teeth

Top + bottom slice past each other like shears

Strong bite force

Open wide ?

Upper - widest part of jaw =UP4

Lower=LM1

Cats

Very sharp + pointy = sectorial

Reduced dentition

No flat molars

?

Healthy mouth

Normal occlusion

pH =7.5

Salica maintains pH + contains enzymes + immunoglobulins that moderate bacterial colonisation

??

Common problems

Congenital malocclusions

Different head shapes

Prognathism

Brachygnathism

Bad orientation

Tooth disease

Struggle to eat

Trauma

Chipped

Incisors + canines often

Periodontal disease

Most common SmallAnimals

First stage gingivitis

Second early periodontal

Third stage - further brake down of support tissues , tooth mobility , tooth loss

Advanced - upper dental arcade can lead to oronasal fistulas

Plague + calculus

Plaque = biofilm on teeth formed by bacteria colonising the dental pellicle

Prevention - tooth brushing, chewing coarse food

Calculus formed by inorganic substances ..??

Tooth decay

Caries, caused by bacteria

Abscesses

From periodontal disease or tooth decay

Clinical signs include swelling????

Pigs

its are omnivores + have more generalised dentition than other domestics

Lower incisors point forwards

In males canines remain open rooted in male and continue to grow throughout life

Upper + lower canines rub against each other to maintain sharpened edge

In females canines main open for 2 years

Little differential between premolars + molars

Teeth get progressively larger towards caudal end of mouth

??

Classification

Hypsodont dentition

All herbivores

Horses have radicular hypsodont teeth

Ruminants have brachydont incisors and canines + radicular hypsodont premolars and molars

Species with aradicular mention include ia????

Dental formula ?

Horse

Radicular hypsodont

Cellulose digested by microorganisms in gut -made available by mechanical break down

This causes wear which teeth are adapted to permit this

All teeth continue to erupt through life

In mandible teeth moves upwards

In maxillary ???

cementum initially covers crown and creates ridging due to different different harness of cement, enamel + dentition

Eruption times ?

Canines often present in the male , absent/vestigal in females

Premolar 1 = wolf tooth, more common in upper arcade but can be present in both upper + lower arcade , deciduous but not shed

???

Gap = diastema / bar

Tertiary dentine formed as response to injury and is also found in horse teeth

?

Incisors

Used to establish age of horse

Diagram?

Stream this

Aging bit

Cheek teeth

Disregard wolf tooth

work as one functioning unit

Upper row curved slightly

Lower row is straighter

Curve of spee?

?

No gaps!

Pocket for food

Develop into pathological problems

Called diastemata

Occlusion

Upper teeth wider + squarer

Lower teeth narrower + rectangular

1/3 contact of occlusal surface ?

Occusal surface

???

Wear

12 transverse ridges

Affect line of lower jaw in younger horses

Sinuses expand in upper jaw

Canines very curved and quite large

Wider underneath

Might need to remove some bone in order to remove

Maxillary sinus

???

Tooth extraction in horses

Small oral opening

Per os

Incisors

Wolf teeth

Premolards

Buccotomy

Through cheek

Remove bone then teeth

pREMOLRS

Repulsion??

Avoid

Infraorbital nerve

Dorsal + ventralbuccal nerves

Parotid duct

Nasolacrimal duct

Infraorbital canal

Cattle + sheep

Dental formula

Canines take form of incisors

Dental pad instead of upper incisors

??

Rodents + lagomorphs

Density of these animals is very important to their husbandry + health

Will cover in year 2

Page 4

Prehension, mastication, salivation

Food prehension

Organs

Lips - labium

Orbicularis oris

Levator labii superioris

Levator nasolabialis

Depressor labii inferioris

Canines

Zygomaticus

Facial nerve

Sensory - trigeminal

Cheek

Buccinator

Facial nerve

Sensory - trigeminal

Teeth

Innervated

Sensory

Trigeminal

Branches

Tongue

Manipulation of foodstuffs

Tasting

Lapping water

Grooming

Vocalisation

Shape

Species variation

Spatulate in horses + dogs

Pointed in ox, sheep + pig

Ruminants have torus lingual

Surface texture

Species variation

Soft in horse, pig dog

Rough in cats + ruminants

Dogs have median sulcus + the lyssa

Extrinsic Muscles

Genioglossus

Styloglossus

Hypoglossus

Hypoglossal nerve

Geniohyoid

Hypoglossal nerve

Sternohyoid

Spinal cervical nerve

Intrinsic

Propria linguae

Hypoglossal nerve

Innervation

Motor

Hypoglossal

Somatic efferent

Sensory

Rostral 2/3 - Somatic afferents, lingual nerve

Caudal 1/3 - Autonomic afferents glossopharyngeal + vagus

Taste

Rostral 2/3 - Lingual then chord tympani then facial SVA/AA

Caudal 1/3 - Glossopharyngeal + vagus SVA/AA

Mucosa

Papillae

Taste buds

Vallate papilli border between rostral + caudal parts of tongue

Horses

Sensitive mobile lips

During grazing lips drawn back and incisors sever grass

Vibrissae locate food

Cattle

Less mobile sensitive lips

More limited lip movement

Tongue main organ

Long

Roughened

Papillae

Curves round grass + draws into mouth

Sideways movement of head lips grass

Less sensitive

Swallow foreign objects

Sheep

Similar to cattle

Cleft upper lip allows cropping of grass more closely

Don't often swallow foreign objects

Pigs?

Cats + Dogs?

Mastication

Tearing, chewing, grinding

Organs

Teeth?

TMJ

Condylar joint

One on each side

Cant move independently of each other in mammals

Joint capsule - mandibular ligament

Meniscus

Menisco temporal

Menisco mandibular

Hinge movement

Herbivores disc is much thicker

In dog

Acts as hinge

Retroglenoid process

Prevents backwards movement of jaw

In horses +ruminants

Mandibular head much larger

Temporal surface large +flat with no retroarticular process

Thick articular disc

Symphysial joint

Fusion varies between species

Unfused in carnivores + cattle

Fused in horses

Thought that this joint allows small changes ????

Muscles

Jaw closers

Temporalis

Largest strongest muscle of the head in carnivores

Wide zygomatic arch

Masseter

Largest muscle of head in herbivores

Lies lateral to the mandible + ventral to zygomatic arch

????

Pterygoids

One structure in carnivores

Separate in herbivores

Medial to mandible

Trigeminal nerve SVE

Jaw openers

Digastricus

Small area on carnivores

Larger area on herbivores

Trigeminal

Facial

Salivation

Small

Labial

Buccal

Lingual

Pharyngeal

Oesophageal

Produce mucous

Act locally

Large

Parotid

Mandibular

Sublingual

Zygomatic

Carnivores - lubrication

Herbivores + omnivores - starts digestive processes + may contain enzymes + ions

Ruminants - produces fluid for fermentation

Nerve supply

Sympathetic

Cranial cervical ganglion

Fight or flight

Parasympathetic

Salivary nuclei of brain stem

??

Parotid lies on top of base of ear

Zygomatic lies very close to eye

DESCRIBE THE FRONTAL SINUS IN THE OX

Page 5

Upper respiratory tract

Nasal cavity + parental sinuses

Mouth

Pharynx

Larynx

Trachea + bronchi

?

Modification of air

Temperature

Humidification

Removal of particulate matter

Defence

Filtration

Coughing

Sneezing

Reflex closure of glottis on mechanical stimulation

Continuous movement of mucous throughout URT

Mucous also contains lysozyme

Lymphoid tissue

Olfaction + gustation

Olfaction

Air drawn to ethmoturbinates

Olfactory cells

Axons pass through cribriform plate into olfactory bulb

SVA neurons

Gustation

Taste

?

Incisive duct

Small duct passes through palatine fissure connecting oral + nasal cavities

??

Vomeronasal organ

Olfaction + gustation play a major role in behaviour

???/

Vocalisation

Communication + behaviour

Caused by vibration of vocal cords

Horses

Very long soft palate

Obligate nose breathers

Shape of URT can be modified during exercise

Dilate externa nares (comma shape to circle)

Vasoconstriction of nasal mucosa

Dilation of glottis ?

See slide 13

Innervation

Olfactory

Maxillary trigeminal

Mandibular trigeminal?

Pharynx

Chamber that is the continuation of the oral + nasal cavities

Functions during nasal breathing, mouth breathing, swallowing , vomiting

Nasopharynx

Above soft palate

Opens into common pharynx via pharangopalatine arch

Openings for auditory tubes line lateral walls

Oropharynx

Under soft palate

Narrower than oral cavity

Landmarks - glossopalatine arch

Involuntary function during swallowing

Glossopharyngeal

Endoderm of foregut

Common pharynx

Space between caudal end of soft palate + epiglottis

Not always present

Species variation

Comes into being during mouth breathing

Oesophageal pharynx

Start of oesophagus

Arytenoid cartilages to ???

Soft palate

???????

Muscles

Palatinus

Levator veli palatini

Tensor veli palatini

Palatopharyngeus

Pharyngeal muscles

Constrict

Ptergopharyngeus

Hyopharyngeus

Thyropharyngeus

Cricopharyngeus

Vago-accessory complex

Dilate

Stylopharyngeus

Glossopharyngeal nerve

Shorten

Palatopharyngeus

Pterygopharyngeus

Vago accessory complex

Swallowing

?

Nerve supply ???

ON DIAGRAM LABEL POSITION OF

NAME BONES THAT ARE ALTERED IN BRACHYCEPHALIC DOG SKULL

DESCRIBE 2 CONSEQUECES

BIG OLE QUESTION

Page 6

Hyoid, Larynx + Swallowing

Hyoid apparatus

Suspends tongue + larynx from the base of the skull

Articulates with petrous temporal bone (caudal to tympanic bulla)

Articulates with larynx

Bones

Paired

Stylohyoid

Epihyoid

Keratohyoid

Thyrohyoids

Unpaired

Basihyoid

Muscles

Sternohyoideus

Draws hyoid caudally

Cervical nerves

Thyrohyoideus

Draws hyoid caudally

Cervical nerves

Mylohyoideus

Draws hyoid rostrally

Trigeminal nerve

Geniohyoideus

Draws hyoid rostrally

Hypoglossal nerve

Larynx

Role

Cartilaginous + muscular tube suspended from skull

Some of the cartilages are mobile so shape + calibre of passage may be altered

Primary role - protect lower respiratory tract from foreign bodies

Secondary role - phonation

Airway

Vestibule

Laryngeal adieus

Rostral

Funnel shaped

Entrance

Epiglottis

Ventral floor

Aryepiglottic fold?

Glottis

Narrow vertical slit

Rima glottidus

Actual airway

Infraglottic cavity

Runs from glottis to the trachea

Cartilages

Thyroid

Unpaired

Very large

Articulates with cricoid

Epiglottis

Unpaired

Forms spout like entrance to larynx

Arytenoid

Paired

Can widen/narrow glottis

Cricoid

Unpaired

Shaped like signet ring

Radiography

Easier to see in older animals - more calcified

Epiglottis usually visible

Cuneiform process of arytenoids visible

Mucosal folds

Vestibular fold

Marks caudal end of vestibule

Vocal fold

Responsible for vocalisation

Aryepiglottic fold

Epiglottis to arytenoid

Muscles

8 pairs

7 pairs close the glottis

Cricoarytenoideus lateralis

Closes glottis

1 pair opens the glottis

Cricoarytenoideus dorsalis

Abducts the arytenoids

Opens the glottis

Vary tension on vocal cords

Innervated by recurrent laryngeal nerve

Except cricothyroid muscle which is innervated by cranial laryngeal nerve

Both branches of sago accessory complex

Supplying SVE

Arytenoid abduction

Arytenoid adduction

Lateral / laryngeal ventricle of the larynx

Blind ending pocket in lateral wall of larynx

Between vestibular fold + vocal fold

Refers to opening

Pocket itself is often called laryngeal saccule

Clinical relevance

Brachycephalic dogs - saccule eversion

Nerve supply

Vagus accessory complex X-XI

Cranial laryngeal nerve

Autonomic afferents

Visceral efferents

Special visceral efferents

Recurrent laryngeal nerve

Autonomic afferents

Autonomic efferents

Special visceral efferent

Left

Given off at ligametum arteriosum

Curves around aorta

Passes between aorta and pulmonary trunk before reascending

Right

Given off just caudal to right subclavian artery curves around and returns back up

Laryngeal collapse in horses

Roaring - noise made on inspiration

Paralysis of the cricoarytenoideus dorsalis muscle preventing abduction of the arytenoid cartilages + vocal cords

Surgery - suture arytenoid cartilage in open position

Reflexes

Laryngeal mucosa is acutely sensitive to mechanical stimulation / stimulation from small particles

Stimulation initiates coughing / reflex closure of glottis

More severe stimulation causes a more prolonged closure due to spasm of laryngeal muscles

LA needed in rabbits + cats as v sensitive mucosa

Swallowing

Bolus squeezed caudally from oral cavity by tongue against soft palate

Bolus projected by tongue into common pharynx. Glottis closing and soft palate moved dorsally closing nasopharyngeal meatus. Hyoid apparatus swings rostral + dorsally carrying layernx

Common pharynx squeezes bolus caudally , glottis is closed

Oesophageal pharynx squeezes bolus towards oesophageal sphincter, soft palate returns ventrally. Hyoid apparatus + with it the larynx moves caudoventrally . Glottis reopens

Reflex

Afferents

Glossopharyngeal + vagus nerves

Cranial laryngeal nerve conveys stimuli from rostral part of larynx

Efferents

Vagus- accessory complex via pharyngeal nerve of vagus supplies all pharyngeal muscles

Except styolopharyngeus which is supplied by glossopharyngeal nerve

Peristaltic contraction conveying food bolus to stomach are under reflex control

Afferents - oesophageal branches of recurrent laryngeal nerve

Efferents - recurrent laryngeal + vagus

Page 7

Adnexa of the eye

Structures

Sebaceous glands

Tarsal glands

Lateral canthus

Initiating membrane

Medial canthus

Palpebral fissure

Space between eyelids when they're open

Eyelids

3 Layers

Skin

Musculofibrous

Pharyngeal arch muscles

Somite muscles

Smooth muscle

Glands

Palpebral conjunctiva

Continues across cornea as bulbar conjuctiva

Tarsal plate

Stiff CT

Support free edge of each lid

Infection of a sebaceous gland

Common stye?

Tarsal gland

Small opens secreting waxy substance

Prevents tears from spilling out of eye

Present in upper + lower eyelids

Muscles of eyelids

Palebral branch of auriculopalpebral supplies

Orbicularis occuli

Eyelid closer

Sweeps tears across front of eye, keeping it clean

When paralysed corneal ulcers develop

Superciliaris

Lifts upper eyelid + eyebrow

Retractor anguli occuli

Draws lateral palpebral angle posteriorly

Occulomotor supplies

Levetor palpebral superioris

Lift upper eyelid

Sympathetics from cervical ganglion supply

Smooth muscles of upper + lower eyelids

Sensory nerve supply to region around eyes is trigeminal nerve

Ophthalmic division

Maxillary

Zygomaticotemporal

Clinical cases

Entropion

Inward rolling of the eyelid margin

Upper or lower eyelids

Causes conjunctivitis + corneal ulcers

Correct with surgery

Ectropian

Eversion of eyelid margin

Typically lower eyelid

Exposure of conjunctiva

Causing epiphora + conjunctivitis

Correct with surgery

Conjunctival flap

Used to treat deep corneal ulcers

Conjuntiva from inner surface of the eyelid is partially detached and swung round + sewn onto cornea

Brings blood supply

Allows cornea to repair itself

After several weeks connection is cut and conductive will die + drop off

Lacrimal apparatus

Lacrimal gland

Flat

Lobulated

Mixed fluid to moisten the eye

Supplies cornea with some nutrients

Small associated glands

Gland of the third eyelid

Lacrimal duct

Nasolacrimal duct

Tears drain from lacrimal lake to the lacrimal sac into lacrimal duct then nasal cavity

Runs through wall of maxilla then on the internal surface covered by mucosa

In horse?

Occusion occurs in rabbits where upper cheek teeth have grown back into their sockets

Down to poor diet / husbandry

Nictitating membrane

At rest its a T shaped cartilage supporting a fold of conjunctiva

Has associated lacrimal gland

Sweeps across cornea when eyeball is retracted

Returns to original position by contraction of SM

Innervated by sympathetic nerves

Prolapsed third eyelid?

Periorbital fascia

Cone shaped fibrous tunic surrounding the eye and extra ocular muscles

3 layers

Most superficial - Periorbita

Middle layer - Superficial muscle fascia

Deep layer - deep muscular fascia

Extraocular muscles

7 muscles in total

4 rectus

Dorsal

Produces dorsal tilting of pupil

Ventral

Produces ventral tilting of pupil

Medial

Abduction of the pupil

Lateral

Adduction of the pupil

Insert rostral to equator

2 oblique

Dorsal

Eyeball pulled medially + ventrally

Ventral

Eyeball pulled medially and dorsally

Inserts rostral to equator

1 retractor

Retractor bulbi

Insert caudal to equator

Retracts eyeball

All except the ventral oblique originate from optic canal + orbital fissure

Ventral oblique arises from ventromedial wall of orbit

Innervation

Oculomotor nerve supplies dorsal , medial + ventral recti muscles , ventral oblique

Trochlear nerve supplies dorsal oblique

Abducent nerve supplies lateral rectus + retractor bulbi

Page 8

External ear, Middle ear + Guttural pouch

Cartilages of the external ear

Auricular cartilage

Annular cartilage

Bony process of external acoustic meatus

Space running inside cartilages to the tympanic membrane is external auditory meatus - ear canal

Meatus is greatly curved making it difficult to see tympanic membrane

GA usually required to see this fully

Muscles of external ear

3 groups

Pre auricular - move ear forward

Ventral auricular - move ear ventrally

Post auricular - move ear caudally + medially

Nerve supply to the external ear

Motor

Rostral auricular nerve

Caudal auricular nerve

Great auricular nerve

Sensory

Auriculartemporal branches of mandibular trigemnal

Cervical spinal nerves

Internal auricular branch of the facial nerve

Middle ear

Cavity that lies within the temporal bone

Ventral floor formed by tympanic bulla

See handle of malleus through it

Laterally lies the tympanic membrane

Medially + dorsally lies with petrous temporal bone that houses inner ear

Facial nerve

Chorda tympani

Auditory tube

Small tubes running from wall of nasopharynx to middle ear cavity

Upon swallowing /yawning the entrance (Ostia) is forced open + air enters them + moves into middle ear cavity where it equalises the pressure o either side of the tympanic membrane

Guttural pouch

Air filled ventral diverticulum of auditory tube

Capacity of 300-500 ml

Only founding Equidae

Divided ventrally into medial + lateral compartments by stylohyoid bone

Unsure of role

Regulation of internal carotid artery pressure?

Cool blood flow to head ?

Found in

Dorsal - skull

Ventral - pharynx

Medial - median septum

Lateral - pterygoid muscles, parotid + mandibular salivary glands

Opens cranially into nasopharynx

Important associated structures

Nerves

VII

IX

X

XI

Arteries -

Internal carotid

External carotid / maxillary

Stylohyoid bone

Pharyngeal lymph nodes

Drainage

Ostia are dorsal to most of pouch when head horizontal

Only drain when head is down + horse swallows

Lateral surgical approach

Viborgs triangle

Caudal border - tendon of insertion of sternocephalicus

Ventral border - linguofacial vein

Cranial border - caudal mandible

Diseases

Tympany - air distension

Empyema - bacterial infection

Mycosis - fungal infection

Erosion of artery - epistaxis (nose bleed)

Can affect nerves - IX, X XI (VII?)

Diagnosis by endoscopy and radiography