The Head and Neck

Upper Respiratory Tract Nose Nostril Nasal Cavity Oral Cavity Pharynx pg 992

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) pg 1023

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) pg 1013

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 pg 1023

Nasal Cavity Divided into R and L by nasal septum Continuous with the nasopharynx through the internal nares (choanae) pg 992

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 pg 1023

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 pg 1018

Pharynx Connects the nasal cavity and mouth to larynx and esophagus Extends from base of skull to level of C 6 vertebra Common passage for food and air Lined with skeletal muscle Divided into:  Nasopharynx  Oropharynx  Laryngopharynx pg 992

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 pg 992

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 pg 992

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 pg 992

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 pg 992

Larynx “Voice box” Extends from C 4 to C 6 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 pg 1001

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 pg 1000 pg 1001

Laryngeal Cartilages Thyroid Cartilage  Large  Shield shaped  Formed by 2 plates  Contains laryngeal prominence Adam’s Apple!! pg 998

Laryngeal Cartilages Cricoid  Inferior to thyroid cartilage  Forms a complete ring  Directly superior to trachea pg 998

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 pg 999

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) pg 1008

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 pg 966

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 pg 966

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, pg 803

Oral Cavity and Associated Organs Mouth  Tongue  Teeth External Salivary glands pg 992

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 pg 1041

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 V 3 ), Facial (CN VII), Glossopharyngeal (CN IX) pg 1037

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 pg 863 pg 1043

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 pg 1046

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 pg 1056

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 = months  4 1 st Molars = months  4 2 nd Molars = 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 X 2 = 20 ****No premolars! Deciduous teeth dental formula: pg 1056

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 years May be absent!!  Adult dental formula: 2I, 1C, 2P, 3M X 2 = 32 pg 1056

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 pg 948

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 pg 954