HEENT Anatomy

General

General

• HEENT (head, ears, eyes, nose, throat)
• This page summarizes the anatomy above the neck

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Head

Anatomy illustration of the human skull

A, Lateral aspect of cranium. B, Superior aspect of cranial base.

Main facial expression muscles of face and key facial areas division

Muscles of mastication

Tongue muscles

Extra occular muscles

The Temporomandibular Joint

Anatomy of cranial nerves. a Pathways of cranial nerves to various innervated tissues of the body

Primary and permanent dentition

Definition

• Head refers to the upper most part of the human body
• Includes the skull, brain, bones, sensory organs, muscles, neurovascular

Areas of the Head

• Scalp
  • Overlies the skull
  • Consists of 5 layers: skin, connective tissue (dense), aponeurosis, loose connective tissue and the periosteum
  • Aponeurosis acts like a tendon with the Frontalis and Occipitalis muscles
  • Receives a rich arterial supply from the external carotid artery
  • Innervation comes the Trigeminal nerve and other cranial nerves
• Infratemporal Fossa
  • Complex area located at the base of the skull
  • It is deep to the masseter muscles
  • Provides a conduit for neurovascular structures entering/leaving the cranium
  • Key structures: mandibular nerve, chorda tympani, otic ganglion, maxillary artery, pterygoid venous plexus, maxillary vein, middle meningeal artery
  • Muscles: lateral pterygoid, medial pterygoid
• Pterygopalantina Fossa
  • Deep to the infratemporal fossa
  • Extends to the nasal cavity
  • Contents: maxillary nerve and its branches, the pterygopalatine ganglion, as well as the maxillary artery and its branches
• Cranial Fossa
  • Can be broken down to anterior, middle, posterior
  • Each accomodates/supports different parts of the brain and transmits neurovascular structures
  • Anterior: frontal lobes, the olfactory bulb, and the anterior and posterior ethmoidal neurovascular structures
  • Middle: pituitary glands, temporal lobes, optic canals, neurovascular structures pass through the supraorbital fissure, foramen rotundum, foramen ovale and foramen spinosum
  • Posterior: brainstem, cerebellum

Bones of the Skull

• There are 22 bones which can be divided into the cranium and facial skeleton
• The cranium encloses and protects the brain
• The facial bones support the soft tissue of the face
• Cranial roof
  • Bones: frontal, occipital, two parietal bones
  • Also known as the calvarium
• Cranial base
  • Bones: frontal, sphenoid, ethmoid, occipital, parietal, and temporal bones
  • Articulate with 1st cervical vertebra (atlas), the facial bones, and the mandible (jaw)
• Facial Bones
  • Zygomatic (2)
  • Lacrimal (2)
  • Nasal (2)
  • Inferior nasal conchae (2)
  • Palatine (2)
  • Maxilla (2)
  • Mandible (jaw)

Muscles of the Head

• Muscles of Facial Expression
  • Scalp/Forehead: Frontalis, Occipitalis
  • Eyes/Eyelids: Orbicularis oculi, Corrugator supercilii, Levator palpebrae superioris
  • Nose: Nasalis, Procerus, Depressor Septi Nasi
  • Mouth/Lips: Orbicularis oris, Buccinator, Risorius, Zygomaticus major, Zygomaticus minor, Levator labii superioris, Levator anguli oris, Depressor anguli oris, Depressor labii inferioris, Mentalis
  • Neck: Platysma
• Muscles of Mastication
  • Masseter
  • Temporalis
  • Medial Pterygoid
  • Lateral Pterygoid
• Muscles of the Tongue
  • Intrinsic: superior longitudinal, inferior longitudinal, transverse and vertical muscles of the tongue
  • Extrinsic: Genioglossus, Hyoglossus, Styloglossus, Palatoglossus
• Extra Ocular Muscles
  • Rectus: Superior rectus, Inferior rectus, Medial rectus, Lateral rectus
  • Accessory Muscle: Levator palpebrae superioris

Nerves of the Head

• Sympathetic Innervation
  • Begins in the spinal cord, enter the sympathetic chain of the cervical ganglion
  • Hitch hike into the neck with other nerves and arteries
  • Responsible for "fight or flight" response
• Parasympathetic Innervation
  • Originate in 4 nuclei located in the brainstem
  • 4 key ganglion: ciliary, otic, pterygopalatine and submandibular
  • Responsible for "rest and digest" response
• Trigeminal nerve
  • Major sensory nerve of the face, also muscles of mastication
  • Ophthalmic (V1): upper forehead and eyelid
  • Maxillary (v2): lower eyelid to upper palate
  • Mandibular (V3): lower third of face and jaw, muscles of mastication

Organs of the Head

• Ears
  • External ear: captures and directs sound to the inner ear
  • Middle ear: tympanic membrane separates external from middle, transmits vibrations via the auditory ossicles
  • Inner ear: vibrations cause movements of ossicles, transmitted to inner ear through oval window
• Eyes
  • Responsible for vision
  • Light enters through pupil, controlled by ciliary muscles
  • Rods/cones, detect light and pass the signal through the retina to optic nerve
• Nose/Sinuses
  • External nose: opens the nasal cavity through nostrils
  • Inner nose: 3 pairs of turbinates which humidify inspired air
  • Nasal cavity drains into 4 pairs of paranasal sinuses (frontal, sphenoid, ethmoid, maxillary)
• Salivary Glands
  • Located in the mouth with 3 pairs of exocrine glands
  • Parotid, submandibular, subinguinal
• Oral Cavity
  • Marks the start of the gastrointestinal tract
  • Major functions: digestion, communication, breathing
  • Roof: hard/soft palates
  • Floor: tongue, salivary glands, hyoid muscles

Joints of the Head

• Temporomandibular Joint: formed by the articulation of the mandible and temporal bones
• Primary joint for communication and mastication

Cranial Nerves

• 12 paired nerves that arise directly from the brain
• Provide majority of motor/sensory innervations of the head

Child and Adult Dentition

• Composed of two sets of teeth, primary (child) and permanent (adult)
• Organized into two opposing arches: maxillary (upper) and mandibular (lower)
• Can be further divided into left and right halves
• Positioned in alveolar sockets, connected to bone by periodontal ligament

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Eyes

Illustration of the eye anatomy

Eye Morphology

schematic anatomy of the eye

Name

• Eye
• Eyeball

General

• Bilateral, spherical organ which houses all the structures for vision
• Lies within the bony cavity of the facial skeleton, known as the bony orbit
• Eye can be divided into fibrous, vascular, inner layers

Fibrous Layer

• Outermost layer consisting of sclera and cornea which are continuous
• They provide shape to the eye, support the deeper structure
• Sclera makes up the majority of the fibrous layer, providing attachment for extra ocular muscles
• Cornea is transparent, positioned centrally and directs light into the inner eye

Vascular Layer

• Lies deep to the fibrous layer, consists of choroid, ciliary body, iris
• Choroid: contains connective tissue and vessels, nourishing the outer layer of the retina
• Ciliary body: controls the shape of the lens, helps create aqueous humor
• Iris: circular structure with aperture in the center (pupil)

Inner Layer

• Formed by the retina, the light detecting part of the eye
• Outer layer: pigmented, absorbs light, continuous with inner surface of eye
• Inner layer: neural, composed of photoreceptors which detect light
• Optic retina: both layers of the retina are present and contributing to vision
• Macula: central part of the retina, yellowish and highly pigmented
• Fovea centralis: depression in the macula which has a higher concentration of light detecting cells

Vitreous Body

• Transparent gel which fills the posterior segment of the eyeball
• Functions:
  • Contributes to the magnifying power of the eye
  • Supports the lens
  • Holds the layers of the retina in place

Lens

• Located anteriorly between vitreous humor and pupil
• Shape is altered by the ciliary body, altering its refractive power

Anterior & Posterior Chambers

• Anterior: located between cornea and iris
• Posterior: located between iris and ciliary processes
• Chambers are filled with aqueous humor which nourishes and protects the eye

Extra Ocular Muscles

• Control movement of the eye within the orbit
• Rectus: Superior rectus, Inferior rectus, Medial rectus, Lateral rectus, superior oblique, inferior oblique
• Accessory Muscle: Levator palpebrae superioris

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Ears

External ear

Name

• Ear

General

• Responsible for hearing and maintaining balance
• Can be divided into external, middle and inner ear

External Ear

• Function is to conduct sound to the internal ear
• Key anatomy: auricle (external ear), external acoustic meatus (ear canal)
• Vascular supply: Posterior auricular, anterior auricular, minor branches of the occipital, deep auricular, stylomastoid, inferior tympanic arteries
• Innervation: Auriculotemporal branch of the mandibular nerve, lesser occipital, great auricular nerve, auricular branch of the vagus nerve, branches of the facial nerve

Muscles of the External Ear

• Intrinsic muscles
  • Contribute to defining the shape of the auricle by passing between its cartilaginous parts
  • Muscles: helicis major, helicis minor, tragus, pyramidal muscle of auricle, antitragus muscle, transverse muscle of auricle, and oblique muscle of auricle.
• Extrinsic muscles
  • Play a role in positioning the auricle, originating from the skull and attaching within the auricle itself
  • Muscles: auricularis anterior, auricularis superior, and auricularis posterior

Tympanic Membrane

• Often called the eardrum
• Separates the external and middle ear
• Function is to transmit sound/vibrations to the inner ear

Middle Ear

• Separated from the external ear by the tympanic membrane
• Function: Transfers vibrations of the tympanic membrane into sound waves and pass them to the internal ear
• Key Anatomy: tympanic cavity, epitympanic recess
• Vasculature: Anterior tympanic, posterior tympanic, superior tympanic, inferior tympanic arteries, mastoid branch of the occipital artery
• Innervation: Tympanic nerve, tensor tympani nerve, stapedius nerve
• Auditory ossicles: small bones of the middle ear which transmit sound (malleus, incus, stapes)
• Muscles of the inner ear: tensor tympani, stapedius

Auditory Tube

• Also called eustachian or pharyngotympanic tube
• Connects the middle ear and the nasopharynx
• Serves primarily to equalize pressure on both sides of the tympanic membrane

Internal Ear

• Also called the labyrinth, most complex part of the ear
• Cochlea is a spiral shaped, fluid filled structure which turns sound into electrical signals for the brain
• Vestibular system includes semicircular canals, utricle, and saccule helps with posture, balance and coordination

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Nose

Nasal cavity anatomy

Gross anatomy of the nasal cavity

Muscles of the nose

Name

• Nose
• Human Nose
• Nasal Cavity

General

• First organ of the respiratory system and principle organ of the olfactory system
• Shaped by nasal bones and cartilage, including a nasal septum, which separates the nostrils dividing the nose in two

Function

• Warms and humidifies the inspired air
• Removes and traps pathogens and particulate matter from the inspired air
• Responsible for sense of smell
• Drains and clears the paranasal sinuses and lacrimal ducts

Divisions

• Extends from the vestibule of the nose to the nasopharynx
• Vestibule: area surrounding the anterior external opening to the nasal cavity
• Respiratory: lined by a ciliated psudeostratified epithelium, interspersed with mucus-secreting goblet cells
• Olfactory: located at the apex of the nasal cavity, lined by olfactory cells with olfactory receptors

Nasal Conchae

• Also called turbinates
• Project out of the lateral walls, creating four pathways for the air to flow
• There are 3 conchae: inferior, middle, superior
• Pathways are called meatus: inferior, middle, superior, sphenoethmoidal
• Function: increase surface area of the nasal cavity

Openings into the Nasal Cavity

• Paranasal sinuses drain into the nasal cavity (frontal, maxillary and anterior ethmoidal)
• Middle ethmoidal sinus drains into the ethmoidal bulla
• Sphenoid sinus drains into the posterior roof
• Nasolacrimal duct: drain tears from the eye, opens into the inferior meatus
• Auditory (Eustachian) tube: opens into the nasopharynx at the level of the inferior meatus

Gateways to the Nasal Cavity

• Cribriform plate allows olfactory nerve to enter/exit
• Sphenopalatine foramen allows sphenopalatine artery, nasopalatine and superior nasal nerves to pass
• Incisive canal transmits nasopalatine nerve, greater palantine artery to oral cavity

Vasculature

• Nose has rich vasculature supply; allows it to monitor/change humidity and temperature of inspired air
• Internal carotid: anterior and posterior ethmoidal arteries (off the ophthalmic artery)
• External carotid: sphenopalatine, greater palatine, superior labial, lateral nasal arteries
• Kesselbechs plexus: anastomosis of multiple vessels in the anterior nose prone to bleeding

Innervation

• Can be divided into special and general
• Special: ability to smell carried out by olfactory nerves
• General sensory comes from nasopalatine and nasociliary nerves
• Sensation of the external skin comes from the trigeminal nerve

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Throat

Anatomy of the pharynx

Regions of the pharynx

Muscles of the pharynx

Name

• Throat
• Pharynx

General

• Pharynx is muscular tube that connects oral and nasal cavity to larynx and esophagus
• Begins at the base of the skull, ends at the inferior border of cricoid cartilage (C6)
• Composed of nasopharynx, oropharynx, laryngopharynx

Nasopharynx

• Found between the base of the skull and the soft palate
• Continuous with nasal cavity
• Respiratory role: humidifies/ warms inspired air, propogates to larynx
• Lined with respiratory epithelium (ciliated pseudostratified columnar epithelium with goblet cell)
• Contains the adenoid tonsils, which enlarge around age 3-8 then regress

Oropharynx

• Middle layer of the pharynx between the soft palate and superior border of epiglottis
• Contents: posterior 1/3 of tongue, lingual tonsils, palatine tonsils, superior constructor muscle
• Waldeyer’s ring: ring of lymphoid tissue formed by the paired palatine tonsils, the adenoid tonsils and lingual tonsil

Laryngopharynx

• The most distal part of the pharynx between superior border of epiglottis and cricoid cartilage
• Continuous inferiorly with the esophagus
• Found posterior to the larynx, communicates via the laryngeal inlet
• Contains middle and inferior pharyngeal constrictors

Muscles of the Pharynx

• Circular
  • Superior pharyngeal constrictor
  • Middle pharyngeal constrictor
  • Inferior pharyngeal constrictor
• Longitudinal
  • Stylopharyngeus
  • Palatopharyngeus
  • Salpingopharyngeus

Innervation

• Pharyngeal plexus
  • Pharyngeal branches from the glossopharyngeal nerve (CN IX)
  • Pharyngeal branch of the vagus nerve (CN X)
  • Branches from the external laryngeal nerve
  • Sympathetic fibres from the superior cervical ganglion

Vascular Supply

• Branches of the external carotid artery
  • Ascending pharyngeal artery
  • Branches of the facial artery
  • Branches of the lingual and maxillary arteries

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Clinical Significance

• Needs to be updated

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See Also

• Anatomy Main
• HEENT Main

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