1. Entry slip: List the five major signs of inflammation.
Lesson 4.12- Describe the physical and chemical
barriers that protect the body from foreign agents.
(pp382-383) of Biology-McGraw-Hill Ryerson)
I. Terms:
a.Barrier: something that prevents the
passage of matter from getting to an area
where it is not wanted (i.e. condoms are
known as a form of “barrier protection”)
b.Foreign pathogens: bacteria, fungi and
viruses
c. Non-specific: does not distinguish
between the foreign pathogens it is trying
to prevent from sickening the body
d.Specific: identifies particular foreign
pathogens to prevent from sickening the
body
II. Physical Barriers (non-specific):

2. a. Skin: although millions of bacteria are on
your skin right now, many of them are
dying due to the skin’s:
i. Dryness (foreign pathogen like a
moist environment)
ii. Toughness of the tissue (outer layer
of skin is dead and hard to digest)
iii. Low temperature (skin is the coldest
part of the body and pathogens like
warm temps)
iv. Low pH (sweat and skin oil is acidic
and pathogens do not like this)
b. Mucus: all of our digestive tract and
upper respiratory tract is covered with
ciliated mucus membrane which secrete a
lot of mucus:
i. Traps foreign pathogens which are
coughed up and spit/sneezed out
c. Stomach acid: some foreign pathogens
may be inside the food we eat. The
stomach acid in the stomach will:

3. i. Creates a very acidic environment
that kills most of the bacteria we
ingest.
III. Chemical Barriers (non-specific):
a.Leucocytes:
i. WBC’s
ii. Transported to the sickened area by
the circulatory system
iii. “Phagocytosis”:Engulf and digest
fungi, viruses and bacteria
b.Macrophages:
i. Naturally occurring in liver, spleen,
brain and lungs
ii. Kills pathogens by Phagocytosis
IV. Chemical Barriers (specific immunity):
a.Lymphocytes:
i. WBC’s
ii. Transported to the sickened area by
the circulatory system

4. iii. Attach to foreign pathogens that have
already been killed to make “memory
cells” that will quickly recognize and
kill similar pathogens in the future
V. Youtube search:
VI.Homework:
i. In your own opinion, which of the
three physical barriers is the most
important? In other words, do you
thing we would die from sickness due
to foreign pathogens quicker if we a)
had no skin b) had no mucus
membranes or c) had no stomach
acid? WHY? At least 100 words. Due
next class.