Anatomy of upper respiratory tract Flashcards
List the components of the upper respiratory tract
- external nose and nasopharynx
- pharynx
- larynx
List the components of the external nose
- Bones: frontal, nasal bones (2), maxillae (2)
- Cartilages: lateral (2), alar (2), septal (1)
- Root: between 2 brows
- Bridge: between 2 eyes
- Piriform aperture: bony opening of nasal cavity
formed by maxilla and nasal bone - Nasal vestibule: inside of nostril up to lower border
of lateral cartilage lined with skin - Rest of nasal cavity is lined with mucous
membrane - supplied by mucous glands and blood vessels
Describe the components and functions of the nasal cavity
- Functions:
- Respiratory epithelium: ciliated pseudo stratified columnar
epithelium containing goblet cells (produce mucous) - Highly vascular mucosa covering conchae - warms and
moistens incoming air (lower ⅔ mucosa) - Olfactory sensation (upper ⅓ mucosa)
- Tissue underlying conchae includes venous plexus that can
become congested, blocking air passage (e.g. a cold) - L and R nasal cavities separated by nasal septum
- Nasal septum:
- Perpendicular plate of ethmoid (superior)
- Vomer (inferior)
- Cartilage (anterior)
- Choanae/posterior nares: opening of nasal cavity to nasopharynx
bounded by vomer (midline), palatine bone (below), medial
pterygoid plates of ethmoid (laterally), body of sphenoid (superiorly) - 12 cranial bones:
- Paired: nasal, maxilla (anterior), palatine, lacrimal
- Unpaired: ethmoid, sphenoid, frontal and vomer
- Roof: ethmoid (w cribriform plate for CN1 olfactory nerve fibres and crista galli above it)
- Sphenoethmoidal recess: highest part of nasal cavity
- Floor: palatine process of maxillae and palatine bones
- Lateral wall: conchae/turbinates (superior (smallest) and middle from ethmoid, inferior separate bone), maxilla, palatine bone
(perpendicular plate) → formed by medial pterygoid plate where the nasal cavity becomes the nasopharynx
Describe the blood supply to the nasal cavity
Arterial supply:
* Supply from 5 small arteries
* Internal carotid artery
* Anterior ethmoid artery
* Posterior ethmoid artery
* External carotid artery
* Maxillary artery
* Sphenopalatine artery (arises through sphenopalatine foramen)
* Greater palatine artery
* Facial artery
* Superior labial artery
* Little’s area: anterior part of septum very rich in blood
* Kiesselbach’s plexus: 5 arteries join together to supply this area ∴ common area for nose bleed
* Nosebleed (epistaxis) from posterior part of nasal cavity requires emergency balloon to block
Venous drainage:
* Similarly arranged to arteries
* Sphenopalatine vein and greater palatine vein drain to the facial vein
Describe the paranasal sinuses: structures and function
- Air-filled cavities lined by epithelial cells in bones that open into nasal cavity
Functions:
* Secrete mucous, which drains into nasal cavity at specific locations
* Cilia beat mucous towards openings
* Speech modification (sinuses) - form resonance
- 4 pairs:
- Frontal (bilateral): between roof of orbit and floor of anterior cranial fossa
- Sphenoidal (midline) separated by septum
- Ethmoidal - smaller subdivisions of ethmoid cells
- Maxillary (bilateral) antrum: extends towards root of upper teeth
- Nasolacrimal duct: sac that drains tears from lacrimal duct (eyes) that empty into nasal cavity
- Ethmoid: big air cell inferiorly = bulla
- Contains superior and middle conchae with a meatus (space) beneath them
- Makes the greatest portion of the nasal skeletal
framework (perpendicular plate, 2 lateral masses) - Inferior concha: separate bone - below is the hard palate
- Conchae covered by mucosa and submucosa so breathing
channels are slit-like
Openings into nasal cavity:
* Superior meatus: posterior ethmoidal cells (lateral
wall)
* Spheno-ethmoidal recess: sphenoidal sinus
* Sphenopalatine foramen: opening for nerves and
blood vessels (opens near back of superior
meatus)
* Middle meatus: infundibulum (frontal and maxillary)
* Anterior: frontal sinus and anterior ethmoidal cells
(anteriorly)
* Hiatus semilunaris: maxillary sinus
* Bulla ethmoidalis: middle ethmoidal cells
* Inferior meatus: nasolacrimal duct
and uncinate process
Update with functions
Describe openings of sinuses
Frontal (2): open into anterior middle meatus
Maxillary (2): open into middle meatus
Ethmoid (2): open into middle and superior meatus
Sphenoid (1): opens into sphenoethmoidal recess
Describe the eustachian tube
- Pharyngotympanic tube, auditory tube
- 3.5cm long tube that connects middle ear to nasopharynx
- Equalises pressure between middle ear and surrounding atmosphere for tympanic membrane to function appropriately
- Lateral ⅓ from temporal bone
- Medial ⅔ cartilaginous (check this)
- Valsalva manoeuvre: blocking nose and blowing - can allows eustachian tube to balance internal and external air pressures (e.g. plane
landing)
Describe the function and components of the pharynx
3 parts:
* Nasopharynx: from basilar part of occipital bone to just in
front of atlas
* Soft palate: valve-like structure that prevents food
from going into nasal cavity (separates naso- and oro-
pharynx)
* Oropharynx: oral cavity opening
* Epiglottis: valve-like structure preventing food from
going into larynx
* Laryngopharynx: laryngeal inlet opening
* Pharyngeal tonsils/adenoids: located in roof of nasopharynx -
can be inflamed in children, blocking breathing
* Lateral wall contains opening of eustachian tube supported by
cartilage elevation = torus tubarius (donut-shaped)
* Pharyngeal recess: lies behind torus tuberius
* Muscles of pharynx
* All innervated by Vagus nerve (CN10), except
stylopharyngeus (innervated by glossopharyngeal CN9)
* Constrictors (superior, middle, inferior): external layer -
contract sequentially to push food bolus down to oesophagus
* L and R muscle bellies join together at pharyngeal raphe
* Superior: arises from pterygomandibular ligament where buccinator also arises
* Middle: overlaps with superior and inserts onto hyoid
* Inferior: largest part that inserts onto thyroid and cricoid cartilages - forms upper oesophageal sphincter
* Longitudinal muscles: internal layer to elevate pharynx during swallowing
* Palatopharyngeus: arises from soft palate and forms posterior facial arch (palatopharyngeal arch) with palatine tonsils between
* Salpingopharyngeus: arises from cartilage of auditory tube - blends into palatopharyngeus
* Stylopharyngeus: arises from styloid process, enters pharynx between superior and middle constrictors
Describe the functions and components of the soft palate
- Function: valve during swallowing (moves up and back to close
nasal pharynx) - 4 muscles:
- Palatoglossus (also extrinsic tongue muscle)
- Palatopharyngeal
- Levator veli palatini: arises from temporal bone then joins in
midline to form a sling - Moves soft palate upwards and backwards
- Tensor veli palatini: arises from sphenoid, then hooks
around pterygoid hamulus and turns 90° to pass medially - Tightens palate when tongue presses up against it in
swallowing - Pterygoid hamulus: bony structure that acts like a pulley to
change direction of muscle
Descrube the components of the larynx
- Controls passage of air into and out of trachea
- 9 Cartilages:
- Thyroid: free posterior edge
- Thyrohyoid membrane: dense connective tissue connecting
superior torn of thyroid cartilage with hyoid bone - Superior horn: small posterior horn that projects to connect to
hyoid bone - Inferior horn: forms joint with cricoid cartilage - allows thyroid
gland to ‘rock’ against cricoid cartilage - Epiglottis: attached with small ligaments to back of thyroid cartilage -
elastic cartilage that can be bent - Vallecula: space between tongue and epiglottis
- Cricoid: forms a complete ring (lamina at the back) to keep trachea
open - Attachment site for muscles - contraction causes lateral rotation/
abduction of vocal cords - Arytenoid (2): ladle-like cartilages that sit above superior-posterior
border of cricoid cartilage (2 articulations with cricoid) - Medial/lateral rotation can manipulate opening between 2 vocal
folds - Vocal process: projects forward and attaches to vocal ligaments
(that then attach to posterior part of thyroid cartilage) - Vocal chord: vocal ligament covered by mucosa (vibrate for
vocalisation) - Muscular process: lateral projection where 4 muscles attach -
cause internal rotation so vocal ligaments move closer together
(adduction) - Corniculate (2): small horn that sits on apex of arytenoid cartilage
- Covered by quadrangular membrane (with free end attached to
epiglottis) - forms cuneiform tubercle - L and R corniculate tubercles join together at interarytenoid
depression - Cuneiform (2): lateral wedge-shaped covered by cuneiform tubercles
- Quadrangular membrane: layer of submucosa
containing cuneiform cartilages - 2 synovial joints:
- Cricothyroid joint: inferior horn of thyroid cartilage with
outer surface of cricoid cartilage - allows rotation and
gliding - Muscle contraction pulse anterior thyroid cartilage
downwards, distending (lengthening) vocal ligaments
= high-pitched - Conus elasticus: lateral portion of cricothyroid
ligament - Cricoarytenoid joint: pivot joint that allows gliding of
arytenoid cartilages forward and closer together - 3 compartments:
- Vestibule/ventricular fold: free edge formed by inferior
border of quadrangular membrane - Laryngeal ventricle: lateral recess between 2 folds
- Infraglottic space: below the vestibule
- Mucous membrane forms 2 pairs of folds:
- Ventricular (vestibular folds): superior pair
- Rima vestibule space between these folds
- Vocal folds (cords): inferior pair
- Rima glottidis space between these folds
- Aryepiglottic fold: free edge of open larynx - space lateral to this is
the piriform recess
LARYNX
Superior laryngeal aperture: faces almost directly backwards
Epiglottic cartilage and Ary-epiglottic fold
List and describe the intrinsic laryngeal muscles and their roles
- All innervated by recurrent laryngeal nerve, except cricothyroid
(innvervated by superior laryngeal nerve) - Control shape of rims glottidis
- Rima vestibuli: gap between ventricular folds
- Rima glottidis: gap between vocal folds
- Control length and tension of vocal folds for sound production
- Transverse arytenoid: adduct arytenoid cartilages to adduct vocal
cords - Oblique arytenoid: adduct vocal cords
- Lateral crico-arytenoid: internally rotate arytenoid cartilages,
adducting vocal cords - Thyro-arytenoid: control anteroposterior position of arytenoid
cartilages (pulls arytenoid forward) - shorten and relax vocal cords - Posterior crico-arytenoid: abduct and externally rotate arytenoid
cartilages - abduct vocal folds - Cricothyroid: between inferior border of thyroid and cricoid -
contraction pulls thyroid cartilage down and forward, distending focal
folds (increases pitch) - Inspiration:
- Rima glottidis open
- Posterior crico-arytenoid abducts vocal cords
- High pitched voice:
- Rima glottidis closed
- Transverse arytenoid, lateral crick-arytenoid and cricothyroid adduct vocal chords
(medial rotation) - Low pitched voice:
- Rima glottidis closed
- Thyro-arytenoid and vocalis muscles abduct vocal cords
Describe the blood supply and innervation of the larynx
Key blood supply sources:
- superior laryngeal artery and vein
- inferior laryngeal artery
Key nerves:
- vagus nerve
- left recurrent laryngeal nerve – looping under aorta or subclavian artery
- vagus and laryngeal n. goes through neurovascular opening
- inferior laryngeal nerve
Note also the presence of many lymph nodes at vessels branch points or on structures of the larynx
Describe the roles of glossopharyngeal and vagus nerves
The glossopharyngeal and vagus nerves contain both sensory and motor fibres.
On the sensory side:
- IX carries taste fibres from the posterior third of the tongue, and visceral sensory fibres from the carotid body to the solitary nucleus
- It also carries tactile fibres from the posterior third of the tongue, upper pharynx and middle ear and transmits this information to the trigeminal nucleus
- X carries visceral sensory information from viscera in the body and aortic baroreceptors to the solitary nucleus, and some tactile fibres (from where?) to the trigeminal nucleus
On the motor side:
- IX and X include motor fibres that innervated striated muscles (i.e. of the pharynx, larynx, soft palate, see also [[Anatomy Lecture 12]]). It does somatic motor innervation.
^involuntary, despite being morphologically skeletal?, emanating from the nucleus ambiguus
NOTE: parasympathetic fibres are included in both IX and X:
- IX fibres synapse in the otic ganglion and innervate the parotid gland (inferior salivatory nucleus - in upper medulla)
- X fibres innervate the heart, bronchi and GIT and synapse in the walls of the viscera (dorsal vagal nucleus, in medulla)
Note 2: both dorsal nucleus of X/dorsal vagal nucleus, and nucleus ambiguus are motor nuclei.
Side note: ambiguus relates to the mixed nature of the nuclei, as it has the cell bodies of both IX and X
What is the role of the accessory nerve?
The accessory nerve or cranial nerve XI is responsible for the shrugging of shoulders. It is thus (primarily) a motor nerve.
Head, neck and shoulder movement is actioned by the trapezius and sternocleidomastoid muscles, and thus XI innervates these.
Accessory nerve also mediates swallowing (via pharyngeal muscles) together with IX and X (via pharyngeal plexus).
Accessory nerve enters skull via foramen magnum and exits via jugular foramen.
Accessory nerve exits from brainstem via medulla, lateral to olive.
Related nuclei include spinal accessory nerve (from C1-5) and nucleus ambiguous. Note that there is a dispute as to whether CNXI is a real cranial nerve, as its nuclei are primarily found in C1-5, as it is relatively superiorly positioned, it “sticks” to the spinal cord and enters via the foramen magnum, where it hitchhikes with CNIX (glossopharyngeal) and CNX (vagal) nerves. ^[ this is clinically important, as damage to cranium and subsequent damage to the pharyngeal plexus]
Damage to the accessory nerve impairs head, neck and shoulder movement.
NOTE: clinicians are typically referring to the spinal root of the accessory nerve. It is this part that supplies the trapezius and sternocleidomastoid muscles, general somatic efferent.
(cranial root, special visceral efferent, innervate laryngeal muscles, merged with X. Generally considered part of X) <- Thieme
Describe glossopharyngeal nerve in terms of nerve fibre type, function, exit from cranium and entry into brainstem
Glossopharyngeal
‘gag reflex’ – innervates
posterior 1/3 of tongue
Baroreceptor (carotid
sinus)
Chemoreceptor – blood
gases
It is a mixed nerve
Branchial Motor: stylopharyngeus muscle
Visceral Motor: parotid gland (via otic ggl)
Visceral Sensory: baroreceptor and chemoreceptors in carotid sinus; mucosa of oropharynx and
isthmus (palatine tonsil, soft palate, post third of tongue) (Moore’s says it is general sensory)
Special Sensory: Posterior third of tongue
exit from jugular foramen
entry medulla
