Anatomy of the Nose and Olfactory NerveNeuroanatomy block-Anatomy-Lecture 12

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● Describe the boundaries and functions of the nose and nasal cavity.● Describe the nasal conchae and meati.● Demonstrate the openings in each meatus.● Describe the arterial supply and innervation of the nose.● Describe the paranasal sinuses and their functions● Describe the clinical significances of the nose and nasal cavity.

At the end of the lecture, students should be able to:

Objectives

Color guide ● Only in boys slides in Green● Only in girls slides in Purple● important in Red● Notes in Grey

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The Nose● The external (anterior) nares or nostrils lead to to the

nasal cavity.● Formed above by bony skeleton.● Formed below by plates of hyaline cartilage

Only in boys slide

Divisions of Nasal Cavity:Vestibule region:

- The area surrounding the external opening to the nasal cavity.- Lined by modified skin, provided with hairs and Sebaceous glands to filter the incoming air. (Exocrine glands in the skin that secrete an oily or waxy matter called sebum to lubricate and waterproof the skin and hairs.)

- The largest region.- Lined with mucous that is continuous with that of Nasal Sinuses, Lacrimal sac, Conjunctiva, and Nasopharynx.

- Located at the apex of the nasal cavity.- It is lined by olfactory cells with olfactory receptors.

Respiratory region: Olfactory Region

● It is a large air filled space above and behind the nose in the middle of the face.

● Each cavity is the continuation of one of the two nostrils.● It communicates with nasopharynx posteriorly.● It consists of Vestibule, Respiratory, and Olfactory regions.● It extends from nostrils anteriorly to turbinate (choanae)

posteriorly.(in both slides)

Nasal Cavity 2

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FunctionsOlfaction: Smell

Respiration: Breathing

Warming the inspired air:submucous venous plexus.

Filtration of dust

Humidification of the inspired air: Mucous

Reception of secretions from the paranasal sinuses and nasolacrimal duct.

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Respiratory mucosa

● It is thick, ciliated highly vascular and contains mucous glands goblet cells

● It lines the lower part of the nasal cavity.(From skin of vestibule to the superior concha).

● It functions to moisten, clean and warm the inspired air● The air is moistened by the secretion of numerous serous glands● It is cleaned by the removal of the dust particles via ciliary

action of the columnar ciliated epithelium that covers the mucosa.

● The air is warmed by a submucous venous plexus.

Nasal (Olfactory) mucosa

● It is delicate and contains olfactory nerve cells.● It is present in the upper part of nasal cavity:

○ Roof○ On the lateral wall, it lines the upper surface of the

superior concha and the sphenoethmoidal recess.○ On the medial wall, it lines the superior part of the

nasal septum.

Nasal Cavity mucosaOnly in girls slide

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It is divided into right and left parts by nasal septum Each part has

Floor Roof Medial wall Lateral wall

It is formed by:The nasal (upper) surface of the hard (bony) palate:-Palatine process of maxilla (Anteriorly). -Horizontal plate of the palatine (Posteriorly).

it is formed by: -Body of sphenoid (Posteriorly).-Cribriform plate of ethmoid (Middle). -Frontal bone (Anteriorly).- Nasal bone (Anteriorly).

The nasal septumVertical plate of ethmoid.Vomer.Septal Cartilage.

Marked by three projections 1. Superior concha. 2. Middle concha. 3. Inferior concha. they Function :to increase the surface area of the nasal cavity to increases the amount of inspired air They also disrupt the fast, laminar flow of the air, making it slow and turbulent. The air spends longer in the nasal cavity, so that it can be humidified.They project into the nasal cavity, creating four pathways for the air to flow:1.Spheno-ethmoidal recess: opening of sphenoid air sinus

2. Superior meatus: receives openings of posterior ethmoidal sinuses.

3. Middle meatus. Contain: (bulla ethmoidalis) for opening of middle ethmoidal sinusHiatus semilunaris for openings of maxillary sinus,Infundibulum opening of Frontonasal duct that drains the frontal sinus and anterior ethmoidal sinus.

4. Inferior meatus: receives opening of nasolacrimal duct.

Nasal Cavity :

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Nerve supply Arterial supply Venous drainage Lymph drainage

● Nerves of smell: Olfactory Nerves (Cr 1).● Nerves of general sensation: Ophthalmic

and Maxillary divisions of Trigeminal nerve (Cr 5).● The anterior part is supplied by:

Anterior Ethmoidal nerve.● The posterior part is supplied by

branches of the pterygopalatine ganglion:

1. Nasopalatine2. Nasal.3. Palatine.

The nasal cavity receives blood from:● Internal carotid branches: Anterior and

Posterior Ethmoidal (ophthalmic).● External carotid branches:1. Sphenopalatine artery (Maxillary).2. Superior labial (Facial).3. Greater palatine artery4. Lateral nasal arteries ● Applied anatomy :The most common site

for epistaxis is at the anterior & inferior part of nasal septum (Little’s area) because of the rich arterial anastomosis.

● Venous plexus in submucosa formed by veins accompanying the arteries

● They drain into the pterygoid venous plexus & facial vein or cavernous sinus.

● Submandibular &● Upper deep cervical

nodes.

Nasal Cavity

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Paranasal SinusesDefinition

● They are a group of four paired air-filled spaces that surround the nasal cavity.

● They are lined with respiratory epithelium mucoperiosteum (ciliated pseudostratified columnar epithelium).

● Open in the lateral wall of the nasal cavity● Divided into subgroups that are named according

to the bones within which the sinuses located:

1. The Maxillary Sinuses: the largest of the paranasal sinuses, located under the eyes, in the maxillary bones.2. The Frontal Sinuses: superior to the eyes, in the frontal bone, which forms the hard part of the forehead.3. The Ethmoidal Sinuses: formed from several discrete air cells within the ethmoid bone between the nose and the eyes.4. The Sphenoidal Sinuses: in the sphenoid bone.

Functions

1. (Lighten the skull weight).2. Increasing resonance of the voice

(Amplify the sound as we speak).3. Providing a buffer against facial

trauma.4. Insulating sensitive structures like

dental roots and eyes from rapid temperature change in the nasal cavity.

5. Humidifying and heating of inhaled air because of slow air turnover in this region.

Clinical significance 1. Inflammation

● The paranasal sinuses are joined to the nasal cavity via small orifices called ostia These become blocked easily by allergic inflammation or by swelling in the nasal lining that occurs with a cold If this happens, normal drainage of mucus within the sinuses is disrupted, and sinusitis may occur.

● Because the maxillary posterior teeth are close to the maxillary sinus, this can also cause clinical problems if any disease processes are present, such as an infection in any of these teeth

2. Cancer● Malignancies of the paranasal sinuses

comprise approximately 0 2 of all malignancies

● About 80 of these malignancies arise in the maxillary sinus, tumors of the sphenoid and frontal sinuses are extremely rare.

● Carcinomas are more frequent than sarcomas.

Olfactory nerve

Mitral cells of olfactory bulbOlfactory receptors

● 1st order neuron● they are specialized, ciliated nerve

cells that lie in the olfactory epithelium

● Once the axon penetrates through the basement membrane, it joins other non-myelinated processes to form the fila olfactoria.(bundles of olfactory axons)

● The axons of these bipolar cells 12-20 fibers from the ture olfactory nerve fibers which pass through the cribriform plate of ethmoid (in the roof of the nasal cavity) and then join the olfactory bulb.

● The first and shortest cranial nerve, it is the nerve that transmits special sensory information to have a sense of smell.● it is one of two cranial nerves that do not emerge from the brainstem.● Elderly people usually have less sensation of smell probably because of progressive reduction in number of olfactory cells.

Olfactory pathway: it is important to note that the olfactory nerve is made up of multiple nerve fibers/rootlets coming from the receptors cells.The pathway can be summarized as follows: olfactory receptor cells, olfactory nerves, olfactory bulb, olfactory tract, olfactory striae, olfactory cortex The only sensory pathway which reaches the cerebral cortex without passing through the Thalamus.

● 2nd neuron● In the cranial cavity, the fibres enter the

olfactory bulb, which lies in the olfactory groove, within the anterior cranial fossa.

● Preliminary processing of olfactory information is within the olfactory bulb which contains interneurons and large Mitral cells.

● The olfactory nerve fibres synapse with the mitral cells, forming collections known as synaptic glomeruli.

● From the glomeruli, second order nerves then pass posteriorly into the olfactory tract

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Olfactory nerveOlfactory tract

● The olfactory tract runs inferiorly to the frontal lobe

● Each tract divides into 2 roots at the anterior perforated substance

● Posterior and anterior to the optic chiasm, the olfactory tract on both sides splits into medial and lateral olfactory striae.

Olfactory STRIAE

● Medial root (Medial stria):❖ crosses midline through anterior

commissure and joins the uncrossed olfactory bulb lateral root of the opposite side.

❖ It connects olfactory centers of 2 cerebral hemispheres, so each olfactory centre receives smell sensation from both halves of nasal cavity.

❖ Lateral root (Lateral stria):❖ Carries olfactory fibers to end in cortex of

the Uncus & adjacent Hippocampal gyrus (center of smell). olfactory area of the cerebral cortex (also known as the primary olfactory cortex)

❖ The primary olfactory cortex sends nerve fibres to many other areas of the brain, like piriform cortex, amygdala, olfactory tubercle and the secondary olfactory cortex.

❖ These areas are involved in the memory and appreciation of olfactory sensations.

The primary olfactory cortex

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Clinical Significance Dysosomia

➝ A distortion in the quality of the perception of an odor.➝ Sometimes, the perception of an odor when no odor is actually present.➝ Damage to olfactory nerve fibers can occur as a complication of upper respiratory tract infections.➝ A decrease in the number of nerve fibers from these infections mean that there are not enough different fibers to accurately differentiate odors resulting in parosmia.

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Only in boys slide

Ansomia

➝ The absence of the sense of smell.➝ It can be temporary or permanent.➝ Temporary anosmia can be caused by infection or by local disorders of the nose.➝ Permanent anosmia can be caused by head injury, or tumours which occur in the olfactory groove (e.g. meningioma).Anosmia can also occur as a result of neurodegenerative conditions, such as Parkinson’s or Alzheimer's disease

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Summary Anatomy of the nose and Olfactory nerve

Nasal Cavity

- Floor:It is formed by:1. The nasal (upper) surface of the hard (bony) palate.2. Palatine process of maxilla (Anteriorly). 3. Horizontal plate of the palatine (Posteriorly).- Roof:It is formed by:1. Body of sphenoid (Posteriorly).2. Cribriform plate of ethmoid (Middle).3. Frontal bone (Anteriorly).4. Nasal bone (Anteriorly).- Medial wall:The nasal septum:Vertical plate of ethmoid.Vomer.Septal Cartilage.- Lateral wall:Marked by three projections:1. Superior concha.2. Middle concha.3. Inferior concha.The space below each concha is called meatus:1. Superior meatus.2. Middle meatus.3. Inferior meatus.*The space (fossa) above the superior concha is called the Sphenoethmoidal recess.

sinuses opening in lateral wall

1. Sphenoethmoidal recess ---> sphenoidal air sinus.2. Superior meatus ---> posterior ethmoidal sinus.3. Middle meatus---> maxillary, frontal, & anterior , middle ethmoidal sinuses.4. Inferior meatus ---> nasolacrimal duct .

Paranasal sinuses

There are four paired of paranasal sinuses, divided into subgroups that are named according to the bones within which the sinuses located:1. Maxillary sinuses.2. Frontal sinuses.3. Ethmoidal sinuses.4. Sphenoidal Sinuses.

Mucosa

Olfactory Mucosa:- is delicate and contains olfactory nerve cells.- It is present in the upper part of nasal cavity.- On the lateral wall, it lines the upper surface of the superior concha and the sphenoethmoidal recess.- On the medial wall, it lines the superior part of the nasal septum.

Respiratory Mucosa:- it is thick, ciliated highly vascular and contains mucous glands goblet cells.-It lines the lower part of the nasal cavity.(From skin of vestibule to the superior concha).- It functions to moisten, clean and warm the inspired air.

Arterial supply

Internal carotid branches:1. Anterior ethmoidal artery.2. Posterior ethmoidal artery.3. Branch of ophthalmic arteryExternal carotid branches:1. Sphenopalatine artery (Maxillary).2. Superior labial (Facial).3. Greater palatine artery (Maxillary).4. Lateral nasal arteries (Facial).

Lymphatic Drainage

To Submandibular &Upper deep cervical nodes.

Venous Drainage

Venous plexus in submucosa formed by veins accompanying the arteriesThey drain into the pterygoid venous plexus & facial vein or cavernous sinus.

Nerve Supply

1. General sensation:General sensory innervation to the septum and lateral walls is delivered by the nasopalatine nerve (branch of maxillarynerve) and the nasociliary nerve (branch of the ophthalmic nerve).The anterior part is supplied by: Anterior Ethmoidal nerve.The posterior part is supplied by branches of the pterygopalatine ganglion: 1-Nasopalatine, 2- Nasal, and 3- Palatine.2. Special sensation.Olfactory nerve:1st neurone:Olfactory receptors, the axons of these bipolar cells form true olfactory nerves which pass through the cribriform plate of ethmoid and then join olfactory bulb.2nd neurone: It is formed by the Mitral cells of olfactory bulb. The axons of these cells form the olfactory tract.Each tract divides into 2 roots at the anterior perforated substance:1. Lateral root: Carries olfactory fibers to end in cortex of the Uncus & adjacent part of Hippocampal gyrus (center of smell).2. Medial root: crosses midline through anterior commissure and joins the uncrossed lateral root of opposite side. It connects olfactory centers of 2 cerebral hemispheres, So each olfactory centre receives smell sensation from both halves of nasal cavity.

Clinical significance

1. Nose bleed. 2. Diseases of the nasal cavity (Viral, bacterial, fungal infection, nasal cavity tumors, inflammations of the nasal mucosa).3. Ansomia (the absence of smell sensation). 4. Dysosmia (distortion in the quality of the smell).

Practice Q1: The floor of the nasal cavity composed of all the following except:

A. The nasal surface of the hard bony palate.

B. Palatine process of maxilla.

C. Body of sphenoid.

D. Horizontal plate of the palatine.

Q2: The roof of the nasal cavity composed of:

A. Cribriform plate of ethmoid.

B. Vomer.

C. Vertical plate of ethmoid.

D. Septal Cartilage.

Q3: The medial wall of the nasal cavity composed of:

A. Body of sphenoid.

B. Vomer.

C. Frontal bone.

D. Nasal bone.

Q4: The openings of posterior ethmoidal sinuses located in:

A. Sphenoethmoidal recess.

B. Superior meatus.

C. Middle meatus.

D. inferior meatus.

Q5: The first order neuron of the olfactory pathway:

A. Olfactory receptors.

B. Mitral cells.

C. Olfactory bulb.

D. Olfactory tract.

Q6: All these cranial nerves emerge from the brainstem except:

A. Glossopharyngeal (IX).

B. Facial (VII).

C. Olfactory (I).

D. Oculomotor (III)

Q7: Which root of 2nd neuron (mitral cells) joins the opposite side?

A. Lateral root

B. Upper root

C. Medial root.

D. Lower root.

Q8 : The lymph drainage of the nasal cavity:

A. Lower deep cervical nodes.

B. Submandibular & Upper deep cervical nodes.

C. Submandibular & Middle deep cervical nodes.

D. Submandibular & Lower deep cervical nodes.

Answers: Q1(C) Q2(A) Q3(B) Q4(B) Q5(A) Q6(C) Q7(C) Q8(B) 12

Girls team :

● Ajeed Al Rashoud● Taif Alotaibi● Noura Al Turki● Amirah Al-Zahrani● Alhanouf Al-haluli● Sara Al-Abdulkarem● Renad Al Haqbani● Nouf Al Humaidhi● Jude Al Khalifah● Nouf Al Hussaini● Rahaf Al Shabri● Danah Al Halees● Rema Al Mutawa● Amirah Al Dakhilallah● Maha Al Nahdi ● Razan Al zohaifi ● Ghalia Alnufaei

Boys team:

● Mohammed Al-huqbani● Salman Alagla● Ziyad Al-jofan● Ali Aldawood● Khalid Nagshabandi● Omar Alammari● Sameh nuser● Abdullah Basamh● Alwaleed Alsaleh● Mohaned Makkawi● Abdullah Alghamdi

Team leaders

● Ateen Almutairi● Abdulrahman Shadid

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