Digastric Muscle: Difference between revisions

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'''Original Editor '''- [[User:Daphne Jackson|Daphne Jackson]]  
'''Original Editor '''-[[User:Priyanka Chugh|Priyanka Chugh]]  


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'''Lead Editors''' - {{Special:Contributors/{{FULLPAGENAME}}}}  
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== Description  ==
== Description  ==


The trapezius is a broad, flat, superficial muscle extending from the cervical to thoracic region on the posterior aspect of the neck and trunk. The muscle is divided into three parts: descending (superior), ascending (inferior), and middle<ref name="Moore">Moore KL, et al. Essential clinical anatomy. 4th ed. Baltimore, MD: Lippincott Williams and Wilkins, 2011.</ref>. The muscle contributes to [[Scapulohumeral Rhythm|scapulohumeral rhythm]] through attachments on the clavicle and [[Scapula|scapula]], and to head balance through muscular control of the cervical spine.
The digastric muscle (also digastricus) has two bellies<ref name=":0">Kenhub 2022, ''Kenhub: Digastric,'' Viewed 16/12/22,https://www.kenhub.com/en/library/anatomy/digastric-muscle</ref>, namely the anterior and posterior belly. It is a small, important muscle in the neck<ref name=":1">Kim SD, Loukas M. [https://synapse.koreamed.org/upload/synapsedata/pdfdata/1049acb/acb-52-1.pdf Anatomy and variations of digastric muscle.] Anatomy & Cell Biology. 2019 Mar;52(1):1-1.</ref>. It has many variations but these variations do not necessarily produce clinical symptoms<ref name=":1" />. It belongs to the suprahyoid muscles group which includes the mylohyoid, geniohyoid and stylohyoid muscles<ref name=":0" />.
[[File:Digastric image.png|center|frameless]]


<br>
== Origin  ==


{| width="100%" cellspacing="1" cellpadding="1" border="0" align="center"
Anterior belly - Mandible's digastric fossa, close to the midline <ref name=":1" /><ref name=":0" />
|-
| [[Image:Trapezius Gray.PNG|center|200px]]
| [[Image:Trapezius animation.gif|center|300px]]
|}


<br>  
Posterior belly - Notch of the mastoid process of the temporal bone<ref name=":1" /><ref name=":0" /><br>  


== Origin ==
== Insertion ==
 
The muscle attaches to the medial third of superior nuchal line; external occipital protruberance, [[Ligamentum nuchae|nuchal ligament]], and spinous processes of C7 - T12 vertebrae<ref name="UW">Department of Radiology, UW Medicine. Trapezius. www.rad.washington.edu/academics/academic-sections/msk/muscle-atlas/upper-body/trapezius (accessed 27 January 2014).</ref>.


== Insertion ==
The two join, forming the intermediate tendon which inserts onto the body and greater cornu of the hyoid bone<ref name=":1" /><ref name=":0" />. The intermediate tendon can sometimes penetrate the stylohyoid muscle<ref name=":1" />.<br>


The muscle inserts on the lateral third of clavicle, acromion, and spine of scapula<ref name="UW" />.
== Nerve Supply  ==


== Nerve Supply  ==
Anterior belly - mandibular division (V3) of the trigeminal (CN V) via the mylohyoid nerve<ref name=":1" />. In some cases, the anterior belly can be innervated by both the mylohyoid nerve and facial nerve<ref name=":1" />.


*Spinal root of accessory nerve (CN XI) (motor)<ref name="UW" />
Posterior belly - facial nerve (CN VII)<ref name=":1" />  
*Cervical nerves (C3 and C4) (pain and proprioception)<ref name="UW" />


== Blood Supply  ==
== Blood Supply  ==


Transverse cervical artery (cervicodorsal trunk)<ref name="UW" /><ref name="Moore" />  
Anterior belly - submental branch of facial artery<ref name=":1" />


= Function =
Posterior belly - posterior auricular and occipital arteries<ref name=":1" /><br>


The superficial muscles of the back (trapezius, latissimus dorsi, rhomboids, levator scapula, serratus anterior) contribute to extension and side flexion of the axial skeleton. The cervical extensor muscles (descending trapezius and cervical erector spinae) counterbalance the pull of gravity on the head, as the head tends to be pulled into flexion due to its anterior centre of gravity<ref name="kisner">Kisner C, Colby LA. Therapeutic exercise: foundations and techniques. 6th ed. Philadelphia: F.A. Davis Company, 2012</ref>
== Function  ==


== Action  ==
* Elevates the hyoid bone to stabilize it during swallowing (protection of the airway)<ref name=":1" /><ref name=":0" />
* Opens the jaw by depressing the mandible<ref name=":1" /><ref name=":0" />
* Plays a role during speech and chewing<ref name=":1" /><br>


*Descending part: elevates pectoral girdle<ref name="Moore" />
*Middle part: retracts scapula<ref name="Moore" />
*Ascending part: depresses shoulders<ref name="Moore" />
*Descending and ascending together: rotates scapula upwards<ref name="Moore" />
*Bilateral contraction: extends neck<ref name="Neumann">Neumann DA. Kinesiology of the musculoskletal system: foundations for rehabilitation. 2nd ed. St. Louis, MO: Mosby Elsevier, 2010.</ref>
*Unilateral contraction:
**Ipsilateral side flexion of neck<ref name="Neumann" />
**Middle part: assists with ipsilateral side flexion and contralateral axial rotation of upper thoracic region<ref name="Neumann" /><br>


== functional contributation ==
== Structure ==


The trapezius muscle is a postural and active movement muscle, used to tilt and turn the head and neck, shrug, steady the shoulders, and twist the arms. The trapezius elevates, depresses, rotates, and retracts the scapula, or shoulder blade.<ref>http://www.healthline.com/human-body-maps/trapezius-muscle</ref>
The digastricus (digastric muscle) consists of two muscular bellies united by an intermediate rounded tendon. The two bellies of the digastric muscle have different embryological origins, and are supplied by different cranial nerves. Each person has a right and left digastric muscle. The digastric muscle stretches between the mastoid process of the cranium to the mandible at the chin, and part-way between, it becomes a tendon which passes through a tendinous pulley attached to the hyoid bone. It


= Trigger Point Referral Pattern =
<u>Posterior belly</u><br>The posterior belly, longer than the anterior belly, arises from the mastoid notch which is on the inferior surface of the skull, medial to the mastoid process of the temporal bone. The mastoid notch is a deep groove between the mastoid process and the styloid process. The mastoid notch is also referred to as the digastric groove or the digastric fossa. The posterior belly is supplied by the digastric branch of the facial nerve.


&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;[[Image:Trapezius1.jpg|130x130px]]&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;[[Image:Trap23.jpg|130x130px]]
<u>Anterior belly</u><br>The anterior belly arises from a depression on the inner side of the lower border of the mandible called the digastric fossa of mandible, close to the symphysis, and passes downward and backward. The anterior body is supplied by the trigeminal nerve via the mylohyoid nerve, a branch of the inferior alveolar nerve, itself a branch of the mandibular division of the trigeminal nerve. It originates from the first pharyngeal arch.  


&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
<u>Intermediate tendon</u><br>The two bellies end in an intermediate tendon which perforates the stylohyoideus muscle, and is held in connection with the side of the body and the greater cornu of the hyoid bone by a fibrous loop, which is sometimes lined by a mucous sheath.


&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;[[Image:Trap4567.jpg|200x200px]][[Image:Trap4567.jpg|200x200px]]
<u>Triangles</u><br>The digastric muscle divides the anterior triangle of the neck into three smaller triangles:  


= Techniques  =
# The submandibular triangle (also called digastric triangle) is formed by the mandible superiorly, laterally but the digastric posterior belly and medially by the digastric anterior belly<ref name=":1" />.
# The carotid triangle is formed by the posterior belly of the digastric muscle superiorly, the sternocleidomastoid muscle laterally and medially but the superior belly of the omohyoid muscle<ref name=":1" />.
# The submental triangle is formed by the hyoid bone inferiorly and by both anterior bellies of the digastric muscles


== Palpation ==
== Trigger Point Referral Pattern ==


superficial, can palpate upper, middle and lower<br>Upper is frequently involved in neck injuries<br>Hold the sloping superior lateral portion between fingers and thumb and palpate from<br>origin (O) toward the clavicle/acromion and its insertion (I)<br>With patient (pt.) standing: abduct shoulders to 90 degrees and retract shoulder girdle.<br>Slightly bend the trunk forward so antigravity.<br>Upper can also be seen with elevation and lower with depression <ref>https://www.fgc.edu/wp-content/uploads/2011/12/palpation-of-muscles.pdf</ref>  
&nbsp;The anterior and posterior bellies of digastric may contain a myofascial trigger point (MTrP). The MTrP in the posterior belly may refer pain over the mastoid process and occasionally to the throat under the chin<ref name=":2" /> . The anterior belly refers to the lower central incisors and to the alveolar ridge below.<ref name=":2">http://www.sciencedirect.com/topics/page/Digastric_muscle</ref> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;


== Length tension testing ==
== Palpation ==


'''Patient:''' Positioned in supine lying with the arms resting by the side and the&nbsp;knees flexed.<br>'''Therapist:''' Standing at the head of the bed.<br>'''Action:''' The therapist supports the posterior aspect of the head with both&nbsp;hands and then passively flexes the craniovertebral joint. The right<br>hand stabilizes the lateral one third of the patient’s right clavicle and&nbsp;acromion palpating the muscle. The therapist then gently and&nbsp;slowly flexes, left side flexes and right rotates the mid and lower&nbsp;cervical spine with the left hand. The hand stabilizing and the hand&nbsp;moving the body part senses the tension in the muscle and barrier.&nbsp;The amount of range and the end feel is assessed and the&nbsp;reproduction of any symptoms is noted. This test is then repeated&nbsp;on the contralateral side and compared. <ref>http://activepotentialrehab.com/docs/pdf/sample_upperextremity11_21.pdf</ref>  
Direct external palpation of posterior digastric is difficult due to the depth of the muscle. The anterior digastric is examined by identifying the lateral margins of the hyoid, and then palpating the inferior surface of the mandible by placing the thumbs on either side of the midline. To confirm the location of the anterior digastric, the patient is requested to swallow; a prominence of the anterior belly can be palpated under the thumb tips as the hyoid is drawn superiorly. <be>


== Strength Testing ==
== Resources ==
{{#ev:youtube|CxqCWyindCI}} <ref>Kenhub - Learn Human Anatomy Digastric muscle - Origin, Insertion, Innervation & Function - Anatomy | Kenhub.Available fromhttps://www.youtube.com/watch?v=CxqCWyindCI. Accessed on 10/03/23</ref>


{{#ev:youtube|9tfVeIhlY-o}}<ref>Physiotutors. Trapezius Strength Test. Available from: https://www.youtube.com/watch?v=9tfVeIhlY-o </ref>
== Treatment  ==
'''Stretching'''
Sit upright in a chair and make sure that your posture is correct. These stretches can be done in repetitions of 15-20 every hour to decrease trapezius muscle pain. Begin by rolling the shoulders back so that the shoulder blades feel like they are being pinched together. Then raise your shoulders up towards the ceiling and lower them down gently. You can then bend your neck from side to side by tilting your head towards your shoulder and counting to 3, then repeating in each direction.
'''Massage'''
Pain in the shoulder and neck can be prevented or reduced with massage.It is possible to reduce trapezius muscle pain through self-massage. Reach back with one hand and find your trapezius muscle. Beginning at the base of the neck, try to knead the trapezius muscles.
'''Pressure'''<br>
You can also apply some pressure to the area along your shoulders and between the shoulder blades. If there is an area that is more tender, apply pressure for ten seconds and then release so that the muscle can relax.<ref>http://www.ehow.com/about_5446034_trapezius-muscle-pain.html</ref>
== Recent Related Research (from [http://www.ncbi.nlm.nih.gov/pubmed/ Pubmed])  ==
<div class="researchbox">
<rss>http://www.ncbi.nlm.nih.gov/entrez/eutils/erss.cgi?rss_guid=1bCr63ThlO2_EjapuTs-VVGCD3KOFO-M4fiVC5BoBJ1z-APsgV|charset=UTF-8|short|max=10</rss>
</div>
== References  ==
== References  ==


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[[Category:Anatomy]] [[Category:Cervical_Anatomy]] [[Category:Cervical_Spine]] [[Category:Muscles]] [[Category:Musculoskeletal/Orthopaedics]]
[[Category:Anatomy]]  
[[Category:Cervical Spine - Anatomy]]  
[[Category:Cervical_Spine]]  
[[Category:Muscles]]  
[[Category:Musculoskeletal/Orthopaedics]]
 
[[Category:Cervical Spine - Muscles]]

Latest revision as of 06:54, 10 March 2023

Original Editor -Priyanka Chugh

Lead Editors - Priyanka Chugh, Wendy Snyders, Kim Jackson, Vidya Acharya, 127.0.0.1 and Chrysolite Jyothi Kommu

Description[edit | edit source]

The digastric muscle (also digastricus) has two bellies[1], namely the anterior and posterior belly. It is a small, important muscle in the neck[2]. It has many variations but these variations do not necessarily produce clinical symptoms[2]. It belongs to the suprahyoid muscles group which includes the mylohyoid, geniohyoid and stylohyoid muscles[1].

Digastric image.png

Origin[edit | edit source]

Anterior belly - Mandible's digastric fossa, close to the midline [2][1]

Posterior belly - Notch of the mastoid process of the temporal bone[2][1]

Insertion[edit | edit source]

The two join, forming the intermediate tendon which inserts onto the body and greater cornu of the hyoid bone[2][1]. The intermediate tendon can sometimes penetrate the stylohyoid muscle[2].

Nerve Supply[edit | edit source]

Anterior belly - mandibular division (V3) of the trigeminal (CN V) via the mylohyoid nerve[2]. In some cases, the anterior belly can be innervated by both the mylohyoid nerve and facial nerve[2].

Posterior belly - facial nerve (CN VII)[2]

Blood Supply[edit | edit source]

Anterior belly - submental branch of facial artery[2]

Posterior belly - posterior auricular and occipital arteries[2]

Function[edit | edit source]

  • Elevates the hyoid bone to stabilize it during swallowing (protection of the airway)[2][1]
  • Opens the jaw by depressing the mandible[2][1]
  • Plays a role during speech and chewing[2]


Structure[edit | edit source]

The digastricus (digastric muscle) consists of two muscular bellies united by an intermediate rounded tendon. The two bellies of the digastric muscle have different embryological origins, and are supplied by different cranial nerves. Each person has a right and left digastric muscle. The digastric muscle stretches between the mastoid process of the cranium to the mandible at the chin, and part-way between, it becomes a tendon which passes through a tendinous pulley attached to the hyoid bone. It

Posterior belly
The posterior belly, longer than the anterior belly, arises from the mastoid notch which is on the inferior surface of the skull, medial to the mastoid process of the temporal bone. The mastoid notch is a deep groove between the mastoid process and the styloid process. The mastoid notch is also referred to as the digastric groove or the digastric fossa. The posterior belly is supplied by the digastric branch of the facial nerve.

Anterior belly
The anterior belly arises from a depression on the inner side of the lower border of the mandible called the digastric fossa of mandible, close to the symphysis, and passes downward and backward. The anterior body is supplied by the trigeminal nerve via the mylohyoid nerve, a branch of the inferior alveolar nerve, itself a branch of the mandibular division of the trigeminal nerve. It originates from the first pharyngeal arch.

Intermediate tendon
The two bellies end in an intermediate tendon which perforates the stylohyoideus muscle, and is held in connection with the side of the body and the greater cornu of the hyoid bone by a fibrous loop, which is sometimes lined by a mucous sheath.

Triangles
The digastric muscle divides the anterior triangle of the neck into three smaller triangles:

  1. The submandibular triangle (also called digastric triangle) is formed by the mandible superiorly, laterally but the digastric posterior belly and medially by the digastric anterior belly[2].
  2. The carotid triangle is formed by the posterior belly of the digastric muscle superiorly, the sternocleidomastoid muscle laterally and medially but the superior belly of the omohyoid muscle[2].
  3. The submental triangle is formed by the hyoid bone inferiorly and by both anterior bellies of the digastric muscles

Trigger Point Referral Pattern[edit | edit source]

 The anterior and posterior bellies of digastric may contain a myofascial trigger point (MTrP). The MTrP in the posterior belly may refer pain over the mastoid process and occasionally to the throat under the chin[3] . The anterior belly refers to the lower central incisors and to the alveolar ridge below.[3]                                                                                                                                               

Palpation[edit | edit source]

Direct external palpation of posterior digastric is difficult due to the depth of the muscle. The anterior digastric is examined by identifying the lateral margins of the hyoid, and then palpating the inferior surface of the mandible by placing the thumbs on either side of the midline. To confirm the location of the anterior digastric, the patient is requested to swallow; a prominence of the anterior belly can be palpated under the thumb tips as the hyoid is drawn superiorly. <be>

Resources[edit | edit source]

[4]

References[edit | edit source]

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Kenhub 2022, Kenhub: Digastric, Viewed 16/12/22,https://www.kenhub.com/en/library/anatomy/digastric-muscle
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 Kim SD, Loukas M. Anatomy and variations of digastric muscle. Anatomy & Cell Biology. 2019 Mar;52(1):1-1.
  3. ↑ 3.0 3.1 http://www.sciencedirect.com/topics/page/Digastric_muscle
  4. ↑ Kenhub - Learn Human Anatomy Digastric muscle - Origin, Insertion, Innervation & Function - Anatomy | Kenhub.Available fromhttps://www.youtube.com/watch?v=CxqCWyindCI. Accessed on 10/03/23


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