Suprahyoid

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Head & Neck • Anatomy

SUPRAHYOID MUSCLES

The suprahyoid muscles are Digastric, Stylohyoid, Mylohyoid and Geniohyoid.

01

Suprahyoid Muscles

The suprahyoid muscles are:

  1. Digastric
  2. Stylohyoid
  3. Mylohyoid
  4. Geniohyoid

Layers

First Layer

Digastric (Greek → two bellies) and stylohyoid

Second Layer

Mylohyoid (Greek → pertaining to hyoid bone)

Third Layer

Geniohyoid and hyoglossus

Fourth Layer

Genioglossus

02

Digastric Muscle (DG)

  • Has two bellies united by an intermediate tendon.
  • Anterior belly → unipennate
  • Posterior belly → bipennate

Origin

Anterior Belly (DGA)

From digastric fossa of mandible.

Posterior Belly (DGP)

From mastoid notch of temporal bone.

Fibres

  • Anterior belly → runs downwards and backwards.
  • Posterior belly → runs downwards and forwards.

Insertion

  • Both bellies meet at the intermediate tendon.
  • The intermediate tendon:
  • Perforates the stylohyoid.
  • Is held by a fibrous pulley to the hyoid bone.

Nerve Supply

Anterior Belly

nerve to mylohyoid (V3)

Posterior Belly

facial nerve (VII)

Actions

  1. Depresses mandible when the mouth is opened widely or against resistance.
  2. It is secondary to lateral pterygoid.
  3. Elevates hyoid bone.
03

Stylohyoid Muscle (SH)

  • Small muscle.
  • Lies on the upper border of posterior belly of digastric (DGP).

Origin

Posterior surface of styloid process.

Fibres

Tendon is perforated by the DGP tendon.

Insertion

Junction of body and greater cornua of hyoid bone.

Nerve Supply

Facial nerve (VII)

Actions

  1. Pulls hyoid bone upwards and backwards.
  2. With other hyoid muscles, it fixes the hyoid bone.
04

Mylohyoid Muscle (MH)

  • Flat, triangular muscle.
  • The two mylohyoid muscles form the floor of the mouth cavity.
  • Lies deep to the anterior belly of digastric (DGA).

Origin

Mylohyoid line of mandible.

Fibres

Run medially and slightly downwards.

Insertion

Posterior Fibres

Body of hyoid bone.

Middle and Anterior Fibres

Median raphe, between mandible and hyoid bone.

Nerve Supply

Nerve to mylohyoid (V3)

Actions

  1. Elevates the floor of mouth in the first stage of deglutition.
  2. Helps in:
    • Depression of mandible
    • Elevation of hyoid bone
05

Geniohyoid Muscle (GH)

  • Short and narrow muscle.
  • Lies above the medial part of mylohyoid.

Origin

Inferior genial tubercle of mandible.

Fibres

Run backwards and downwards.

Insertion

Anterior surface of body of hyoid bone.

Nerve Supply

C1 through hypoglossal nerve.

Actions

  1. Elevates hyoid bone.
  2. May depress mandible when the hyoid is fixed.
06

Hyoglossus

  • It is a muscle of tongue.
  • It forms an important landmark in this region.

Origin

Whole length of greater cornua and lateral part of body of hyoid bone.

Fibres

Run upwards and forwards.

Insertion

Side of tongue between:

  • Styloglossus
  • Inferior longitudinal muscle of tongue

Nerve Supply

Hypoglossal (XII) nerve.

Actions

  • Depresses tongue.
  • Makes dorsum convex.
  • Retracts the protruded tongue.
07

Genioglossus

  • It is the bulkiest muscle of tongue.
  • It is fan-shaped.

Origin

Superior genial tubercle of mandible.

Fibres

Fibres radiate.

Insertion / Distribution of Fibres

Upper Fibres

Pass upwards and forwards to the tip of tongue.

Middle Fibres

Pass along the whole length of dorsum.

Lower Fibres

Pass into the body of hyoid.

Nerve Supply

Hypoglossal (XII)

Action

  • Pulls the posterior part of tongue forwards → protrudes tongue.
  • It is a life-saving muscle.
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Relations of Posterior Belly of Digastric

Superficial

  1. Mastoid process with:
    • Sternocleidomastoid
    • Splenius capitis
    • Longissimus capitis
  2. Stylohyoid
  3. Parotid gland with retromandibular vein
  4. Submandibular salivary gland and lymph nodes
  5. Angle of mandible with medial pterygoid

Deep

  1. Transverse process of atlas with:
    • Superior oblique
    • Rectus capitis lateralis
  2. Internal carotid, external carotid, lingual, facial and occipital arteries
  3. Internal jugular vein
  4. Vagus, accessory and hypoglossal cranial nerves
  5. Hyoglossus muscle

Upper Border

  1. Posterior auricular artery
  2. Stylohyoid muscle

Lower Border

Related to occipital artery.
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Relations of Mylohyoid

Superficial

  1. Anterior belly of digastric
  2. Superficial part of submandibular salivary gland
  3. Mylohyoid nerve and vessels
  4. Submental branch of facial artery

Deep

Hyoglossus

Its superficial relations are:

  • Styloglossus
  • Lingual nerve
  • Submandibular ganglion
  • Deep part of submandibular salivary gland
  • Submandibular duct
  • Hypoglossal nerve
  • Venae comitantes hypoglossi

Genioglossus

Its superficial relations are:

  • Sublingual salivary gland
  • Lingual nerve
  • Submandibular duct
  • Lingual artery
  • Hypoglossal nerve
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Relations of Hyoglossus

Superficial

  • Styloglossus
  • Lingual nerve
  • Submandibular ganglion
  • Deep part of submandibular gland
  • Submandibular duct
  • Hypoglossal nerve
  • Veins accompanying it

Deep

  1. Inferior longitudinal muscle of tongue
  2. Genioglossus
  3. Middle constrictor of pharynx
  4. Glossopharyngeal nerve
  5. Stylohyoid ligament
  6. Lingual artery

Structures Passing Deep to Posterior Border of Hyoglossus

From above downwards:

  1. Glossopharyngeal nerve
  2. Stylohyoid ligament
  3. Lingual artery
SUPRAHYOID MUSCLES
Anatomy study notes.