The Head and Neck

Upper Respiratory Tract

Nasal Cavity Nostril Oral Cavity Larynx Pharynx

Nose

Only portion of the RT that is externally visible

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

Air enters here during breathing Passes through the

nares (nostrils)

Divided into R and L by nasal septum

Continuous with the nasopharynx through the internal nares

Nasal Cavity

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

palatine (horizontal plate) Lateral walls – nasal bones, superior and middle nasal

conchae (ethmoid bone), inferior nasal conchae, maxilla, palatine bone

Hard palate Palatine bones and maxillary bone

Soft palate Muscular posterior portion

Nasal Cavity 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)

Lining of the Nasal Cavity

Olfactory Mucosa Roof of nasal cavity Houses small receptors

Respiratory Mucosa Pseudostratified ciliated

columnar epithelium Goblet cells Lamina propria

Mucous and serous cells Venous plexus Function is to filter and

warm inhaled air

Nasal Conchae

Project medially from each lateral wall 3 structures:

Superior of ethmoid bone Middle of ethmoid bone Inferior

Functions: 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 (throat)

Lined with skeletal muscle Divided into:

Nasopharynx Oropharynx Laryngopharynx

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: Postreior 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

Tonsils

Lymphoid organ Swellings of the mucosa

lining the pharynx Form ring around the

entrance to the pharynx 4 groups:

Palatine Lingual Pharyngeal Tubal

Remove pathogens MALT

Laryngopharynx

Location: Lies posterior to larynx Continuous with the

esophagus and larynx

Common passageway for food and air

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 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 Composed of laryngeal

prominence Adam’s Apple!!

Laryngeal Cartilages

Cricoid Inferior to thyroid

cartilage Forms a complete ring Perched on top of the

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

Vocal Cords

Located in the larynx Mucosal folds formed by vocal

ligaments Composed of elastic fibers Run from arytenoid cartilages to

the thyroid cartilages 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 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,

Triangles of the Neck

Neck subdivided into two trianglesSeparated by the sternocleidomastoid

muscleAnterior trianglePosterior triangle

Triangles of the Neck: Posterior

Boundries: Anterior - sternocleidomastoid Posterior - trapezius Inferior – clavicle

Contents: Nerves: accessory nerve,

cranial plexus, 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: Carotid Vein: Internal jugular, External

jugular Nerve: Acccessory

Mouth and Associated Organs

Mouth Tongue Salivary glands Teeth

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 (pg 266-67)

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 smooth 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)

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 Lie in sockets (alveoli) in

gum-covered margins in mandible and maxilla

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

Function: Ingestion and mechanical

breakdown of food Periodontal ligaments

(collagen fibers) anchor tooth in bony socket Gomphosis - form of

immovable articulation; a peglike part fits into a cavity

Continous with gingiva (gum)

Teeth

Regions: Crown

Covered with enamel Area above gingiva

Neck (gumline) Root

Area below 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 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 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

X 2 = 20

****No premolars!

Deciduous teeth dental formula:

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, 3M2I, 1C, 2P, 3M

X 2 = 32

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!!!!!!