NECK

• Neck


  • Compartmentalized
  • Posterior compartment - Vertebrae and muscles which support and move head & neck
  • Anterior compartment - Viscera and rostral continuation GI & Respiratory System
  • Lateral compartment - Blood vessels & nerve

  
• Posterior compartment


  • Muscles move head and neck
• Anterior compartment


  • Viscera
  • Larynx is part of upper end of respiratory system - specialized for sound production
  • Acts as 'sphincter' of respiratory system - Thyroid cartilage is Adam's apple
  • Larynx & Esophagus open into pharynx
  • Pharynx - a tube of muscles & fascia that opens to nasal and oral cavities

  
• Hyoid bone


  • Moveable, changes shape in swallowing, speech
  • Attached to larynx & tongue; free floating; attached by ligaments and moved by muscles
  • Muscles that move hyoid bone move larynx & tongue, for Swallowing, Talking

  
• Lateral compartment


  • Carotid Sheath
  • Contained in Carotid Sheath: Common and Internal Carotid arteries, Int. jugular vein, Vagus nerve

  
• Muscles of neck


  • Sternocleidomastoid
  • Scalenus Anterior and Scalenus Medius
  • Infrahyoid muscles
  • Suprahyoid muscles
• Sternocleidomastoid


  • Two heads - Manubrium of Sternum, Clavicle - medial 1/3
  • Inserts to Mastoid process of temporal bone
  • Acts - bilateral - flex head unilateral rotated head, face to directed opposite side
  • Innervated by CN XI Accessory nerve

  
• Scalenus Anterior and Scalenus Medius


  • Origin - Vertebrae - trans processes upper cervical
  • Insertion - rib 1
  • Action - flex neck & elevate rib 1
  • Innervated by ventral rami of cervical spinal nerve

  
• Infrahyoid muscles


  • Omohyoid
  • Sternohyoid
  • Sternothyroid
  • Thyrohyoid
• Omohyoid


  • Two bellies - Inferior belly from Scapula - medial to suprascapular notch, Intermediate tendon to clavicle, rib1; Superior belly to hyoid
  • All depress hyoid
• Sternohyoid


  • Origin - Manubrium & clavicle
  • All depress hyoid
• Sternothyroid


  • Origin - manubrium
  • Insertion - thyroid cartilage; also depresses larynx
  • All depress hyoid
• Thyrohyoid


  • Origin - thyroid cartilage; also elevates larynx
  • All depress hyoid

  
• Suprahyoid muscles


  • Digastric
  • Stylohyoid
  • Mylohyoid
  • Geniohyoid
• Digastric


  • Two bellies - Posterior belly from Temporal Bone, mastoid notch (medial to mastoid process), Anterior belly from Mandible
  • Innervated by CN VII and CN V
  • Acts - Depress mandible; Major effect is to Open Mouth

  
• Stylohyoid


  • Origin - styloid process of temporal bone
  • Tendon splits to surround digastric tendon
  • Innervated by CN VII
  • All elevate hyoid

  
• Mylohyoid


  • Forms muscular floor of mouth
  • Origin - mylohyoid line one Inner side of mandible
  • Action - Elevates floor of mouth in swallowing
  • Innervated by CN V - from V3
  • All elevate hyoid
• Geniohyoid


  • Origin - inner side of mandible above mylohyoid
  • Action - Elevates hyoid and draws forward
  • Innervated by C1 branch hitch-hiking with Hypoglossal nerve (CN XII)
  • All elevate hyoid

  
• Nerves of neck


  • Cervical plexus (C2-C4)
  • Ansa cervicalis
• Cervical plexus


  • From C2 - C4 ventral primary rami
  • Branches: Lesser occipital, Great auricular, Transverse cervical, Supraclavicular

  
• Ansa cervicalis


  • Fibers from C1 join Hypoglossal Nerve (XII)
  • Some leave & join fibers of C2 & C3 to form ANSA (loop) Cervicalis
  • Other fibers continues with XII to innervate Thyrohyoid & Geniohyoid
• Arteries of head and neck


  • Subclavian artery
  • External carotid artery

  
• Subclavian artery

  • Divided into 3 parts by scalenus anterior muscle
  • Part 1 (medial to scal. ant): Vertebral a., Int. thoracic a., Thyrocervical trunk
  • Part 2 (posterior to scal. ant.): Costocervical trunk
  • Part 3 (lateral to scalenus ant): No Branches

  
• External carotid artery


  Branches: Superior thyroid, Ascending pharyngeal a, Lingual a, Facial a, Occipital a, Posterior auricular a

  
• Veins of neck


  • Superficial Temporal & Maxillary vv. form Retromandibular V.
  • Retromand. V. Divides Ant. (AD) and Post (PD) divisions
  • Ant. Division joins Facial V. to form Common Facial V. - Int. jugular V.
  • Post. Division joins post. Auricular V. to form External Jugular V - Subclavian V.
  • Ant. Jugular from veins below mandible - Ext. Jugular above clavicle

  
• Fascia of neck


  • Superficial fascia - Encloses platysma muscle
  • Deep cervical fascia - Investing layer, Pretracheal layer, Prevertebral layer, Carotid sheath

  
• To locate structures in neck on patient or in practical exam most useful landmark is STERNOCLEIDOMASTOID MUSCLE

  
• Carotid sheath


  A local condensation of the prevertebral, the pretracheal, and the investing layers of the deep fascia that surrounds the common and internal carotid arteries, the internal jugular vein, the vagus nerve, and the deep cervical lymph nodes

  
• Investing layer


  • A thick layer that encircles the neck, splitting to enclose the trapezius and the sternocleidomastoid muscles
• Pretracheal layer


  • A thin layer attached above to the laryngeal cartilages, surrounding the thyroid and the parathyroid glands and enclosing the infrahyoid muscles

  
• The sternocleidomastoid muscle is the most useful landmark to locate structures in the neck on a patient or in a practical exam

  
• Anterior triangle of the neck


  Bounded by the midline of the neck anteriorly, the sternocleidomastoid muscle posteriorly, and the mandible superiorly

  
• Posterior triangle of the neck


  Bounded by the sternocleidomastoid muscle anteriorly, the trapezius muscle posteriorly, and the clavicle inferiorly

  
• The thyroid gland weighs 10 to 20 grams in normal adults
• Thyroid volume measured by ultrasonography is slightly greater in men than women
• Thyroid volume increases with age and body weight, and decreases with increasing iodine intake
• The thyroid is one of the most vascular organs in the body

  
• Arterial blood supply to the thyroid gland

  • Primarily from the right and left superior and inferior thyroid arteries, derived from the external carotid arteries and thyrocervical trunk, respectively

  
• Venous drainage of the thyroid gland


  • Superior, middle, and inferior thyroid veins that drain into the internal jugular vein and innominate vein
• Superior thyroid artery


  • Branch of the external carotid artery, extending inferiorly to the superior pole of the thyroid lobe, and is the landmark for identification of the superior laryngeal nerve