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==Overview==
[[Image:Jaw Articulation.jpg|thumb|right|250px|Jaw Articulation (horse) - Copyright RVC]]
[[Image:Temperomandibular Joint.jpg|thumb|right|250px|Temperomandibular Joint (dog) - Copyright RVC]]
Mastication is the process whereby food is broken down by mechanical digestion in the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]]. The [[Cheeks|cheeks]] and [[Tongue - Anatomy & Physiology|tongue]] function to position food over the [[:Category:Teeth - Anatomy & Physiology|teeth]], where grinding can occur. Mastication requires correct muscle movements and jaw articulation.
'''[[Rumination|Rumination]]''' allows food to undergo mastication more than once. This is also called 'chewing the cud', it allows greater nutrients to be extracted and absorbed from the food particles.
==Muscles of Mastication==
==Muscles of Mastication==
The muscles of mastication are well developed.
The muscles of mastication are well developed.
===Jaw Opening Muscles===
===Jaw Opening Muscles===
The '''Digastricus muscle''' is the 'jaw opening' muscle. Its origin is the '''paracondylar process''' of the '''[[Skull and Facial Muscles - Anatomy & Physiology#Occipital Bone (os occipitale)|occipital bone]]'''. It inserts at the angle of the '''[[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]]'''. The muscle has two bellies; The '''caudal half''' from the second visceral arch innervated by the '''facial''' nerve ([[Cranial Nerves - Anatomy & Physiology|CN VII]]) and the '''cranial half''' from the first visceral arch, innervated by the '''mandibular''' branch of the '''trigeminal''' nerve ([[Cranial Nerves - Anatomy & Physiology|CN V3]]).
===Jaw Closing Muscles===
===Jaw Closing Muscles===
All jaw closing muscles are derived from the first visceral arch and are innervated by the mandibular branch of the trigeminal nerve ([[Cranial Nerves - Anatomy & Physiology|CN V3]])
All jaw closing muscles are derived from the first visceral arch and are innervated by the '''mandibular''' branch of the '''trigeminal''' nerve ([[Cranial Nerves - Anatomy & Physiology|CN V3]]).
The '''masseter muscle''' originates from the [[Skull and Facial Muscles - Anatomy & Physiology#Maxilla|maxillary]] region of the skull and the zygomatic arch. It inserts on the wide area on the caudal side of the [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]]. It has several divisions and causes '''unilateral''' and '''bilateral''' contraction. It also protrudes the jaw.
The '''lateral pterygoid muscle''' originates from the [[Skull and Facial Muscles - Anatomy & Physiology#Pterygoid Bone (os pterygoideum)|pterygopalatine]] region of the skull. It inserts on the lateral aspect of the [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]]. It also protrudes the jaw (one-sided contraction).
The '''medial pterygoid muscle''' originates from the [[Skull and Facial Muscles - Anatomy & Physiology#Pterygoid Bone (os pterygoideum)|pterygopalatine]] region of the skull. It inserts on the medial aspect of the [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]]. It causes one-sided contraction to close the jaw.
'''Lateral Translation of Mandible'''
The '''temporal muscle''' originates from the lateral surface of the cranium. It inserts on the coronoid process. It pulls the [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]] dorsally and also pulls the [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]] rostrally (overbite) and caudally (underbite).
===Lateral Translation of the Mandible===
The '''masseter muscle''' and the contralateral medial and lateral '''pterygoids''' are involved in the lateral translation of the mandible.
==Jaw Articulation==
==Jaw Articulation==
===Temporomandibular Joint===
'''Mandibular Symphasis'''
The articulation between the condylar process of the [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]] and the mandibular process of the skull. It is a compartmentalised joint for rotational movement and lateral slide (grinding). It is a '''synovial joint'''. Caudal dislocation is prevented by a prominent retro-articular process (enlargement of the fossa).
===Mandibular Symphysis===
Located at the rostral end of the [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]]. It is a secondary cartilaginous joint between the left and right halves of the [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]]. It is only found in dogs and ruminants. It has a precise occlusion and the [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|Mandibular]] bones can move apart independently by rotation. It stops jaw breakages (Canid).
==Species Differences==
==Species Differences==
===Hebivores===
===Hebivores===
Herbivores have large '''masseter''' and '''pterygoid''' muscles for extensive chewing. Herbivorous species have a limited '''digastricus''' muscle. In the horse, the muscle insertion site for the '''masseter''' is large to snap jaw shut.
===Carnivores===
===Carnivores===
Carnivores have a large '''temporalis''' muscle for snapping the jaw shut, e.g. in lions and pitbull terriers. Canids have a larger '''digastricus''' muscle than herbivores (but smaller in comparison with jaw closing muscles). In the dog, large forces are needed to shut the jaws, so the point of articulation of the '''temporomandibular joint''' is level with the teeth.
==Links==
==Links==
'''Video'''
'''Click here for [[Skull and Facial Muscles - Anatomy & Physiology]]'''
[http://stream2.rvc.ac.uk/Anatomy/canine/head_neck/Pot0258.mp4 Pot 258 Lateral section through the head of a dog]
{{Template:Learning
|flashcards = [[Mastication Flashcards]]<br>[[Facial_Muscles_-_Musculoskeletal_-_Flashcards|Facial Muscles flashcards]]
|videos = [http://stream2.rvc.ac.uk/Anatomy/canine/head_neck/Pot0220.mp4 Lateral surface of the head of a dog]<br>[http://stream2.rvc.ac.uk/Anatomy/canine/head_neck/Pot0258.mp4 Lateral section through the head of a dog]
|dragster= [[Canine Head Skeletal Anatomy Resource (VI)]]
}}
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