The mouth Flashcards
Outline the embryological development of the tooth
1: Bud stage. Line of epithelial cells condenses along jaw margins, invaginate to form dental bud. Surrounded by proliferating mesenchymal cells
2: Cap stage. Bud infolds to form dental cap, neural crest derived mesenchyme forms dental papilla. Remains connected to epithelium via cord of cells, give off-shoots to form more buds.
3: Epithelial cells => ameloblasts => form enamel
4: Mesenchymal cells => odontoblasts =>form dentine
5: Bell stage. Mesenchyme around bud forms vascular dental sac (dental follice). Inner layer forms cementoblasts => cementum. Outer layer form osteoblasts => alveolar bone
6: Enamel organ comprises stellate reticulum plus ameloblasts and outer enamel epithelium
7: Dental sac differentiates into the periodontal ligament
Describe the features of dental anatomy used to age animals
- Number of teeth
- The type of teeth present (incisors, premolar, molar)
- Deciduous vs permanent teeth
- Degree of wear on teeth
- Presence of cups, dental star, Galvayne’s groove
- Spurs or hooks on teeth
Name the salivary glands
- Parotid
- Mandbular
- Zygomatic
- Sub-lingual
- Buccal
- Numerous minor ones (caudal third of tongue, buccal mucosa, labial mucosa and soft palate)
Describe the structure of the salivary glands
- All paired
- Vary in shape and size depending on species
- Empty via large ducts, minor have multiple short ducts
- Made up of multiple salivons
Describe the structure of a basic salivon (top to exit)
- Acinus at top, producing area, made up of mucus and serous cells
- Serous cells: water secretion similar to plasma
- Mucus cells: mucoid secretion
- Plasma cells: around acini, produce IgA
- Intercalated duct: the gathering of the acinus area, secrete HCO3- and absorb Cl-
- Striated duct: exchange of ions, many mitochondria give striated appearance, secrete K+ and HCO3- and absorb Na+
- Secretory ducts: convey saliva to the mouth
Outline the components of saliva and give basic species differences
- Colourless
- Electrolytes
- Proteins
- Amylase
- Desquamated cells from mucosa
- Lymphocytes
Mucin (if mucus secreting gland) - Bicarbonate (buffer)
- Human: acidic
- Most other species alkaline (depends on food eaten)
- Composition modified in strated region
Outline the functions of saliva and describe some species differences
- Wetting agent/lubricant
- Enzyme action
- Buffering action in rumen and to maintain oral pH
- Anti-foaming
- Antibacterial (peroxide based)
- Taste (water soluble components dissolve in saliva)
- Phosphate present as buffer
- Urea for fermentation
- Thermoregulation in dogs and cats
Indicate how and why the electrolyte composition of saliva varies with salivary flow rate and how it compares to plasma
- Primary secretion from acini
- Modified in ducts
- Na reabsorbed, HCO3 and K secreted
- Level of alteration depends on flow
- Greater volume produced, closer to primary secretion concentrations achieved (increased flow rate)
What is the composition of saliva from the mandibular gland in man, ungulates, dogs and cats and rodents? (Serous, mucoid, mixed)
- Mixed in man, ungulates, dogs and cats
- Serous in rodents
What is the composition of saliva from the sub-lingual gland in horses, cattle, pigs, dogs, cats and rodents? (Serous, mucoid, mixed)
- Mixed in horse, cattle, pigs, dogs and cats
- Mucoid in rodents
Describe stimuli to saliva secretion
- Produced in response to neural and hormonal stimuli
- Feeding (taste, smell, composition)
- Reflex
- Can be conditioned
- Balance of sympathetic and parasympathetic
Describe how salivary secretion can be modified by the autonomic nervous system
- Sympathetic:
- Viscous, amylase, protein, increased flow in response to taste, visual and olfactory stimuli
Parasympathetic:
- Water, high volume, continuous basal flow
- Cr. nn VII: mandibular, sublingual, palatine
- Cr. nn IX: parotid (and zygomatic)
Describe the parotid gland
- Ventral to base of ear (base of auricular cartilage in retromandibular position)
- V shaped
- Produces mixed saliva
- Single duct
- Duct runs craniomedially across masseter muscle (dog, sheep) or ventral to it (cattle, horse, pig)
- Duct opens into upper buccal area by maxillary 4th premolar
Describe the zygomatic gland
- Only in dog and cat
- Rostral portion of pterygopalatine fossa on floor of orbit ventral and medial to zygomatic arch and dorsolateral to last maxillary molar tooth
- Duct opens in upper buccal mucosa, opposite upper first molar or caudal to this
- Usually caudal to parotid duct opening
- May have several (~4) minor openings nearby
- Ridge with several small red dots
Describe the mandibular gland
- Caudal and medial to angle of mandible
- Limited by linguofacial vein ventrally and maxillary vein caudally
- Produces mixed saliva
- Capsule shared with monostomatic portion of sublingual salivary gland
- Duct opens at sublingual papilla (caruncle) at base of lingual frenulum
- In 30% of dogs, mandibular and sublingual ducts merge
- Can underogo cystic change
Describe the sublingual gland
- Polystomatic and monostomatic parts
- Mono: long sublingual duct, next to mandibular duct, opens at sublingual caruncle
- Poly: 6-12 lobules with independent short ducts opening sublingually near frenulum
- Mucus mainly, lesser serous component
Describe the minor buccal and palatine glands
- Many small ducs opening locally from gland to the mucosa
Describe the phases of swallowing (deglutition)
- 3 stages: voluntary, involuntary, reflex
- 1: masticated food and saliva formed into bolus, pushed up and back to pharynx
- 2: Swallowing reflex, soft palate elevates. Posterior nares closed, epiglotis covers larynx and trachea, breathing suspended
- 3: Oesophagus dilates, bolus passes, oesophagus closes and epiglottis uncovers trachea, bolus moves down oesophagus to stomach
Briefly outline the function of the tongue (especially in swallowing)
- Muscular organ
- Prehends food, controls food delivery to teeth
- Forms food bolus
- Pushes bolus caudally to be swallowed
- Freely mobile in mammals, variably fixed to floor of mouth in others
- Papillae for taste, molecules dissolve in saliva so can taste
Briefly outline the function of the hyoid apparatus
- Supports larynx from the skull
- Series of bones
Present in many animals, not just mammals - Attachment for muscles
Briefly outline the structure and function of the pharyngeal wall in relation to swallowing
- Made up of striated muscles
- Constriction and shortening: rostral (palatopharyngeus), middle (hyopharyngeus), caudal (thyropharyngeus)
- Insert on roof of pharynx = dorsal and lateral arches allowing passage of food
- Dilation: stylopharyngus caudalis
- Innervated by vagus and glossopharyngeal nerve
Compare swallowing in mammals and reptiles
Mammals: hard palate present, freely mobile tongue, sllows suckling and breathing at same time, can drink by sucking due to 3 seals: lips, tongue against soft palate and soft palate against epiglottis
- Reptiles: secondary hard palate incomplete in many species, no lip seal, minimal chewing, skull types affect prehension
What are the motor nerve supplies in the mouth?
- Masticatory: V3 trigeminal
- Jaw opening: rostral portion is V3, caudal portion is VII
- Swallowing: IX and X
- Intrinsic tongue muscles: XII
What are the sensory nerve supplies to the mouth?
- Touch (GSA):
-> tongue/buccal mucosa: V3
-> teeth: V2 and V3
-> pharynx/larynx: IX/X
Taste (SVA):
-> rostral 2/3 of tongue: VII
-> caudal 1/3 of tongue: IX
-> caudal pharynx and larynx: X
Give the names and numbers of the cranial nerves.
I: Olfactory II: Optic III: oculomotor IV: trochlear V: trigeminal V1: ophthalmic V2: maxillary V3: mandibular VI: abducens VII: facial VIII: vestibulocochlear IX: glossopharyngeal X: vagus XI: Accessory XII: hypoglossal
Describe basic dental anatomy and function relevant to common species
- Found in all bones of the skull across species
- Mammals: incisive, maxilla and mandible
- Snakes: palatine teeth
- Heterodont vs heterodont
- Monophyodont vs polyphyodont vs diphyodont
- Scrodont vs pleurodont vs thecodont
- 4 quadrants of the mouth
- Upper teeth on maxillary bone, close to nasal chamber and maxillary sinus
- Lower teeth on mandible, mandibular canal runs ventrally
Define heterodont and homodont
- Hetero: different types of teeth in one mouth
- Homodont: one type of teeth in one mouth
Define monophyodont, polyphyodont and diphyodont
Mono: teeth not replaced
Poly: teeth continuously replaced
Di: 2 sets of teeth, teeth replaced once
Define acrodont, pleurodont and thecodont
Acro: teeth on marginal border of jaw
Pleuro: teeth on medial border of jaw
Theco: teeth in deep sockets
What is meant by: labial/buccal, lingual, palatal, mesial, distal and occlusal when referring to teeth surfaces?
Labial/buccal: lateral/cheek side Lingual: medial side of mandibular teeth Palatal: medial side of maxillary teeth Mesial: rostral side Distal: caudal side Occlusal: meeting surface of the teeth
Describe the modified Triadan system and how it is used
- Each toth has a 3 digit number
- 1st digit = quadrant
- 2nd and 3rd identify the tooth
- Clockwise from top left quadrant (permanent): 1-2-3-4
- Clockwise from top left (temporary): 5-6-7-8
- Numbers are not skipped even if tooth is missing
- Incisors: 01,02,03
- Canines: 04
- Premolars: 05, 06, 07, 08
- Molars: 09, 10, 11
Describe the regional and species differences in tooth structure and relate them to food intake
- Flesh: soft, need sharp teeth
- Bone, shells: hard, need crushing teeth
- plants: hard, need grinding teeth to break down cells
- Dentition designed for food
- At back of mouth mostly chewing teeth, at front mostly prehension and holding onto prey
What are the main parts of the anatomy of a tooth?
- Crown (exposed part)
- Enamel
- Dentine
- Pulp
- Periodontium
- Root (buried part)
- Nerve
- Cementum
- Periodontal ligament
- Alveolar bone
- Gingiva
Describe the structure of the tooth crown.
- Visible/supragingival
- Made up of enamel, dentine and cementum in herbivores
- Enamel: hard, smooth
- Dentine: hard, tubules
- Cusps formed
- Contains some of pulp cavity
Describe the structure of the enamel of teeth
- Very hard
- 97% hydroxyapatite
- Acellular
- No repair possible
- Dissolves in acid
- Only on crown
- Not always present
Describe the structure of dentine
- Living tissue (odontoblasts with processes in dentinal tubules)
- Primary: most of dentine, formed as tooth grows, mineralised collagen
- Secondary: grows slowly, formed after eruption, makes the pulp cavity smaller
- Tertiary: reaction to damage, irregular structure, helps fill in damage
Describe the structure of tooth pulp
- Pulp cavity is same as root canal
- Contains blood vessels, lymph, nerves
- Narrows with ages due to secondary dentine deposition
- Closed apex when finished erupting
- Open apex in continually erupting teeth
- Apical delta - many small canals at apex
Describe the structure and function of periodontium
- Attach, support, protect
- Alveolar bone
- Periodontal ligament between the alveolar bone and the cementum and gingiva
Describe the structure of the gingiva
- Made up of squamous epithelium
- Dense fibrous layer
- Closely bound to periosteum
- Reflects onto cemento-enamel junction to form a pocket
- Pocket called gingival sulcus (food trapped, site where inflammation may start)
Describe the structure and function of dental cementum
- Similar to bone
- Peripheral to dentine or enamel
- In herbivores is on the outside
- Attachment for periodontal fibres
Describe the structure and function of the periodontal ligament
- Series of angled collagen fibres
- Supports tooth
- Shock absorber
- Spreads load into whole socket
Describe the structure and function of the tooth root
- Made up of cementum, dentine and root canal
- Apical delta at the apex of the root
- Can be single or multi rooted
- Can be closed or open
- Closed: tooth erupts slowsly and continuously (horses and cattle) or erupts to fixed height
- Open: root apex si open, tooth continually grows and erupts e.g. rodent teeth
Describe basic tooth replacement
- Deciduous dentition: eruption followed by replacement, law of succession (new pushes out older)
- Permanent dentition eruption: eruption process unknown, dental follicle importnat and only occurs when crown is complete
- Remnants of deciduous teeth fall off as caps
- As tooth grows, primary dentine grows, pulp remains large, open root
- Mature tooth: secondary dentine gradually replaces pulp, closed root
Describe the structure-function relationships for other structures (bones, muscles ad joints) involved in the process of mastication in mammalians
- Simple jaw joint (also true for crocodilia)
- Akinetic jaw
- Teeth in sockets in mandible, maxilla and incisive bone
- Temporomandibular joint has meniscus and so is in 2 parts
- Synovial joint
- Skull side compartment for translation movements
- Mandible side for hinge movements
- Hinge joint but has lateral and rostro-caudal movement (grinding and opposing of teeth
What is the difference in the vertical ramus of the mandible of the herbivore compared to carnivores?
Longer in herbivores, allows more occlusion
Describe the dental anatomy and its function in carnivores
- Brachydont
- Erupt to set height
- Incisors: nibbling/nipping
- Canines: puncture/graps
- Carnassials: cut/shear
- Molars: crush
- Jaw move laterally to bring carnassials into action (crushing of bones)
Describe the dental anatomy and its function in herbivores
- Hypsodont
- Most of tooth hidden within socket, so all of teeth enamel covered by cementum
Adapted dentition (flat surfaced, folded enamel) - Grinding purpose
- Continuous eruption/growth to match wear
- Slow eruption: horses/ruminants
- Slow growth: small furries
- Incorrect diet can lead to growth being faster than wear (tooth overgrowth, elongation, spurs etc)
Describe ruminant eruption patterns with age
- Cattle: adult central incisors erupt at 2 years
- Called broad teeth (physical appearance)
- Sheep adult incisors erupt 1, 2, 3 and 4 years (canine incisor shaped)
- As fall out called broken mouthed
Describe the dentition of pigs
- low, rounded cusps (bunodont)
- Typical omnivore teeth
- Has all the teeth it is possible to have
Define hyperdontia
Supernumerary teeth (poodles, terriers usually canine tooth does not shed, traps food)
Define hypodontia
Fewer teeth than normal
Describe how a radiograph of dogs’ teeth are obtained
- Use bisecting line technique
- If beam perpendicular to jaw then root will appear to short
- If beam is perpendicular to tooth then root will appear too long
- Place plate in mouth, make line parallel to tooth
Do bisecting line between tooth and plate - Direct beam 90degrees to bisectin line
List the extrinsic muscles of the tongue
- Genioglossus
- Styloglossus
- Hyoglossus
- Geniohyoideus
Give the attachments, innervation, blood supply and function of the genioglossus muscle
- Origin: Dorsally on the incisive part of tha mandible
- Insertion: Fans upward in the sagittal plane
- Innervation: Hhypoglossal nerve
- Function: bundles at apex of tongue retract that part. Bundles at root of tongue drag tongue forward
Give the attachments, innervation, blood supply and function of the styloglossus muscle
- Origin: stylohyoid bone
- Innervation: hypoglossal nerve
- Function: draw back tongue and elevate it
Give the attachments, innervation, blood supply and function of the hyoglossus muscle
- Origin: basihyoid bone
- Insertion: runs forward lateral to genioglossus
- Innervation: hypoglossal
- Function: draw tongue back
Give the attachments, innervation and function of the geniohyoideus muscle
- Origin: incisive part of mandible
- Insertion: hyoid bone
- Innervation: hypoglossal nerve
- Function: draw hyoid and thus the tongue forward
List the muscles of mastication
- Masseter
- Temporalis
- Digastricus
- Pterygoideus
Give the attachments, innervation and function of the masseter muscle
- Origin: maxillary region of skull and zygomatic arch
- Insertion: wide insertion on caudal part of mandible
- Innervation: V3 (mandibular part of trigeminal nerve)
- Function: Raise mandible and draw towards active side, more developed in herbivores due to more chewing
Give the attachments, innervation and function of the temporalis muscle
- Origin: lateral surface of the cranium
- Insertion: coronoid process of the mandible
- Innervation: V3
- Function: raise mandible (larger in dogs and cats due to scissor like closing of jaw)
Give the attachments, innervation and function of the digastricus muscle
- Origin: skull caudal to the temporomandibular joint
- Insertion: ventral margin of the mandible
- Innervation: Digastric branch of the facial nerve
Give the attachments, innervation and function of the pterygoideus
- Origin: pterygopalatine region of the skull
- Insertion: mandible (medial side)
- Innervation: V3
- Function: raise mandible and draw inwards
Describe the general structure of the tongue
- Can be divided into root, body and apex
- Attached to floor of teh oral cavity cranially by the frenulum
- Dorsal surface covered in papillae
- Can be mechanical or gustatory
- 4 main muscles
Describe the mechanical papillae of the tongue
- Filiform, conical and marginal
- More numerous, give raspy texture of tongue (cows, cats)
- marginal papillar present in newborn carnivores, aid suckling
Describe gustatory papillae of the tongue
- Vallate, fungiforme and foliate
- For taste, named by shape
- Often situated near salivary glands in order to allow molecules to dissolve to taste
