Nasal Cavity and Smell

Question 1

alar cartilage

Answer 1

• this along with the lateral cartilage is the most anterior portion of the nose

Question 2

nasal septum

Answer 2

• this is made up of the perpendicular plate of the ethmoid bone and the vomer
• the septum separates the left and right aspects of the nasal cavity

Question 3

nasal conchae

Answer 3

• there is a superior, medial, and inferior
• these form the the lateral wall for each cavity and are very important for the warming, moistening and conditioning of the air
• they cause the air to swirl and come in contact with the mucus for a longer amount of time

Question 4

nasal cavity

Answer 4

• the inferior boarder is formed by the maxilla and the palatine bone (the bones of the roof of the mouth)
• the superior boarder is formed by the cribriform plate of the ethmoid bone

Question 5

cribiform plate foramina

Answer 5

this is where the olfactory nerve travels through to get to the olfactory bulb

Question 6

what does the mucus layer do in the nasal cavity

Answer 6

this is what is conditioning the air, it moistens it and warms it before entering the lungs to protect the gas exchange surfaces of the lungs

Question 7

paranasal sinuses

Answer 7

• these are air filled spaces in the skull around the nasal cavity
• have a mucus lining

functions:
- lighten the skull
- humidify/warm air
- can trap things in the mucus lining
- they are resonance chambers in sound production

• frontal sinus
• ethmoid air cells
• sphenoidal sinus
• maxillary sinus

Question 8

what does it mean that the sinuses aid in sound production

Answer 8

• if someone has a sinus infection of a bad cold and the sinuses get clogged up then the can affect how people sounds when they speak

Question 9

frontal sinus

Answer 9

this is within the frontal bone

Question 10

ethmoid air cells

Answer 10

these are within the ethmoid bone and they are smaller openings within the bone

Question 11

sphenoidal sinus

Answer 11

• this is in the sphenoid bone

Question 12

maxillary sinus

Answer 12

• this is in the maxillary bone

Question 13

olfactory epithelium

Answer 13

specialized region of tissue lining

• this is at the superior aspect of the nasal cavity
• this contains a mucus layer that traps particles
• contains olfactory receptor cells
• contains olfactory hairs

Question 14

what happens at the mucus layer

Answer 14

this is what captures the molecules of the substance that is causing the odor and the breakdown of these molecules allows for the stimulation of the olfactory hairs

Question 15

olfactory receptor cells

Answer 15

• these are bipolar neurons

- their axons form CN I (olfactory nerve)

Question 16

olfactory hairs

Answer 16

• these are free nerve endings (cilia) projectioning into the mucous layer
• they contain receptors for the airborne molecules
• they are able to rapidly adapt and that is why we get used to smells (good or bad)

Question 17

describe what happens when the olfactory hairs come in contact with smell molecules

Answer 17

• the mucus layer traps and breaks them down, allowing the hairs to come in contact
• the hairs sense the smell and send information through the bipolar cells (olfactory receptor cells)
• the axons of these form the olfactory nerve and travel through the foramina of the cribriform plate to the olfactory bulb

Question 18

how long is CN I

Answer 18

the olfactory nerve is very short and only travels from the olfactory epithelium to the olfactory bulb and synapses there

Question 19

olfactory bulb

Answer 19

receive information about smells from the nose and send it to the brain by way of the olfactory tracts

Question 20

olfactory tract

Answer 20

a bundle of nerve fibers that connect the olfactory bulb with olfactory nuclei and the olfactory cortex

• this travels to the primary olfactory cortex of the brain
• this is not part of CN I
• the axons travel posteriorly away from the olfactory bulb

Question 21

primary olfactory cortex

Answer 21

• this provides conscious awareness of smell
• this is highly connected to the hippocampus and the limbic systems allowing for smell to be tied to different memories and emotions and smells can trigger memories

Question 22

primary smells

Answer 22

there are up to 50 of these

• these are things like mint, fishy, or sweat

Question 23

secondary smells

Answer 23

• these are produced by a combination of chemicals
• flower blossoms can have ~100 different compounds
• what we smell is ultimately the CNS’s interpretation of the activity of the different receptors on the olfactory hairs

Question 24

olfactory discrimination

Answer 24

neurons have different sensitivities to different molecules of odor

Question 25

how does aging relate to smells

Answer 25

• olfactory neurons are continually replaced throughout life
• this is unique because as we have learned neurons typically do not divide
• this makes sense evolutionarily because many animals rely on smell for survival so it makes sense to have a replenishment of them
• the total number of neurons declines with age and the sensitivity becomes less

Question 26

does the nose grow with age

Answer 26

• the nose is not technically growing
• the nose is getting more cross sectioning and scaring of collagen fibers and unlike other collagen in the body, the collagen here does not degrade, so it may appear to get larger but it is not growing