Mastication Flashcards
Glossus
Of or pertaining to the tongue.
Glottis (or glottidis)
Relative to the larynx
Brachio
Relative to the upper arm
Brachy
Short
Cephal
Head
Lingual
Relative to tonge
Oral (oris)
Relative to the mouth
Mental (mentis)
– Relative to the chin
Mylo
– molar tooth or tail tooth in Greek
The muscles of mastication are innervated by
Trigeminal nerve
Oral cavity
Starting point of GIT Lips, tongue, gum, dentition, palate & salivary glands
Neck muscles
- Sternohyoideus (and the rest of hyoideus muscles: thyroi, crycoth, myohyoid)
- Sternocephalicus
- Brachiocephalicus
Muscles of mastication
- Temporalis
- Masseter
- Pterygoideus medialis
- Digastricus
- Mylohyoid
Sternohyoideus
The sternohyoid is a strap like infrahyoid muscle that connects the hyoid bone with the clavicle and sternum.
Along with the omohyoid muscle, it comprises the superficial plane of infrahyoid muscles, while the sternothyroid and thyrohyoid belong to the deep layer. The function of this muscle is to reestablish the breathing process by pulling the hyoid bone and larynx inferiorly after deglutition.
Origin: Manubrium of sternum, medial end of clavicle
Insertion: Inferior border of body of hyoid bone
Action: Depresses hyoid bone (from elevated position)
Innervation: Anterior rami of spinal nerves C1-C3 (via ansa cervicalis)
Blood supply: Superior thyroid artery
Sternocephalicus
Origin: It arises as a unit on the manubrium sterni.
Insertion: Mastoid part of the temporal bone and to the dorsal nuchal line of the occipital bone.
Action: To draw the head and neck to one side.
Nerve: Ventral branches of the cervical nerves and branches of the accessory nerve.
Brachiocephalicus
The brachiocephalicus lies on the neck deep to the sphincter colli superficialis and platysma. It is a long, flat muscle that extends from intersection clavicularis between brachium and the head and neck. It contents on its deep part a claviuclar remnant.
Origin: Clavicular tendon and the distal end of the cranial surface of the humerus.
Insertion: Dorsal surface of the neck.
Action: Bilateral fixation of the neck.
Nerve: Brachiocephalic.
Temporalis
The temporalis muscle is a thin, fan-shaped muscle situated within the temporal fossa of the skull. Along with the medial pterygoid, lateral pterygoid and masseter muscles, it belongs to the group masticatory muscles. The temporalis muscle runs superficially, from the temporal bone to the coronoid process of mandible.
Origin: Temporal fossa (up to inferior temporal line), Temporal fascia
Insertion: Apex and medial surface of coronoid process of mandible
Action: Anterior fibres: Elevates mandible
Posterior part: Retracts mandible
Innervation: Deep temporal branches (of mandibular nerve (CN V3))
Blood supply: Deep temporal branches of maxillary artery, middle temporal branches from superficial temporal artery
Masseter
Masseter muscle is a paired, strong, thick and rectangular muscle that is originating from the zygomatic arch and extends down to the mandibular angle. It consists of a superficial and a deep part.
Origin: Superficial part: maxillary process of zygomatic bone, Inferior border of zygomatic arch (anterior 2/3)
Deep part: deep/inferior surface of zygomatic arch (posterior 1/3)
Insertion: Lateral surface of ramus and angle of mandible
Innervation: Masseteric nerve of mandibular nerve (CN V3)
Blood supply: Masseteric artery
Function: Elevates and protrudes mandible
Pterygoideus medialis
The primary function of the pterygoid muscles is to produce movements of the mandible at the temporomandibular joint. Both muscles are innervated by branches of the mandibular division of the trigeminal nerve (CN V3), and receive their blood supply from branches of the maxillary artery.
Protrusion, elevation, medial movement of mandible
Digastricus
Digastric is a small paired muscle located in the anterior compartment of the neck. It belongs to a group of muscles called the suprahyoid muscles
Origin: Anterior belly: digastric fossa of mandible
Posterior belly: mastoid notch of temporal bone
Insertion: Body of hyoid bone (via intermediate tendon and its fibrous sling)
Action: Depresses mandible
Elevates hyoid bone during chewing, swallowing
Innervation: Anterior belly: mylohyoid nerve (of inferior alveolar nerve) (CN V3)
Posterior belly: digastric branch of facial nerve (CN VII)
Blood supply: Anterior belly: facial artery
Posterior belly: occipital artery
Mylohyoid
Mylohyoid muscle is one of the suprahyoid muscles that, together with geniohyoid muscle forms the floor of the oral cavity.
Along with the other suprahyoid muscles (digastric, geniohyoid and stylohyoid), it connects the hyoid bone to the skull. The functions of this muscle are to facilitate speech and deglutition by elevating the floor of the mouth and hyoid bone and depressing the mandible.
Origin: Mylohyoid line of mandible
Insertion: Mylohyoid raphe, body of hyoid bone
Action: Forms floor of oral cavity, elevates hyoid bone and floor of mouth, depresses mandible
Innervation: Nerve to mylohyoid (of inferior alveolar nerve (CN V3))
Blood supply: Sublingual, inferior alveolar and submental arteries
Orbicularis oris
around the lips – important in herbivores
Origin: Medial aspects of maxilla and mandible, perioral skin and muscles, modiolus
Insertion: Skin and mucous membrane of lips
Action: Closes mouth, compresses and protrudes lips
Innervation: Buccal branch of facial nerve (CN VII)
Blood supply: : Facial artery - Superior and inferior labial arteries
Maxillary artery - Mental and infraorbital arteries
Superficial temporal artery - Transverse facial artery
Incisive
raise upper lip and pull lower lip downwards
elevates, everts and protrudes the lower lip, and wrinkles the skin of the chin.
Origin: Incisive fossa of mandible
Insertion: Skin of chin (Mentolabial sulcus)
Action: Elevates, everts and protrudes lower lip, wrinkles skin of chin
Innervation: Mandibular branch of facial nerve (CN VII)
Blood supply: Inferior labial branch of facial artery, mental branch of the maxillary artery
Nasolabial elevator
– opens nostrils and elevates upper lip
Levator of the upper lip
The levator labii superioris muscle is a three-part muscle useful for facial expression and dilation of the mouth. It runs down alongside the lateral aspect of the nose. Its primary function is in raising the upper lip.
Caninus muscle
The levator anguli oris (caninus) is a facial muscle of the mouth arising from the canine fossa, immediately below the infraorbital foramen. It elevates angle of mouth medially. Its fibers are inserted into the angle of the mouth, intermingling with those of the zygomaticus, triangularis, and orbicularis oris.
Depressor of upper lip
only in ruminants and
suids
Depressor of lower lip,
, all species but carnivores
Levator muscle of the chin
The levator anguli oris (caninus) inserts at the corners of the mouth at an angle, and is associated with other muscles including the zygomaticus, triangularis, and orbicularis oris. When innervated, this muscle contracts to lift the corners of the mouth,
Zygomatic muscle
Origin: (Posterior part of) Lateral aspect of zygomatic bone
Insertion: Modiolus, blends with muscles of upper lip
Function: Elevates and everts angle of mouth
Innervation: Buccal branch of facial nerve (CN VII)
Blood supply: Superior labial artery (facial artery)
Buccinator
Origin: (External lateral surface of) Alveolar process of maxilla, buccinator ridge of mandible, pterygomandibular raphe
Insertion: Modiolus, blends with muscles of upper lip
Function: Compresses cheek against molar teeth
Innervation: Buccal branch of facial nerve (CN VII)
Blood supply: Buccal artery (maxillary artery), facial artery
Cranial nerves that help Mastication:
facial
trigeminal
Cranial nerves that help Taste:
facial
glossopharyngeal
Cranial nerves that help Salivation:
facial
glossopharyngeal
Cranial nerves that help Swallowing:
glossopharyngeal
vagus
hypoglossal
Bones and joints relevant to mastication
- Maxillary bones (and incisive bone) – paranasal
sinuses.
Maxillary sinus or recess in dogs – home for tooth roots (molars) - Mandible
- Temporomandibular joint
Temporomandibular joint or TMJ
The temporomandibular joint consists of articulations between three surfaces; the mandibular fossa and articular tubercle (from the squamous part of the temporal bone), and the head of mandible.
This joint has a unique mechanism; the articular surfaces of the bones never come into contact with each other – they are separated by an articular disk. The presence of such a disk splits the joint into two synovial joint cavities, each lined by a synovial membrane.
There are three extracapsular ligaments. They act to stablise the temporomandibular joint.
Lateral ligament – runs from the beginning of the articular tubule to the mandibular neck. It is a thickening of the joint capsule, and acts to prevent posterior dislocation of the joint.
Sphenomandibular ligament – originates from the sphenoid spine, and attaches to the mandible.
Stylomandibular ligament – a thickening of the fascia of the parotid gland. Along with the facial muscles, it supports the weight of the jaw.
How does mastication link to digestion and to the GIT?
Mastication permits easier deglutition (swallowing) and faster chemical breakdown in the digestive tract (smaller pieces means bigger surface area) During mastication, salivary glands secrete saliva to soften the food into a bolus (semi-solid lump).
Mastication – The process of chewing
Digestion – The process of breaking down foods into the smallest components
How does chewing help digestion?
Breaks down food items into smaller parts to increase the surface area to aid chemical breakdown
Sublingual mucosa
The salivary glands consist of lobules of cells which secrete saliva through the salivary ducts into the mouth. The three pairs of salivary glands are the parotid, the submandibular and the sublingual which lies on the floor of the mouth
buccal
mucosa
The inner lining of the cheeks and lips.
Dental gum line
the line separating the gum from the exposed part of the tooth.
Pharynx
Cross-point between respiratory and digestive system
Oropharynx
part of the pharynx connected with mouth and entry hall to oesophagus. Responsible for deglutition
deglutition
the action or process of swallowing.
Roof of oropharynx
soft palate
floor is of oropharynx i
tongue
Walls of oropharynx
pharyngeal walls
Muscles associated with the tongue
- Lingual muscles (muscles of the tongue)
- Extrinsic: paired (styloglossus - elevator, hyoglossus - retracts and represses –
thyrohyoid/basihyoid, and genioglossus – mand symphysis, protrudes tongue
and retracts tip) + all the other hyoideus! - Intrinsic: longitudinal, transvers and vertical bundles responsible for stiffness
of the tongue. Tongue fat that does not disappear (culinary in some species!!)
Hypoglossal nerve
muscles
glossopharyngeal and facial nerve
Sensation
List the salivary glands in dogs
Zygomatic
• Parotid
• Sub-lingual
• Mandibular
Four types of tooth
• Incisors
• Canines
• Pre molars
Molar
Incisors
- Small, pointed, single rooted
- Nibbling off and cutting flesh
- Also for delicate grooming
Canines
• Very sharp with a single root
embedded deep into the
bone
• Holding prey
Pre Molar
- Usually have 2 or 3 roots
* Shearing meat and grinding flesh
Molar
• Similar in shape to pre molars • Usually have 3 roots • Shearing meat and grinding flesh • N.B. Not found in the deciduous set of teeth
Carnassial teeth
- Dogs - Upper 4th premolar and lower 1st molar
* Cats - Upper 3rd premolar and lower 1st molar
Deciduous / hulk / temporary dentition (milk teeth)
- Present from birth
- Erupt during first few months of life
- Whiter and smaller than adult teeth
- Also known as temporary or milk teeth
Permanent dentition
- Follow deciduous teeth
- Remain with animal for rest of life
- Develop signs of wear as animal gets older • Also known as permanent or adult teeth
Enamel
the hard glossy substance that covers the crown of a tooth.
Pulp cavity
the space within a tooth that contains the pulp.
Root
The root is the part of the tooth that extends into the bone and holds the tooth in place. It makes up approximately two-thirds of the tooth. It’s made up of several parts: Root canal. The root canal is a passageway that contains pulp
Gingiva
The tissue of the upper and lower jaws that surrounds the base of the teeth. Also called gums.
Dentine
hard dense bony tissue forming the bulk of a tooth, beneath the enamel.
Dental formulas and charts
Dog
• Deciduous • 3/3, 1/1, 3/3, 0/0 = 28 teeth • Permanent • 3/3, 1/1, 4/4, 2/3 = 42 teeth
Dental formulas and charts of cat
• Deciduous • 3130 3120 = 26 teeth • Permanent • 3131 3121 = 30 teeth
