1-2 April 2015
Lymphatic System Function
The lymphatic system consists of two main parts, each
with different functions:
1.
Lymphatic vessels collect interstitial fluid and return
it to the blood vessels
2. Lymphoid organs house immune cells and help
protect the body from disease
Lymphatic Capillaries
 Lymphatic capillaries collect interstitial fluid and dissolved
particles, including proteins, cell debris, and pathogens
 Surround blood capillaries in loose connective tissue
 Blind-ended (have a true start)
 Minivalves ensure fluid only goes in one direction – towards
heart.
Lymphatic capillaries are MUCH
more permeable than blood
capillaries. Large particles,
including pathogens and cancer
cells, cannot directly get into
blood capillaries but they easily
enter lymphatic capillaries
Lymphatic Vessels
 Lymphatic capillaries
join together to form
lymphatic vessels.
 Lymphatic vessels pass
through multiple lymph
nodes for cleansing
 Lymphatic vessels empty
into the subclavian veins
What makes lymph flow?
 Pressure differences provide the force
 Higher pressure of interstitial fluid than of lymph
in capillaries starts flow
 Respiratory and skeletal muscle pumps help
maintain flow in lymph vessels
 Largest lymph vessels have smooth muscle walls
that contract rhythmically to push lymph along
 Valves ensure that flow is unidirectional
 Minivalves in capillaries
 ‘true’ valves in large lymph vessels
Think, Pair, Share
Compare and contrast blood vessels and lymphatic
vessels in terms of structure and function.
5 min
Lymph Nodes
 House immune cells (phagocytes and lymphocytes)
 Filter lymph, breaking down cell debris and destroying
pathogens and cancer cells
There are thousands of lymph
nodes scattered throughout the
body.
Large clusters of lymph nodes
occur in cervical (neck), axillary
(arm pit), and inguinal (groin)
area.
Lymph Nodes
When you are sick, your lymph nodes often swell as they collect
and fight pathogens.
Other lymphoid organs
 House immune cells, but do There are other, small patches of
not filter lymph
 Tonsils: trap and remove
pathogens that enter throat
 Thymus: produces
hormones and develops Tlymphocytes
 Spleen: filters blood,
destroys old erythrocytes
 Peyer’s patches: destroy
pathogens in intestines
lymph tissue throughout body
Closure
 What was our objectives,
and what did we learn?
 What was our learner
profile trait and how did
we demonstrate it?
 How does what we did
today tie to our unit
question?
Exit Ticket
Questions 1 - 6:
A = Lymph vessel only,
C = both,
1.
2.
3.
4.
5.
6.
B = Blood vessel only,
D = neither
Fluid moves due to heart pump
Fluid moves due to respiratory pump
Contain valves
Make a full loop
Contains oxygen and nutrients
Permeable to large molecules and small cells
Exit Ticket
7. What functions to cleanse blood and destroy old
RBCs?
8. What functions to cleanse lymph?
9. What functions to destroy pathogens in the
intestines?
10. What serves as a site for lymphocyte maturation?
Extra Credit (3 pts):
What are the three regions with clusters of lymph
nodes?