Head Flashcards
What makes up the skeleton of the head?
Skull, mandible, hyoid apparatus, ossicles of the ear, cartilages of the ear and nose.
Define the face, cranium and the mandible.
Face - boney extension of the skull enclosing nasal cavity and forming the roof of the mouth. Cranium - boney box protecting the brain. Mandible - lower jaw bone
The skull has two materials of origin, name and describe them with an example of a structure from each.
Endochondrial bones - arise from unpaired (mainly) structure - eg Basisphenoid. Intramembranous bones - arise from foci developing in mesenchyme, paired - Frontal.
Name the unpaired bones of the skull.
Supraoccipital, Basioccipital, Basisphenoid, Presphenoid, Ethmoid, Vomer
Name four paired bones of the skull.
Temporal, Frontal, Parietal, Exoccipital, Nasal, Maxilla, Zygomatic, Palatine, Lacrimal, Pterygoid, Mandible, Dorsal, Ventral and ethmoid turbinates.
Label the bones of this laterally placed skull. (x7)
Incisive, nasal, maxilla, frontal, parietal, zygomatic, temporal
Label the bones of the ventral skull. (x9)
Occipital, bulla, pterygoid, vomer, maxilla, incisive, palatine, presphenoid, basisphenoid
Draw the structure of the primary and secondary palate and describe their development. What definitive structures does each form?
What does failure do close of the primary and secondary palates result in?
Primary - unpaired semilune shape - lip and incisive bone,
Secondary - paired, move to midline from the side - hard and soft palate.
Failure to close the primary palate results in cleft lip, and failure to close the secondary palate results in cleft palate. AKA Congenital oronasal fistula – an abnormal communication between the oral and nasal cavity. Aspiration pneumonia
Describe the structure of the occipital bone.
What condition can be caused with improper development of this bone? Describe
Foramen magnum bordered dorsally by the supraoccipital, laterally by paired extraoccipital and ventrally by the baseoccipital.
Syringomyelia - Congenital condition (CKCS), undersized occipital bone (hypoplasia) . Cerebellum becomes pressed against the foramen magnum & interrupts normal flow of CSF. Pockets of CSF build up within the brain causing the neurological conditions. FM may be keyhole shaped.
Describe the anatomy of the tympanic bulla.
Part of the temporal bone. Contains the middle ear. Filled with air in the healthy animal. Bounded laterally by the tympanic membrane covering the external auditory meatus.
Draw and label the bones and cartilages of the hyoid apparatus.
What is the function of this structure?
Which structure is unique to the horse?
The hyoid apparatus forms a suspensory mechanism for the tongue and larynx. Lingual process of the basehyoid bone
Name the foramina of the skull (x9)
- Ethmoidal foramina 2. Optic canal 3. Orbital fissure 4. Rostral alar foramen 5. Caudal alar foramen and oval foramen 6. Internal carotid foramen 7. Jugular foramen 8. Stylomastoid foramen 9. Hypoglossal foramen
What problems arise from the abnormal shape of the brachycephalic dog skull?
- Stenotic nares - occluded nostrils - > cartilage and soft tissue for the underlying tiny nasal bones to support. Difficulty breathing through nose.
- Long soft palate. Soft palate occludes larynx = difficulty breathing
- Often, have crowded teeth at unusual orientations. Difficulty eating and increased dental disease. Malocclusion due to mandible being less reduced than maxilla so mandible protrudes (prognathism)
- Exopthalmic eyes – bulgy (reduced facial bone). Can also be more prone to proptosis (acute forward displacement of the eyeball.
- Wrinkly skin - Infections
What are the three main dog and cat head shapes? Name a breed with each.
- Dolichocephalic - greyhound, oriental.
- Mesaticephalic - GSD, DSH.
- Brachycephalic - Bulldog, persian.
What is the function of the nasal cavity and how are these achieved? (x3)
- Warm and humidify air going to lungs. - Air brought into contact with large surface area for water and heat exchange.
- Filtering particles from air going to lungs. - Contact surface covered in mucous to trap small particles - hairs at entrance to nasal cavity trap large particles
- Detecting odour molecules in air - Many sensory receptor cells to detect odour molecules
Describe the turbinate bones (x3) (basic description)
- Ethmoturbinates - small and lie towards the back of the nasal cavity. They are attached to the nasal septum, lateral nasal wall and cribriform plate.
- Dorsal Turbinates - single scroll attached to the nasal wall.
- Ventral Turbinate - double scroll attached to the maxilla.
Name the four meati found within the nasal cavity. What are their functions?
- Dorsal meatus – to olfactory mucosa.
- Middle meatus – to the sinus system.
- Ventral meatus – principal airway.
- Common meatus – the medial communicating part
What is a paranasal sinus? Name the main ones of clinical importance. What functions do they serve?
Air-filled diverticula (out pocketing) of the nasal cavity. Frontal and maxillary. Mechanical protection, Thermal protection, Enlarge skull without adding weight
Draw and describe the frontal sinus. (of the dog)
- Lies within the frontal bone
- Has up to five separate compartments
- In the ox and sheep one of the 5 compartment is the CORNUAL PROCESS. This extends into the horn.
- In all domestic species except the horse the frontal sinus communicates directly with the nasal cavity by way of small openings between the ethmoturbinates.
What rules two rules are vital to remember when euthanasing animals via shooting?
- Aim for MEDULLA OBLONGATA – the respiratory and cardiovascular centre of the brain
- Avoid midline on species with a strong bony midline septum - species dependent
Draw and describe the maxillary sinus of the dog and cat.
Often known as the maxillary recess since it communicates so freely with the nasal cavity.
How do the palatine and maxillary sinus communicate in the horse?
(HINT: Draw)
Draw the arangement of the sinuses in the horse.
How does the maxillary sinus of the horse alter with age?
Young horse: Lateral parts of the maxillary sinus are much smaller due to the unerupted cheek teeth occupying the maxillary space.
Name the trephine points used to gain access to the maxillary sinus in the horse.
Describe the anatomical landmarks used to determine trephine points in the horse.
Dorsal and ventral
Define Sinus.
An airfilled diverticula of the nasal cavity.
Name and label the cranial nerves seen in this picture of the ventral surface of the brain.
- Olfactory
- Optic
- Occulomotor
- Trochlear
- Trigeminal
- Abducens
- Facial
- Vestibulo-cocchlear
- Glossopharyngeal
- Vagus
- Accessory
- Hypoglossal
TRUE OR FALSE
Cavitation does not occur during development of the head.
What effect does the answer have on development?
True
- Lateral plate mesoderm remains as solid belt of tissue surrounding gut tube
- Intermediate mesoderm fails to develop
Name the different embryological structure of the developing head. What do they eventually form and how are they innervated? (x6)
- Ectoderm - forms outer epithelial covering - somatic afferents - cutaneous sensation
- Endoderm - forms inner epithelial covering - Sensation = autonomic afferents, Motor autonomic efferents.
- Lateral plate mesoderm - Special visceral striated muscle of the gut - Special visceral efferents
- Somites - Form striated muscle of eyeball & tongue - Somatic efferents
- Segmental arteries - Aortic arches - Autonomic afferents / efferents
- Neuraxis - Brain
Which structures of the developing head are obliterated, fail to develop further or migrate to another area of the head?
- Obliteration:
- Somites 4 & 5 (& associated nerves)
- Pharyngeal arch 5 (& associated endoderm, ectoderm, lateral plate mesoderm, nerves & arterial arches)
- Arterial arches 1 & 2
- Pharyngeal clefts / pouches 5 & 6
- Ectoderm of segments 6 & 7
- Fails to develop further:
- Endoderm of arch 2
- Ectoderm of segments 3-5
- Migration:
- Somites 6 & 7
Describe the embryological origin of the tongue.
- Epithelium
- Rostral 2/3 = ectoderm of arch 1
- Caudal 1/3 = endoderm of arch 3
- (Endoderm of arch 2 fails to develop further)
- Muscle
- Migration of paired somites 6 & 7
Describe the embryological origin of the pituitary and thyroid glands.
- Anterior Pituitary -Invagination of arch 1 (ectodermal)
- Thyroid - Invagination of arch 2 (endodermal
Describe the embryological origin of the different areas of skin of the head. (x3)
Which of the cranial nerves therefore provides crainial sensation to each of these areas?
Ectoderm
- Segment 1 - top of the head - Opthalmic branch of the trigeminal
- Segment 2 - rest of the head and jaw - Maxillary/ mandibular branch of the trigeminal
- Secments 3/4/5 - external ear - Facial (internal auricular) , glossopharyngeal and vagus
Which cranial nerve branch runs through the infraorbital canal?
Name the splits of this nerve and which structures they provide innervation to.
Ophthalmic branch of the trigeminal - sensory fibres only
- Zygomatic
- Ethmoidal
- Long ciliary - eyeball
- Infratrochlear - medial canthus of the eye
- Cornual - cornual process
- Elongation - to the turbinates
Draw and label a generic canine tooth. (+brief description)
Describe the embryological origin of each layers of the tooth.
Which of the cranial nerve innervates the teeth?
- Enamel - Ectodermal (ameloblasts) - Hardest layer
- Dentine - Mesodermal (odontoblasts)
- Cementum - Mesodermal - calcified connective tissue
- Pulp cavity - Nerves, blood vessels and lymphatics
- Periodontal ligament - Shock absorbers, form a sling around the tooth
Trigeminal - superior and inferior alveolar branches of the maxillary and mandibular nerves.
Draw a generic herbivore cheek tooth and label the layers.
How does the structures of the incisor differ with age?
What is meant by the infundibulum and dental star of these teeth?
With age the cheek teeth wear though each material wears at a different rate leaving a ridged appearance. This allows us to roughly age horses.
- Young - can see infundibulum (cementum filled cup)
- Middle aged - see infundibulum and dental star (pulp cavity
- Elderly - dental star only can be seen.
Define
- Diphydont
- Heterodont
- Brachdont
- Hypsodont
- x2 sets (deciduous and mature)
- Specialised
- Low crowned, quick erruption - carnovore teeth
- High crowned, slow erruption - herbivores
Name and describe the muscles of the lips which are involved in food prehension.
Which cranial nerves provide somatic afferent and efferent supply to these muscles?
- Orbicularis oris - sphincter like muscle - closing the mouth and sucking
- Levator labii superioris - lifts the upper lip
- Levator nasolabialis - lifts upper lip and nostril
- Depressor labii inferioris - lowers the lower lip
SA - Trigeminal nerve
SE - Facial nerve
Buccinator muscle
Innervation sources.
Cheeck muscle.
Diaphragm-like muscle used in taughting the skin of the cheek and therefore keeping food on occlusal surface of the teeth.
SA - Trigeminal
SE - Buccinator branch of the facial nerve
Name the intrinsic and extrinsic muscles of the tongue.
Outline the origin and insertion of each and describe their action.
Which cranial nerve provide the efferent supply to these muscles?
Extrinsic
- Genioglossus - Pulls tongue out - within the frenulum
- Hyoglossus - Retracts and depresses tongue
- Styloglossus - Retracts the tongue
Intrinsic
- Propria Lingua - changes tongue shape
Supplies by the hypoglossus
Draw and describe the temporo-mandibular joint.
How does this joint differ in morphology between herbivores and carnivores?
Large joint capsule divided by fibrocartilagenous disc into the meniscotemporal and meniscomandibular sections.
- Temporal bone
- Herbivore - mandibular fossa is large and flat with no retroglenoid process - caudal movement is possible
- Carnivore - The RGP means no caudal movement is poss.
- Mandibular bone
- H - occlusal fossa large - < gape & forwards movement
- C - small occlusal surface - > gape & little movement
Describe the anatomy of the parotid, mandibular, sublingual and zygomatic salivary glands.
How is each innervated?
P - Base of the auricular cartillage. Parotid duct courses across the masseter and opens near UP4 - CN IX (via the trigeminal)
M - Caudal to jaw angle. Mand and subling run together, open on sublingual caruncles - CN VII (Via trigeminal chorda tympani)
S - Continuous with the mandibular gland.
Z - Below the eye (buccinator is more developed in the herbivores)
How is the pharynx separated?
How can the pharynx be distinguished from the rest of the upper respiratory tract?
- Nasopharynx - internal nares > caudal soft palate
- Oropharynx - last molar to epiglottis
- Oesophageal pharynx - arytenoid cartilage > cricoid cartilage
- Common pharynx - caudal soft palate > arytenoid cartilage. POTENTIAL SPACE - only present at swallowing and breathing
Pharynx - narrower than the oral cavity, involuntary innervation, CNIX supply, endodermal origin
Name and draw the pharyngeal constrictors.
(x4)
Innervation?
Rostral - Pterygopharyngeus
Middle - Hyopharyngeus
Caudal - Thyropharyngeus & cricopharyngeus
Innervated by IX & X
Name and draw the pharyngeal dilators.
Innervation?
Stylohyoid > pharynx
CN IX
Name and draw the pharyngeal shorteners.
(x2)
Palatopharyngeus
Pterygopharyngeus
These muscles insert onto the roof of the pharynx, when they contract they pull the pharynx rostrally
Describe the hyoid apparatus, its attachments and function in all domestic species.
Holds the larynx in place
- Attached to temporal region by synchondrosis joint
- Palpable through pharynx and visible when pharynx is viewed through the mouth
- Basihyoid is palpable within the intermandibular space.
- Sternohyoid muscle pulls the hyoid caudally and the geniohyoid muscle pulls the hyoid rostrally
Describe the extrinsic muscles of the tongue, their attachments, innervation and function.
Styloglossus - retract tongue
Genioglossus - stick out tongue
Hyoglossus - depresses/retracts tongue
Geniohyoid - moves mandible & assists in swallowing
Sternohyoid - depresses hyoid bone & elevates tongue
Identify and describe the lingual papillae and appreciate their function.
Rostral 2/3
- filiform papillae - grip food
- circumvallate/vallate - taste/grip
- fungiform - taste
Caudal 1/3
- Foliate - taste
How many muscles are there controlling the larynx?
Which cranial nerves are they suppied by?
8 pairs
- Glottis openers - Cricoarytenoid dorsalis (abducts arytenoid)
- Glottis closers - Cricoarytenoid lateralis (adducts arytenoid)
Cricothyroid - Cranial Laryngeal
All others are caudal laryngeal (recurrent laryngeal nerve)
Draw and describe the nictating membrane.
T shaped
Sweeps across the third eyelid when the retractor bulbi retracts the eyeball. Returns to position involuntarily by smooth muscle (sympathetic middle ear nerves)
May contain lymphoid tissue
Name the extraoccular muscles of the eye.
How are each innervated?
- Rectus muscles
- Dorsal – produces dorsal tilting of the pupil - III
- Ventral produces ventral tilting of the pupil - III
- Lateral – abduction of the pupil - VI
- Medial – adduction of the pupil - III
- Oblique muscles
- Dorsal- dorsal eyeball pulled medially and ventrally - IV
- Ventral – ventral part moved medially ad dorsally - III
- Retractor bulbi – retracts eyeball - VI
Draw and label the eyelid.
Name the three layers.
- Skin
- Musculofibrous - smooth muscle, CT, skeletal muscle, PA muscle
- Palpebral conjunctiva - stratified columnar epithelium and goblet cells
Others: hair, sebaceous gland, tarsal plate
Describe the drainage of the gutteral pouch.
- Ostia are dorsal to most of pouch when head horizontal
- Drainage channels are constricted during exercise
- Only drain when head is down and horse swallows
What does this radiograph show?
Pyema - pus in the GP - due to bacterial infection
What does this radiograph show?
Tympany of the GP - air distension
Which muscles lie beneath the platysma?
Describe their action.
The parotidoauriculatis (ear depressor) and the zygomaticus (snarling muscle), innervated by the facial nerve
Name the nine branches of the facial nerve and pinpoint them on this diagram.
What are the motor, SVA and general visceral efferent functions of the facial nerve?
- Facial nerve root
- Caudal Auricular
- Internal Auricular
- Rostral Auricular
- Palpebral
- Auriculopalpebral
- Dorsal buccal
- Ventral buccal
- Cervical
Motor - Superficial head and ear muscles and platysma, digastricus and stylohyoideus.
SVA - Taste to rostral 2/3rds of the tongue
GVE - PNS fibres to lacrimal gland, mand and sublingual salivary glands & other mucosal glands
Describe the venous drainage of the superficial structures of the head.
- External Jugular
- Maxillary
- Caudal Auricular
- Superficial Temporal
- Linguofacial
- Lingual
- Facial
- Deep Facial
Name the lymphnodes of the head.
Why are they of clinical importance?
Retropharyngeal (all drain into here)
Mandibular
Parotid
The mandibular lymphnodes are palpable in the live animal and the others can be examined on PM.
What are the main salivary glands of the head?
(x4)
Zygomatic, parotid, mandibular, sublingual
