Changes

==Introduction==

==Overview==

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.

'''[[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===

*Digastricus muscle

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]]).

**Origin: paracondylar process of [[Skull and Facial Muscles - Anatomy & Physiology#Occipital Bone (os occipitale)|occipital bone]]

**Insertion: angle of [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]]

**Two bellies:

***Caudal half from the second visceral arch innervated by facial nerve ([[Cranial Nerves - Anatomy & Physiology|CN VII]])

***Cranial half from the first visceral arch innervated by the mandibular branch of the trigeminal ([[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]]).

*Masseter muscle

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.

**Origin: [[Skull and Facial Muscles - Anatomy & Physiology#Maxilla|maxilliary]] region of skull and zygomatic arch

**Insertion: wide area on caudal side of [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]]

**Several divisions

**Unilateral and bilateral contraction

**Also protrudes jaw

*Lateral Pterygoid muscle

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).

**Origin: [[Skull and Facial Muscles - Anatomy & Physiology#Pterygoid Bone (os pterygoideum)|pterygopalatine]] region of skull

**Insertion: lateral aspect of [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]]

**Also protrudes jaw (one-sided contraction)

*Medial Pterygoid muscle

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.

**Origin: [[Skull and Facial Muscles - Anatomy & Physiology#Pterygoid Bone (os pterygoideum)|pterygopalatine]] region of skull

**Insertion: medial aspect of [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]]

**One-sided contraction to close jaw

*Temporal muscle

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).

**Origin: lateral surface of cranium

**Insertion: coronoid process

**Pulls [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]] dorsally

**Also pulls [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]] rostrally (overbite) and caudally (underbite)  

'''Lateral Translation of Mandible'''

===Lateral Translation of the Mandible===

*Masseter muscle

The '''masseter muscle''' and the contralateral medial and lateral '''pterygoids''' are involved in the lateral translation of the mandible.

 

*Contralateral medial and lateral pterygoids

==Jaw Articulation==

==Jaw Articulation==

*[[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|Mandibular]] bones can move apart independently by rotation

===Mandibular Symphysis===

*Stops jaw breakages (Canid)

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===

*Large masseter and pterygoid muscles for extensive chewing

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.

 

*Herbiverous species have a limited digastricus muscle

 

*In the horse the muscle insertion site for the masseter is large to snap jaw shut

===Carnivores===

===Carnivores===

*Large temporalis muscle for snapping the jaw shut, e.g. in lions and pitbull terriers

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.

 

*Canids have a larger digasticus muscle than herbivores (but smaller in comparison with jaw closing muscles)

 

*In the dog large forces are needed to shut jaws so the point of articulation of the temporomandibular joint is level with the teeth

 

 

 

==Links==

==Links==

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