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Eyes, ears, nose, and throat
Anatomy and physiology of the ear
Auditory transduction and pathways
Taste and the tongue
Olfactory transduction and pathways
Vestibulo-ocular reflex and nystagmus
Anatomy and physiology of the eye
Optic pathways and visual fields
Phosphate, calcium and magnesium homeostasis
The tongue is a muscular organ in the mouth, and it’s used for many things like speech, chewing and swallowing food, and most important of all, tasting delicious foods, which is called gustation.
The surface of the entire tongue is covered by a mucus membrane called the mucosa, and below that there’s a combination of intrinsic and extrinsic muscles which are all innervated by the hypoglossal nerve which is cranial nerve 12.
Intrinsic muscles start and end within the tongue, and help change its shape, whereas extrinsic muscles attach to structures outside the tongue and help guide its movement.
Now, on the tongue, there’s a V shaped groove called the sulcus terminalis that runs across the posterior portion of the tongue dividing it into an posterior ⅓ and anterior ⅔.
The posterior ⅓ of the tongue is covered in bumps made of lymphoid tissue called lingual papillae which contains B and T cells that help fight off pathogen that enters the mouth.
The anterior ⅔ which is covered in smaller lumps called papillae that help increase the surface area and give it a rough texture that helps food particles stick to the tongue.
There are four different types of papillae and they’re found in different regions of the tongue. The most numerous type are the thread-like, filiform papillae which are scattered all over the anterior ⅔ of the dorsal surface of the tongue.
The filiform papillae are in charge of the sensation of touch on the tongue but not taste.
Next are the mushroom-shaped fungiform papillae which are most common at the tip of the tongue.
Then there are the leaf-like foliate papillae, which are most common on the sides of the tongue.
And finally there are 8-12 very large round circumvallate papillae, which are located at the back of the anterior ⅔ of the tongue, just in front of the sulcus terminalis.
The tongue is a muscular organ located in the mouth that is involved in a variety of functions, including speech, swallowing, and taste. Taste is believed to be one of the most pleasurable human special senses, and is possible thanks to taste receptor cells in various types of papillae that covers the tongue. Circumvallate, fungiform, and foliate papillae are where the majority of taste buds are located. After chemical tastants excite specific taste receptor epithelial cells, neurotransmitters are released to transduce the signal to afferent sensory nerves. Ultimately, the stimulus terminates in the insula, hypothalamus, and limbic system to determine and appreciate the gustatory sensation.
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