Special Sub-Topic: What's That Smell? - The Nasal Cavity
|Olfaction is the term given to the sense of smell. Which cranial nerve is the olfactory nerve?|
I. The olfactory nerve is unusual in that the neurons continue to divide throughout a person's life. Also, they do not form trunks; instead, the fibers travel to the olfactory bulb, which is part of the forebrain. To test the integrity of each olfactory nerve, the patient's nostril is blocked on one side, and a strong odor is introduced to the other nostril.
|Through which sieve-like structure of the ethmoid bone do the fibers of the olfactory nerve travel?|
Cribriform plate. The name comes from the Latin "cribrum", which means sieve. The cribriform plate is filled with foramina (holes) which transmit the olfactory fibers to the roof, the septum, and superior concha of the nose. There is also a foramen for the nasociliary nerve, which is a branch of the ophthalmic nerve (which in turn comes from the fifth cranial nerve, the trigeminal nerve).
|While the superior concha is part of the ethmoid bone, both the middle and inferior conchae are formed from a separate bone.|
f. In fact, both the superior and middle conchae are part of the ethmoid bone, while the inferior concha is regarded as a separate bone. The conchae are sometimes called turbinates. Their shapes leave curved gaps between them called meatuses - when air is breathed in, it circles around these meatuses and becomes warmed and humidified.
|Why do we sniff when we want to smell something?|
To divert air to the sphenoethmoidal recess. As suggested by its name, the sphenoethmoidal recess sits at the junction between the sphenoid sinus (within the sphenoid bone) and the air cells of the ethmoid bone. It is lined by olfactory epithelium, which is a special type of nervous tissue. Neurons project from the epithelium to the olfactory nerve, which is responsible for the sense of smell. By sniffing, air is diverted past the meatuses in the nose toward this olfactory epithelium, which allows the detection of odors.
|Which part of the nostril is lined with skin and hair?|
Vestibule. The vestibule is covered with stratified squamous, keratinized epithelium. The hairs that are present are called vibrissae, otherwise known as whiskers. The vibrissae filter dust and other particles that are breathed in, and they can be seen most prominently on older males.
|Of which bone is the lamina papyracea part?|
Ethmoid bone. The lamina papyracea is also called the orbital lamina of the ethmoid bone and it forms part of the medial wall of the orbit. "Papyracea" means "paper-like"; the lamina papyracea is very thin and is one of the weakest parts of the orbit, thus it is easily fractured.
|Which of these is false about the paranasal sinuses?|
They are lined by olfactory epithelium.. The development of the paranasal sinuses begins in the womb, and continues throughout a person's life. No one knows their function for sure - one theory is that they are an elaboration of the nasal cavity, supported by the fact that they are lined by respiratory epithelium. Other theories include that they serve as echochambers for the voice - you know yourself that your voice sounds funny when you have a cold and your sinuses are filled with mucus! A further theory is that they serve to cool the brain's blood supply; the internal carotid artery runs by the sphenoidal sinus before it enters the brain.
|Generally, the more complex an animal, the more paranasal sinuses it has.|
t. Humans have the most paranasal sinuses: four on each side; frontal, maxillary, ethmoid, and sphenoid. Some people also regard the middle ear cavity as a paranasal sinus. Birds, on the other hand, only have one: the infraorbital sinus. There appears to be an evolutionary trend toward more paranasal sinuses, but as the exact function of the sinuses remains unknown, this trend cannot be explained very well.
|Which cranial nerve is responsible for sensory innervation of the nose?|
Trigeminal (V). Two branches of the trigeminal nerve, V1 and V2, relay sensory information from the nose, particularly the nasociliary nerve (from V1), the nasopalatine nerve (from V2) and parts of the maxillary nerve (from V2).
The olfactory (I) nerve is responsible for the sense of smell.
|Which of these is not contained in Waldeyer's ring in humans?|
Paraepiglottic tonsil. Waldeyer's ring, sometimes called Waldeyer's-Pirogov tonsillar ring, is lymphoid tissue in the pharynx, and contains the pharyngeal, tubal, palatine, and lingual tonsils. The pharyngeal tonsils are called the adenoids when infected, and the tubal tonsils are the ones referred to as just "tonsils" in general usage. While some animals do have paraepiglottic tonsils, humans do not.
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