SUPRAHYOID MUSCLES

Posterior belly of digastric

• The posterior belly of the digastric (latin: venter posterior musculi digastrici) is the largest of the two bellies of the digastric muscle, and it develops from the second pharyngeal arch.

Origin

• The posterior belly originates from the mastoid notch medial to the mastoid process on the temporal bone.

Insertion

• From the origin site the posterior belly of the digastric stretches forward and becomes or inserts into the intermediate tendon, which attaches to the hyoid bone.

Action

• Upon activation the posterior belly of the digastric elevates the hyoid bone.

Innervation

• The posterior belly of the digastric muscle receives nerve supply from the digastric branch of the facial nerve (CN VII).

Buccinator Muscle 

• Muscle of the cheek.
• The buccinator forms the muscular component of the cheek and is used every time air expanding the cheeks is forcefully expelled.
• It is in the space between the mandible and the maxilla, and is quite deep to the other facial muscles in the area.

 Origin

• The buccinator arises from the posterior part of the maxilla and mandible opposite the molar teeth and the pterygomandibular raphe, which is a tendinous band between the pterygoid hamulus superiorly and the mandible inferiorly and is a point of attachment for the buccinator and superior pharyngeal constrictor muscles.

Insertion

• Motor supply is from the buccal branch of the facial nerve (Cranial Nerve VII).
• Sensory supply is from the buccal branch which is one of the muscular branches of the trigeminal nerve (Cranial Nerve V).

Action

• Aids mastication, tenses cheeks in blowing and whistling, aids closure of mouth

The anterior belly of the digastric muscle is innervated by the mandibular division of the trigeminal nerve.

• The inferior alveolar nerve which give rise to the mylohyoid nerve innervates the mylohyoid muscle. 

• Masseter
• Temporalis
• Mylohyoid
• Anterior belly of digastric
• Tensor tympani
• Tensor veli palatini
• Lateral and medial pterygoid

• Inferior constrictor of pharynx
• Cricothyroid

• All the intrinsic muscles of the larynx except cricothyroid
• All the muscles of the pharynx except stylopharyngeus
• All the muscles of palate except tensor palati

D i.e. Sternocleidomastoid

Digastric, Omohyoid, Occipitofrontalis, Gastrocnemius, and Suspensory muscle of duodenum (i.e., muscle in Ligament of Treitz) are all digastric muscles i.e, muscles with two muscle bellies. Mn- “DOGS”

Sternocleidomastoid muscle has two heads not two bellies

D i.e. Facial nerve

 The main laryngeal elevators are: Digastric anterior and posterior, the stylohyoid, mylohyoid, geniohyoid, genioglossus, hyoglossus, and thyropharyngeus muscles

Ans. C. Mylohyoid

Submandibular gland

• This walnut sized gland lies below the mandible in the anterior part of digastric triangle. It is .1-shaped and consists of a large superficial and a small deep parts, separated by mylohyoid muscle and continuous with each other around the posterior border of mylohyoid muscle.

Superficial part

• It is situated in the anterior part of digastric triangle. The gland is partially closed in a capsule formed by two layers of deep cervical fascia. It has three surfaces : (i) inferior, (ii) lateral, and (iii) medial.

1. Inferior surface is covered by skin, platysma, cervical branch of facial nerve, deep fascia, facial vein and submandibular lymph nodes.
2. Lateral surface is related to submandibular fossa (on mandible), medial pterygoid (insertion) and facial artery.
3. Medial surface is related to mylohyoid, hyoglossus and styloglossus muscles.

Deep part

• It lies on the hyoglossus muscle deep to mylohoid. It is related above to lingual nerve and submandibular ganglion; and below to hypoglossal nerve.

Ans. is `a’ i.e., Facial nerve

Anterior belly of digastric is supplied by nerve to mylohyoid (a branch of mandibular nerve) & posterior belly is supplied by facial nerve.

Ans.C. Digastric

Anterior belly of digastric is supplied by nerve to mylohyoid (a branch of mandibular nerve) & posterior belly is supplied by facial nerve.

Ans.A. Mylohyoid

The mylohyoid muscle of each side unite to make a thin sheet of the muscular floor (oral diaphragm) of the oral cavity.

It arises from the mylohyoid line of mandible. Fibers run medially and slightly downwards.

function:

Elevates floor of the mouth in the first stage of deglutition. It helps in the depression of mandible, and elevation of the hyoid bone.