The Head and Neck, Pharynx, and Oral Cavity

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The Head and Neck, Pharynx, and Oral Cavity
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Neck Regions

• When dissecting the neck from the anterior
  surface, you will come across the HYOID BONE.
• The hyoid bone is the only bone in the body that
  does not articulate with other bones.

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• The base of the tongue is attached to the hyoid
  bone.
• The hyoid bone is attached by muscles to the
  skull, providing for flexibility for speech.
• It also attaches to the styloid process of the
  TEMPORAL BONE.
• The muscles in the neck are named for their
  points of attachment.

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• From the STERNUM to the THYROID CARTILAGE lies
  the STERNOTHYROID MUSCLE. This muscle lies
  lateral and deep to the STERNOHYOID MUSCLE.
• From the STERNUM to the MASTOID PROCESS lies the
  STERNOMASTOID MUSCLE.

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• From the CLAVICLE to the MASTOID PROCESS lies the
  CLEIDOMASTOID MUSCLE.
• In humans, the STERNOMASTOID and the
  CLEIDOMASTOID are one muscle called the
  STERNOCLEIDOMASTOID MUSCLE.

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• The DIGASTRIC MUSCLE opens the jaw and attaches
  to the mastoid process and the inner border of
  the mandible at the central portion (midline
  fusion area).

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stylohyoid
digastric
sternohyoid
omohyoid
sternocleidomastoid
thyrohyoid
trapezius
clavicle
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Cadaver Specimen of Lateral Neck
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Regions of the Neck

• Anterior Triangle
• -bounded by sternohyoid muscle, the
  digastric muscle, and the sternomastoid muscle.
• Posterior Triangle
• - bounded by the cleidomastoid muscle, the
  clavotrapezius muscle, and the clavicle.

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Anterior Triangle

• Thyroid Gland
• -bilobate
• -endocrine gland
• Common Carotid Arteries and Branches
• - cranial thyroid artery
• - muscular branch (lateral to the CTA)
• - cranial laryngeal artery
• - lingual artery (sublingual artery)
• - internal (brain) and external carotid
  arteries (passes deep to the digastric muscle

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• INTERNAL JUGULAR VEIN runs with the common
  carotid artery in the anterior triangle.
• The HYPOGLOSSAL NERVE (cranial nerve XII) runs
  with the sublingual artery.
• The SPINAL ACCESSORY NERVE (cranial nerve XI)
  innervates the cleidomastoid and trapezius
  muscles.
• The nerve that runs with the common carotid
  artery is the VAGUS NERVE (cranial nerve X) which
  is joined by the SYMPATHETIC TRUNK.

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Posterior Triangle

• The EXTERNAL JUGULAR VEIN runs obliquely across
  this triangle.
• The SPINAL ACCESSORY NERVE runs from the
  cleidomastoid and clavotrapezius. This nerve is
  the only structure found in both triangles.
• The SUBCLAVIAN ARTERY and VEIN are found deep to
  the clavicle.

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• Deep to the clavicle you will find the BRACHIAL
  PLEXUS. This complex of nerves are VENTRAL RAMI
  from
• C5-T1. It innervates the muscles and provides
  sensation to the upper extremity.

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Muscles of the Posterior Neck
Identify the Following Splenius
capitis Rhomboid major Rhomboid minor Supraspinal
ligament Trapezius Semispinalis capitis Splenius
cervicis Sternocleidomastoid
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The Larynx and Thyroid Gland

• The LARYNX (voice box) is a modified portion of
  the trachea.
• It is superior to the trachea.
• There are cartilaginous rings that are connected
  by dense connective tissue forming a tube.

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• The TYROID CARTILAGE is shaped like a shield when
  viewed from the anterior surface. This is the
  ADAMS APPLE. This is not a complete ring.
• On the posterior side of the thyroid cartilage,
  the CRICOID CARTILAGE extends superiorly to where
  the thyroid cartilage would be. This cartilage
  is sometimes called the SIGNET RING CARTILAGE.

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• It has a narrow band across the anterior side.
• It is superficial to the thyroid cartilage
  posteriorly where it is connected by the
  CRICOTHYROID LIGAMENT (dense connective tissue).
• Inferiorly, the cricoid is attached to the first
  ring to the trachea by dense CT.

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• The EPIGLOTTIS is a spade shade cartilage that is
  important during swallowing.
• It tips inferiorly to seal off the glottis and
  prevents food from entering the trachea.
• The ARYTENOID CARTILAGE is below the epiglottis
  at the entrance to the GLOTTIS.
• The GLOTTIS is a passageway into the trachea.
  The thyroid cartilage forms the walls of the
  glottis. The arytenoid cartilage extends
  inferiorly into the glottis.

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• The arytenoid cartilages anchor the vocal cords.
• The true vocal cords are located inferiorly
  inside the glottis.
• As air passes over the vocal cords they flutter,
  producing sound from the vibration.
• Pitch can be changed by tightening or loosening
  the cords.
• In humans, the tongue is used to make sense of
  the sounds (make words). You cannot talk if your
  tongue is not functioning.
• There are folds covering part of the epiglottis
  called FALSE VOCAL CORDS.

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Pharynx and Oral Cavity

• Superior to the ORAL CAVITY is the HARD PALATE
  composed of the MAXILLARY and PALATINE bones.
• Superior and posterior to the oral cavity are the
  INTERNAL NARES.
• From the internal nares, if we go anteriorly we
  will find the EXTERNAL NARES or NOSTRILS.

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• Posterior to the hard palate is the SOFT PALATE.
  This is muscular tissue that is moved during
  swallowing.
• Hanging from the soft palate is a conical
  structure called the UVULA.
• The two nasal cavities are separated by the NASAL
  SEPTUM which is formed by the union of the VOMER
  and PERPENDICULAR PLATE of the ETHMOID bones.

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3 Areas of the Oral Cavity

• OROPHARYNX
• -soft palate to epiglottis
• -two sets of TONSILS
• a. Palatine
• b. Lingual
• -the tonsils remove pathogens that enter
  the pharynx. They contain lymphocytes

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• 2. NASOPHARYNX
• -located superior and posterior to the
  soft palate.
• -contains the PHARYNGEAL TONSILS and
  TUBAL TONSILS

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• 3. LARYNGOPHARYNX
• -inferior to the epiglottis and
  posterior to the larynx.
• - this division opens into the esophagus
  and larynx.

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Sagital section of cadaver head Notice the nasal
conchae. They serve to expand the surface area
to warm and moisten breathed air. Also, notice
the position of the spinal cord within the
vertebral canal.
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Epiglottis
Hyoid Bone
Thyrohyoid Ligament
Thyroid Cartilage
Aryetnoid cartilage
Cricoid cartilage
trachea
ANTERIOR
Tracheal rings
POSTERIOR
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5 Openings into the Pharynx

• Mouth
• Left and right nasal passages
• Eustachian tubes (connect middle ear to the
  throat)
• Larynx
• Esophagus

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Swallowing

• Is a reflex.
• When the mouth closes, the soft palate is pushed
  superiorly and closes the nasal passages
• A sphincter valve closes off the eustachian tubes
• The glottis closes and respiration stops. The
  glottis also bends and closes the entrance into
  the larynx.
• The esophagus is opened by pressure of the food.
  This allows the epiglottis to open.
• Food then enters the esophagus.

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Teeth

• Very similar to bone.
• Three major components
• 1. hydroxyapatite Ca5(PO4)3(OH)
• 2. bone collagen
• 3. cells

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• The pH of the mouth is usually 7.2
• There are acids in the mouth that come from three
  sources
• 1. stomach acid during vomiting
• 2. foods
• 3. waste products of mouth bacteria

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Types of Teeth

• INCISORS chisel shaped for nipping food.
• CANINES cone shaped for tearing
• PREMOLARS
• MOLARS - grinding food
• 32 teeth in the Permanent Dentition
• 20 teeth in the Deciduous Dentition

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Tooth Anatomy

• Enamel hardest substance in the body
• Pulp Cavity contains arteries, veins, and
  nerves.
• Alveolus made of alveolar bone
• Root made of dentin
• Gingiva gum
• Periodontal membrane periosteum found around
  the tooth
• Cementum material that holds the tooth in the
  alveolus.

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Identify the Following
Incisors Molar Premolars Canines
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Salivary Glands

• When you dissect your cat, you will notice two
  muscles on the inside of the cheek.
• The DIGASTRIC MUSCLE opens the jaw.
• The MASSETER MUSCLE closes the jaw.

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• The masseter inserts on the mandible.
• Superficial to part of the masseter and anterior
  to the ear is the large PAROTID GLAND. This
  gland produces SALIVARY AMYLASE (ptyalin), a
  digestive enzyme.
• The parotid gland is GRANULAR, it is attached by
  fascia. It is also the largest of the salivary
  glands.

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• The parotid empties into the PAROTID DUCT which
  empties between the last two molars at the angle
  of the jaw.
• The parotid gland is an EXOCRINE GLAND. Exocrine
  glands empty via a duct to a specific location.
  The other type of gland is an ENDOCRINE GLAND
  that empties directly into the bloodstream.

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• Caudal and ventral to the parotid gland is the
  SUBMANDIBULAR GLAND (SUBMAXILLARY).
• The SUBMAXILLARY DUCT empties this gland. It
  runs on the lateral aspect of the digastric
  muscle.
• This gland carries saliva into the angle of the
  lower jaw.

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• The SUBLINGUAL GLAND is on the submaxillary duct.
  It is wedge shaped and it is lateral to the
  digastric muscle.
• The DORSAL and VENTRAL FACIAL NERVES run around
  the outline of the masseter muscle. These nerves
  come out in front of the ear from the
  STYLOMASTOID FORAMEN and branch across the face.

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Parotid Duct
Masseter muscle
Parotid gland
Submandibular gland
Sublingual gland
Submandibular Duct
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