Head and Neck 2: Muscles and Viscera

• The ear is divided into three sections: external (until the tympanic membrane), middle (contains the ossicles), and the inner ear (contains bony labrynth and receptors for balance and hearing)
• Between the middle ear and pharynx is the Eustachian tube (origin of clicking sound when swallowing)
• Two major landmarks are the two superficial muscles of the neck: trapezius and sternocleidomastoid, they form the anterior/posterior triangles of the neck and are both enclosed in investing fascia
• The anterior triangle of the neck is bordered by the SCM and mandible, and contains structures of the vascular and visceral compartments of the neck
• The posterior triangle of the neck is bordered by the SCM, clavicle and trapezius, and contains structures of the vertebral compartment of the neck
• Visceral compartment of the neck: structures such as pharynx, larynx, esophagus, thyroid gland, trachea, etc. enclosed in pretracheal fascia
• Vascular compartment of the neck: structures such as carotid arteries, internal jugular vein, and some cranial nerves
• Vertebral compartment of the neck: structures such as muscles, cervical spine, cervical spinal nerves
• Auricular group of muscles of facial expression: auricular muscles
• Nasal group of muscles of facial expression: procerus, nasalis, levator labii superioris alaeque nasi, depressor septi
• Procerus: depresses eyebrows and wrinkles glabellar skin (frowning)
• Nasalis: dilates the nostrils
• Levator labii superioris alaeque nasi: widens nostrils and elevates the upper lip (snarling)
• Depressor septi: pulls nasal septum inferiorly to widen the nasal opening
• Orbital group of muscles of facial expression: occipitofrontalis, corrugator supercilii, orbicularis oculi
• Occipitofrontalis: wrinkles forehead and raises eyebrow
• Corrugator supercilii: moves eyebrows down and inwards, makes the vertical wrinkles
• Orbicularis oculi: closes the eyelids
• Platysma: wrinkles the neck

  A)
• Orbicularis ori: closes oral fissure and forms the lips
• Mentalis: raises and protrudes lower lip (pout)
• Depressor labi inferioris: pulls lower lip down/to the side
• Depressor anguli oris: depress corners of the mouth (frown)
• Risorius: pulls angle of the mouth sidewise (smile)
• Zygomaticus major: draws angle of mouth superiorly and posteriorly (smile)
• Zygomaticus minor: pulls upper lip backward, upward and outward (smile)
• Levator labii superioris: elevates upper lip
• Levator anguli oris: elevates angle of the mouth medially
• Buccinator: forms the cheek
• muscles of facial expression

  A) auricular muscles

  B) procerus

  C) nasalis

  D) levator labii superioris alaeque nasi

  E) depressor septi

  F) occipitofrontalis

  G) corrugator supercilii

  H) orbicularis oculi

  
• Muscles of facial expression

  A) platysma

  B) levator anguli oris

  C) buccinator

  D) mentalis

  E) orbicularis ori

  F) risorius

  G) zygomaticus major

  H) zygomaticus minor

  I) levator labii superioris

  J) depressor anguli oris

  K) depressor labi inferioris

  
• At the zygomatic arch, above is the temporalis muscle and below is the masseter
• Temporalis: elevates and pulls back mandible, attached to zygomatic bone and lateral surface of the ramus of the mandible
• Masseter: elevates mandible, attached to the floor of the temporal fossa and the coronoid process, temporal crest and retromolar fossa of the mandible
• In the infratemporal fossa are the medial pterygoid and lateral pterygoid
• Medial pterygoid: elevates and allows sidways movement (contralateral excursion) of mandible, attached to the medial surface of the lateral plate of the pterygoid process and the medial surface of the angle of the mandible
• Lateral pterygoid: protrudes and allows sideways movement (contralateral excursion) of mandible, only muscle of mastication to open the mouth, attached to the lateral surface of the lateral plate of the pterygoid and the TMJ and neck of the condyle of the mandible
• Muscles of mastication

  A) temporalis

  B) medial pterygoid

  C) lateral pterygoid

  D) masseter

  
• Trapezius: rotates, elevates and depresses the scapula; attaches to the spine of scapula and clavicle, and the occipital bone and spinous process of thoracic vertebrae
• Sternocleidomastoid: flexes and turns head and neck sideways, attaches to the mastoid process and the sternum and clavicle