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10. Diseases and Immunity (Cambridge IGCSE Biology 0610 for exams in 2023, 2024 and 2025) | IGCSE Study Buddy | YouTubeToText
YouTube Transcript: 10. Diseases and Immunity (Cambridge IGCSE Biology 0610 for exams in 2023, 2024 and 2025)
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hi everyone welcome to IGCSE study buddy
where you can revise biology topics from
the Cambridge IGCSE syllabus
if you are enjoying this video so far
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this video summarizes chapter 10
a transmissible disease is a disease in
which a pathogen can be passed from one
a pathogen is transmitted by direct
contact including Through Blood and
other body fluids
so if a person directly gets in contact
with the sufferer they might also get
infected and may spread the disease
examples include chickenpox that can
spread just by touching or HIV that
requires sexual contact for spreading
a pathogen can also be transmitted
indirectly including from contaminated
surfaces food animals and Air
so indirect contact transmission occurs
when there is no direct human to human contact
contact
examples include getting infected by
eating contaminated food or through a
mosquito that may be carrying the
pathogen or even by inhaling droplets
that are spreading the air through
coughs and sneezes from an infected person
person
the body defends itself against disease
in several ways
kin the skin acts as a physical barrier
to prevent pathogens from entering our
body if the skin gets wounded it
immediately starts healing itself
s in the nose nose hairs act as a
natural filter to prevent the entry of
mucus mucus is a sticky substance so it
traps pathogens before they can enter
the lungs the trapped pathogen may be
removed by blowing the nose swallowing Etc
stomach acid stomach acid is a chemical
barrier against infection stomach acid
contains hydrochloric acid which is
strong enough to kill pathogens that may
and finally white blood cells
white blood cells defend the body
against infections they fight off
infections by carrying out phagocytosis
and antibody production
in the previous video we learned that
there are two types of white blood cells
phagocytes and lymphocytes
phagocytes engulf and digest pathogens
this is called phagocytosis
lymphocytes produce antibodies we will
learn more about this shortly
the simplest way to prevent disease is
to stop pathogens from spreading
the following measures play an important
role in controlling the spread of disease
disease
a clean water supply
hygienic food preparation
good personal hygiene
waste disposal
so a clean water supply would control
the spread of disease because
contaminated water and poor sanitation
are linked to the transmission of
diseases such as cholera diarrhea
dysentery and typhoid
so having clean water means being able
hygienic food preparation
washing hands before handling food and
making sure the surfaces and utensils
are clean before cooking food thoroughly
at high temperatures help kill pathogens
covering food ensures that flies can't
land on it thereby making it difficult
for them to transfer the germs they carry
good personal hygiene washing hands with
soap covering the mouth when sneezing or
coughing washing hands after going to
the toilet are good personal hygiene
practices to follow and helps avoid the
waste disposal when rubbish is exposed
it attracts flies which may carry
disease so rubbish must be covered and
sewage treatment homes and other
buildings must have a proper sewage
disposal method to remove feces from
toilets safely
sewage should be treated to kill
pathogens before being disposed off in
let's learn about active immunity
active immunity is a defense against a
pathogen by antibody production in the body
body
active immunity is gained after an
infection by a pathogen
so as we know a pathogen is a
disease-causing organism
each pathogen has a uniquely shaped
marker on the surface of their membranes
called antigens
it is very important to understand that
antigens are very specific in shape
every pathogen is unique because they
have differently shaped antigens on
their cell surfaces
each pathogen has its own antigens which
have specific shapes
lymphocytes produce proteins called
antibodies which are a complementary
shape to the antigens on the surface of pathogens
antibodies are proteins that bind to
antigens leading to direct destruction
of pathogens
or marking of pathogens for Destruction
specific antibodies have complementary
shapes which fit specific antigens
so let's look at an example let's say
there's a pathogen with antigen a
lymphocyte a has receptors that have a
complementary shape to antigen a
lymphocyte a gets activated and produces
antibodies that have a complementary
shape to antigen a
these antibodies can lock onto antigen a
and Destroy them
the antibodies made by lymphocyte B on
the other hand will not be able to fit
so how do the antibodies destroy the pathogen
pathogen
they attach themselves to the antigen
and cause them to Clump or be stuck together
together
this makes it difficult for the pathogen
then they can be killed directly
or marked for Destruction by phagocytes
the antibody sends a chemical signal for
phagocytes to come and engulf the pathogen
pathogen
so how do phagocytes destroy the pathogen
pathogen
we learned in the previous video that
phagocytes engulf pathogens by a process
called phagocytosis
so basically when a phagocyte comes
across a germ or pathogen it engulfs or
surrounds it completely taking it inwards
inwards
then it releases digestive enzymes on it
which digests the pathogen and destroys it
lymphocytes that have made antibodies
for a particular pathogen also produce
memory cells
these are cells that remain in the blood
even after the infection is over
they are able to quickly produce the
original antibodies if they were to come
across the same pathogen again
this is how people can become immune to
certain diseases after only having them once
once
an example is chickenpox most people who
have had chickenpox will be immune to
the disease for the rest of their lives
therefore memory cells give long-term immunity
immunity
let's move on to vaccination
vaccination is a way of protecting the
body against harmful diseases before we
come into contact with them
the process of vaccination is as follows
weakened pathogens or their antigens are
put into the body
since the pathogen is weak it cannot
cause illness but it can trigger an
the antigens stimulate an immune
response by lymphocytes which produce antibodies
antibodies
memory cells are produced that give
long-term immunity
the memory cells remain in the blood and
will quickly respond to the antigen if
it is encountered again in an infection
by a live pathogen
so vaccination is done to stimulate the
so once again weakened pathogens are put
into the body
the antigens stimulate the lymphocytes
to produce antibodies
and memory cells are produced that give
long-term immunity
what is the role of vaccination in
controlling the spread of diseases
the effectiveness of a vaccine in a
population depends on the proportion of
when the majority of a population is
vaccinated against a pathogen it breaks
the pathogens Chain of Infection
this means that the pathogen will have
fewer places to breed and therefore it
is unable to pass from person to person
hence vaccination prevents the spread of
now let's learn about passive immunity
passive immunity is a short-term defense
against a pathogen by antibodies
acquired from another individual
examples of where these antibodies may
be obtained are
from across the placenta antibodies from
mothers are passed to their unborn
babies through the placenta
breastfeeding is important for the
development of passive immunity in infants
infants
antibodies pass from the mother to
infant through breast milk
this is important because a baby's
immune system is not well developed and
so the mother's antibodies can protect
it against any diseases to which she is
immune for the first few months of its
life until their immune system is stronger
passive immunity is a fast acting
short-term defense
memory cells are not produced in passive immunity
now let's learn about cholera
cholera is a disease caused by a
bacterium which is transmitted in
contaminated water
cholera causes diarrhea which is the
how does this happen
the cholera bacteria attached to the
wall of the small intestine
the toxin causes the cells lining the
intestine to secrete chloride ions into
the small intestine
this causes the water potential inside
the intestine to reduce
the water potential in the cells lining
the intestine is higher therefore water
moves from the cells to inside the small
large quantities of water are lost from
the body in watery feces or diarrhea
this also leads to dehydration and loss
of ions from the blood
diarrhea can be effectively treated by
Oral rehydration therapy
this is a drink with a small amount of
so that concludes chapter 10 diseases
and Immunity hope this video helped you
thank you for watching and please don't
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