Nasal cavity, paranasal sinuses, oral cavity Flashcards
Describe the nasal cavity and function
Nasal cavity
- Houses receptors for olfaction
- adjust temperature and humidiyt of inspired air
- trap and remove particulate matte from airway by filtering air through hair in vestibule; trapping foreign material in abundant mucus (i.e. first line of defence, physical barriers, see [[Immunology Lecture 2]])
Describe the skeletal framework of the nasal cavity
The skeletal framework of the nasal cavity is comprised of the following bones:
- nasal
- maxilla
- ethmoid (which extends into cranial cavity, crista galli, note dura mater attaches here)
- vomer
- lacrimal
- inferior concha
- palatine
- sphenoid (medial pterygoid)
The septum is composed of septal cartilage, vomer, and perpendicular plate of the ethmoid bone.
In a lateral section you can see the following bones:
![[Pasted image 20230510130112.png]]
In the medial wall you can see the following bones:
![[Pasted image 20230510130032.png]]
In lateral section:
- frontal process maxilla
- inf middle and superior
- perpendicular plate of palatine bone
- medial pterygoid plate of sphenoid
- uncinate process*** of sphernoid
- nasal bone
- lacrimallbone
- lateral process of septal cartilage
- major and minor alar cartilage
In medial:
- frontal bone; nasal spine
- perpendicular plate of ethmoid bone
- sphenoidal sinus
- frontal sinus
- nasal crest of maxillary and palatine bone
- vomer
- basal one
- septal cartilage
Describe the regions of the nasal cavity
- the nasal vestibules - small space, just internal to naris (Anterior opening). It is lined by skin and contains hair follicles ^[Gray’s for students]
- respiratory regions - largest part. Well vascularises and supplied by nerves. Lined by respiratory epithelium (mainly ciliated and mucous cells) [see [[Histology Lecture 2]]]
- olfactory regions - small, at apex. Lined by olfactory epithelium, contains olfactory receptors.
![[Pasted image 20230510125929.png]]
Overview of lateral wall of nasal cavity
The lateral wall of the nasal cavity is complex. Its major features are the three conchae (known clinically as turbinates). The conchae increase the surface area of the nasal cavity and help to warm the air going into the pharynx.
The three conchae create four regions, and covers them:
- the spheno-ethmoidal recess, which is located superior to the superior nasal conchae
- the superior meatus, which lies between the superior and middle conchae
- the middle meatus, which is found between the middle and inferior conchae
- the inferior meatus, which is found inferior to the inferior nasal conchae
![[Pasted image 20230510125851.png]]
List the four paranasal sinuses and their drainage
There are four groups of paranasal sinuses:
- frontal (bilateral)
- sphenoidal (midline)
- ethmoidal (‘air cells’)
- maxillary
Note: drainage of sinuses usually follows gravity i.e. draining downwards, with the exception of the sphenoidal sinus, which drains into an adjacent structure (the spheno-ethmoidal recess, above the superior nasal concha)
Note 2: naso-lacrimal duct drainage explains why sniffly nose when crying
Describe innervation of nasal cavity
The nasal cavity is the site of one of the special sensations (see [[Anatomy Lecture 6]]- general and special sensations).
The nerve responsible for this is the olfactory nerve or CNI (see [[Anatomy Lecture 7]]).
This is an old or primitive sensation. It thus has no connection to either thalamus or brainstem.
Olfactory nerve
The olfactory receptors are fascicles/chemoreceptors embedded in the nasal mucosa in the olfactory region of the nasal cavity.
It has a bony entry to the skull: the cribriform plate of ethmoid - this enables its entry into the anterior cranial fossa to the olfactory bulb, where it synapses and travels down olfactory tract (medial to temporal lobe) to pyriform lobe (uncus).
Its function is sense of smell.
Damage to this nerve results in anosmia.
It also affects taste as well (taste involves chemoreceptors)
General sensation
The remainder of the nasal cavity is innervated by branches of the trigeminal nerve (CN V).
The ophthalmic nerve V1 innervates the anterior portion (respiratory region/nasal vestibules), while the maxillary V2 innervates the conchae and meatuses (respiratory region).
![[Pasted image 20230510133051.png]]
Describe the arterial supply of nasal cavity
The nasal cavities and the external surface of the nose are supplied by branches of both external and internal carotid arteries.
The external carotid artery supplies the face, the internal carotid artery supplies nerves, especially autonomic SNS ^[very small fibres, and thus looks for hitchhikes e.g. arteries].
- ophthalmic artery, a branch of internal carotid artery (the first branch), supplies anterior and posterior ethmoid
- maxillary artery, off the external carotid artery: supplies sphenopalatine and greater palatine.also supplies facial nerves?
- facial artery, off external carotid artery, supplies superior labial i.e. front of nose
Note: arterial branches form extensive anastomoses with each other. Kiesselbach’s plexus - source of spontaneous nosebleeds. Push on it to close vessels, stop bleed.
Route of sympathetic nerve out ouf JI?
Describe the arterial supply of nasal cavity
The nasal cavities and the external surface of the nose are supplied by branches of both external and internal carotid arteries.
The external carotid artery supplies the face, the internal carotid artery supplies nerves, especially autonomic SNS ^[very small fibres, and thus looks for hitchhikes e.g. arteries].
- ophthalmic artery, a branch of internal carotid artery (the first branch), supplies anterior and posterior ethmoid
- maxillary artery, off the external carotid artery: supplies sphenopalatine and greater palatine.also supplies facial nerves?
- facial artery, off external carotid artery, supplies superior labial i.e. front of nose
Note: arterial branches form extensive anastomoses with each other. Kiesselbach’s plexus - source of spontaneous nosebleeds. Push on it to close vessels, stop bleed.
Route of sympathetic nerve out ouf JI?
Describe venous drainage of nasal cavity
Venous drainage
- veins usually follow arteries and are thus named the same
- veins running with maxillary atery along lower, posterior wall, drain into pterygoid plexus (infratemporal fossa)
- veins from anterior region drain into facial vein
- anterior and posterior ethmoidal veins (upper wall) drain into the ophthalmic vein which in turn drains into the cavernous sinus (emissary veins - connect extra and intracranial venous systems)
![[Pasted image 20230510133934.png]]
![[Pasted image 20230510133953.png]]
Clinical significance of emissary veins:
- infection on facial surface -> -> brain
- thus give antibiotics
Sneeze reflex:
trigeminal nerve and sensation, facial nerve for action (among others)
Describe the divisions of the oral cavity
Oral cavity is composed of two main parts:
- oral cavity proper or area behind teeth
- vestibule or area in front of teeth
Recall the muscles of the oral cavity:
- orbicularis oris: the thick fleshy muscle making up the bulk of the lips –purses the lips
- buccinator: fibres that make up the bulk of the cheeks. The buccinator muscle sits parallel to the teeth ad keeps food inside the mouth.
Note: the orbicularis oris and buccinator muscles together interlace around the lips and make up the anterior and lateral boundaries of the mouth
As these muscles are involved in facial expression, they are supplied by the facial nerve or CNVII.
Describe the skeletal framework fo the oral cavity
- maxilla and palatine bones: these make up the hard palate or the roof of the mouth; maxilla is the insertion of upper maxillary teeth
- sphenoid bone: an attachment site for the soft palate or the back of the mouth, as well as blood vessels and nerve communications
- temporal bones: anchor and attachement for muscles as well as blood vessels and nerve communications
- mandible: holds lower mandibular teeth, involved in food processing
- hyoid: attachemet fro suprahyoid muscle, forms base of the cavity, and helps make the floor of the mouth along with the tongue
Describe the muscles that comprise the floor of the mouth
There are four muscles that comprise the floor of the mouth (Rule of four). These muscles include:
- mylohyoid and geniohyoid muscles (forming the suprahyoid muscle)
- stylohyoid muscle
- digastric muscle
The purpose of the four muscles of the floor of the mouth is to keep food inside, as well as to assist in making sounds
The mylohyoid muscle forms a sling:
- O: attaches to mylohyoid line on the mandible
- I: into midline raphe that extends from mandible to hyoid bone, and directly into body of **hyoid bone
- A: supports weight of tongue and tenses the floor of the mouth
The geniohyoid muscle sits in the midline on top or above the mylohyoid:
- O: inferior mental spines of mandible
- I: body of hyoid
- A: draws hyoid bone forward
The stylohyoid muscle pulls the hyoid up:
- O: posterior aspect of styloid process, pierced by digastric?
- I: lesser cornu of hyoid bone
- A: elevates the hyoid and draws it posteriorly
The digastric muscle has two parts: an anterior belly and posterior belly
- O: of the posterior belly is the anterior mastoid process. It forms a tendon that passes through a sling attached tot he lesser horn of the hyoid bone
- I: anterior bellow- anterior, inner aspect of the mandible below the mylohyoid muscle
- A: elevates the hyoid, like the stylohyoid muscle, and helps to tense the floor of the mouth
Nerve supply:
- the stylohyoid is innervated by VII (i.e. the facial nerve - coming through the stylomastoid foramen)
- the mylohyoid is innervated by V3 i.e. the mandibular branch of the trigeminal nerve
- the digastric, anterior belly, is innervated by V3
- the digastric, posterior belly is innervated by facial nerve
- geniohyoid, is innervated by C1 (by way of XII - hypoglossal nerve ) (see [[Anatomy Lecture 7]])
Note: geniohyoid is close to tongue and is thus innervated by the same nerve. Note that sometimes C1 is missing***, and thus XII serves as a redundancy
Recall the temporomandibular joint (see [[Anatomy 1 - Skeletal system]])
- formed by the mandibular fossa of the temporal bone (Anterior border = articular tubercle)
- and head of mandible
- the joint type is = bilateral synovial, hinge or condyloid***
- joint cavity is divided horizontally by a mobile ‘intra-articular disc’
- the head of the mandible rotates and glides during normal movements of the jaw
- The joint capsule is strong and contains intracapsular ligaments
Describe the muscles of mastication
mastication
There are four muscles of mastication, and they are:
1. Temporalis muscle
- sits in temporal bone
- fan shaped (technical name is?)
- origin is temporal fossa. the fibres converge on a tendon that passes under the zygomatic arch
- insertion: coronoid process of the mandible and anterior margin of ramus of mandible
- works to elevates and retracts mandible
2. Masseter muscle
- origin is zygomatic arch, inferior margin and inner aspect. Deep fibres are short, superficial fibres are long
- insertion at angle of mandible, on its outer surface
- work to elevate the jaw (very powerful)
3. Lateral pterygoid
- origin: from lateral surface of the lateral pterygoid plate
- insertion: anterior aspect of the TMJ capsule, and into the anterior border of the intra-articular disc
- action: pulls disc and mandible forward i.e. protraction or protrusion
- Medial pterygoid
- origin: medial surface of the lateral pterygoid plate
- insertion: angle of mandible on its inner surface
- action: elevates mandible
Innervation:
all muscles of mastication are innervated by anterior division of V3 (mandibular branch of trigeminal nerve)
(direction of fibres in the muscle)
Actions of muscles of mastication
- protrusion: lateral pterygoid, assisted by medial pterygoid
- retraction: posterior fibres of temporalis, deep portion of masseter, geniohyoid, digastric
- elevation: temporalis, masseter, medial pterygoid
- depression: gravity, and digastric, geniohyoid and mylohyoid muscles
Describe the components of teeth*
The tooth acan be divided into three main parts:
- crown
- neck
- root
- dentin: bulk of tooth, inside
- crown: sits above gingiva, where dentin is covered by enamel
- neck: sits at gingival border
- cementum: covers the dentin in the alveolar socket, forms the gomphosis/synarthrosis (fibrous joint) to fix the teeth in place
- root: within mandible and maxilla, has hollowed pulp cavity filled iwth pulp, alveolar vessels and nerves; it continues in root canal. The root canal opens at apical foramen to allow crossing of blood vessels and nerves to supply each tooth.
Describe the tongue
The tongue
- Apex: blunt (anterior part), sits behind incisors
- root: attached to mandible and hyoid
- anterior 2/3s of tongue forms floor of mouth
- posterior 1/3 forms part of the oropharynx
- the anterior and posterior portions are divided by V-shaped terminal sulcus, which is itself the inferior margin of the oropharyngeal isthmus (not shown on diagram)
- the foramen cecym sits at the apex of the sulcus - the closed off throglosssal duct*
The anterior 2/3 and posterior 1/3 have different embryological origins and as a result have different nerves supplies.
The anterior 2/3 is relatively smooth, but contains hundred of papillae, increasing the surface area.
The pharyngeal surface (posterior?) is irregular. This irregularity is created by many small lymphoid tissues - the lingual tonsils.
The tongue is a strong muscular tissue.
It contains intrinsic and extrinsic muscles.
- intrinsic muscles remain entirely within the tongue i.e. do not attach to anything outside the tongue.
- The fibres of intrisic muscles are arranged in x, y, z planes
- this facilitates changes of shape needd for speeech and chewing and helps alter the shape of the tongue
- it also enables preision movement required for speech, eating and swallowing
- the extrinsic muscles originate outside the tongue and insert within the tongue, and work to protrude, depress, elevate and retract the tongue
