Nasal cavities
- Upper part of respiratory tract
- Warm and humidify air, help trap pathogens
What are the structural components of the nasal cavities?
- Anterior & posterior regions
- Contain conchae
- Meatus (meatuses) in between
- make up the upper part of the respiratory tract
What are the functions of the larynx?
- Principal: protect the airway from food (valve)
- produce sound (phonation)
What are the functions of the sinuses?
- make the the skull lighter
- can have clinical implications as they can become infected
- provide a cruel zone to protect the brain
- resonant sound production
What are conchae?
- turbinate bones and associated soft tissue that
- curled shelf of bone that protudrudes into the breathing passage in the nose
- superior, middle and inferior
What are meatuses in the nose?
- They are the spaces in between conchae
- superior, middle and inferior
- inferior meatus is inferior to the inferior conchae
What are the functions of conchae?
- warm and humidify air
- immune function by catching pathogens
- drainage routes for sinuses
What are the potential complications of sinus infections?
- some sinuses can drain into the cranial cavity
Innervation of the nasal cavities
- Olfactory nerve (I)
- > Olfaction
- Trigeminal nerve (V)
- V1 – anterior region, V2 – posterior region
- Facial nerve (VII)
- > Glands
- Sympathetic nerves (from T1)
- > Vascular smooth muscle
Arterial Blood supply of the nasal cavities
- largely from the internal carotid artery
- also from external carotid artery
Extremely good blood supply -> can lead to Epistaxis (nose bleeds)
Venous drainage of the nasal cavities
- superior parts of the nasal cavities drain into the brainiac cavity
- this is almost like a flaw in design because pathogens that are filtered in the nose could enter that way
- e.g. nasal vein passes through foramen caecum
- some veins drain into the cavernous sinus in cranial cavity
- inferiorly there is drainage into the facial vein
- drainage to pterygoid plexus in infra temporal fossa.
What is the sensory innervation of the sinuses?
Branches of the trigeminal nerve.
What are the different sinuses? (+ innervation)
- frontal (V1)
- ethmoid air cells (V1 and V2)
- maxillary (V2)
- sphenoid (V1 and V2)
Why do you have a runny nose when you cry?
- the opening of the nasolacrimal duct is in the nose
- when lacrimation occurs, tears drain into the nasal cavity
How do sinuses drain?
- into the nasal cavities (meatuses)
- depending on the place of the sinus opening, it can drain in different positions of the head.
What is the larynx made up of?
- cartilages
- membrane
- muscle
How does the thyroid cartilage rock on the cricoid cartilage?
Due to the cricothyroid joint
Where would you insert an instrument to open the airway in an emergency?
- incision through the skin and cricothyroid membrane
- “cricothyrotomy” or “cric”
- in between thyroid cartilage and cricoid cartilage
Arytenoid cartilages
- pair of small three-sided pyramids which form part of the larynx, to which the vocal folds (vocal cords) are attached. - These allow and aid in the vocal cords’ movement.
Rima glottidis
hole between the 2 vocal chords (seen through endoscope)
Know how to label an endoscopic view of the larynx
:)
What are the main muscles of the larynx that are important for phonation?
- cricothyroid muscles (straight + oblique): put tension on the vocal chords; rocking of thyroid cartilage on cricoid cartilage with the cricothyroid joint.
- transverse + oblique arytenoid muscles -> adduction and abduction of vocal chords (opening and closing)
- lateral arytenoid muscles
- vocals muscle (antagonist to cricothyroid muscle)
Innervation of the larynx
- superior laryngeal N (splits into internal (top) and external (bottom) laryngeal N.
- recurrent laryngeal N.
What do the recurrent laryngeal nerves wind around?
- right: right subclavian A.
- left: ligamentum arteriosum
What does a lesion in the vagus nerve cause?
- complete paralysis of muscles of the larynx (on that side)
What does a lesion in the internal laryngeal N cause?
- can cause loss of sensation above the vocal folds.
What does a lesion in the external laryngeal N cause?
Paralysis of cricothyroid
What does a lesion in the recurrent laryngeal nerve cause?
- paralysis of all muscles in the larynx except cricothyroid and loss of sensation below vocal folds
What do the different nerves that innervate the larynx supply?
- internal laryngeal N: huge involvement in sensation + muscles (does much more than the external laryngeal N.)
Q: is it only sensory or also motor? - external laryngeal N: innervates muscles, supplies the cricothyroid muscle.
- recurrent laryngeal N: innervates muscles as well
Which arteries do the laryngeal nerves travel with?
- superior laryngeal N with the superior thyroid artery
- recurrent laryngeal nerve with the inferior thyroid artery
What is the left recurrent laryngeal nerve particularly vulnerable to?
- bronchial or oesophageal tumor/swollen mediastinal lymph nodes (pleural cavity)
What are the protective mechanisms for the airway?
- coughing
- sneezing
- gag-reflex
- swallowing
Management of the airway
Chin lift/ jaw thrust Oropharyngeal or nasopharyngeal airway Endotracheal intubation Cricothyroidotomy Tracheostomy
What are the differences between sneezing and coughing?
Sneezing:
- soft palate is depressed against the tongue
- afferent via V2
Coughing:
- soft palate is raised
- afferent via X
COMMON:
- Inspiration
Intrathoracic pressure raised
(glottis closed, abdominal muscles contracted
- Sudden abduction of vocal folds to release intrathoracic pressure through nose or mouth
Facial Nerve
- Lateral surface of brainstem between pons and medulla
- passes through internal acoustic meatus
- Motor (large)
- > Muscles of facial expression, stapedius, digastric (posterior belly), stylohyoid.
- Sensory (smaller – intermediate nerve)
- > Taste (ant 2/3 tongue), parasympathetic (lacrimal glands, mucous glands of nasal cavity, hard and soft palates, sublingual and submandibular glands).
- > General sensation from external acoustic meatus and deeper parts of auricle.
Mastoid air cells
- very tightly packed
- honeycomb appearance of bone
- sitting below the middle cranial fossa
- infections can spread to the cranial cavity by eroding the bone superiorly
