muscles and mastication how this happen which muscles help us in this process all we can figure out in this simple overview

1. MUSCLES OF MASTICATION
BY:
AHMED REDA ABDEL-HAMEED
1

2. 1. Table of figures.................................................................................................2
2. Abstract.............................................................................................................3
3. Embryology.......................................................................................................4
4. Blood Supply and Lymphatics..........................................................................5
5. Nerves...............................................................................................................7
6. Muscles.............................................................................................................8
7. Temporalis Muscle............................................................................................9
ORIGIN......................................................................................................................9
INSERTION...............................................................................................................9
NERVE SUPPLY.....................................................................................................10
ACTIVITIES............................................................................................................10
8. Medial Pterygoid.............................................................................................11
ORIGIN....................................................................................................................11
INSERTION.............................................................................................................11
ACTIVITIES............................................................................................................11
9. Lateral Pterygoid.............................................................................................13
ORIGIN....................................................................................................................13
INSERTION.............................................................................................................13
NERVE SUPPLY.....................................................................................................13
ACTIVITIES............................................................................................................13
Things to Remember................................................................................................13
CONNECTIONS......................................................................................................14
10. Masseter..........................................................................................................16
ORIGIN....................................................................................................................16
INSERTION.............................................................................................................16
Key Points................................................................................................................16
NERVE SUPPLY.....................................................................................................17
ACTIVITIES............................................................................................................17
11. Accessory Muscles of Mastication.................................................................18
12. Clinical Significance.......................................................................................19
13. Conclusion......................................................................................................20
14. References.......................................................................................................21
2

3. Table of figures
figure1. 1 structure of muscles...................................................3
figure1. 2 The Pharyngeal Arches...............................................4
figure1. 3Maxillary artery branches. Sagittal reconstructed
image from rotational angiographic data.....................................6
figure1. 4 anterior division of mandibular nerve.........................7
figure1. 5 primary and accessory muscles of mastication...........8
figure1. 6 temporalis muscle.....................................................10
figure1. 7 Medial pterygoid muscle...........................................12
figure1. 8 lateral pterygoid........................................................15
figure1. 9 masseter muscle........................................................17
figure1. 10 suprahyoid and infrahyoid muscles.........................18
3

4. Abstract
The muscles that power the jaw movements during chewing are known as
the muscles of mastication or masticatory muscles and are functionally
classified as:
 Jaw elevators muscles.
 Jaw depressors muscles. [1]
About 40 per cent of the body is skeletal muscle, and perhaps another 10
per cent is smooth and cardiac muscle. Some of the same basic principles
of contraction apply to all these different types of muscle.
The primary muscles of mastication (chewing food) are the temporalis,
medial pterygoid, lateral pterygoid, and masseter muscles.
The four main muscles of mastication attach to the rami of the mandible
and function to move the jaw (mandible).The cardinal mandibular
movements of mastication are elevation, depression, protrusion,
retraction, and side to side movement. To augment the process of eating,
the muscles of mastication also move the mandible in a side to side
motion to assist in the grinding of food. The muscles of mastication also
function to approximate (bring together or close) the teeth. The
superficial muscle of the neck, the platysma muscle, also assists with
depression of the mandible against resistance.
[2]
figure1. 1 structure ofmuscles
4

5. Embryology
The muscles of mastication develop from the first pharyngeal arch. Thus,
they are innervated by a branch of the trigeminal nerve (CN V), the
mandibular nerve.
It is important to note that all the muscles mentioned here are bilateral
structures.
figure1. 2 The PharyngealArches
5

6. Blood Supply and Lymphatics
The blood supply to the muscles of mastication is derived from the
external carotid artery. This is mainly through its major terminal branch,
the maxillary artery.
The maxillary artery (Latin: arteria maxillaris) is the largest terminal
branch of the external carotid artery that arises at the back of the neck of
the mandible. It supplies deep structures of the face, such as the
mandible, maxilla, teeth, and muscles of mastication, palate, nose, and
part of the cranial dura mater.
Topographically the maxillary artery can be divided into three portions:
 mandibular part,
 pterygoid part, and
 Pterygopalatine part.
Branches
From the mandibular part, the maxillary artery gives off five branches
that enter the skull and supply bones of the skull, including:
 deep auricular artery,
 anterior tympanic artery,
 middle meningeal artery,
 accessory meningeal artery,
 Inferior alveolar artery.
The pterygoid part of the maxillary artery gives off the following four
branches:
 deep temporal artery,
 pterygoid artery,
 masseteric artery,
 Buccal artery.
These branches supply the corresponding muscles.
6

7. The pterygopalatine part of the maxillary artery provides four branches
that accompany similarly named branches of the maxillary nerve. These
branches include:
 posterior superior alveolar artery,
 infraorbital artery,
 descending palatine artery,
 Sphenopalatine artery.
Temporalis is supplied from the second part of the maxillary artery (via
posterior and anterior deep temporal branches) together with the middle
temporal artery, a branch of the superficial temporal artery (the other
terminal branch of the external carotid artery). The pterygoid muscles
receive a suitable different number of pterygoid branches from the
maxillary artery. Masseter is supplied by masseteric branches of the
maxillary artery as well as by the facial artery (a branch of the external
carotid artery) and transverse facial branch of the superficial temporal
artery. 3]
4]
figure1. 3Maxillary artery branches. Sagittal reconstructed image from rotational
angiographic data.
2 7

8. Nerves
The four main muscles of mastication are all innervated by the anterior
trunk of the mandibular nerve which is the third division of the trigeminal
nerve (CN V3).The mandibular nerve (CN V3) is the largest and inferior
most division of the trigeminal nerve (CN V). The trigeminal nerve (CN
V) exits the skull via foramen ovale of the greater wing of the sphenoid
bone. The mandibular nerve contains both sensory and motor fibers. The
mandibular nerve is the only division of the trigeminal nerve that carries
motor fibers. The mandibular nerve (CN V3) further subdivides as it
innervates the four main muscles of mastication.
The temporalis muscle receives innervation by deep temporal branches of
the mandibular nerve.
The medial pterygoid muscle is innervated medial pterygoid nerve, a
division of the mandibular nerve.
The lateral pterygoid muscle gets its nerve supply from the lateral
pterygoid nerves, divisions of the mandibular nerve.
The masseter muscle receives nerve input from the masseteric nerve, a
division of the mandibular nerve. [5]
figure1. 4 anterior division of mandibular nerve
8

9. Muscles
The primary and accessory muscles of mastication work in a coordinated
fashion to produce mandibular movement for chewing food. The
accessory muscles of mastication are the buccinator, suprahyoid muscles
(digastric muscle, mylohyoid muscle, and geniohyoid muscle), and
infrahyoid muscles (the sternohyoid, sternothyroid, thyrohyoid and
omohyoid muscle).
It is important to note that all the muscles mentioned here
are bilateral structures. [6]
figure1. 5 primary and accessory muscles of mastication.
9

10. Temporalis Muscle
The temporalis muscle is a fan-shaped muscle with anterior fibers that
have a vertical orientation, mid fibers have an oblique orientation, and
posterior fibers have a more of a horizontal orientation. The origin of the
temporalis muscle spans from the temporal fossa to the inferior temporal
line of the lateral skull. The temporalis muscle fibers converge inferiorly
forming a tendon that exits the temporal fossa, passing underneath the
zygomatic arch and inserting on the coronoid process of the mandible.
The function of the anterior and mid fibers of the temporalis muscle is to
elevate the mandible. The posterior fibers of the temporalis muscle
function to retract the mandible.
It’s connected above to the temporal line and below to the zygomatic arch
and is covered by tough temporal fascia. It’s located in the temporal fossa
and is a fan-shaped muscle.
ORIGIN
It appears from:
 Whole of the floor of temporal fossa with the exception of the part
created by the zygomatic bone.
 Deep surface of the temporal fascia.
INSERTION
The fibres converge and descend to create a tendon, which goes through
the gap between the zygomatic arch and the side of the skull. The muscle
is added into:
 The medial surface, apex, anterior, border of the coronoid process
of ramus of mandible
 The anterior border of the ramus of mandible, nearly up to the final
molar tooth.
10

11. NERVE SUPPLY
The temporalis is supplied by the anterior and posterior deep
temporal nerves, the branches of the anterior section of the
mandibular nerve.
ACTIVITIES
The temporalis muscle elevates the mandible and so shuts the
mouth and approximates the teeth. This movement needs both the
upward pull of the anterior fibres and backward pull of the
posterior fibres.Posterior fibres retract the mandible after it’s been
protruded.
7]
figure1. 6 temporalis muscle
11

12. Medial Pterygoid
The medial pterygoid is a thick quadrilateral muscle and is composed of 2
heads: superficial and deep.
ORIGIN
 The small superficial head (a small slide of muscle) originates from
maxillary tuberosity and lateral surface of the pyramidal process of
palatine bone.
 The large deep head (creating the majority of muscle) appears from
medial surface of the lateral pterygoid plate and grooved surface of
the pyramidal process of palatine bone.
INSERTION
The fibres run downwards, backwards and laterally to be added by a
powerful tendinous lamina into a roughened area on the posteroinferior
part of the medial surface and angle of ramus of mandible as high as the
mandibular foramen and as forwards as the mylohyoid groove.
NERVE SUPPLY
The medial pterygoid is supplied by a nerve to medial pterygoid, a branch
from the primary trunk of the mandibular nerve.
CONNECTIONS
Superficial:
 Lingual nerve
 Inferior alveolar nerve
 Inferior alveolar vessels
Deep:
 Levator palati and tensor palati muscles
 Superior constrictor of pharynx
 Styloglossus and stylopharyngeus muscles.
ACTIVITIES
 Medial pterygoids of 2 sides elevate the mandible to assist in
closure of mouth.
2 12

13.  Acting with lateral pterygoids, the medial pterygoids protrude the
mandible.
 When medial and lateral pterygoids of 1 side act collectively, the
corresponding side of the mandible is rotated forwards and to the
opposite side.
 Medial and lateral pterygoids of 2 sides when contract alternately
generate side to side movements that are utilized to grind the food.
8]
figure1. 7 Medial pterygoidmuscle
13

14. Lateral Pterygoid
It’s a short, thick conical muscle with its apex pointing backwards. It
enters backwards and somewhat laterally from the roofing and medial
wall of the fossa to the neck of the mandible.
ORIGIN
The lateral pterygoid is composed of 2 heads, upper and lower:
 The upper smaller head appears from the temple surface and crest
of the higher wing of the sphenoid bone.
 The lower bigger head originates from the lateral surface of the
lateral pterygoid plate of the sphenoid bone.
INSERTION
The fibres of 2 heads run backwards and laterally and converge to create
a thick tendon that is added into:
 Pterygoid fovea on the very front of the neck of the mandible.
 Articular disc and capsule of the temporomandibular joint.
NERVE SUPPLY
Lateral pterygoid is supplied by a branch of anterior section of the
mandibular nerve.
ACTIVITIES
 Lateral pterygoids of 2 sides depress the mandible (opens the
mouth) by pulling forwards the condylar processes of the mandible
and the articular discs of the temporomandibular joints.
 Medial and lateral Pterygoid muscles of 2 sides acting jointly
protrude the mandible.
 Medial and lateral pterygoid muscles of the 2 sides contract
alternately to generate side to side movements of the lower jaw as
in mastication.
Things to Remember
 The lower head of lateral pterygoid enters between the 2 heads of
the medial pterygoid muscle.
 It’s the only masticatory muscle, which opens the mouth.
14

15.  The articular disc of temporomandibular joint is developmentally a
part of tendon of lateral pterygoid muscle.
CONNECTIONS
The lateral pterygoid is regarded as the key muscle of the infratemporal
region because its connections supply a rational idea about the layout of
structures in this region. Its connections are:
Superficial:
 Ramus of the mandible
 Masseter
 Tendon of temporalis
 Superficial head of medial pterygoid
 Maxillary artery and its temporal and masseteric branches
Deep:
 Mandibular nerve
 Middle meningeal artery
 Sphenomandibular ligament
 Deep head of medial pterygoid muscle
Structures appearing at the upper border:
 Deep temporal nerves (2 in number)
 Masseteric nerve
Structures appearing at the lower border:
 Inferior alveolar nerve and artery
 Lingual nerve
 Middle meningeal artery (it enters up deep to the lower border)
Structures going through the gap between the 2 heads:
 Maxillary artery, which enters the gap to get to the pterygopalatine
fossa via pterygomaxillary fissure
 Buccal nerve, a branch of mandibular nerve.
15

16.  It comes out via the gap to supply sensory innervation to the skin
and mucus membrane of the cheek.
Error: Reference source not found]
figure1. 8 lateral pterygoid
16

17. Masseter
The masseter (Greek: masseter = a chewer) is a thick quadrilateral muscle
covering the lateral surface of the ramus of the mandible consisting of its
coronoid process. The condylar process is left uncovered.
ORIGIN
The masseter is composed of the following 3 layers:
 Superficial layer.
 Middle layer.
 Deep layer.
Superficial layer is largest of the 3 layers of masseter and originates by a
thick aponeurosis from: maxillary process of zygomatic bone and anterior
two-third of the inferior border of the zygomatic arch.
Middle layer originates from lower border of the posterior one-third of
the zygomatic arch.
Deep layer originates from deep surface of the zygomatic arch.
INSERTION
Superficial fibres pass downwards and backwards at 45° to be added into
the angle and lower posterior half of the lateral surface of the ramus of
the mandible.
Middle fibres pass vertically downwards to add into the central part of the
ramus.
Deep fibres pass vertically downwards to fit into the upper part of the
mandibular ramus and its coronoid process.
Key Points
Intramuscular tendinous septa in the superficial layer are liable for
creating ridges on the ramus of the mandible.
2 17

18. Middle and deep fibres collectively represent the deep part of the
masseter.
NERVE SUPPLY
The masseter is supplied by a masseteric nerve, a branch from anterior
section of the mandibular nerve.
ACTIVITIES
The masseter muscle elevates the mandible to shut the mouth.
10]
figure1. 9 massetermuscle
18

19. Accessory Muscles of Mastication
The strap muscles are composed of the suprahyoid and infrahyoid
muscles are located on the side of the neck bilaterally.
The strap muscles primarily function to raise and depress the hyoid bone
and larynx. The strap muscles also assist with depression of the mandible
when opening the mouth against an opposing force.
The buccinator is a facial expression muscle that helps in mastication by
keeping food pushed back within the oral cavity.
figure1. 10 suprahyoid and infrahyoid muscles
19

20. Clinical Significance
The muscles of mastication and their motor innervation can be analyzed
medically by requesting the patient to clench his teeth repeatedly and
after that palpating the temporalis and masseter in the temporal fossa and
over the ramus of mandible, respectively.
Temporomandibular joint (TMJ) dysfunction can result from an
imbalance of forces within the muscles of mastication. Grinding of teeth
at night (bruxism) is a common cause of TMJ dysfunction secondary to a
resultant imbalance in the muscle of mastication forces from excessive
grinding of the teeth.[
Temporomandibular joint dislocation can result from traumatic accidents
such as whiplash from an auto accident.
Muscles spasm of the muscles of mastication (trismus) can be a symptom
of masseter space tumor or infection.
.
20

21. Conclusion
ORIGIN, INSERTION, NERVE SUPPLY AND
ACTIVITIES OF MAIN MUSCLES OF MASTICATION
Muscles Origin Insertion Nerve
supply
Actions
Temporalis
(fan shaped)
Floor of
temporal
fossa
Tip, anterior
border, and
medial
Mandibular
division of
trigeminal
Elevation of
mandible by
anterior and
Temporal surface of nerve middle
fascia coronoid fibres
process Retraction
Anterior of mandible
border of by posterior
ramus of fibres
mandible
Masseter
(quadrilateral)
Zygomatic
arch adjoining
part of
Lateral
surface of
ramus of
Mandibular
division of
trigeminal
Elevation of
mandible to
occlude the
zygomatic mandible nerve teeth for
process of Coronoid forceful bite
maxilla process
Lateral
pterygoid
(Short, thick
conical)
Upper head
from
infratemporal
surface and
crest of
Pterygoid
fovea on
anterior
surface of
neck of
Mandibular
division of
trigeminal
nerve
Depression
of mandible
by pulling
the neck of
mandible
greater wing mandible forward
of sphenoid. Articular Protraction
Lower head disc and
from lateral capsule of
surface of TMJ
lateral
pterygoid
plate
Medial
pterygoid
(quadrilateral)
Superficial
head from
tuberosity of
maxilla Deep
Medial
surface of
angle
adjoining
Mandibular
division of
trigeminal
nerve
Elevation of
mandible
Protraction
head from ramus of
medial mandible
surface of
lateral
pterygoid
plate
21

22. References
1. Stomato 202 Abdelghani, A. & Mahmoud, M.
(2017).STONATOGNATHIC SYSTEM (ortho-function). Misr
University for Science & Technology. 5503/2017
2. Alomar X, Medrano J, Cabratosa J, Clavero JA, Lorente M, Serra
I, Monill JM, Salvador A. Anatomy of the temporomandibular
joint. Semin. Ultrasound CT MR. 2007 Jun; 28(3):170-
83. [PubMed].
3. https://www.anatomynext.com/maxillary-artery/
4. © Servicio de Radiología. Hospital General Universitario de
Alicante/Alicante-ES
5. Ghatak RN, Ginglen JG. StatPearls [Internet]. StatPearls
Publishing; Treasure Island (FL): Feb 7, 2019. Anatomy, Head and
Neck, Mandibular Nerve.
6. Ghatak RN,Ginglen JG, Anatomy, Head and Neck, Mandibular
Nerve 2018 Jan
7. https://www.earthslab.com/anatomy/temporalis-muscle/
8. Gray's Anatomy: The Anatomical Basis of Medicine and Surgery
(British Edition. 38th Ed) (Hardcover)
9. Parent text: Clinically oriented anatomy / Keith L. Moore, Arthur
F. Dalley, Anne M.R. Agur. 7th ed. c2014
10.HOUGHTON MIFFLIN HARCOURT, THE AMERICAN HERITAGE
DICTIONARY OF THE ENGLISH LANGUAGE, HOUGHTON MIFFLIN
HARCOURT, ARCHIVED FROM THE ORIGINAL ON 2015-09-25,
RETRIEVED 2015-09-27.
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