Difference between revisions of "Mastication"

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==Introduction==
 
  
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.
+
==Overview==
  
[[Rumination - Anatomy & Physiology|Rumination]] allows food to undergo mastication more than once. Also called 'chewing the cud', it allows greater nutrients to be extracted and absorbed from the food particles.
+
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 - Anatomy & Physiology|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.
  
Mastication requires correct muscle movements and jaw articulation.
 
  
 
==Muscles of Mastication==
 
==Muscles of Mastication==
[[Image:Muscles of Mastication.jpg|thumb|right|150px|Muscle of Mastication (dog) - Copyright C.Clarkson and T.F.Fletcher University of Minnesota]]
+
[[Image:Muscles of Mastication.jpg|thumb|right|250px|Muscle of Mastication (dog) - Copyright C.Clarkson and T.F.Fletcher University of Minnesota]]
 
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
 
**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 '''masseter muscle''' originates from the  [[Skull and Facial Muscles - Anatomy & Physiology#Maxilla|maxilliary]] 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#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 '''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: medial aspect of [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]]
 
**One-sided contraction to close jaw
 
  
*Temporal 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: 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'''
+
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).
  
*Masseter muscle
+
===Lateral Translation of the Mandible===
  
*Contralateral medial and lateral pterygoids
+
The '''masseter muscle''' and the contralateral medial and lateral '''pterygoids''' are involved in the lateral translation of the mandible.
  
 
==Jaw Articulation==
 
==Jaw Articulation==
[[Image:Jaw Articulation.jpg|thumb|right|150px|Jaw Articulation (horse) - Copyright RVC]]
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[[Image:Jaw Articulation.jpg|thumb|right|250px|Jaw Articulation (horse) - Copyright RVC]]
'''Temperomandibular Joint'''
 
 
 
*Articulation between the condylar process of the [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]] and the mandibular process of the skull
 
 
 
*Compartmentalised joint for rotational movement and lateral slide (grinding)
 
 
 
*Fibro-cartilagenous disc between bones
 
 
 
*Synovial joint
 
 
 
*Caudal dislocation prevented by a prominent retro-articular process (enlargement of the fossa)
 
 
 
'''Mandibular Symphasis'''
 
 
 
*Rostral end of [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]]
 
[[Image:Temperomandibular Joint.jpg|thumb|right|150px|Temperomandibular Joint (dog) - Copyright RVC]]
 
*Fibrous joint between the left and right halves of the [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]]
 
  
*Only in dogs and ruminants
+
===Temperomandibular Joint===
  
*Precise occlusion
+
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).
  
*[[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|Mandibular]] bones can move apart independently by rotation
+
===Mandibular Symphasis===
 +
[[Image:Temperomandibular Joint.jpg|thumb|right|250px|Temperomandibular Joint (dog) - Copyright RVC]]
  
*Stops jaw breakages (Canid)
+
Located at the rostral end of the [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]]. It is a '''fibrous 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. Herbiverous 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 '''digasticus''' 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)
+
==Links==
 
 
*In the dog large forces are needed to shut jaws so the point of articulation of the temporomandibular joint is level with the teeth
 
 
 
==Test yourself with the Mastication & Facial Muscles Flashcards==
 
 
 
[[Oral Cavity - Anatomy & Physiology - Flashcards#Mastication Flashcards|Mastication Flashcards]]
 
  
[[Facial_Muscles_-_Musculoskeletal_-_Flashcards|Facial Muscles Flashcards]]
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'''Test yourself with the [[Oral Cavity - Anatomy & Physiology - Flashcards#Mastication Flashcards|Mastication Flashcards]] and the
 +
[[Facial_Muscles_-_Musculoskeletal_-_Flashcards|Facial Muscles Flashcards]].'''
  
==Links==
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'''Click here for [[Skull and Facial Muscles - Anatomy & Physiology]]'''
[[Skull and Facial Muscles - Anatomy & Physiology]]
 
  
 
'''Video'''
 
'''Video'''
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[[Category:Musculoskeletal System - Anatomy & Physiology]]
 
[[Category:Musculoskeletal System - Anatomy & Physiology]]
 
[[Category:Feeding Control]]
 
[[Category:Feeding Control]]
[[Category:To Do - A&P]]
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[[Category:To Do - AimeeHicks]]

Revision as of 12:59, 9 September 2010

Overview

Mastication is the process whereby food is broken down by mechanical digestion in the oral cavity. The cheeks and tongue function to position food over the teeth, where grinding can occur. Mastication requires correct muscle movements and jaw articulation.

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

Muscle of Mastication (dog) - Copyright C.Clarkson and T.F.Fletcher University of Minnesota

The muscles of mastication are well developed.

Jaw Opening Muscles

The Digastricus muscle is the 'jaw opening' muscle. Its origin is the paracondylar process of the occipital bone. It inserts at the angle of the mandible. The muscle has two bellies; The caudal half from the second visceral arch innervated by the facial nerve (CN VII) and the cranial half from the first visceral arch, innervated by the mandibular branch of the trigeminal nerve (CN V3).

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 (CN V3).

The masseter muscle originates from the maxilliary region of the skull and the zygomatic arch. It inserts on the wide area on the caudal side of the mandible. It has several divisions and causes unilateral and bilateral contraction. It also protrudes the jaw.

The lateral pterygoid muscle originates from the pterygopalatine region of the skull. It inserts on the lateral aspect of the mandible. It also protrudes the jaw (one-sided contraction).

The medial pterygoid muscle originates from the pterygopalatine region of the skull. It inserts on the medial aspect of the mandible. It causes one-sided contraction to close the jaw.

The temporal muscle originates from the lateral surface of the cranium. It inserts on the coronoid process. It pulls the mandible dorsally and also pulls the 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 (horse) - Copyright RVC

Temperomandibular Joint

The articulation between the condylar process of the 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 Symphasis

Temperomandibular Joint (dog) - Copyright RVC

Located at the rostral end of the mandible. It is a fibrous joint between the left and right halves of the mandible. It is only found in dogs and ruminants. It has a precise occlusion and the Mandibular bones can move apart independently by rotation. It stops jaw breakages (Canid).

Species Differences

Hebivores

Herbivores have large masseter and pterygoid muscles for extensive chewing. 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 have a large temporalis muscle for snapping the jaw shut, e.g. in lions and pitbull terriers. 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 the jaws, so the point of articulation of the temporomandibular joint is level with the teeth.

Links

Test yourself with the Mastication Flashcards and the Facial Muscles Flashcards.

Click here for Skull and Facial Muscles - Anatomy & Physiology

Video Pot 220 Lateral surface of the head of a dog

Pot 258 Lateral section through the head of a dog