Vaccines get inside the body through the lymphatic system, which transports lymph fluid containing nutrients, waste, and white blood cells throughout the body. Lymph fluid carries vaccines to lymph nodes where white blood cells can detect and respond to the vaccine, developing immunity. In this way, the lymphatic system plays a crucial role in protecting the body by filtering lymph fluid and initiating immune responses to pathogens like viruses and bacteria contained in vaccines.

1. Entry slip: How do vaccines get inside the patient’s
body?
Lesson 4.14- Explain the role of the lymphatic
system in protecting the human body.
(pp322-324) of Biology-McGraw-Hill Ryerson)
I. Terms:
a.Lymph: blood plasma that has escaped
outside the circulatory system’s vessels
b. Interstitial fluid: fluid that surrounds
every cell of our body. A.k.a
“extracellular” fluid.
II. Lymphatic System:
a.A system of vessels and capillaries that
extends throughout the human body.
i. The lymphatic vessels and capillaries
run beside each and every circulatory
system vessel and capillary.

2. b. Instead of transporting blood, it
transports LYMPH, which is very much
like blood plasma.
c. Due to blood pressure and the small size
of the molecules that make up blood
plasma, some blood plasma squeezes out
of the circulatory system’s capillaries.
i. If this continued, the blood in the circ
system would become very viscous,
or slow-moving.
ii. As well, we would have severe
swelling due to the escaped plasma
being in our tissues instead of our
blood.
d.The lymph is carried back to the center of
the body from the arms and legs, and
rejoins the circulatory system in the big
veins near the heart.
III. How the lymphatic system protects:
a. Fluid balance.

3. i. The lymphatic system’s function of
bringing escaped plasma, or lymph,
back to the circulatory system helps
to prevent blood from being
dehydrated.
ii. As well, it is the plasma in the blood
that carries dissolved nutrients. If this
plasma left the circulatory system
never to return, areas of the body
that need certain nutrients may be
damaged.
iii. Our ability to move our joints would
be reduced if we had severe swelling
and this could be dangerous (i.e. we
could trip and get injured).
b. White Blood Cells.
i. Lymphocytes are made in special
collecting areas along our lymphatic
vessels, called lymph nodes. All lymph
in the lymphatic system runs through
these nodes which act like filters to
inspect the lymphatic fluid for foreign

4. pathogens. These are based mainly in
our neck, armpits and pelvis.
ii. Macrophages, similar to leukocytes,
also are found in the lymph nodes
and will engulf and digest bacteria.
iii. When we are sick and more
lymphocytes and macrophages are
needed, production of these in the
lymph nodes increases, and the
lymph nodes actually swell up. This is
why your doctor will feel your neck
when you feel sick to check if your
body is fighting a foreign pathogen.
IV.Youtube search:
a. LYMPHATIC SYSTEM-dr. Moffet
b.lymphatic system - aaronnelsonn
V. Homework:
a. Create a concept map outlining the
movement of blood plasma from the
blood of the circulatory system, through
the lymphatic system, back to the

5. circulatory system. Include information
about lymph nodes.