Upper Airway and digestive tract

Question 1

Describe the basic structure of the nasal cavity

Answer 1

The smaller anterior regions of the cavities are enclosed by the external nose, whereas the larger posterior regions are more central within the skull. The anterior apertures of the nasal cavities are the nares, which open onto the inferior surface of the nose. The posterior apertures are the choanae, which open into the nasopharynx.
The nasal cavities are separated:
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from each other by a midline nasal septum,
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from the oral cavity below by the hard palate, and
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from the cranial cavity above by parts of the frontal, ethmoid, and sphenoid bones.
Lateral to the nasal cavities are the orbits.
Each nasal cavity has a floor, roof, medial wall, and lateral wall

Question 2

What is important to remember about the nasal cavity

Answer 2

Drians into the cranial cavity (venous)- can transfer infections from the outside world into the cranial cavity,

Question 3

Summarise the structure of the nasal cavity

Answer 3

Upper part of respiratory tract
Anterior & posterior regions
Contain conchae
Warm and humidify air, help trap pathogens
Meatus (meatuses) in between

Question 4

What type of epithelium lines the conchae

Answer 4

Respiratory Epithelium
It increases the surface area for warming and humidifying the inspired air (conchae are also referred to as turbinate bones)
Conchae= bone + epithelium
Turbinate = bone

Question 5

What are the key structures of the lateral wall of the nasal cavity

Answer 5

The lateral wall is characterized by three curved shelves of bone (conchae), which are one above the other and project medially and inferiorly across the nasal cavity (Fig. 8.226B). The medial, anterior, and posterior margins of the conchae are free.
The conchae divide each nasal cavity into four air channels (Fig. 8.226C,D):
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an inferior nasal meatus between the inferior concha and the nasal floor,
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a middle nasal meatus between the inferior and middle concha,
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a superior nasal meatus between the middle and superior concha, and
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a spheno-ethmoidal recess between the superior concha and the nasal roof.
These conchae increase the surface area of contact between tissues of the lateral wall and the respired air.

Question 6

Which sinus drains into the sphenoethmoidal recess

Answer 6

the sphenoidal sinus

Question 7

Name two important openings into the lateral wall of the nasal cavity

Answer 7

The openings of the paranasal sinuses, which are extensions of the nasal cavity that erode into the surrounding bones during childhood and early adulthood, are on the lateral wall and roof of the nasal cavities (Fig. 8.227). In addition, the lateral wall also contains the opening of the nasolacrimal duct, which drains tears from the eye into the nasal cavity.

Question 8

What are the 3 regions of the nasal cavity

Answer 8

Each nasal cavity consists of three general regions—the nasal vestibule, the respiratory region, and the olfactory region (Fig. 8.228):
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The nasal vestibule is a small dilated space just internal to the naris that is lined by skin and contains hair follicles.
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The respiratory region is the largest part of the nasal cavity, has a rich neurovascular supply, and is lined by respiratory epithelium composed mainly of ciliated and mucous cells.
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The olfactory region is small, is at the apex of each nasal cavity, is lined by olfactory epithelium, and contains the olfactory receptors.

Question 9

Summarise the innervation of the nasal cavity

Answer 9

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Olfaction is carried by the olfactory nerve [I].
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General sensation is carried by the trigeminal nerve [V], the anterior region by the ophthalmic nerve [V1], and the posterior region by the maxillary nerve [V2].
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All glands are innervated by parasympathetic fibers in the facial nerve [VII] (greater petrosal nerve), which join branches of the maxillary nerve [V2] in the pterygopalatine fossa.
Sympathetic fibers are ultimately derived from the T1 spinal cord level. They synapse mainly in the superior cervical sympathetic ganglion, and postganglionic fibers reach the nasal cavities along blood vessels, or by joining branches of the maxillary nerve [V2] in the pterygopalatine fossa.- innervate vascular smooth muscle

Question 10

Which bones contribute to the skeletal framework of the nasal cavity

Answer 10

Bones that contribute to the skeletal framework of the nasal cavities include:
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the unpaired ethmoid, sphenoid, frontal, and vomer bones, and
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the paired nasal, maxillary, palatine, and lacrimal bones and inferior conchae.
Of all the bones associated with the nasal cavities, the ethmoid is a key element.

Question 11

Describe the key features of the ethmoid bone

Answer 11

The single ethmoid bone is one of the most complex bones in the skull. It contributes to the roof, lateral wall, and medial wall of both nasal cavities, and contains the ethmoidal cells (ethmoidal sinuses).
The ethmoid bone is cuboidal in overall shape (Fig. 8.229A) and is composed of two rectangular box-shaped ethmoidal labyrinths, one on each side, united superiorly across the midline by a perforated sheet of bone (the cribriform plate). A second sheet of bone (the perpendicular plate) descends vertically in the median sagittal plane from the cribriform plate to form part of the nasal septum.

Question 12

Describe the medial wall of the nasal cavity

Answer 12

The medial wall of each nasal cavity is the mucosa-covered surface of the thin nasal septum, which is oriented vertically in the median sagittal plane and separates the right and left nasal cavities from each other.
The nasal septum (Fig. 8.232) consists of:
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the septal nasal cartilage anteriorly,
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posteriorly, mainly the vomer and the perpendicular plate of the ethmoid bone,
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small contributions by the nasal bones where they meet in the midline, and the nasal spine of the frontal bone, and
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contributions by the nasal crests of the maxillary and palatine bones, rostrum of the sphenoid bone, and the incisor crest of the maxilla.

Question 13

Describe the consequences of a deviated nasal septum

Answer 13

The nasal septum is typically situated in the midline; however, septal deviation to one side or the other is not uncommon, and in many cases is secondary to direct trauma. Extreme septal deviation can produce nasal occlusion. The deviation can be corrected surgically.

Question 14

Describe the floor of the nasal cavity

Answer 14

The floor of each nasal cavity (Fig. 8.233) is smooth, concave, and much wider than the roof. It consists of:
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soft tissues of the external nose, and
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the upper surface of the palatine process of the maxilla and the horizontal plate of the palatine bone, which together form the hard palate.

The naris opens anteriorly into the floor, and the superior aperture of the incisive canal is deep to the mucosa immediately lateral to the nasal septum near the front of the hard palate.

Question 15

Describe the roof of the nasal cavity

Answer 15

The roof of the nasal cavity is narrow and is highest in central regions where it is formed by the cribriform plate of the ethmoid bone
Anterior to the cribriform plate the roof slopes inferiorly to the nares and is formed by:
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the nasal spine of the frontal bone and the nasal bones, and
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the lateral processes of the septal cartilage and major alar cartilages of the external nose.
Posteriorly, the roof of each cavity slopes inferiorly to the choana and is formed by:
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the anterior surface of the sphenoid bone,
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the ala of the vomer and adjacent sphenoidal process of the palatine bone, and
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the vaginal process of the medial plate of the pterygoid process.

Question 16

Describe the lateral wall of the nasal cavity

Answer 16

The lateral wall of each nasal cavity is complex and is formed by bone, cartilage, and soft tissues.
Bony support for the lateral wall (Fig. 8.235A) is provided by:
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the ethmoidal labyrinth, superior concha, middle concha and uncinate process,
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the perpendicular plate of the palatine bone,
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the medial pterygoid plate of the sphenoid bone,
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the medial surfaces of the lacrimal bones and maxillae, and
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the inferior concha.

Question 17

What is the semilunar hiatus

Answer 17

Inferior to the ethmoidal bulla is a curved gutter (the semilunar hiatus), which is formed by the mucosa covering the lateral wall as it spans a defect in the bony wall between the ethmoidal bulla above and the uncinate process below.
The anterior end of the semilunar hiatus forms a channel (the ethmoidal infundibulum), which curves upward and continues as the frontonasal duct through the anterior part of the ethmoidal labyrinth to open into the frontal sinus.

Question 18

Describe the sphenopalatine foramen

Answer 18

One of the most important routes by which nerves and vessels enter and leave the nasal cavity is the sphenopalatine foramen in the posterolateral wall of the superior nasal meatus. This foramen is just superior to the attachment of the posterior end of the middle nasal concha and is formed by the sphenopalatine notch in the palatine bone and the body of the sphenoid bone.
The sphenopalatine foramen is a route of communication between the nasal cavity and the pterygopalatine fossa. Major structures passing through the foramen are:
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the sphenopalatine branch of the maxillary artery,
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the nasopalatine branch of the maxillary nerve [V2], and
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superior nasal branches of the maxillary nerve [V2].

Question 19

Describe the foramen cecum

Answer 19

In addition, there is a connection in some individuals between nasal veins and the superior sagittal sinus of the cranial cavity through a prominent foramen (the foramen cecum) in the midline between the crista galli and frontal bone.

Question 20

Describe the arteries of the nasal cavity

Answer 20

Arteries that supply the nasal cavity include vessels that originate from both the internal and external carotid arteries (Fig. 8.239):
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Vessels that originate from branches of the external carotid artery include the sphenopalatine, greater palatine, superior labial, and lateral nasal arteries.
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Vessels that originate from branches of the internal carotid artery are the anterior and posterior ethmoidal arteries

Significant anastomoses- clinically relevant in nose bleeds

Question 21

Describe the venous drainage of the nasal cavity

Answer 21

Veins draining the nasal cavities generally follow the arteries (Fig. 8.240):
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Veins that pass with branches that ultimately originate from the maxillary artery drain into the pterygoid plexus of veins in the infratemporal fossa.
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Veins from anterior regions of the nasal cavities join the facial vein.

In some individuals, an additional nasal vein passes superiorly through a midline aperture (the foramen cecum), in the frontal bone anterior to the crista galli, and joins with the anterior end of the superior sagittal sinus. Because this nasal vein connects an intracranial venous sinus with extracranial veins, it is classified as an emissary vein. Emissary veins in general are routes by which infections can track from peripheral regions into the cranial cavity.
Veins that accompany the anterior and posterior ethmoidal arteries are tributaries of the superior ophthalmic vein, which is one of the largest emissary veins and drains into the cavernous sinus on either side of the hypophyseal fossa.

Question 22

Summarise the paranasal sinuses

Answer 22

There are four paranasal air sinuses—the ethmoidal cells, and the sphenoidal, maxillary, and frontal sinuses (Fig. 8.231A,B). Each is named according to the bone in which it is found.
The paranasal sinuses develop as outgrowths from the nasal cavities and erode into the surrounding bones. All of the paranasal sinuses:
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are lined by respiratory mucosa, which is ciliated and mucus secreting,
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open into the nasal cavities, and
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are innervated by branches of the trigeminal nerve [V].

Question 23

Describe the role of sinuses in the skull

Answer 23

It makes the skull lighter
Acts as a crumple one for the brain
Increases projection of the voice - role in resonation

Question 24

Describe the frontal sinuses

Answer 24

The frontal sinuses, one on each side, are variable in size and are the most superior of the sinuses (Fig. 8.231A–C). Each is triangular in shape and is in the part of the frontal bone under the forehead. The base of each triangular sinus is oriented vertically in the bone at the midline above the bridge of the nose and the apex is laterally approximately one-third of the way along the upper margin of the orbit.
Each frontal sinus drains onto the lateral wall of the middle meatus via the frontonasal duct, which penetrates the ethmoidal labyrinth and continues as the ethmoidal infundibulum at the front end of the semilunar hiatus.
The frontal sinuses are innervated by branches of the supra-orbital nerve from the ophthalmic nerve [V1]. Their blood supply is from branches of the anterior ethmoidal arteries.

Question 25

Describe the ethmoidal air cells

Answer 25

The ethmoidal cells on each side fill the ethmoidal labyrinth (Fig. 8.231A,B). Each cluster of cells is separated from the orbit by the thin orbital plate of the ethmoidal labyrinth, and from the nasal cavity by the medial wall of the ethmoidal labyrinth. The ethmoidal cells are formed by a variable number of individual air chambers, which are divided into anterior, middle, and posterior ethmoidal cells based on the location of their apertures on the lateral wall of the nasal cavity: ▪ The anterior ethmoidal cells open into the ethmoidal infundibulum or the frontonasal duct. ▪ The middle ethmoidal cells open onto the ethmoidal bulla, or onto the lateral wall just above this structure. ▪ The posterior ethmoidal cells open onto the lateral wall of the superior nasal meatus.

Question 26

Describe the blood supply and innervation of the ethmoidal air cells

Answer 26

Because the ethmoidal cells often erode into bones beyond the boundaries of the ethmoidal labyrinth, their walls may be completed by the frontal, maxillary, lacrimal, sphenoid, and palatine bones. The ethmoidal cells are innervated by: ▪ the anterior and posterior ethmoidal branches of the nasociliary nerve from the ophthalmic nerve [V1], and ▪ the maxillary nerve [V2] via orbital branches from the pterygopalatine ganglion. The ethmoidal cells receive their blood supply through branches of the anterior and posterior ethmoidal arteries.

Question 27

Describe the maxillary sinus and its drainage

Answer 27

The maxillary sinuses, one on each side, are the largest of the paranasal sinuses and completely fill the bodies of the maxillae (Fig. 8.231A,B). Each is pyramidal in shape with the apex directed laterally and the base deep to the lateral wall of the adjacent nasal cavity. The medial wall or base of the maxillary sinus is formed by the maxilla, and by parts of the inferior concha and palatine bone that overlie the maxillary hiatus. The opening of the maxillary sinus is near the top of the base, in the center of the semilunar hiatus, which grooves the lateral wall of the middle nasal meatus.

Question 28

Describe the structural relationships, innervation and blood supply of the maxillary sinus

Answer 28

Relationships of the maxillary sinus are as follows: ▪ The superolateral surface (roof) is related above to the orbit. ▪ The anterolateral surface is related below to the roots of the upper molar and premolar teeth and in front to the face. ▪ The posterior wall is related behind to the infratemporal fossa. The maxillary sinuses are innervated by infra-orbital and alveolar branches of the maxillary nerve [V2], and receive their blood through branches from the infra-orbital and superior alveolar branches of the maxillary arteries.

Question 29

Describe the sphenoidal sinuses

Answer 29

The sphenoidal sinuses, one on either side within the body of the sphenoid, open into the roof of the nasal cavity via apertures on the posterior wall of the spheno-ethmoidal recess (Fig. 8.231C,D). The apertures are high on the anterior walls of the sphenoid sinuses. The sphenoidal sinuses are related: ▪ above to the cranial cavity, particularly to the pituitary gland and to the optic chiasm, ▪ laterally, to the cranial cavity, particularly to the cavernous sinuses, and ▪ below and in front, to the nasal cavities.

Question 30

Describe the clinical relevance, blood supply and innervation of the sphenoidal sinuses

Answer 30

Because only thin shelves of bone separate the sphenoidal sinuses from the nasal cavities below and hypophyseal fossa above, the pituitary gland can be surgically approached through the roof of the nasal cavities by passing first through the anteroinferior aspect of the sphenoid bone and into the sphenoidal sinuses and then through the top of the sphenoid bone into the hypophyseal fossa. Innervation of the sphenoidal sinuses is provided by: ▪ the posterior ethmoidal branch of the ophthalmic nerve [V1], and ▪ the maxillary nerve [V2] via orbital branches from the pterygopalatine ganglion. The sphenoidal sinuses are supplied by branches of the pharyngeal arteries from the maxillary arteries.

Question 31

Describe the clinical relevance of the structural relationships of the different sinuses

Answer 31

1. Roots of upper teeth and the maxillary sinus – root infections can form fistulas into the maxillary sinus and cause infection. 2. Mastoid air cells and middle ear – mastoid air cells can become eroded by infection and the erode through tegmen tympani into the cranium and cause infection to the brain. 3. Sphenoid sinus and pituitary gland – trans-sphenoidal surgery to access the pituitary gland

Question 32

Describe the mastoid air cells

Answer 32

They are small sinuses within the mastoid part of the temporal bone The mastoid air cells communicate with the middle ear via the aditus ad antrum and the mastoid antrum This is a possible route for infection of the middle ear

Question 33

Describe mastoiditis

Answer 33

Infection within the mastoid antrum and mastoid cells is usually secondary to infection in the middle ear. The mastoid cells provide an excellent culture medium for infection. Infection of the bone (osteomyelitis) may also develop, spreading into the middle cranial fossa. Drainage of the pus within the mastoid air cells is necessary and there are numerous approaches for doing this. When undertaking this type of surgery, it is extremely important that care is taken not to damage the mastoid wall of the middle ear to prevent injury to the facial nerve [VII]. Any breach of the inner table of the cranial vault may allow bacteria to enter the cranial cavity and meningitis will ensue.

Question 34

Summarise the larynx

Answer 34

``` Hollow structure Composed of: Cartilages Membrane Muscles ``` Acts as a: Valve Sound producer

Question 35

Describe the structural relationships of the larynx

Answer 35

The cavity of the larynx is continuous below with the trachea, and above opens into the pharynx immediately posterior and slightly inferior to the tongue and the posterior opening (oropharyngeal isthmus) of the oral cavity

Question 36

What does the larynx consist of

Answer 36

The larynx is both a valve (or sphincter) to close the lower respiratory tract, and an instrument to produce sound. It is composed of: ▪ three large unpaired cartilages (cricoid, thyroid, and epiglottis), ▪ three pairs of smaller cartilages (arytenoid, corniculate, and cuneiform), and ▪ a fibro-elastic membrane and numerous intrinsic muscles. The larynx is suspended from the hyoid bone above and attached to the trachea below by membranes and ligaments. It is highly mobile in the neck and can be moved up and down and forward and backward by the action of extrinsic muscles that attach either to the larynx itself or to the hyoid bone. During swallowing, the dramatic upward and forward movements of the larynx facilitate closing the laryngeal inlet and opening the esophagus. Motor and sensory innervation of the larynx is provided by the vagus nerve [X].

Question 37

Summarise the cricoid cartilage

Answer 37

The cricoid cartilage is the most inferior of the laryngeal cartilages and completely encircles the airway (Fig. 8.206). It is shaped like a signet ring with a broad lamina of cricoid cartilage posterior to the airway and a much narrower arch of cricoid cartilage circling anteriorly.

Question 38

Describe the key features of the cricoid cartilage

Answer 38

The posterior surface of the lamina is characterized by two shallow oval depressions separated by a vertical ridge. The esophagus is attached to the ridge and the depressions are for attachment of the posterior crico-arytenoid muscles. The cricoid cartilage has two articular facets on each side for articulation with other laryngeal cartilages: ▪ One facet is on the sloping superolateral surface of the lamina and articulates with the base of an arytenoid cartilage. ▪ The other facet is on the lateral surface of the lamina near its base and is for articulation with the medial surface of the inferior horn of the thyroid cartilage.

Question 39

Summarise the thyroid cartillage

Answer 39

The thyroid cartilage (Fig. 8.207) is the largest of the laryngeal cartilages. It is formed by a right and a left lamina, which are widely separated posteriorly, but converge and join anteriorly. The most superior point of the site of fusion between the two broad flat laminae projects forward as the laryngeal prominence (Adam’s apple). The angle between the two laminae is more acute in men (90°) than in women (120°) so the laryngeal prominence is more apparent in men than women.

Question 40

Describe the thyroid notches

Answer 40

Just superior to the laryngeal prominence, the superior thyroid notch separates the two laminae as they diverge laterally. Both the superior thyroid notch and the laryngeal prominence are palpable landmarks in the neck. There is a less distinct inferior thyroid notch in the midline along the base of the thyroid cartilage.

Question 41

Describe the horns of the thyroid cartilage

Answer 41

The posterior margin of each lamina of the thyroid cartilage is elongated to form a superior horn and an inferior horn: ▪ The medial surface of the inferior horn has a facet for articulation with the cricoid cartilage. ▪ The superior horn is connected by a lateral thyrohyoid ligament to the posterior end of the greater horn of the hyoid bone.

Question 42

Describe the thyroid tubercles

Answer 42

The lateral surface of each thyroid lamina is marked by a ridge (the oblique line), which curves anteriorly from the base of the superior horn to a little short of midway along the inferior margin of the lamina. The ends of the oblique line are expanded to form superior and inferior thyroid tubercles. The oblique line is a site of attachment for the extrinsic muscles of the larynx (sternothyroid, thyrohyoid, and inferior constrictor).

Question 43

Describe the epiglottis

Answer 43

The epiglottis is a leaf-shaped cartilage attached by its stem to the posterior aspect of the thyroid cartilage at the angle (Fig. 8.208) and projects posterosuperiorly from its attachment to the thyroid cartilage. The attachment is via the thyro-epiglottic ligament in the midline approximately midway between the laryngeal prominence and the inferior thyroid notch. The upper margin of the epiglottis is behind the pharyngeal part of the tongue. The inferior half of the posterior surface of the epiglottis is raised slightly to form an epiglottic tubercle.

Question 44

Describe the anatomy of the arytenoid cartilage

Answer 44

The two arytenoid cartilages are pyramid-shaped cartilages with three surfaces, a base of arytenoid cartilage and an apex of arytenoid cartilage Base is concave base articulates with facets on superior surface of cricoids while apex articulates with corniculate cartilages; lateral surfaces have depressions for muscle and ligament attachments while the posterior surface is covered by the transverse arytenoid muscle medial surfaces of cartilage face each other anterolateral surface has two depressions, separated by a ridge, for muscle (volalis) and ligament (vestibular ligament attachment.

Question 45

Describe the vocal process of the arytenoid cartilage

Answer 45

The anterior angle of the base is elongated into a vocal process to which the vocal ligament is attacched. The lateral angle is similarly elongated into a muscular process for attachment of the posterior and lateral cricoid-arytenoid muscles

Question 46

Describe the corniculate cartilage

Answer 46

Two small conical cartilages whose bases articulate with the apices of the arytenoid cartilages. Their apices project posteromedially toward each other

Question 47

Describe the Cuneiform

Answer 47

two small-club shaped cartilages lie anterior to the corniculate cartilages and are suspended in the part of the fibrosis-eastic membrane of the larynx tahat attaches the arytenoid cartilage to the lateral margin of the epiglottis.

Question 48

Describe the thryohyoid membrane (extrinsic ligament)

Answer 48

The thyrohyoid membrane is a tough fibro-elastic ligament that spans between the superior margin of the thyroid cartilage below and the hyoid bone above ( Fig. 8.215 ). It is attached to the superior margin of the thyroid laminae and adjacent anterior margins of the superior horns, and ascends medial to the greater horns and posterior to the body of the hyoid bone to attach to the superior margins of these structures.

Question 49

Describe the key features of the thyrohyoid membrane

Answer 49

An aperture in the lateral part of the thyrohyoid membrane on each side is for the superior laryngeal artery, the internal branch of the superior laryngeal nerve, and lymphatics. The posterior borders of the thyrohyoid membrane are thickened to form the lateral thyrohyoid ligaments . The membrane is also thickened anteriorly in the midline to form the median thyrohyoid ligament . Occasionally, there is a small cartilage ( triticeal cartilage ) in each lateral thyrohyoid ligament.

Question 50

Describe the other extrinsic ligaments

Answer 50

Hyo-epiglottic ligament The hyo-epiglottic ligament ( Fig. 8.215 ) extends from the midline of the epiglottis, anterosuperiorly to the body of the hyoid bone. Cricotracheal ligament The cricotracheal ligament ( Fig. 8.215 ) runs from the lower border of the cricoid cartilage to the adjacent upper border of the first tracheal cartilage.

Question 51

Summarise the intrinsic fibre-elastic ligaments of the larynx

Answer 51

The fibro-elastic membrane of the larynx links together the laryngeal cartilages and completes the architectural framework of the laryngeal cavity. It is composed of two parts—a lower conus elasticus and an upper quadrangular membrane.

Question 52

Describe the conus elasticus (cricovocal membrane)

Answer 52

The conus elasticus ( Fig. 8.216 ) is attached to the arch of cricoid cartilage and extends superiorly to end in a free upper margin within the space enclosed by the thyroid cartilage. On each side, this upper free margin attaches: ▪ anteriorly to the thyroid cartilage, and ▪ posteriorly to the vocal processes of the arytenoid cartilages. The free margin between these two points of attachment is thickened to form the vocal ligament , which is under the vocal fold ( true vocal cord ) of the larynx. The conus elasticus is also thickened anteriorly in the midline to form a distinct median cricothyroid ligament , which spans the distance between the arch of cricoid cartilage and the inferior thyroid notch and adjacent deep surface of the thyroid cartilage up to the attachment of the vocal ligaments.

Question 53

Describe the clinical relevance of the median cricothyroid ligament

Answer 53

In emergency situations, when the airway is blocked above the level of the vocal folds, the median cricothyroid ligament can be perforated to establish an airway. Except for small vessels and the occasional presence of a pyramidal lobe of the thyroid gland, normally there are few structures between the median cricothyroid ligament and skin.

Question 54

Describe the quadrangular membrane

Answer 54

The quadrangular membrane on each side runs between the lateral margin of the epiglottis and the anterolateral surface of the arytenoid cartilage on the same side ( Fig. 8.217 ). It is also attached to the corniculate cartilage, which articulates with the apex of arytenoid cartilage. Each quadrangular membrane has a free upper margin, between the top of the epiglottis and the corniculate cartilage, and a free lower margin. The free lower margin is thickened to form the vestibular ligament under the vestibular fold ( false vocal cord ) of the larynx.

Question 55

Describe the attachments of the vestibular ligament

Answer 55

The vestibular ligament is attached posteriorly to the superior depression on the anterolateral surface of the arytenoid cartilage and anteriorly to the thyroid angle just superior to the attachment of the vocal ligament. On each side, the vestibular ligament of the quadrangular membrane is separated from the vocal ligament of the cricothyroid ligament below by a gap. Because the vestibular ligament attaches to the anterolateral surface of the arytenoid cartilage and the vocal ligament attaches to the vocal process of the same cartilage, the vestibular ligament is lateral to the vocal ligament when viewed from above

Question 56

Describe the cricothyroid joints

Answer 56

The joints between the inferior horns of the thyroid cartilage and the cricoid cartilage, and between the cricoid cartilage and arytenoid cartilages are synovial. Each is surrounded by a capsule and is reinforced by associated ligaments. The cricothyroid joints enable the thyroid cartilage to move forward and tilt downward on the cricoid cartilage Because the vocal ligaments pass between the posterior aspect of the thyroid angle and the arytenoid cartilages that sit on the lamina of cricoid cartilage, forward movement and downward rotation of the thyroid cartilage on the cricoid cartilage effectively lengthens and puts tension on the vocal ligaments.

Question 57

Describe the cricoid-arytenoid joint

Answer 57

The crico-arytenoid joints between articular facets on the superolateral surfaces of the cricoid cartilage and the bases of the arytenoid cartilages enable the arytenoid cartilages to slide away or toward each other and to rotate so that the vocal processes pivot either toward or away from the midline. These movements abduct and adduct the vocal ligaments

Question 58

Summarise the cavity of the larynx

Answer 58

The central cavity of the larynx ( Fig. 8.221 ) is tubular and lined by mucosa. Its architectural support is provided by the fibro-elastic membrane of the larynx and by the laryngeal cartilages to which it is attached. The superior aperture of the cavity (laryngeal inlet) opens into the anterior aspect of the pharynx just below and posterior to the tongue The inferior opening of the laryngeal cavity is continuous with the lumen of the trachea, is completely encircled by the cricoid cartilage, and is horizontal in position unlike the laryngeal inlet, which is oblique and points posterosuperiorly into the pharynx. In addition, the inferior opening is continuously open, whereas the laryngeal inlet can be closed by downward movement of the epiglottis.

Question 59

Describe the boundaries of the laryngeal cavity

Answer 59

▪ Its anterior border is formed by mucosa covering the superior margin of the epiglottis. ▪ Its lateral borders are formed by mucosal folds ( ary-epiglottic folds ), which enclose the superior margins of the quadrangular membranes and adjacent soft tissues, and two tubercles on the more posterolateral margin of the laryngeal inlet on each side mark the positions of the underlying cuneiform and corniculate cartilages. ▪ Its posterior border in the midline is formed by a mucosal fold that forms a depression ( interarytenoid notch ) between the two corniculate tubercles.

Question 60

Describe the divisions of the laryngeal cavity

Answer 60

Two pairs of mucosal folds, the vestibular and vocal folds, which project medially from the lateral walls of the laryngeal cavity, constrict it and divide it into three major regions—the vestibule, a middle chamber, and the infraglottic cavity ( Fig. 8.221B ): ▪ The vestibule is the upper chamber of the laryngeal cavity between the laryngeal inlet and the vestibular folds, which encloses the vestibular ligaments and associated soft tissues. ▪ The middle part of the laryngeal cavity is very thin and is between the vestibular folds above and the vocal folds below. ▪ The infraglottic space is the most inferior chamber of the laryngeal cavity and is between the vocal folds (which encloses the vocal ligaments and related soft tissues) and the inferior opening of the larynx.

Question 61

Describe the laryngeal ventricles and saccules

Answer 61

On each side, the mucosa of the middle cavity bulges laterally through the gap between the vestibular and vocal ligaments to produce an expanded trough-shaped space (a laryngeal ventricle ) ( Fig. 8.221A ). An elongate tubular extension of each ventricle (laryngeal saccule) projects anterosuperiorly between the vestibular fold and thyroid cartilage and may reach as high as the top of the thyroid cartilage. Within the walls of these laryngeal saccules are numerous mucous glands. Mucus secreted into the saccules lubricates the vocal folds.

Question 62

Describe the rima vestibuli and rima glottidis

Answer 62

When viewed from above ( Fig. 8.221C,D ), there is a triangular opening (the rima vestibuli ) between the two adjacent vestibular folds at the entrance to the middle chamber of the laryngeal cavity. The apex of the opening is anterior and its base is formed by the posterior wall of the laryngeal cavity. Inferior to the vestibular folds, the vocal folds (true vocal cords) and adjacent mucosa-covered parts of the arytenoid cartilages form the lateral walls of a similar, but narrower, triangular opening (the rima glottidis between the two adjacent vocal folds). This opening separates the middle chamber above from the infraglottic cavity below. The base of this triangular opening is formed by the fold of mucosa ( interarytenoid fold ) at the bottom of the interarytenoid notch. Both the rima glottidis and the rima vestibuli can be opened and closed by movement of the arytenoid cartilages and associated fibro-elastic membranes.

Question 63

Summarise the roles of the intrinsic muscles of the larynx

Answer 63

The intrinsic muscles of the larynx ( Table 8.19 ) adjust tension in the vocal ligaments, open and close the rima glottidis, control the inner dimensions of the vestibule, close the rima vestibuli, and facilitate closing of the laryngeal inlet. They do this mainly by: ▪ acting on the cricothyroid and crico-arytenoid joints, ▪ adjusting the distance between the epiglottis and arytenoid cartilages, ▪ pulling directly on the vocal ligaments, and ▪ forcing soft tissues associated with the quadrangular membranes and vestibular ligaments toward the midline.

Question 64

Summarise the innervation of the intrinsic muscles of the larynx

Answer 64

All innervated by the recurrent laryngeal branch of the vagus nerve Except for the criothyroid- which is innervated by the superior laryngeal nerve from the vagus nerve

Question 65

Describe the cricothyroid muscle

Answer 65

Origin- Anterolateral aspect of arch of cricoid cartilage Insertion - Oblique part—inferior horn of the thyroid cartilage; straight part—inferior margin of thyroid cartilage Function - Forward and downward rotation of the thyroid cartilage at the cricothyroid joint

Question 66

Describe the posterior crico-arytenoid muscle

Answer 66

Origin- Oval depression on posterior surface of lamina of cricoid cartilage Insertion- Posterior surface of muscular process of arytenoid cartilage Function - Abduction and external rotation of the arytenoid cartilage. The posterior crico-arytenoid muscles are the primary abductors of the vocal folds. In other words, they are the primary openers of the rima glottidis.

Question 67

Describe the lateral cricoid-arytenoid muscle

Answer 67

Origin- arytenoid Superior surface of arch of cricoid cartilage Insertion- Anterior surface of muscular process of arytenoid cartilage Function- Internal rotation of the arytenoid cartilage and adduction of vocal folds

Question 68

Describe the transverse arytenoid muscle

Answer 68

Origin- Lateral border of posterior surface of arytenoid cartilage Insertion- Lateral border of posterior surface of opposite arytenoid cartilage Function- Adduction of arytenoid cartilages

Question 69

Describe the oblqiue arytenoid muscle

Answer 69

Origin- Posterior surface of muscular process of arytenoid cartilage Insertion - Posterior surface of apex of adjacent arytenoid cartilage; extends into ary-epiglottic fold Function - Sphincter of the laryngeal inlet

Question 70

Describe the three-arytenoid muscle

Answer 70

Origin- Thyroid angle and adjacent cricothyroid ligament Insertion - Anterolateral surface of arytenoid cartilage; some fibers continue in ary-epiglottic folds to the lateral margin of the epiglottis Function - Sphincter of vestibule and of laryngeal inlet

Question 71

Describe the vocalis muscle

Answer 71

Origin- Lateral surface of vocal process of arytenoid cartilage Insertion - Vocal ligament and thyroid angle Function -adjusts tension in vocal folds

Question 72

Describe how the functions of the larynx are achieved

Answer 72

The larynx is an elaborate sphincter for the lower respiratory tract and provides a mechanism for producing sounds. Adjustments of the size of the central cavity of the larynx result from changes in the dimensions of the rima glottidis, the rima vestibuli, the vestibule, and the laryngeal inlet ( Fig. 8.225 ). These changes result from muscle actions and laryngeal mechanics

Question 73

Describe the role of the larynx in respiration

Answer 73

During quiet respiration, the laryngeal inlet, vestibule, rima vestibuli, and rima glottidis are open. The arytenoid cartilages are abducted and the rima glottidis is triangular shaped ( Fig. 8.225A ). During forced inspiration ( Fig. 8.225B ), the arytenoid cartilages are rotated laterally, mainly by the action of the posterior crico-arytenoid muscles. As a result, the vocal folds are abducted and the rima glottidis widens into a rhomboid shape, which effectively increases the diameter of the laryngeal airway.

Question 74

Describe the role of the larynx in phonation

Answer 74

When phonating, the arytenoid cartilages and vocal folds are adducted and air is forced through the closed rima glottidis ( Fig. 8.225C ). This action causes the vocal folds to vibrate against each other and produce sounds, which can then be modified by the upper parts of the airway and oral cavity. Tension in the vocal folds can be adjusted by the vocalis and cricothyroid muscles Vestibule open Vocal folds adducted and stridulating as air is forced between them

Question 75

Describe effort closure of the larynx

Answer 75

Effort closure of the larynx ( Fig. 8.225D ) occurs when air is retained in the thoracic cavity to stabilize the trunk, for example during heavy lifting, or as part of the mechanism for increasing intra-abdominal pressure. During effort closure, the rima glottidis is completely closed, as is the rima vestibuli and lower parts of the vestibule. The result is to completely and forcefully shut the airway. Vestibular and vocal folds are adducted

Question 76

Describe the role of the larynx in swallowing

Answer 76

During swallowing, the rima glottidis, rima vestibuli, and vestibule are closed and the laryngeal inlet is narrowed. In addition, the larynx moves up and forward. This action causes the epiglottis to swing downward toward the arytenoid cartilages and to effectively narrow or close the laryngeal inlet ( Fig. 8.225E ). The up and forward movement of the larynx also opens the esophagus, which is attached to the posterior aspect of the lamina of the cricoid cartilage. All these actions together prevent solids and liquids from entry into the airway and facilitate their movement through the piriform fossae into the esophagus.

Question 77

Describe cricothyrotomy

Answer 77

In emergency situations, when the airway is blocked above the level of the vocal folds, the median cricothyroid ligament can be perforated and a small tube inserted through the incision to establish an airway. Except for small vessels and the occasional presence of a pyramidal lobe of the thyroid gland, normally there are few structures between the median cricothyroid ligament and the skin.

Question 78

Describe tracheostomy

Answer 78

A tracheostomy is a surgical procedure in which a hole is made in the trachea and a tube is inserted to enable ventilation. A tracheostomy is typically performed when there is obstruction to the larynx as a result of inhalation of a foreign body, severe edema secondary to anaphylactic reaction, or severe head and neck trauma. The typical situation in which a tracheostomy is performed is in the calm atmosphere of an operating theater. A small transverse incision is placed in the lower third of the neck anteriorly. The strap muscles are deviated laterally and the trachea can be easily visualized. Occasionally it is necessary to divide the isthmus of the thyroid gland. An incision is made in the second and third tracheal rings and a small tracheostomy tube inserted. After the tracheostomy has been in situ for the required length of time, it is simply removed. The hole through which it was inserted almost inevitably closes without any intervention. Patients with long-term tracheostomies are unable to vocalize because no air is passing through the vocal cords.

Question 79

Describe laryngoscopy

Answer 79

Laryngoscopy is a medical procedure that is used to inspect the larynx. The functions of laryngoscopy include the evaluation of patients with difficulty swallowing, assessment of the vocal cords, and assessment of the larynx for tumors, masses, and weak voice. The larynx is typically visualized using two methods. Indirect laryngoscopy involves passage of a small rod-mounted mirror (not dissimilar to a dental mirror) into the oropharynx permitting indirect visualization of the larynx. Direct laryngoscopy can be performed using a device with a curved metal tip that holds the tongue and epiglottis forward, allowing direct inspection of the larynx. This procedure can be performed only in the unconscious patient or in a patient in whom the gag reflex is not intact. Other methods of inspection include the passage of fiberoptic endoscopes through either the oral cavity or nasal cavity.

Question 80

Describe the blood supply of the larynx

Answer 80

▪ The superior laryngeal artery originates near the upper margin of the thyroid cartilage from the superior thyroid branch of the external carotid artery, and accompanies the internal branch of the superior laryngeal nerve through the thyrohyoid membrane to reach the larynx. ▪ The inferior laryngeal artery originates from the inferior thyroid branch of the thyrocervical trunk of the subclavian artery low in the neck and, together with the recurrent laryngeal nerve, ascends in the groove between the esophagus and trachea—it enters the larynx by passing deep to the margin of the inferior constrictor muscle of the pharynx.

Question 81

Describe venous drainage of the larynx

Answer 81

Veins draining the larynx accompany the arteries: ▪ Superior laryngeal veins drain into superior thyroid veins, which in turn drain into the internal jugular veins ▪ Inferior laryngeal veins drain into inferior thyroid veins, which drain into the left brachiocephalic vein.

Question 82

Describe the lymphatics of the larynx

Answer 82

Lymphatics drain regions above and below the vocal folds: ▪ Those above the vocal folds follow the superior laryngeal artery and terminate in deep cervical nodes associated with the bifurcation of the common carotid artery. ▪ Those below the vocal folds drain into deep nodes associated with the inferior thyroid artery or with nodes associated with the front of the cricothyroid ligament or upper trachea.

Question 83

Describe the superior laryngeal nerves

Answer 83

The superior laryngeal nerves originate from the inferior vagal ganglia high in the neck ( Fig. 8.228 ). On each side, the nerve descends medial to the internal carotid artery and divides into internal and external branches just above the level of the superior horn of the hyoid bone: ▪ The external branch ( external laryngeal nerve ) descends along the lateral wall of the pharynx to supply and penetrate the inferior constrictor of the pharynx and ends by supplying the cricothyroid muscle. ▪ The internal branch ( internal laryngeal nerve ) passes anteroinferiorly to penetrate the thyrohyoid membrane—it is mainly sensory and supplies the laryngeal cavity down to the level of the vocal folds.

Question 84

Describe the recurrent laryngeal nerves

Answer 84

The recurrent laryngeal nerves are ( Fig. 8.228 ): ▪ sensory to the laryngeal cavity below the level of the vocal folds, and ▪ motor to all intrinsic muscles of the larynx except for the cricothyroid. The left recurrent laryngeal nerve originates in the thorax, whereas the right recurrent laryngeal nerve originates in the root of the neck. Both nerves generally ascend in the neck in the groove between the esophagus and trachea and enter the larynx deep to the margin of the inferior constrictor. They may pass medial to, lateral to, or through the lateral ligament of the thyroid gland, which attaches the thyroid gland to the trachea and lower part of the cricoid cartilage on each side.

Question 85

33. Why is the left recurrent laryngeal nerve more susceptible to damage by bronchial/oesophageal tumours and swollen mediastinal lymph nodes than the right recurrent laryngeal nerve?

Answer 85

Because the left recurrent laryngeal nerve branches off the vagus much more inferiorly than the right so it has more of its length that is near the bronchus, oesophagus and mediastinal lymph nodes Be suspect of hoarseness of the voice and coughing

Question 86

Summarise lesions of the nerve supply to the larynx

Answer 86

Vagus: complete paralysis External laryngeal: loss of sensation above folds Internal laryngeal: paralysis of cricothyroid Recurrent laryngeal: paralysis of all muscles except cricothyroid and loss of sensation below folds

Question 87

What else can damage the nerve supply to the larynx

Answer 87

Thyroidectomy Supperior laryngeal nerve- enters with superior thyroid artery Recurrent laryngeal nerve- enters with inferior thyroid artery

Question 88

Summarise the protective mechanisms of the airway

Answer 88

Swallowing Gag reflex Sneezing Coughing

Question 89

Describe the sneezing pathway

Answer 89

Afferents via V2 Inspiration Intrathoracic pressure raised (glottis closed, abdominal muscles contracted) Soft palate depressed against tongue (palatopharyngeus/palatoglossus (X)) - TO PREVENT RELEASE OF PRESSURE THROUGH THE MOUTH Sudden abduction of vocal folds to release intrathoracic pressure through nose

Question 90

Describe the cough reflex

Answer 90

Afferents via X Inspiration Intrathoracic pressure raised (glottis closed, abdominal muscles contracted) Soft palate raised and tensed against posterior wall of pharynx. (Levator veli palatini (X), tensor veli palatini (V3), sup. Constrictor (X))- TO FORCE RELEASE OF PRESSURE THROUGH THE MOUTH Sudden abduction of vocal folds to release intrathoracic pressure through nose or mouth

Question 91

35. What is the difference in the oropharyngeal isthmus in coughing compared to sneezing?

Answer 91

In coughing, the oropharyngeal isthmus is open | When sneezing, it is closed

Question 92

What is the vallecula

Answer 92

Behind the root of the tongue between the folds in the throat – they serve as spit traps, saliva is temporarily held in the valleculae to prevent initiation of the swallowing reflex

Question 93

Summarise management of the airway

Answer 93

``` Chin lift/ jaw thrust Oropharyngeal or nasopharyngeal airway Endotracheal intubation Cricothyroidotomy Tracheostomy ```