The Head and Neck Lecture Presentation

The Head and Neck
Upper Respiratory Tract

• Nose
• Nostril
• Nasal Cavity
• Oral Cavity
• Pharynx

Nose

• Nose is the only portion of the RT that is externally visible
• CT, bone, hyaline cartilage
• Air enters here during breathing
• Passes through the external nares (nostrils)

Vestibule

• Superior to nostrils
• Skin lined with:
•  Sebaceous glands
• Greasy secretion
• Collect dirt
• Lubricate
• Kill bacteria
• Sweat glands
• Acidic
• Slows growth of bacteria
• Hair follicles
• Trap small particles of dirt
• Vibrissae
• Nose hairs
• Filter large particles (insects)

Nasal Cavity
Functions:
Provides airway for respiration
Moistens and warms air
Filters inhaled air
Resonating chamber for speech
Houses olfactory receptors
2 divisions:
External nose
Internal nasal cavity
Nasal Cavity

• Divided into R and L by nasal septum
• Continuous with the nasopharynx through the internal nares (choanae)

Nasal Cavity

• Boundries:
• Roof – ethmoid bone (cribiform plate)
• Floor – maxilla (palatine process)

                    palatine (horizontal plate)

• Lateral walls – nasal bones, superior and middle nasal conchae of ethmoid bone, inferior nasal conchae, maxilla, palatine bone
• Hard palate
• Palatine bones and maxillary bone
• Soft palate
• Skeletal muscle posterior portion
• End in uvula

Lining of the Nasal Cavity

• Respiratory Mucosa    
• Pseudostratified ciliated columnar epithelium
• Goblet cells
• Lamina propria
• Mucous and serous cells
• Venous plexus
• Function is to filter and warm inhaled air
• Highly innervated
• Sneeze!
• Olfactory Mucosa
• Roof of nasal cavity
• Houses smell receptors
• No goblet cells
• Cilia modified for olfaction

Nasal Conchae

• Project medially from each lateral wall
• 3 structures:
• Superior of ethmoid bone
• Middle of ethmoid bone
• Inferior
• Functions:
• Create turbulence to increase:
• Filters air
• Heats air
• Moistens air
• Reclaim heat and moisture during exhalation

Paranasal Sinuses

• Air filled cavities that surround the nasal cavity
• Lined by mucosa
• Perform same function as nasal cavity and lightens skull
• Located in Frontal, Ethmoid, Sphenoid, Maxilla bones

Pharynx

• Connects the nasal cavity and mouth to larynx and esophagus
• Extends from base of skull to level of C6 vertebra
• Common passage for food and air
• Lined with skeletal muscle
• Divided into:
• Nasopharynx
• Oropharynx
• Laryngopharynx

Tonsils

• Lymphoid organ
• MALT
• Swellings of the mucosa lining the pharynx
• Form ring around the entrance to the pharynx
• 4 groups:
• Palatine
• Lingual
• Pharyngeal
• Tubal
• Remove pathogens

Nasopharynx

• Location:
• Posterior to nasal cavity
• Inferior to sphenoid bone
• Superior to level of soft palate
• ONLY an air passageway
• Closed off during swallowing by the soft palates’ uvula
• Giggling!
• Ciliated pseudostratified epithelium
• Contain:
• Pharyngeal tonsils (adenoids)
• Tubal tonsils

Oropharynx

• Location:
• Posterior to the oral cavity
• Extends inferiorly from level of the soft palate to level of the esophagus
• Swallowed food and inhaled air pass through here
• Stratified squamous epithelium
• Contain:
• Palatine tonsils
• Lingual tonsils

Laryngopharynx

• Location:
• Lies posterior to larynx
• Continuous with the esophagus and larynx
• Common passageway for food and air
• Food – esophagus
• Air - larynx
• Stratified squamous epithelium

Larynx

• “Voice box”
• Extends from C4 to C6
• Attachments:
• Hyoid bone superiorly
• Continuous with trachea inferiorly
• Functions:
• Vocalization
• Provides open airway
• Switches to route air and food into proper channels
• Innervation: Vagus
• Superior part = stratified squamous epithelium
• Below vocal cords= ciliated pseudostratified columnar

Larynx

• All hyaline cartilage except epiglottis
• Composed of 9 cartilages connected by membranes and ligaments:
• 1 Thyroid
• 1 Cricoid
• 1 Epiglottis
• 2 Arytenoid
• 2 Corniculate
• 2 Cuneiform

Laryngeal Cartilages

• Thyroid Cartilage
• Large
• Shield shaped
• Formed by 2 plates
• Contains laryngeal prominence
• Adam’s Apple!!

Laryngeal Cartilages

• Cricoid
• Inferior to thyroid cartilage
• Forms a complete ring
• Directly superior to trachea

Laryngeal Cartilages

• Epiglottis
• Composed of elastic cartilage
• Covered by mucosa
• Projects upward from anterior wall of laryngeal inlet to level of base of tongue
• Close off larynx during swallowing

Vocal Cords

• Located in the larynx
• Mucosal folds formed by vocal ligaments
• Composed of elastic fibers
• Run from arytenoid cartilages (posterior) to the thyroid cartilages (anterior)
• Exhaled air passes over them and causes vibration
• Force of air = volume
• Length & tension of folds = pitch
• False vocal cords
• Vestibular folds (superior to true)

Thyroid Gland

• Location:
• In anterior neck
• On trachea, inferior to larynx
• 2 lateral lobes
• Connected by the isthmus
• Butterfly shape
• Largest endocrine gland in body
• Produces Thyroid hormone (TH)
• Increases metabolic rate
• Calcitonin
• Depresses excess levels of Ca+ in blood

Thyroid Gland

• Internally, composed of follicles
• Follicular cells
• TH
• Parafollicular cells
• Calcitonin
• Blood supply
• Superior thyroid arteries
• Branches of external carotids
• Inferior thyroid arteries
• Branches of subclavians

Parathyroid Gland

• Two pairs
• Located on the deep surface of the lateral lobes of the thyroid gland
• Produce parathyroid hormone
• Increases blood calcium levels

Hyoid Bone

• Location:
• Inferior to mandible
• In anterior neck
• Associated with the skull
• Only bone in skeleton that does not articulate directly to another bone!!!
• Attaches via ligaments to temporal bone, larynx
• Composed of:
• Body
• 2 pairs of horns
• Functions:
• Moveable base for tongue
• Points of attachment for larynx and neck muscles
• Sternohyoid, thyrohyoid,

Oral Cavity and Associated Organs

• Mouth
• Tongue
• Teeth
• External Salivary glands

Mouth - Oral Cavity

• Food enters alimentary canal through here
• Mucosa-lined
• Thick stratified squamous epithelium, with keratinization in some areas
• Boundaries:
• Lips anteriorly
• Cheeks laterally
• Palate superiorly
• Tongue inferiorly
• Oropharynx posteriorly
• Mouth divided into 2 parts:
• Vestibule
• Oral cavity proper

Mouth

• Lips (labia) and Cheeks
• Keep food inside mouth during chewing
• Composed of skeletal muscle surrounded by skin
• Lips formed by orbicularis oris muscle
• Cheeks; Muscles of Mastication
•  Temporalis & Masseter (elevate mandible, close mouth)
•  Buccinator (chewing)
•  Digastric (lower mandible against resistance, opens mouth)
•  Pterygoids (lateral movements)
• Palate: forms the roof of the mouth
• Soft palate (posterior) rises to close off nasopharynx during swallowing; made of skeletal muscle
• Hard palate (anterior) provides surface for tongue to force food against during chewing

Tongue

• Functions
• Grips and moves food between teeth

          during chewing

• Mixes food with saliva = BOLUS
• Moves bolus down pharynx
• Speech production
• Houses taste buds (= gustation)
• Creates floor of mouth
• Attachments: hyoid, mandible, styloid process, soft palate
• Made of Skeletal muscle with a CT septum
• Intrinsic muscles (change shape; rolling)
• Extrinsic muscles (movement; protrude, retract)
• Motor = Hypoglossal (CN XII)
• Sensory = Mandibular (CN V3), Facial (CN VII), Glossopharyngeal (CN IX)

Moving Bolus

• Swallowing voluntarily initiated (pharynx)
• Peristalsis = propulsion
• Involuntary
• Alternate waves of contraction and relaxation of muscles in organ walls (e.g. esophagus)
• Squeezes food from one organ to next
• Some mixing

Salivary Glands

• Compound tubuloalveolar glands
• Intrinsic salivary glands
• In mucosa of tongue, palate, lips and cheeks
• Keeps mouth moist at all times
• Extrinsic salivary glands
• Lie external to mouth
• Connected by ducts
• Secrete only during eating or prior to (“mouth watering”)
• 3 paired glands:
• Parotid
• Submandibular
• sublingual

Salivary Glands

• Produce saliva
• Mixture of water, ions, mucus and enzymes
• Moistens mouth
• Dissolves food for taste
• Binds food into a bolus
• Enzymes digest starch
• Bicarbonate buffer neutralizes acids
• Kill microorganisms
• Contains proteins to promote growth of beneficial bacteria

Teeth – From Eruption to Edentate

• Function:
• Ingestion and mechanical breakdown of food
• Have 2 sets of teeth (dentitions)
• Primary dentition / deciduous (milk) teeth
• Permanent dentition
• Incisors: rip, cut
• Canines: tear and pierce
• Premolars: grinding
• Molars: grinding

Teeth

• Gomphosis
• Synarthrosis
• Peg in socket with ligament
• The sockets (alveoli) are in gum-covered margins in mandible and maxilla
• Periodontal ligaments (collagen fibers) anchor tooth in bony socket
• Continous with gingiva (gum)

Teeth Substances

• Enamel
• Made of calcium salts
• Avascular, acellular
• Not renewed or replaced
• HARDEST substance in body!!!!
• Dentin
• Underlines enamel
• Forms bulk of tooth
• Made of minerals and collagen
• Maintained during life
• Harder than bone
• Cementum
• Calcified external surface
• Attaches tooth to periodontal ligament

Teeth

• Regions:
• Crown
• Covered with enamel
• Projecting into oral cavity
• Neck (gumline)
• Root
• Area beyond neck in alveolus
• Pulp cavity
• Center of tooth
• Loose CT with vessels and nerves
• Supplies nutrients to hard tissues

Teeth

• Root Canal
• Portion of the pulp cavity in the root
• Apical foramen
• Opening into the root canal at the tip of each root
• Blood supply
• Superior/Inferior Alveolar artery, branches of External Carotid artery
• Innervation
• Maxilla = Superior Alveolar Nerves
• Mandible = Inferior Alveolar Nerves

Teeth at Birth

• Number of erupted teeth = 0
• Jaws covered by gingiva (gums)
• Lots of drooling!!!

First Teeth – 6 Months

• Lower central incisors first to appear
• 8 Incisors = 6-10 months
• 4 Canines = 16-20 months
• 4 1st Molars = 12-16 months
• 4 2nd Molars = 20-24 months
• 20 deciduous teeth emerge by age 2
• Dental formula
• Describes the number and position of classes of teeth (half of the mouth)

2I, 1C, 2M   
2I, 1C, 2M
Adolescence – Adult

• Permanent teeth enlarge and develop
• Roots of deciduous teeth reabsorbed
• Teeth loosen and fall out
•  Begin to erupt from 7-13 years of age
• Third molars (wisdom teeth) emerge from 17-25 years
• May be absent!!

• Adult dental formula:

2I, 1C, 2P, 3M
2I, 1C, 2P, 3M
Tooth Troubles

• Cavities (caries)
• Demineralization of enamel by bacteria
• In severe cases, erodes the dentin of tooth
• Most severe cases erosion penetrates pulp cavity

Tooth Troubles

• Gingivitis
• Inflammation of the gingiva caused by plaque accumulation
• Leads to…….
• Periodontitis
• Infection of periodontal ligament leading to its destruction along with the bone around the teeth
• Leads to toothlessness!

Triangles of the Neck

• Neck subdivided into two triangles
• Separated by the sternocleidomastoid muscle
• Anterior triangle
• Posterior triangle

Triangles of the Neck: Posterior

• Boundries:
• Anterior - sternocleidomastoid
• Posterior - trapezius
• Inferior – clavicle
• Contents:
• Nerves: accessory nerve, phrenic nerve, brachial plexus
• Artery: Subclavian
• Vein: External jugular

Triangles of the Neck: Anterior

• Boundries:
• Anterior - midline
• Posterior - sternocleidomastoid
• Superior – inferior margin of the mandible
• Contents:
• Glands: Submandibular
• Muscles: Suprahyoid and infrahyoid muscles
• Artery: Common carotid
• Vein: Internal jugular, External jugular
• Nerve: Accessory

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