04-10-21 - Structure of the Airway Flashcards
What does the Conduction portion consist of?
- Nose, nasal cavity, paranasal sinuses
- Pharynx (nasopharynx, oropharynx, laryngopharynx
- larynx
- Trachea
- Bronchi, bronchial tree
- Terminal bronchioles
What does the Respiratory portion (gas exchange) consist of?
- Respiratory bronchioles
- Alveoli (ducts and sacs):
-400 million per lung
-Large surface area
-Rich vascular supply
What is respiration?
What are the 2 processes involved?
How do they occur?
What must happen when air is taken in?
- Respiration is providing oxygen to the body and removing carbon dioxide through inhalation and exhalation
- Inhalation/inspiration is achieved by increasing the size of the thorax
- This is done by:
- Contraction (and lowering) of the diaphragm and raising the ribs
- Creative a negative intra-thoracic pressure that sucks air through the conductive passages (nasal-cavity, nasopharynx, larynx, trachea, bronchi) and down into the lungs
- This air must be warmed, filtered and humidified (increased in moisture) (vascular mucosa, cilia, mucus)
- Exhalation/expiration is achieved by decreasing the size of the thorax, via relaxation
- This is generally a passive process and does not require energy unless forced.
What is the nose?
What is the nasal cavity?
Where is it found?
How does air enter into the nasal cavities?
What membrane are they lined with?
What is this membrane lined with?
- The nose is the external structure which anteriorly encloses the nasal cavities
- The nasal cavities are the start of the respiratory tract
- They are found above the oral cavity, between the two orbits (eyes), posterior to the nose, and anterior to the nasopharynx
- Entry into the nasal is via the nares (nostrils)
- The nasal cavities are lined with a highly vascularised mucosal membrane lined with respiratory epithelium
- This epithelium is pseudostratified, ciliated, columnar epithelium interspersed with goblet cells (simple columnar epithelial cells), which secrete mucus
What is the nasal septum?
What is it made of?
What are the boundaries of the nasal septum?
Where is smell restricted to in relation to the nasal septum?
What happens if the nasal septum is not in the midline)
- The nasal septum is the mid line structure which separates the left and right nasal cavities
- Anteriorly, the septum is made of septal cartilage, while posteriorly, it is made of bone (perpendicular plate of ethmoid and vomer bones)
- The nasal septum is medial
- Nasal conchae laterally
- Hard and soft plates on the floor
- Bone (ethmoid, frontonasal, sphenoid) on the roof
- Olfactory epithelium (smell) is restricted to roof and adjacent lateral wall
- If the septum deviates from the midline, sinus drainage may be compromised.
Nasal cavity – olfactory anatomy
- Cranial nerve 1 (CN I) – olfactory nerve
- Olfactory nerves (R+L) are forebrain extensions
- Olfactory mucosa -> olfactory nerves (passing through cribriform plate) -> olfactory bulb -> olfactory tract -> medial and lateral striae -> piriform cortices
What are nasal conchae/turbinates?
How many of them are there?
What are they responsible for and how do they do this?
What also helps them with this?
- Nasal conchae are shelves of bone that protrude into the nasal cavity from the lateral wall
- There are 3 nasal conchae (superior, middle, inferior)
- These conchae filter, humidify and warm air in the nasal cavity (sinuses also help to warm air)
- They provide turbulence and increase the surface areas for air flow and heat exchange
What are each nasal conchae paired up with and why?
What meatus connects to which sinuses?
- Under/lateral to each conchae is a meatus.
- Adjacent air sinuses open up into the meati, which allows for communicating between the sinuses and the nasal cavity.
- The opening to the posterior ethmoidal and sphenoidal sinuses exists under the superior meatus
- The middle meatus connects to the frontal and maxillary sinuses
- The nasolacrimal duct drains into the inferior meatus to empty tears from the conjunctiva of the eye (why crying causes you to blow your nose)
Label the sinuses and conchae from this diagram.
1
How is maxillary mucus cleared and why?
What can cause sinusitis?
What is sinusitis?
- Frontal, anterior + middle ethmoidal, maxillary = middle meatus
- Posterior ethmoidal = superior meatus
- Sphenoidal = spheno- ethmoidal recess
- Nasolacrimal duct = inferior meatus (not a sinus, but just for completeness)
- Maxillary sinus particularly prone to sinusitis
9) Label the sinuses on this diagram.
1
What is the pharynx made of?
What are the 3 parts of the pharynx?
Where are they located?
What is each part responsible for?
- The pharynx is a tube of fibrous and muscular tissues that can be divided into 3 parts, which lie behind:
- The nasal cavity (nasopharynx)
- The oral cavity (oropharynx)
- The larynx (laryngopharynx)
- The nasopharynx - Transports air into lungs, and is divided from oropharynx by soft palate
- The oropharynx - transports air, food, and fluid, but these must be separated so air passes into the larynx, while food and fluid continue into the oesophagus
- The laryngopharynx – crucial connection point from which air, food, and fluid pass. It is the point at which the pharynx divides anteriorly into the larynx and posteriorly into to the oesophagus.
What is the larynx?
How is its position altered?
When might the larynx be moved?
- Composed of muscle, cartilage and ligaments/membranes
- Anterior neck spanning C3-6 vertebral levels
- Phonation
- Guarding airway during swallowing
- Allow voluntary increase in intra-abdominal pressure
What is the larynx made of?
What are the different parts of the larynx?
Where is the site of emergency access to the airway?
- The entire structure of the larynx is 9 cartilages (3x2 paired and 3 unpaired) and the hypoid bone (supported by cartilage), which is the only bone part of the larynx
- The site of emergency access to the airway is the cricothyroid membrane.
What is the laryngeal inlet?
What do we want to go down it?
What is the ary-epiglottic fold?
What are its functions?
What is the epiglottis?
What does it do?
How do these all work together?
When is this process used?
- The laryngeal inlet is the opening that connects the pharynx and the larynx
- Air goes down this opening, while food and fluid goes down the sides into the oesophagus
- The ary-epiglottic fold forms the laryngeal inlet.
- Its main functions are to protect the airway when swallowing, and also widen the laryngeal inlet
- The epiglottis is the flap of tissue that sits beneath the tongue at the back of the windpipe.
- Its main function is to close over the windpipe (trachea) while you are eating (swallowing) to prevent food from entering your airway.
- Contraction of muscles in the ary-epiglottic fold results in the epiglottis closing over the laryngeal inlet, preventing any food from going down the airway.
- The epiglottis shuts like a toilet seat, while the larynx and other cartilaginous structures move up and forward while swallowing via muscular contractions to meet the epiglottis.
What are the additional components of the cricoid?
What attaches do these additional structures?
- The cricoid has gate like structures called arytenoids, with corniculate sitting on top.
- The vocal cords attach to muscular structures at the front of the arytenoids and the lamina of the cricoid, and stretch to the arch of the cricoid.
- The voice sounds different whether the arytenoids are open or closed.
Where is the ary-epiglottic fold, the vestibular fold and the vocal fold?
What are the vestibular fold and vocal fold for?
What is the ary-epiglottic fold for?
- The ary-epiglottic fold is at the upper edge of the quadrangular membrane
- The vestibular fold is formed by the lower edge of the quadrangular membrane
- The vocal fold is the upper edge of the cricovocal/cricothyroid membrane
- The vestibular fold and the vocal fold are membranous structures that form a protective sphincter, which allows you to close off the airway and speak.
- The aryepiglottic fold also forms the laryngeal inlet, which is the protective sphincter.
How are vocal cords lubricated?
• Within the opening of the laryngeal ventricle, there is the saccule, where there are mucosal glands which help to lubricate the vocal cords.
What is the rima glottidis?
How is it altered?
What is its function?
- The rima glottidis is the opening between the vocal cords.
- Muscles (posterior crico-arytenoid) adjacent to and within the vocal cords narrow or widen this opening, or alter the tension of the opening.
- It serves as the primary channel for airflow within in the larynx
What are the 3 main actions of laryngeal muscles?
What is the name of the muscle?
- Close/open the laryngeal inlet using ary-epiglottic folds.
- Close/open the rima glottidis (arytenoids gliding and rotation) - done by the posterior crico-arytenoid muscle
- Shorten/lengthen the vocal cords (rocking at the cricothyroid joints)
Larynx blood supply & lymphatics
- Superior thyroid artery (external carotid branch)
- Inferior thyroid artery (from thyrocervical trunk, subclavian artery branch)
- Superior, middle, inferior thyroid veins to internal jugular and brachiocephalic trunks
- Above vocal folds = Superior deep cervical lymph nodes
- Below vocal folds = pretracheal or paratracheal -> inferior deep cervical nodes
