Difference between revisions of "Mastication"

Revision as of 16:42, 30 June 2008

BACK TO CHEEKS - ANATOMY AND PHYSIOLOGY

Introduction

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.

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 requires correct muscle movements and jaw articulation.

Muscles of Mastication

The muscles of mastication are well developed.

Jaw Opening Muscles

Digastricus muscle

   -Origin: paracondylar process of occipital bone
   -Insertion: angle of mandible
   -Two bellies: caudal half from the second visceral arch innervated by facial nerve (CN VII)
                 cranial half from the first visceral arch innervated by the mandibular branch of the trigeminal (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)

Masseter muscle

   -Origin: maxilliary region of skull and zygomatic arch
   -Insertion: wide area on caudal side of mandible
   -Several divisions
   -Unilateral and bilateral contraction
   -Also protrudes jaw

Lateral Pterygoid muscle

   -Origin: pterygopalatine region of skull
   -Insertion: lateral aspect of mandible
   -Also protrudes jaw (one-sided contraction)

Medial Pterygoid muscle

   -Origin: pterygopalatine region of skull
   -Insertion: medial aspect of mandible
   -One-sided contraction to close jaw

Temporal muscle

   -Origin: lateral surface of cranium
   -Insertion: coronoid process
   -Pulls mandible dorsally
   -Also pulls mandible rostrally (overbite) and caudally (underbite)

Lateral Translation of Mandible

Masseter muscle

Contralateral medial and lateral pterygoids

Jaw Articulation

Temperomandibular Joint

Articulation between the condylar process of the 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 mandible

Fibrous joint bewteen the left and right halves of the mandible

Only in dogs and ruminants

Precise occlusion

Mandibular bones can move apart independently by rotation

Stops jaw breakages (Canid)

Species Differences

Large masseter and pterygoid muscles in the horse for extensive chewing

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

Herbiverous species have a limited digastricus muscle

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

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

@@ Line 1: / Line 1: @@
-{{OpenPagesTop}}
+<big><center>[[Cheeks - Anatomy & Physiology|'''BACK TO CHEEKS - ANATOMY AND PHYSIOLOGY]]</center></big>
-==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.
+==Introduction==
+Mastication is the process whereby food is broken down by mechanical digestion in the oral cavity. The [[Cheeks - Anatomy & Physiology|cheeks]] and tongue function to position food over the teeth where grinding can occur.
+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 requires correct muscle movements and jaw articulation.
 ==Muscles of Mastication==
 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]]).
+*Digastricus muscle
+    -Origin: paracondylar process of occipital bone
+    -Insertion: angle of mandible
+    -Two bellies: caudal half from the second visceral arch innervated by facial nerve (CN VII)
+                  cranial half from the first visceral arch innervated by the mandibular branch of the trigeminal (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 (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: maxilliary region of skull and zygomatic arch
+    -Insertion: wide area on caudal side of mandible
+    -Several divisions
+    -Unilateral and bilateral contraction
+    -Also protrudes jaw
-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.
+*Lateral Pterygoid muscle
+    -Origin: pterygopalatine region of skull
+    -Insertion: lateral aspect of mandible
+    -Also protrudes jaw (one-sided contraction)
-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).
+*Medial Pterygoid muscle
+    -Origin: pterygopalatine region of skull
+    -Insertion: medial aspect of mandible
+    -One-sided contraction to close jaw
-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.
+*Temporal muscle
+    -Origin: lateral surface of cranium
+    -Insertion: coronoid process
+    -Pulls mandible dorsally
+    -Also pulls mandible rostrally (overbite) and caudally (underbite)
-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 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==
-===Temporomandibular Joint===
+'''Temperomandibular Joint'''
+*Articulation between the condylar process of the 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 mandible
+*Fibrous joint bewteen the left and right halves of the mandible
+*Only in dogs and ruminants
-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).
+*Precise occlusion
-===Mandibular Symphysis===
+*Mandibular bones can move apart independently by rotation
-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).
+*Stops jaw breakages (Canid)
 ==Species Differences==
-===Hebivores===
+*Large masseter and pterygoid muscles in the horse 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.
-===Carnivores===
+*Large temporalis muscle in the carnivores 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.
-==Links==
+*Herbiverous species have a limited digastricus muscle
-'''Click here for [[Skull and Facial Muscles - Anatomy & Physiology]]'''
+*Canids have a larger digasticus muscle than herbivores (but smaller in comparison with jaw closing muscles)
-{{Template:Learning
+*In the dog large forces are needed to shut jaws so the point of articulation of the temporomandibular joint is level with the teeth
-|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)]]
-}}
-==Webinars==
+*In the horse the muscle insertion site for the masseter is large to snap jaw shut
-<rss max="10" highlight="none">https://www.thewebinarvet.com/gastroenterology-and-nutrition/webinars/feed</rss>
-[[Category:Teeth - Anatomy & Physiology]]
-[[Category:Musculoskeletal System - Anatomy & Physiology]]
-[[Category:Feeding Control]]
-[[Category:A&P Done]]

Difference between revisions of "Mastication"

Revision as of 16:42, 30 June 2008

Contents

Introduction

Muscles of Mastication

Jaw Articulation

Species Differences

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