Video Transcript
Which first line of defense is the
most common way to spread COVID-19? (A) Tears, (B) mucous membranes,
(C) skin secretions, (D) saliva, (E) expulsive reflexes.
This question is asking us about
the first line of defense, which is another way of saying the innate immune
system. The immune system is a network of
cells and proteins that defend us against infection. It can be divided into innate, or
nonspecific, immunity, and adaptive, or specific, immunity.
Innate immunity is the first line
of defense while the adaptive response develops. Innate immunity is nonspecific,
meaning it fights all pathogens in the same way. It is rapid and includes barriers,
like our skin, that can prevent pathogens from entering and causing infection.
Other methods used to prevent
infection are listed as answer choices. Unfortunately, some of these
methods might help to spread infection, as is the case with COVID-19. COVID-19 is caused by a virus that
infects our respiratory system. Let’s go over the answer choices to
see how each of these methods work and which one can spread COVID-19.
The eyes are protected and
lubricated by tears. Tears are secretions of glands
called lacrimal glands, or tear glands, found in the tissue surrounding the eye. The lacrimal glands are constantly
secreting fluid that keeps the surface of the eye moist. This fluid also contains enzymes
that can destroy certain pathogens. COVID-19 is not spread by tears, so this answer
is incorrect.
Here’s an example of a mucous
membrane. Goblet cells secrete mucus, which
can trap foreign particles and pathogens. Ciliated epithelial cells contain
cilia, which are hairlike structures that can push that mucus along away from the
body. Mucous membranes are often found in
openings to the body, like the nose or ears. They are effective at trapping
particles and can capture the virus that causes COVID-19. But this isn’t really how it’s
spread, so this is incorrect.
Skin secretions provide a physical
barrier that traps pathogens and prevents them from entering the body. Again, this is not how COVID-19
spreads, so this answer is incorrect.
Saliva is produced in the salivary
glands of the mouth and has enzymes in it that can destroy certain pathogens. The virus that causes COVID-19 can
be found in saliva, but this isn’t how the virus is commonly spread. So, this answer is incorrect.
Expulsive reflexes are reflexes
that forcefully expel foreign substances that can be trapped in the mucus or saliva
from the body. Here you can see someone
coughing. If someone else happens to be
nearby, they can inhale these particles. And if the person who coughed or
sneezed, was infected with the virus that causes COVID-19, then these particles will
also contain the virus and can infect the second person. Once the virus is inside their
body, it can replicate and cause the disease. This is actually the primary way
that COVID-19 is spread, and is what makes masks so effective by preventing these
particles from spreading to other people.
Therefore, the first line of
defense that is the most common way to spread COVID-19 is given by answer choice
(E), expulsive reflexes.
