Muscles of head and neck

• Muscles of the head


  Include the tongue, muscles of facial expression and muscles of mastication
• Tongue


  Comprises of intrinsic and extrinsic muscles, receives motor innervation from the hypoglossal nerve, sensation can be divided into taste and general sensation
• Muscles of facial expression


  Located in the subcutaneous tissue, attach into the skin and contract to exert their effects, can be divided into orbital, nasal and oral groups
• Orbital muscles of facial expression


  Exert control over movement of the eyelids
• Nasal muscles of facial expression


  Exert control over movements of the nose and the skin around it
• Oral muscles of facial expression


  Responsible for movements of the mouth and lips
• Extra-ocular muscles


  Located within the orbit, control the movements of the eyeball and superior eyelid
• Muscles of the neck

  Consist of 3 main groups: anterior, lateral and posterior
• Anterior neck muscles


  • Superficial muscles (platysma, sternocleidomastoid)
  • Suprahyoid muscles
  • Infrahyoid muscles
  • Scalene muscles
• Platysma


  Sheet-like muscle that lies within the subcutaneous tissue of the anterior neck, superficial to the investing layer of deep cervical fascia
• Suprahyoid muscles


  Group of four muscles located superior to the hyoid bone, act to elevate the hyoid bone
• Stylohyoid

  Thin muscular strip located superiorly to the posterior belly of the digastric muscle, arises from the styloid process of the temporal bone and attaches to the lateral aspect of the hyoid bone, initiates a swallowing action by pulling the hyoid bone in a posterior and superior direction
• Sternocleidomastoid


  Large, two-headed muscle of the neck, clavicular head originates from the medial third of the clavicle, sternal head arises from the manubrium of sternum, heads come together and ascend diagonally to insert onto the mastoid process of the temporal bone
• Digastric


  Comprised of two muscular bellies connected by a tendon, anterior belly arises from the digastric fossa of the mandible, posterior belly arises from the mastoid process of the temporal bone, depresses the mandible and elevates the hyoid bone
• Mylohyoid


  Broad, triangular shaped muscle that forms the floor of the oral cavity and supports the floor of the mouth, originates from the mylohyoid line of the mandible and attaches onto the hyoid bone, elevates the hyoid bone and the floor of the mouth
• Geniohyoid


  Located close to the midline of the neck, deep to the mylohyoid muscle, arises from the inferior mental spine of the mandible and travels inferiorly and posteriorly to attach to the hyoid bone, depresses the mandible and elevates the hyoid bone
• Infrahyoid muscles


  • Superficial plane (omohyoid, sternohyoid)
  • Deep plane (sternothyroid, thyrohyoid)
• Omohyoid


  Comprised of two muscle bellies connected by a muscular tendon, inferior belly arises from the scapula and runs superomedially underneath the sternocleidomastoid muscle, superior belly ascends to attach to the hyoid bone, depresses the hyoid bone
• Sternohyoid


  Located within the superficial plane, originates from the sternum and sternoclavicular joint and ascends to insert onto the hyoid bone, depresses the hyoid bone
• Sternothyroid


  Wider and deeper than the sternohyoid, located within the deep plane, arises from the manubrium of the sternum and attaches to the thyroid cartilage, depresses the thyroid cartilage
• Thyrohyoid


  Short band of muscle, thought to be a continuation of the sternothyroid muscle, arises from the thyroid cartilage of the larynx and ascends to attach to the hyoid bone, depresses the hyoid, can elevate the larynx if the hyoid bone is fixed
• Lateral neck muscles


  Also called the lateral vertebral muscles, include the anterior, middle and posterior scalene muscles
• Scalene muscles

  Three paired muscles (anterior, middle and posterior) that form part of the floor of the posterior triangle of the neck, act as accessory muscles of respiration and perform flexion at the neck
• Anterior scalene


  Lies on the lateral aspect of the neck, deep to the sternocleidomastoid, originates from the anterior tubercles of the transverse processes of C3-C6 and attaches onto the scalene tubercle on the first rib, elevation of the first rib, ipsilateral contraction causes ipsilateral lateral flexion of the neck, bilateral contraction causes anterior flexion of the neck
• Middle scalene


  Largest and longest of the three scalene muscles, has several long, thin muscle bellies arising from the cervical spine which converge into one large belly that inserts into the first rib, elevation of the first rib, ipsilateral contraction causes ipsilateral lateral flexion of the neck
• Posterior scalene


  Smallest and deepest of the scalene muscles, unlike the anterior and middle scalene muscles it inserts into the second rib, elevation of the second rib, ipsilateral lateral flexion of the neck
• Brachial plexus and subclavian artery


  Pass between the anterior and middle scalene muscles, important anatomical landmark for interscalene block
• Subclavian vein and phrenic nerve


  Pass anteriorly to the anterior scalene, subclavian vein courses horizontally across it, phrenic nerve runs vertically down the muscle
• Posterior neck muscles


  Can be divided into three layers: superficial (trapezius, splenius capitis, splenius cervicis), deep (cervical transversospinalis muscles), and deepest (suboccipital muscles)
• Splenius capitis


  Originates from the spinous processes of vertebrae C7-T3 and the nuchal ligament, inserts just below the lateral superior nuchal line of the occipital bone and the mastoid process of temporal bone
• Splenius cervicis


  Arises from the spinous processes of vertebrae T3-T6, inserts onto the transverse processes of vertebrae C1-C3
• Suboccipital muscles


  Group of four muscles situated underneath the occipital bone, deep to the sternocleidomastoid, trapezius, splenius and semispinalis muscles, collectively act to extend and rotate the head
• Rectus capitis posterior major


  Largest of the rectus capitis muscles, located laterally to the rectus capitis posterior minor, originates from the spinous process of C2 and inserts into the lateral part of the inferior nuchal line of the occipital bone, extension and rotation of the head
• Rectus capitis posterior minor


  Most medial of the suboccipital muscles, runs from the posterior tubercle of C1 to the medial part of the inferior nuchal line of the occipital bone, extension of the head
• Obliquus capitis inferior


  Most inferiorly positioned of the suboccipital muscles, originates from the spinous process of C2 and attaches into the transverse process of C1, extension and rotation of the head
• Obliquus capitis superior


  Located laterally in the suboccipital compartment, originates from the transverse process of C1 and attaches into the occipital bone between the superior and inferior nuchal lines, extension of the head
• Muscles of facial expression


  Located in the subcutaneous tissue, originating from bone or fascia and inserting onto the skin, contract to pull on the skin and exert their effects
• Innervation of facial muscles


  All the muscles of facial expression are innervated by the facial nerve (CN VII)
• Groups of facial muscles


  • Orbital
  • Nasal
  • Oral
• The orbital group of facial muscles contains two muscles associated with the eye socket, controlling the movements of the eyelids