Veterinary Anatomy: Head and Neck PDF

2.1 Headgut, Pharynx & Larynx Prehension: ​ Get food into mouth ​ Domestic animal: lip, teeth, tongue, head & jaw movement Mastication: ​ Mechanical breakdown ​ Food mix w/ saliva Deglutition: ​ Swallowing ​ Initial phase: voluntary ​ Remaining phases (pass soft pellet,...

2.1 Headgut, Pharynx & Larynx Prehension: ​ Get food into mouth ​ Domestic animal: lip, teeth, tongue, head & jaw movement Mastication: ​ Mechanical breakdown ​ Food mix w/ saliva Deglutition: ​ Swallowing ​ Initial phase: voluntary ​ Remaining phases (pass soft pellet, in pharynx): involuntary Horse: X vomit under normal condition → Severe disease Musculature (muscles) of prehension: ​ Zygomaticus (jaw): retract mouth angle ​ Levator (up) labii superioris: elevate upper lip → draw it to 1 side ​ Buccinator (side): keep food between upper & lower molar teeth ​ Orbicularis oris: close lips, help to gather food Oral cavity: ​ Start of GIT ​ Extend: lip → pharynx ○​ Pharynx: naso- & oro- ​ Structure: tongue, teeth, salivary glands ​ Dog: 1.​ Vestibule 1.​ Buccal cavity 2.​ Canine tooth 2.​ Palatine raphe: 1 a.​ Philtrum single line (midline) 3.​ Hard palate 3.​ Transverse ridges 4.​ Soft palate 4.​ Soft palate 5.​ Tongue 5.​ Medial Sulcus: help 6.​ Sublingual caruncle drinking water, 7.​ Palatoglossal arch centre of tongue 8.​ Palatine tonsil 6.​ Vestibule: entrance 9.​ Frenulum of GIT  1.​ Tongue 2.​ Hard palate: separate nasal & oral cavity (ceiling) 3.​ Nasopharynx 4.​ Soft palate: separate nasal & oral pharynx 5.​ Oropharynx 6.​ Epiglottis: cartilage, close (flip & cover) trachea when swallowing → prevent water & food going through 7.​ Larynx 8.​ Trachea 9.​ Oesophagus (caudal) Blue: passage of air Green: page of food & water ​ Crossover ​ Air can come in through mouth ​ Liquid (eg. water) can get out through nose Brachycephalic (short nostril): disease ​ Mostly dogs ​ X thermoregulation, filtering ​ Extremely elongated soft pellet ○​ Block larynx & trachea entrance ○​ Difficulty in breathing, snoring ​ BOAS surgery ○​ Brachycephalic obstructive airway syndrome ○​ Make cuts around nose, cut part of soft pellet ○​ Expand potential for breathing ○​ → Improve life quality, extend life expectancy ​ Horse: 1.​ Tongue 2.​ Hard palate 3.​ Pharynx 4.​ Soft palate: elongated, might touch epiglottis 5.​ Epiglottis 6.​ Larynx 7.​ Trachea 8.​ Oesophagus: collapsed 9.​ Guttural pouch: blind end & dead space in skull, extension of nasopharynx ​ Reduce head density ​ Thermoregulation: cold air ​ Inflammation ​ Phonation: sound echoing ​ X dog, cat, ruminant  Musculature of deglutition (soft palate): ​ Soft palate: elevated by tensor & levator veli palatini (muscles) → caudal free edge seal off nasopharynx: protection ○​ Food X enter nasal cavity ​ Tongue: compress food against soft palate → bolus, muscle contraction → transfer to laryngopharynx & oesophagus ​ CN 9 (glossopharyngeal) & 10 (vagus) Salivary gland: ​ Across headgut: cheek, tongue, lip, oesophagus, soft palate, pharynx ​ Produce serous (watery) / mucous (viscous, foamy & bigger) / mixed secretion ○​ Saliva: water, amylase, NaHCO3, antimicrobial agent, lingual lipase ​ Innervation: ○​ Sympathetic: vasoconstriction → decrease production ○​ Parasympathetic: ​ Facial (CN 7), glossopharyngeal (CN 9), trigeminal (CN 5) ​ Increase flow → vasodilation Monostomatic Polystomatic ​ Away from oral cavity → singular ​ Multiple openings, adjacent → X connective duct duct Major ​ Parotid: @ mouth, serous (horse & ​ Zygomatic: next to eye, carnivores ruminant) / mixed (dog) only ​ Mandibular: @ neck, mixed ​ Sublingual: across mouth ventrally, ​ Sublingual (caudal & rostral): mixed across mouth ventrally, mixed Minor ​ Palatine ​ Labial: mucous ​ Lingual ​ Buccal: mucous Hyoid apparatus: ​ Larynx (voice box): between pharynx & trachea ​ 5 diff. bone: ○​ Unpaired: ​ Basihyoid: connect both sides ○​ Paired (both sides of neck): ​ Stylohyoid: articulate w/ skull base @ petrous temporal ​ Epihyoid ​ Ceratohyoid ​ Thyrohyoid: articulate w/ thyroid cartilage of larynx ​ Hold larynx in place, attachment for pharynx & tongue → support ​ Cartilage: ○​ W/in larynx, provide rigidity & stability ○​ Unpaired (3): ​ Epiglottis ​ Thyroid: Adam’s apple: bump of cartilage, front of throat, protect voice box ​ Cricoid ○​ Paired (1): arytenoid ​ Cuneiform, corniculate, vocal & muscular processes Laryngeal muscle: ​ Swallowing: elevate / depress larynx ​ Move individual parts of larynx → breathing, phonation (vocalisation) ​ → Ventricularis: ○​ Vocal fold adduction ○​ Glottis constriction ​ → Cricoarytenoideus dorsalis: ○​ Abduct arytenoid cartilage → open glottis for easy breathing ​ → Thyroarytenoideus ​ → Vocalis: ○​ Control vocal cord (bird: syrinx) ○​ Contract → air pass through → voice production ​ Innervation to larynx: cranial & caudal laryngeal nerves (from vagus nerve CN 10) ○​ Damage: roaring (horse), air pass through → noise Tongue: ​ -glossal ​ Fill oral cavity & oropharynx ​ Striated muscle: mobile, voluntary contraction ​ Hyoid bone: support (caudal) ​ Grooming, lapping, prehension, deglutition, vocalisation ​ Taste bud: taste, temp. sensation, mix food w/ saliva ​ More muscular near root (caudal, back) > tip ​ Vasculature:  ○​ Lingual artery (main) ○​ Branches of external carotid, facial, ascending pharyngeal artery Musculature: ​ Intrinsic: ○​ Dorsal & ventral longitudinal muscle ○​ W/in mouth ​ Extrinsic (diff. directions): ○​ Styloglossus: retract & elevate ○​ Genioglossus: protrude & depress ○​ Hyoglossus: retract & depress ○​ Geniohyoideus: below tongue, draw hyoid & tongue forward Innervation: ​ Movement: hypoglossal (CN 12) ​ Sensory: ○​ Temp., touch, pain sensation: rostral ⅔, lingual branch of trigeminal (CN 5) ○​ Taste: caudal ⅓, glossopharyngeal (CN 9) Lyssa (dog): ​ Thick cartilage ​ Tongue remain in retracted position ​ Water traps in small cup Papillae: small bumps on tongue, contain taste buds, help with chewing, swallowing & speech ​ Mechanical Conical ​ Caudal ⅓ ​ Thick epithelium ​ X horse  Filiform ​ Most numerous ​ Rostral ⅔ ​ Point caudally ​ X taste bud, gland, lymphatic ​ Smallest, thick keratin on stratified squamous epithelium ​ Cat: prominent ​ Gustatory (taste) Foliate ​ Caudal ⅓ ​ 8-12 in parallel fold, 1 either side of tongue midline ​ Stratified squamous epithelium ​ X ruminant Fungiform ​ Rostral ⅔ ​ Red dot ​ Keratinised stratified squamous epithelium, w/ blood vessel ​ Dog: panting → heat loss Vallate ​ Lymphatics 2.2 Teeth, Sinuses & Mastication Shark: 3000 teeth Development: focal (most important) thickening w/in thickened oral epithelium ​ Medial of labiogingival band ​ Mesenchyme (under laminae) condense ​ Dental lamina form ○​ + Neural crest: travel around & stay ​ Dental bud: expand, enlarge → enamel ○​ Surround dental papilla → form deciduous tooth 乳齒 ​ 1st dentine formed on enamel ○​ Odontoblast: continue to form dentine, displaced from enamel ​ Primordium (precursor 先導) of permanent tooth: bud off dental lamina ○​ Small mass of cells ​ (Epithelium →) inner layer of enamel → ameloblast ○​ Make enamel ​ (Neural crest cell-derived →) dental papilla → odontoblast ○​ Outer: columnar → make dentine: surround pulp → tooth ‘root’ ​ Cementoblast (epithelial cell, distal): become follicle cell, secrete cementum (calcified, for support) around ‘root’ (Inductive) interaction between epithelial & mesenchymal precursors: ​ Epithelial: initial signal  ​ Mesenchyme (neural crest cell): ○​ Stable morphogenetic → determine tooth form (type / shape) ○​ Unstable differentiation ○​ Eg. molar tooth mesenchyme + limb ectoderm → ‘tooth-shaped’ cartilage ​ Start @ crown, progress towards root ​ Crown emerge (start erupting) → full length Eruption: ​ Premature loss of temporary tooth → disorganised (non-occluding 遮擋) permanent teeth Temporary tooth Permanent tooth ​ Crown fully formed → erupt ​ Migrate into ‘socket’ of temporary tooth ○​ Root X completely ​ Increasing pressure formed ​ Temporary tooth root: resorb overlying hard tissue ​ → Space for root completion (bone, baby tooth) w/ osteoblast, remodel ​ Epithelial covering w/ gum ○​ Hydrostatic pressure: push tooth gradually ​ ‘Wear’: remove epithelium into mouth ○​ Periodontal ligament: metabolism → eruptive force: pull tooth upward ○​ → Loosen → shed ​ Replace: migrate into socket Mammal: diphyodont (2 sets of teeth: deciduous → permanent) Alligator (reptile): polyphyodont (> 2 sets) ​ Dental lamina: maintained as replacement tooth Rat: monophyodont (X ever be lost) ​ Constantly maintained ​ Stem cell reservoir Enamel: ​ Only in crown ​ X repair ​ Ameloblast: ○​ Lost on eruption ○​ ‘Crown’ characteristic of each tooth type ○​ Projecting into Tomes’ Fibres ​ Maintain contact w/ new (un-mineralised) enamel ○​ Produce matrix (X remodel) ​ Hardest biological material ​ Mineralisation: enamelin, amelogenin Dentine: ​ Major part ​ Produce continually ​ Repair: rate increase ​ Innervated ​ Mineralised matrix: type I collagen, dentine, specific proteins ​ Odontoblast: recede 退 from newly formed surface ​ ~ Bone, acellular Gingiva 牙齦 / 牙肉: ​ Adhere to tooth: @ interface, between root & crown Alveolus & periodontal ligament: ​ Periodontal ligament: suspend tooth in alveolar socket ​ Alveolar bone: ○​ 2 plates of cortical bone, separated by spongy bone ○​ Fibre: bridge (w/ cementum) ○​ Lined by compact bone ○​ Alveoli: remodel → translation Pulp cavity: ​ Contain blood vessels & nerves ○​ Blood & nerve supply: superior & inferior alveolar (arteries, veins, nerves) ○​ ≥ 1 branch in each major elevation of crown Cementum: ​ Calcified & mineralised, surround dentine (root) ​ Acellular ​ X readily resorbed, X remodel → orthodontic work ​ Contain type I collagen ​ Form strong connection ​ Tooth pushed against alveolar bone → move around Homodont: teeth similar in shape & size Heterodont: diff. Brachydont: Hypsodont (hypso-: death): ​ Fixed: X further ​ Continuous eruption: move tooth continuously eruption ​ Worned & repaired (below gumline) ​ Eg. carnivore: tiger ​ Eg. herbivore (cat), dog Aradicular: Radicular: ​ ‘Open’ rooted: X true root ​ ‘Closed’ roots ​ Continuously erupt & ​ Continuous eruption, grow under gumline fixed growth ​ Diet: enough wear → X ​ → Form hollow, teeth clip teeth move rostrally w/ age ○​ Malocclusion ​ Eg. horse ​ Eg. rabbit Tooth age: ​ → Diet, weaning time, lifetime → rough aging, sexual maturity ​ Carnivore: bigger mouth → change teeth ​ Horse: less dependent on mother, start eating grass Deciduous Permanent Cat Incisor 3-4 weeks 3-5 months Canine 2-4 weeks 5-6 months Premolar 5-6 weeks 4-5 months Molar / 5-6 months Formula 2 (I33, C11, P32) 2 (I33, C11, P32, M11) Dog Incisor 4-6 weeks 3-5 moths Canine 3-5 weeks 5-7 months Premolar 5-6 weeks 4-6 months Molar / 4-7 months Formula* 2 (I33, C11, P33) 2 (I33, C11, P44, M23) Horse Incisor 1 1 week 2.5 years Incisor 2 4 weels 3.5 years Incisor 3 5-9 months 4.5 years Premolar (1-4) < 1 week 6 months - 4 years Molar 1-3 / 1-4 years Formula 2 (I33, P32) 2 (I33, P3/4 3, M33) Dentition: ​ Heterodonty: diff. regions →distinct development ​ Eruption time: diff. between breeds ​ Gum recede w/ age → expose ‘cervical’ part (non-enamel coated surface) ​ Herbivore: crown remain concealed below gumline ​ ‘Contact surface’: adjacent teeth touch ​ ‘Occlusal surface’: opposing (up & down) teeth touch Incisor: Canine: ​ Upper: tricuspid, lower: bi-lobed ​ Large, curved, laterally compressed ​ Smaller rostrally ​ Length: root > crown ​ Single root ​ Single root ​ Top stone of arch, provide integrity Premolar: Molar: ​ Irregular, closely spaced ​ Broader ​ Complex, larger caudally ​ No. of cusps in all (dog) breeds: similar ​ Discontinuous cutting crown  Dog: ​ Sharp & rounded: shearing & tearing ​ Brachycephalic: ○​ X have all canine cheek teeth → ‘fused’ roots ○​ ‘Carnassial’: modified molars 裂齒 ​ Upper premolar 4 & lower molar 1 Horse: ​ Continuous & considerable wear ○​ Enlarged surface ○​ Higher crown ○​ Delayed development of root ○​ Complicated folding of enamel ​ Incisor (33): ○​ High crown ○​ Folded enamel surface ○​ Narrowing jaw → roots converge (shift rostrally) ​ Canine (11): ○​ Rudimentary 基礎 in diastema 牙間隙 ○​ Size: root > crown ​ Premolar (3/4 3), molar (33): ○​ Wolf tooth: vestigial ○​ Continuous surface ○​ High wear, erupt continuously ○​ Width: upper > lower Rodent & lagomorph: ​ No. of teeth: reduced ○​ X canine, large diastema ​ X pulp cavity → insensitive (can clip) Ox: ​ X upper canine & incisor → replaced by hard, fibrous dental pad ​ Incisor X erupt continuously ​ Lower canine: similar to incisor ​ Premolar & molar: ○​ Size: increase caudally ○​ Similar to horse ○​ Erupt continuously ○​ Enamel ridge: noticeable Pig: ​ Incisor: project rostrally ​ Canine: continuously erupting ‘tusk’ → digging & tearing ​ Premolar & molar: rounded cusp (crown) → crushing & grinding ​ Unerupted premolar 4 ○​ All occlusal surface: covered by thin coronal cementum ○​ Extend onto subgingival ​ Apical: ○​ Thin cementum ○​ Deposition → enamel resorption Elephant: ​ Only 1 pair of teeth (molar): very elaborate ​ 5 spare replacement teeth ​ Enamel: highly folded → resistant to massive amount of wearing Mastication: ​ Jaw articulation: allow jaw to move around ○​ Temporomandibular joint ○​ Mandibular symphysis ​ Left & right meet ​ Jaw muscle: ○​ Open: digastricus ​ Single muscle, 2 bellies ○​ Close (3 sets): temporalis, masseter, (lateral & medial) pterygoids ​ Buccinator: X close, only push food ​ Small cheek → large gait ​ Swallowing: jaw X actively shut → create partial vacuum  Temporomandibular joint: ​ Between condylar process of mandible & mandibular process of skull ​ Single joint: include left & right ​ Retro-articular process: caudal enlargement of fossa: mandibular condyle → prevent caudal dislocation Mandibular symphysis: ​ Fibrous ​ Between left & right half of mandible ○​ Independent rotation: can move apart ​ Dog & ruminant: biting bone / flesh, grass / stone → integrity (X break) ​ Fine adjustment → precise occlusion Digastricus: ​ Jaw-opening ​ Origin: paracondylar of occipital bone ​ Insertion: angle of mandible ​ Single muscle, 2 bellies: ○​ Caudal: 2nd pharyngeal arch (CN 7: facial) ○​ Cranial: 1st pharyngeal arch (mandibular branch of CN 5: trigeminal) Masticatory muscles: Temporalis: ​ Derive: 1st pharyngeal arch ​ Origin: lateral of cranium 魂精 ​ Innervation: mandibular ​ Insertion: coronoid process branch of trigeminal (CN 5) ​ Pull mandible dorsal > unilateral (rostral & caudal) ​ Origin: upper jaw ​ Insertion: lower jaw Masseter: ​ Maxillary of skull & zygomatic arch ​ Insertion: caudal of mandible ​ Several divisions: unilateral & bilateral ​ Protrude jaw Pterygoid: ​ Origin: pterygopalatine of skull ​ Insertion: medial of mandible ​ Medial: ○​ Close jaw: 1 sided contraction (move to left / right) ​ Lateral: ○​ Close & protrude jaw: 1 sided contraction ​ W/ masseter: lateral translation of mandible Nasal & paranasal (side of nose) cavity: External nose: rostral end of nasal cavity ​ Nasal plate, philtrum ​ Flexible & cartilaginous ​ Unmodified skin ​ Extend into vestibule, covered by mucosa ○​ Nasolacrimal duct: open Nasal cavity: ​ Nasal septum: ○​ Separate paired cavities ○​ Caudal: bone (ossified), rostral: cartilage ○​ Meet hard palate (cephalic: near head) ○​ Length: horse (join entire hard palate, into pharynx) > dog ​ Head conformation: affect size ○​ Long head → long cavity ​ Turbinate bone: create turbine, air move swiftly ○​ Warm air before getting into lungs ○​ Covered by mucosa ​ Neighbouring: reduce size ○​ Paranasal sinuses ○​ Embedded part of upper cheek teeth (esp. horse) ○​ Turbinate bone ○​ Mucosa: line inner wall ​ Conchae: ○​ Folding of inner nasal wall (toward septum) ○​ Separated by narrow clefts → compartmentalise 劃分 into meatus(es) ​ Common, dorsal & ventral (large), middle (small) ○​ Most caudal: ethmoid turbinate ​ More complex (carnivore > herbivore) → sense of smell  Paranasal sinus(es): ​ Diverticula (outfolding) of nasal cavity, excavate (dig) skull bones ○​ Extent of excavation: diff. between species ​ Thicken border bones of nasal cavity → communicate ○​ Connect: small openings, X contra-lateral (between left & right) ​ → All domestic species: ○​ Frontal: ​ Through ethmoid meatus ​ Horse: via caudal maxillary sinus ○​ Maxillary: ​ Through caudal / lateral of upper jaw ​ Associated w/ hard palate, sphenoid bone, orbit, ventral concha ​ Horse: connect to middle nasal meatus, extensive (w/ caudal & rostral parts) ​ Frontal sinus → caudal maxillary sinus → middle nasal meatus → nasal cavity Horse: ‘rostral shift’ of cheek teeth w/ age ​ Projection of maxillary sinuses ​ Erupt, X grow → space ​ Remodel → shrink in size 2.3 GI Histology Oesophagus wall: ​ Tubuloalveolar gland: most dense cranially ○​ Lubrication ○​ Eg. salivary gland: secrete saliva ​ Non-keratinised stratified squamous epithelium ○​ Protective ○​ X mucosal glands (in submucosa) 4 main layers: ​ Mucosa ​ Submucosa ​ Tunica muscularis ​ Serosa Villi: isolated islands of tissue ​ Cut through when collecting sample ​ Between epithelia: lamina propria (in mucosa) / crypt of Lieberkühn ​ Lie in epithelium: enterocyte, goblet cells, lymphocytes ​ Gland: simple columnar shape, for secretion Stomach: ​ Gastric pit → gastric gland: secrete gastric juice ​ Contain diff. types of cells → secrete variety of enzymes ○​ Eg. HCl: activate pepsin (protein digesting enzyme) ​ Chambers: ○​ Horse stomach: non-glandular more proximal ○​ Rumen & canine / equine stomach: ​ Epithelium type: diff. ​ Muscular layers: same (mucosa, submucosa, tunica muscularis, serosa) ​ Glands: X in rumen & equine stomach, present in canine stomach ​ Function: only mechanical in rumen & equine stomach, both mechanical & chemical in canine stomach  Canine stomach Rumen Abomasum Horse stomach Epithelium Simple Stratified Simple Glandular: Non-glandular: type columnar squamous columnar simple stratified columnar squamous Mucosal Present X Present Present X glands Reticulum: ​ Keratinised stratified squamous epithelium ○​ Upper keratinised layer: protect against abrasion ○​ Deeper layers: metabolise volatile fatty acid ​ X gland ​ ‘Honeycomb’ appearance: ○​ Mucosal layer: short & tall fold ○​ Meet rumen: merge into papillae ​ Conical / secondary papillae: present on folds → rough surface: increase food breakdown ​ Lamina muscularis: ○​ Discrete bands of smooth muscle ​ Tunica muscularis: ○​ 2 thick layers: inner (circular) & outer (longitudinal) Omasum: ​ Keratinised stratified squamous epithelium ​ Texture: firm, size: vary ​ Lamellae: divide lumen into narrow & uniform recesses ​ X gland ​ Papillae: small & lenticular (biconvex) ○​ Some: large & conical ○​ Circular tunica muscularis: extend into papillae of long laminae ○​ Lamina muscularis: extend into papillae encircling tunica muscularis ​ 3 smooth muscle layers → motile 能動的 Small intestine Colon ​ Have villi ​ X villi ​ Absorption & digestion ​ Only absorption: water & electrolyte ​ Secrete enzyme ​ X secrete & digest 2.4 Dentistry Anatomy: ​ Crown: ○​ Covered by enamel ○​ Meet root @ cemento-enamel junction (CEJ, neck of tooth, X normally visible) ​ Enamel: ○​ 96% inorganic (hydroxyapatite) ​ Hexagonal prisms / rods ​ Held tgt by cementing organic matrix ○​ 4% water & fibrous organic material ○​ Highest substance in body ○​ Cover exterior surface of crown only ○​ Formed by ameloblasts w/in tooth bud before eruption ○​ Very limited repair once erupted ​ Pulp: ○​ Living tissue ○​ In pulp chamber & root canal ○​ Well innervated & vascularised ○​ Comprise connective tissue, nerves, lymph, blood vessels, collagen, undifferentiated reserve mesenchymal cells (eg. odontoblast) ​ Odontoblast: line pulp cavity, branch into dentine tubules ​ + Nerve endings → sensitive to temp. & pain ​ Lay down dentine & reduce pulp cavity through time ○​ Pulp: nourished via vessels entering & leaving root canal @ apical delta (occasionally: accessory canal) ○​ Potential danger: ​ Physical trauma: bruising, haemorrhage, pulpitis 牙髓病 ​ Accidental overheating from polishing / scaling → pulp necrosis ​ Tooth fracture → pulp exposure → pulpitis & pulp necrosis ​ Loss of blood supply → ischaemic (reduced blood supply) necrosis ​ Dentine: ○​ Main supporting structure ○​ 2nd hardest tissue in body ○​ 70% mineral (eg. hydroxyapatite): acellular  ○​ 30%: water, collagen, mucopolysaccharide ○​ Main structure: dentinal tubule ​ Extend from external surface to pulp ○​ Tubule: ~ 30000-40000 / mm2 ​ Dentine exposed → transmit pain to pulp ○​ Type: ​ Primary: form before tooth eruption ​ Secondary: form after eruption, develop w/ age from odontoblast w/in pulp, lay down in layers w/in pulp cavity ​ Reparative / tertiary: thermal / chemical / bacterial / mechanical trauma to odontoblast, few tubules, darker in colour, very dense ​ Root: ○​ ≥ 1 root ○​ Diverge point: (bi- / tri-)furcation angle ○​ End: apex ​ Apical area: site of nerve, blood vessel & lymphatic travelling into pulp ​ → Human: single foramen ​ → Cat & dog: multiple canal delta arrangement ​ → Herbivore: remain open ​ → Horse: close eventually ​ Alveolar bone: ○​ Root: encased in alveolar processes of jaws ​ Comprise alveolar, trabecular, compact bone ○​ Cribriform plate: densest bone, line alveolus ​ Lamina Dura: seen as white line through radiography (uninterrupted: good periodontal health) ​ Cementum: ○​ Cover enamel free roots ○​ Provide attachment point for periodontal ligament ○​ Composition: ​ Similar to woven bone ​ 45-50% inorganic (hydroxyapatite) ​ 50-55% organic ​ Periodontal ligament: ○​ Sharpey’s fibres (taut collagen fibre bundles) ​ Inserted in & anchored to cementum & alveolar bone Gingival 牙齦 landmark: Gingival sulcus: ​ Between tooth & free gingival margin ​ Crevice 縫隙: surround tooth ​ Renew every 4-6 days ○​ Oral epithelium: 6-12 days ​ Bathed in crevicular fluid: contain antibody, neutrophil, lymphocyte → immunity ​ Normal depth: 0.5-1 mm (cat), 1-3 mm (dog)  ○​ > 4 mm in dog = danger ○​ Active disease & attachment loss → deepen ​ Junctional epithelium inflamed & oedematous: separate from root surface ○​ Tissues infiltrated w/ primary & secondary cells ○​ → Migration of polymorphonuclear granulocyte & fluid Junctional epithelium: ​ Bottom of sulcus ​ Control of periodontal disease ​ Attach gingival tissue to tooth w/ hemidesmosomes ​ Apical (towards root) extent: cemento-enamel junction Free gingiva: ​ Form gingival margin (visible) ​ Surround crown of tooth Attached gingiva: ​ Tightly adherent to subgingival connective tissue & bone, via deep rete pegs ​ Keratised: withstand stress of ripping & tearing food Cemento-enamel junction: ​ Between anatomical crown & root ​ Healthy: X visible ○​ Visible: clear division between shiny enamel & slightly dull root cementum ○​ Recession of attachment of tooth Mucogingival junction: ​ Between soft, fleshy mucus membrane of oral cavity & tough, collagen rich gingiva ​ Stationary ○​ Hyperplasia / recession / attachment loss → gingiva change in height ​ Interdental papilla: ○​ Gingival peak between closely adjacent teeth ​ Prevent impaction of food & debris ​ → Preserve during surgery ○​ Coronal aspect: col (indentation) ​ Epithelium: X keratinised Function of teeth: ​ Incisor ○​ Small, single-rooted ○​ Periodontal disease → mobile easily ○​ → Cutting, scooping, picking up objects, grooming ​ Canine ○​ Front of mouth  ○​ Loss: ​ Lower: weaken rostral mandible 顎, tongue fall out of mouth → excessive drying, trauma to tongue ​ Upper (esp. cats): upper lip fall inward → lower canine occlude (close up) lateral to displaced lip → excoriation (wearing off skin) / puncture 刺穿 ○​ → Holding prey, display, slashing & tearing when fighting, cradle (shelter) for tongue ​ Premolar ○​ Pinking shear (side) ​ Tip of upper tooth: point to interdental space on lower jaw ​ X → bite defect (eg. mandibular prognathism 倒及牙, brachygnathism: parrot mouth, under/overbite) ○​ → Holding, carrying, breaking food into small pieces ​ Molar ○​ Dog: high masticatory force ​ Passive bite force: 300-800 psi ​ Sudden localised bite force (snap jaws shut): 30000-80000 psi ○​ Affected by dental caries: 7% in mature dogs ○​ → Grinding food into small pieces w/ flat occlusal (biting surface of the teeth) table Modified Triadan System: tooth no.ing ​ Consistent across species ​ Based on permanent dentition of pig ○​ 11 teeth in each quadrant: 3 incisors, 1 canine, 4 premolars, 3 molars ○​ Grand total: 44 teeth ​ Quadrant: ○​ 1st digit: denote ○​ 1-4: permanent (恒齒), 5-8 deciduous (falling off, 乳齒) ​ Tooth position & no.ing (dog): ○​ 2nd & 3rd digit: denote position ○​ Sequence start @ midline ​ Other species: definite landmark ○​ Central incisor: 01 (following: 02 & 03) ○​ Canine: 04  ○​ Premolar: 05-08 ○​ Molar: 09-11 ○​ Cat: reduced tooth no. → carnassial as landmark ​ Upper: last premolars (108, 208) ​ Lower: 1st molars (309, 409) Cat Horse Rabbit X 105, 205, 305, 405, 306, 406 105, 205: vestigial premolar 1 X 3rd incisor & canine 2.5 Mastication (DL) Clinical case study: Name Information Condition Diagnosis Flash Equine Drop food bolus from → Tooth root abscess ​ Thoroughbred mouth ​ Swelling gelding ​ Normal ○​ X-ray: X swelling & Male chewing discharge in sinuses 4 y/o Runny nose ​ Centre of teeth: worn out Normal BCS ○​ Feed composition: ​ Losing weight concentrate Flora Canine Sunken face (concave) https://onlinelibrary.wiley.com/doi/ful ​ Labrador l/10.1111/jvim.15373 Female → Cancer: trigeminal nerve 18 months old ​ Temporalis muscle atrophy 萎縮 Aladdin Camelid Eyelid & lower lip https://www.researchgate.net/publicat ​ Dromedary drooping ion/303664110_UNILATERAL_FAC camel Regularly vaccinated IAL_PARALYSIS_IN_A_DROMED Male ARY_CAMEL 13 y/o ​ (May have) traumatic fight history → CN7 damage ​ Face muscle (motor): depressor labii inferioris ​ Unilateral & bilateral ear drooping, paralysis ​ Other large animals: bovine