Tongue在线视频

Hello everyone.

The topic today is about the structures

and functions of the tongue.

Let's start with a research report.

COVID-19 is a global pandemic disease

in 2019 and 2020.

The main symptoms after this viral infection

include fever, cough, sore throat,

and lethargy etc.

In a telephone interview,

Italian researchers had successfully collected

information of 202 patients with COVID-19.

They found that 130 patients, or 64.4%,

reported changes in their sense of smell or taste,

while complaint of lethargy was 68.3%,

cough 60.4%, and fever 55.5%.

Moreover,

patients developed olfactory or taste changes

earlier than other symptoms.

The results were published in JAMA in May 2020,

suggesting that alterations in taste

and smell are among the most common

and earliest symptoms

after this coronavirus infection.

After finishing this session,

you should be able to describe the structures

and functions of each part of the tongue

and explain some of its clinical correlations.

Taste is one of the functions of the tongue.

In addition to taste,

the tongue also participates in articulation,

mastication, and swallowing.

The tongue is a muscular structure

in the floor of the mouth

and is covered with a mucous membrane.

Under the microscope,

you will find that the main body of the tongue

is made up of skeletal muscles

arranged in different directions.

Skeletal muscles

are controlled by autonomic nerves.

Because of the different directions

of the skeletal muscles,

the tongue is very flexible.

This forms the structural basis

for the tongue to manipulate food

for mastication and to engage in articulation.

The whole tongue is covered with mucosa.

The lower surface is smooth

especially the sublingual region

beneath the front of the tongue.

Here the oral mucosa is very thin

and is enriched with venous plexuses.

This is an ideal location

to give certain medications,

such as nitroglycerin for the chest pain

due to heart disease.

The sublingual route takes advantage of the highly

and thinly covered oral cavity

that allows speedy delivery of the medications

to the cardiovascular system.

Moreover,

this route bypasses the digestive processes

in the gastrointestinal (GI) tract

and metabolism in the liver

which would make the medication less effective.

In addition,

if the patient is unconscious,

sublingual administration

is convenient and efficacious.

Besides the lower side,

we have the dorsal side of the tongue.

Dorsal surface of the tongue is irregular

since there are many lingual papillae.

According to the different shapes,

papillae are classified as filiform,

fungiform, foliate and vallate papillae.

No matter which type,

the papilla all have a core of connective tissue

covered with stratified squamous epithelium.

The diversely shaped papillae

are located in different regions of the tongue.

Fungiform papillae,

shaped like button mushrooms,

are mostly concentrated at the tip

and sides of the tongue.

Peg-like vallate papillae on the back of the tongue

are arranged in a V-shape

pointing towards the throat.

We have the foliate papillae

clustered on each side of the tongue

in the transverse folds.

Fungiform, foliate, and vallate papillae

have taste buds

within the stratified squamous epithelium.

Filiform papillae are most abundant

but have no taste buds.

They contribute to the rough appearance

of the dorsal side of the tongue

and provide friction

for the movement of food in the mouth.

Taste evokes the nutritional qualities of the food

we are going to eat and stimulate our appetite.

But how do we get the taste of the food?

Let's see the structure of taste buds

under the microscope.

Look at this,

taste buds are ovoid structures

embedded in the fungiform,

foliate, and vallate papillae.

About half of the cells

in the taste bud are gustatory cells,

that is, for taste.

Other cells include supportive cells

and basal stem cells.

At the apical end of the taste cell,

microvilli project through pores

that open into the oral cavity.

So, molecules dissolved in saliva

come in contact with the microvilli

and the taste receptors transport the information.

The receptor of gustatory cell

can distinguish the different tastes:

sweet, sour, bitter, and salty.

Supporting cells are located between taste cells,

similar to glial cells in nerve tissue,

providing protection

and insulation for the gustatory cells.

Basal stem cells are pyramidal

and have the potential

to differentiate into other types of cells for repair.

At the time of birth,

the taste of the newborn baby is underdeveloped,

so plain water, sugar water, mother's milk

or cow's milk has no special taste to the baby.

Then the taste sensation will gradually become stronger.

It will weaken as one becomes older.

Besides age,

there are also other factors

which can affect the taste sensitivity.

For example,

after radiotherapy to the head and neck,

the patients often lose interest in food.

One of the reasons

is damage of the taste buds by radiation.

Above is the brief introduction of the tongue.

Please summarize the structures

and functions of each part of the tongue

by yourself

and try to find clues to explain

why COVID-19 patients have taste disorders.

Here are the references.

Thank you for joining us!