Digestive Components of the Head

Oral Cavity

Extends from lips to pharynx

Includes: commissures, teeth, jaws, and vestibule

Commissures

Where upper and lower lips meet at the angle of the mouth

Labial Vestibule

Between the lips and teeth

Buccal vestibule

Between cheeks and teeth

Oral Cavity proper

space within dental arcade, communicates with vestibule through interdental spaces

Borders of the oral cavity proper

Dorsal: hard palate

Ventral: tongue and floor

Lateral/Medial: Dental Arcade

Hard Palate

Formed by the palatine process of the maxilla and incisive bones, and the horizontal plate of palatine bone, covered by 8-10 rugae

Median Palatine Raphe

Divides the hard palate into two symmetrical halves, less distinct in dogs

Incisive papilla

A small median swelling located caudal to upper central incisor

Incisive Ducts

Open on either side of incisive papilla, leads to nasal cavity and vomeronasal organ

Vomeronasal Organ AKA Jackobson’s Organ

Plays a role in sexual behavior and kin recognition via pheromones, associated with flehman response

Soft Palate

Continues caudally to the intrapharyngeal opening

Borders of the soft palate

Ventral Surface: oral mucosa

Dorsal: respiratory mucosa

Intermediate: salivary glands and muscles

Shortens the soft palate

Palatine muscle and tensor veli palatini

Levator veli palatini

Raises the soft palate

Maxillary nerve

Branch of Trigeminal nerve, innervates minor and major palatine nerves (sensory to soft and hard palate, respectively)

Mandibular nerve

Branch of the trigeminal nerve, innervates the tensor veli palatini nerve

Vagus and Glossopharyngeal nerve

Innervates the levator veli palatini and palatine muscles

Tongue

Composed of skeletal muscle

Parts of the tongue

Apex (lyssa)

Body

Root

Frenulum

Joins the tongue to the oral floor

Intrinsic tongue muscles

Not attached to the hyoid process, myofibers in all directions, prevents the tongue from being bitten

Extrinsic tongue muscles

Originate from a bone and radiate into tongue

Styloglossus, hyoglossus, and genioglossus

Styloglossus origin

stylohyoid bone

Styloglossus insertion

middle portion of the tongue

Styloglossus action

shortens tongue, elevates apex, pulls midportion laterally

Hyoglossus Origin

basihyoid bone

Hyoglossus insertion

caudal 2/3rd of tongue, passes between lingual a. and hypoglossal n

Hyoglossus action

retracts and depresses the tongue

Genioglossus origin

mandibular symphysis

Genioglossus insertion

ventral surface of tongue

Genioglossus action

protrusion of the tongue

Lingual n.

Sensory to rostral 2/3rd of tongue

Chorda tympani

Taste from rostral 2/3rd of tongue

Glossopharyngeal n.

Taste from caudal 1/3rd of tongue

Hypoglossal n.

the only motor to muscles of the tongue

Parotid, mandibular, and sublingual glands

Major salivary glands, produce serous secretion and most saliva, longer ducts

Zygomatic and buccal salivary glands

Minor salivary glands, produce mucusy secretion, shorter ducts

Parotid Salivary Gland

paired, triangular mixed

Ventral to auricular cartilage

Duct opens into buccal vestinule opposite P4

Mandibular Salivary gland

paired, ovoid, mixed

shares capsule with major sublingual s. g.

Duct opens at sublingual caruncle

Major Sublingual Salivary Gland

monostomatic, share common capsule with mandibular s. g., cranially located, duct opens at sublingual caruncle

Minor sublingual salivary gland

polystomatic, many small isolated lobules, ducts open into oral cavity

Zygomatic Salivary Glands

Located medial to the rostral end of zygomatic arch, ventral to periorbita, lateral to medial pterygoid m., duct opens into buccal vestibule 1 cm caudal to parotid papilla

Brachydont

Short teeth, do not grow after the completion of eruption, consists of a crown, neck, and root

Enamel

Hardest component of the body, 96% hydroxyapatite, no collagen, secreted by ameloblasts

Dentin

Harder than bone, consists of 70% hydroxyapatite, type 1 collagen present, secreted by odontoblasts

Cementum

Resembles bone, consists of 45% hydroxyapatite, type 1 collagen present, secreted by cementoblasts

Pulp Cavity

Contains sensory nerves, arteries, veins, and lymphatic capillaries, enter through apical foramen

Pulp chamber

Pulp cavity of the crown

Root canal

Pulp cavity of the root

Peridontium

Supporting tissues of the teeth, includes: gum, cementum on the root, periodontal ligament, and alveolar bone

Gums (gingivae)

surround the teeth, composed of dense fibrous tissue covered by mucous membrane

Gingival margin

the edge of gingiva not attached to the crown

Gingical sulcus

space between gingival margin and tooth, 1-3 mm (dog), 0.2-1 mm (cat)

Mucogingival junction

an indistinct line that separates gingiva from oral mucosa

Periodontal ligament

Attaches the root to the alveolar bone

Alveolar bone

alveolar socket, houses the tooth

Interalveolar septa

bone between adjacent teeth

Interradicular septa

bone between roots of same tooth

Alveolar juga

bony elevation over the lateral surface of tooth

Lamina Dura

Dense bone surrounding teeth

Occlusal surface

The contact surface with the tooth of the opposite jaw

Contact surface

face adjacent teeth in the same dental arch

Mesial surface

toward the first incisor

Distal surface

away from the first incisor

Lingual surface

faces the tongue

Vestibular surface

facing the lips or the cheeks

Labial

Facing the lips

Buccal

Facing the cheeks

Bite

Superior teeth are lateral to the inferior teeth, inferior teeth are rostral to the superior teeth

Diphyodont type

two sets of teeth develop sequentially

Deciduous teeth

develop 20 days after birth

Di3 Dc1 Dp3

Di3 Dc1 Dp3

x2 = total 28

Permanent teeth

replace deciduous by 6 months

i3 c1 p4 m2

i3 c1 p4 m3

x2 =total 42

Dog deciduous teeth

missing upper and lower Dp1

no molars

carnassial teeth Dp3/ Dp/4

Dog adult teeth

M3/ missing

carnassial teeth p4/ and m/1

Cat deciduous teeth

Dp1/ missing

Dp/1 and Dp/2 missing

No molars

carnassial teeth Dp3/ and Dp/4

Cat adult teeth

p1/ missing

p/1 and p/2 missing

carnassial teeth p3/ and m/1

Teeth with 2 roots

P1/-P3/

P/2-M/2

Teeth with 3 roots

P4/-M2/

Pharynx

Common cavity through which air and the food pass

Parts of the pharynx

Rostral compartment- nasopharynx and oropharynx

Caudal compartment

Intrapharyngeal ostium

Nasopharynx and oropharynx meet, formed by soft palate and palatopharyngeal arch

Oropharynx

From the Palatoglossal fold to the base of the epiglottis

Borders of the oropharynx

dorsal- soft palate

ventral- root of the tongue

lateral- tonsillar fossa

Palatine tonsil

located in the lateral wall soft the oropharynx, coved by the semilunar fold

The oropharynx comminicates-

Rostrally with the oral cavity

Caudally with laryngopharynx

dorsally with caudal opening of nasopharynx

Nasopharynx

From the Choanae to the intrapharyngeal opening, part of the respiratory channel

Contains the openings of the auditory tube in the lateral wall

Borders of the nasopharynx

Ventral- soft palate

Caudal- Epiglottis

Lateral- Hyopharyngeus muscles, ceratohyoideus muscles

Nasopharynx communicates-

Rostrally with the nasal cavity

Caudally with the laryngealpharynx

Caudoventrally with the oropharynx

Laryngopharynx

From the epiglottis to the haryngoesophageal limen

Common segment of the respiratory and the digestive systems

Located dorsal to the larynx

Pharyngoesophageal limen

Annular mucosal boundary between laryngopharynx and esophagus

located at the level of the axis and cricoid cartilage

Piriform recesses

Located on each side of the base of the epiglottis

Continue the floor of the oropharynx around the entrance of the larynx

Serves as gutters for fluids

Layrngopharynx communicates

Caudally with the esophagus

Rostrally with nasopharynx and oropharynx

Pterygopharyngeus origin

Pyterygoid bone

Rostral Pharyngeal constrictors

Pterygopharyngeus, Palatopharyngeus

Palatopharyngeus origin

soft palate

Middle Pharyngeal constrictor

Hypoharyngeus

Hypoharyngeus origin

hyoid bone (thyrohyoid, ceratohyoid

Caudal pharyngeal constrictors

Thyropharyngeus, Cricopharyngeus

Thyropharyngeus origin

thyroid cartilage