What Is This Module About?

Every day, you are in contact with your environment. You use your body to do a
lot of things. You touch and hold objects and shake hands with other people and pat
your pet animals. In activities like these, your body makes contact with other people,
animals and objects in your surroundings. However, your environment is not perfect.
It contains many organisms and substances that can harm your body. Nevertheless, you
can carry out your everyday activities without any grave danger to your health. This is
because of a special group of organs in your body that protect you from danger. Your
body’s ability to ward off harmful organisms is called immunity. Maintaining this
ability is the function of your lymphatic system. Do you ever wonder how your
lymphatic system carries out this function?
Without your being aware of it, a war rages on inside your body every day. This is
a war between harmful organisms and your lymphatic system. When your lymphatic
system wins, you stay healthy. When it loses the fight, you get sick.
In this module, you will learn about the parts and functions of the lymphatic
system. You will also find out about some injuries and diseases that can affect the
lymphatic system and the ways by which you can take care of it.
This module is divided into three lessons. These are:
Lesson 1 — The Parts and Functions of the Lymphatic System
Lesson 2 — Diseases That Can Affect the Lymphatic System
Lesson 3 — Taking Care of the Lymphatic System

What Will You Learn From This Module?

After studying this module, you should to be able to:

♦ describe the parts of the lymphatic system of the human body;
♦ state the functions of the lymphatic system;
♦ identify and describe diseases that can affect the lymphatic system; and
♦ demonstrate how to take proper care of the lymphatic system.

1
 Let’s See What You Already Know

To find out how much you already know the topic to be discussed in this module,
take the following test. Write your answers on the lines .
1. Enumerate the parts of the lymphatic system.
a. ______________________________________________________
b. ______________________________________________________
c. ______________________________________________________
2. State two functions of the lymphatic system.
a. ______________________________________________________
b. ______________________________________________________
3. Identify two diseases associated with the lymphatic system.
a. ______________________________________________________
b. ______________________________________________________
4. State four ways of taking care of the lymphatic system.
a. ______________________________________________________
b. ______________________________________________________
c. ______________________________________________________
d. ______________________________________________________
5. Name two organisms that can trigger an immune reaction from the body.
a. ______________________________________________________
b. ______________________________________________________

Well, how was it? Do you think you fared well? Compare your answers with those
in the Answer Key on page 25.
If all your answers are correct, very good! This shows that you already know
much about the topic. You may still study the module to review what you already
know. Who knows, you might learn some more new things.
If you got a low score, don’t feel bad. This module is for you and it will help you
to understand some importants concepts that you can apply in your daily life. If you
study this module carefully, you will learn the answers to all the items in the test and a
lot more! Are you ready?
You may go now to the next page to begin lesson 1.

2
 LESSON 1

The Parts and Functions of the

Lymphatic System

If you’re the last person to leave your house, what are the things you do? Do you
lock the doors? Do you check if the windows are closed, the lights are turned off and
the gas tank is sealed? These habits manifest your need for security. If you
accidentally leave your door unlocked, what could possibly happen?

Life nowadays is full of uncertainties. Every day, you face danger from sickness,
accidents and other events that threaten your well-being and health. You know how
important security is in your life. You lock the doors of your house before you leave
because you don’t want intruders to get in.There are always bad people who can harm
your family and damage your property.
You are fortunate to have a built-in security system inside your body. This is the
immune or lymphatic system, which maintains the immunity of your body. The
lymphatic system keeps you safe from harmful organisms that can make you sick. It
works as your own “army” to defend your body from harm. But do you know what
exactly make up your lymphatic system and how it works?
In this lesson, you will be introduced to the parts and functions of the lymphatic
system. The lymphatic system keeps the body immune to infections, enabling it to
fight off organisms that can harm the body. Indeed, the lymphatic system is a very
important part of the body. Without it, staying healthy would not be possible.

3
 Let’s Read

Recall a time when you got sick and had to stay in bed for some time. How did it
feel to be sick? What did you do in order to get well?
Read the following story:
Ben was a twelve-year old boy who liked to play a lot. He loved to roll in the mud
with his playmates and he often swam in the river that ran through his town. One day,
he felt sick. He was running a high fever and he could hardly move. His mother took
him to a doctor who said that he should be confined in a hospital. In the hospital, a
doctor gave Ben some medicine to make him well.

After a few days, Ben was up and about again. When his doctor saw him, the
doctor smiled and said, “It’s a good thing Ben’s immune system is strong. He would
have been worse if his immune system didn’t help him fight the disease.”

Let’s Think About This

Answer the following questions:

1. Why do you think Ben got sick?
______________________________________________________________
_________________________________________________________________

2. How do you think Ben was able to recover from his illness?
______________________________________________________________
_________________________________________________________________

Check your answers in the Answer Key on page 25.

4
 Let’s Learn

In the previous section, you read the story of Ben and how he got sick and
recovered from his illness. Ben was able to get well because, as his doctor said, his
immune or lymphatic system helped him.
The lymphatic system is a network of vessels whose primary function is to assist
in circulating body fluids. These vessels transport excess fluid away from the
interstitial spaces (spaces between cells in body tissues) and return it to the
bloodstream. This prevents tissues from swelling up. The lymphatic system also
filters out disease–causing organisms, produces a type of white blood cells and
generates antibodies.

arteriole plasma fibroblast red blood cells capillary bed plasma

The picture above shows a capillary network through which blood passes and
reaches the cells of the body. When blood reaches the cells, exchange of food,
oxygen and nutrients takes place. As this occurs, a little liquid from the plasma (the
liquid part of blood) leaks out of the capillary wall. This liquid reaches the spaces
between the body cells (interstitial spaces) and is collected by and stored in tubes
called lymphatic vessels. Once inside the lymphatic vessel, the liquid is called
lymph. Lymph is a milky fluid that continuously bathes the cells of the body.
Wherever there are cells, lymph is also found. It needs to be circulated like blood in
order to remove excess fluid and harmful materials from interstitial spaces.

5
 cells of the body

This is a lymph
vessel which
circulates lymph
fluid that bathes
the cells of the
body.

Lymph is found all over the body except the central nervous system, eyeballs,
inner ear, cartilage and the epidermis of the skin. The walls of lymph vessels are lined
with a single layer of endothelium which permits fluid and large particles, such as
plasma proteins and foreign substances, to enter.
Lymph has components similar to those of blood, except that is has no red blood
cells and platelets. It has a type of white blood cells called lymphocytes as well as
cells that engulf foreign materials, which are called macrophages.

adenoid
tonsil
left subclavian vein

thymus
lymph nodes

thoracic duct
spleen

appendix
bone marrow

The Lymphatic System of the Human Body

6
The lymphatic system is made up of the following parts:
1. Lymphatic vessels – As was mentioned earlier, the lymphatic vessels are
tubes through which lymph passes as it circulates the body. They return the
lymph to the blood through veins near the heart.
There are two major lymphatic vessels. These are the thoracic duct and
right lymph duct. All the lymph collected from the left side of the body,
the digestive tract and the right side of the lower part of the body flows into
the thoracic duct. The thoracic duct then empties the lymph into the left
subclavian vein, which then brings the lymph to the heart. On the other
hand, all the lymph from the right side of the head, neck and chest go to the
right lymph duct which then deposits it into the right subclavian vein.
2. Lymph nodes – These are clumps of tissue that are found mainly in the
neck, groin and armpits. However, they are found all over the lymphatic
vessels. Lymph passes through the lymph nodes before it returns to the
blood. The primary function of the lymph nodes is to produce lymphocytes.
3. Lymphoid organs – These are organs that contain a large amount of
lymphocytes. Among these are the:
♦ Spleen – a soft, purplish organ lying high above the abdomen. This
organ receives blood from an artery that branches off to the aorta, the
largest artery in the body. The blood vessels of the spleen are
sorrounded by lymphocytes and macrophages. The macrophages remove
harmful microorganisms from the blood and destroy them by
phagocytosis.
♦ Tonsils – masses of tissue located in a protective ring under mucous
membranes in the mouth and back of the throat. These help protect the
body against bacteria that invade tissues around the openings of the
mouth and nose.
♦ Thymus – a soft, flattened, pinkish-gray organ located in the upper
chest under the breastbone. The thymus serves as a site for the
development of lymphocytes in the fetus. Soon after birth, the thymus
begins secreting a group of hormones that enable lymphocytes to
develop into T cells, groups of cells that protect the body against
invasions by foreign organisms. If the thymus fails to develop, the
immune system cannot develop completely as well.

7
 Let’s Review

It is said that the circulatory and lymphatic systems are similar. Can you identify
the similarities and differences between these two organ systems? List them in the
table below.

Similarities Differences

Compare your answers with those in the Answer Key on page 26.

Let’s Learn

Now let us discuss the functions of the lymphatic system. The lymphatic system
has two main functions: maintaining fluid balance in the body and immunity.
Maintaining fluid balance in the body is accomplished by the lymphatic vessels,
which collect lymph from the interstitial spaces and return it to the blood. Drainage of
the lymph is important, because if the fluid accumulates in the interstitial spaces over
a period of time, the tissues would swell up. This could lead to the destruction of the
tissues.
Immunity or the ability of the body to fight off infection is accomplished by the
lymphatic system through the actions of its components. The lymph nodes filter the
air that passes through the mouth and the spleen filters the blood that passes through
it.
The lymph nodes, tonsils and spleen accomplish their tasks by trapping and
destroying antigens in the lymph, air and blood, respectively. Antigens are molecules
that cause the body to produce antibodies, which are proteins. Bacteria, viruses,
malignant (cancer-causing) cells and foreign tissues are examples of antigens.

8
 Destruction of antigens is carried out by the lymphocytes. If you recall,
lymphocytes are a group of white blood cells. There are two types of lymphocytes
that are active in the immunity function of the lymphatic system. These are the T
lymphocytes (T cells) and B lymphocytes (B cells).
B lymphocytes produce antibodies. Antibodies are able to recognize specific
antigens and attach themselves to these antigens. This action causes the antigens to
become inactive and prevents them from harming the cells of the body.
T lymphocytes are further divided into groups, each having a specific function.
When these cells recognize foreign antigens on the surface of a body, they change
into active cells that attack the infected cells directly. Some T cells also release
chemicals that draw the macrophages, which then engulf and absorb the infected cells.

Macrophage
Pathogen enters body
and meets a barrier of
Pathogen lymphocytes.

Lymphocyte

Antibody
Covered pathogen
can now be destroyed
by a macrophage.

Lymphocytes grow, divide, and

produce antibodies which attach to
the pathogen.

9
 Let’s Try This

Palpate for your lymph nodes. Feel the lymph nodes in your body by gently
pressing your hand against your armpits, groin or neck.

If you weren’t able to feel any tiny lumps, that means you are not suffering from
any infection. You can actually see your lymphatic system at work when you are sick.
When you are sick, you will notice that you have some lumps in your neck. These
lumps are swollen lymph nodes that are helping you get well. Your lymph nodes swell
because your lymphatic vessels are carrying the infection there so that your
lymphocytes can act on it immediately.

Let’s See What You Have Learned

Match the items in Column A with those in Column B.

A B
____ 1. lymphatic system a. the organ where T lymphocytes
develop
____ 2. immunity b. molecules that cause the body to
produce antibodies
____ 3. spleen c. interstitial fluid
____ 4. lymphocyte d. destroys antigens in the air that
enters the body

10
 ____ 5. antigens e. network of vessels that
circulate lymph
____ 6. thymus f. swells during infections
____ 7. B lymphocytes g. a type of white blood cell that
maintains the body’s immunity
____ 8. lymph node h. ability of the body to fight off
infections
____ 9. lymph i. lymphocytes that produce
antibodies
____ 10. tonsils j. a lymphoid organ
Compare your answers with those in the Answer Key on page 26. If your score is
6 or higher, congratulations. You did great! You have learned a lot about the parts and
functions of the lymphatic system. Review the parts you missed then proceed to the
next lesson.

Let’s Remember

♦ The lymphatic system is a network of organs and vessels that collect excess
fluid from the interstitial spaces and return it to the bloodstream. Its primary
functions are maintenance of fluid balance in the body and immunity.
♦ Lymph is a milky fluid that continuously bathes the cells of the body, and is
circulated around the body in order to remove excess fluid and harmful
materials from interstitial spaces.
♦ Lymph contains a type of white blood cells called lymphocytes as well as
macrophages, cells that eat foreign materials in the body.
♦ The lymphatic system is composed of lymphatic vessels, lymph nodes and
lymphoid organs such as the spleen, tonsils and thymus.
♦ The lymph nodes and lymphoid organs play an important role in immunity.
They contain lymphocytes that destroy antigens.
♦ The two types of lymphocytes that are active in maintaining the immunity of
the body are the T lymphocytes or T cells and B lymphocytes or B cells. B
lymphocytes produce antibodies that attach themselves to antigens, while T
lymphocytes attack infected cells directly.

11
 LESSON 2

Diseases That Can Affect the Lymphatic

System
In the previous lesson, you learned about the parts and functions of the lymphatic
system. You also discovered the role of your lymphatic system in keeping you healthy
by preventing bacteria and other foreign materials from harming your body. The
lymphatic system does its work so well that you are able to avoid infectious diseases.
In this lesson, you will learn about some diseases that can affect the lymphatic
system. Ironic as it may seem, the primary organ system that defends the body from
harm is also prone to diseases. Hence, it is important to know what these diseases are.

Let’s Try This

As of 1999, there were already 23,000 Filipinos 15 to 49 years old who were
infected with HIV. Still, a lot of us remain ignorant of the causes and effects of this
virus and the disease it brings—AIDS. The following are a list of statements about
AIDS and HIV. Some of them are correct, others are not. Can you distinguish the
correct statements from the incorrect ones? Put their numbers in the appropriate
boxes on the next page.
1. You can get HIV in swimming pools.
2. If you are infected with HIV, you will surely get sick with AIDS.
3. HIV-positive women can infect their babies through breastfeeding.
4. If you hug someone who has HIV or AIDS, you will also get infected.
5. You can get HIV from mosquito and animal bites.
6. AIDS is a disease that attacks the immune system.
7. So far, no cure for AIDS has been discovered.
8. AIDS stands for acquired immune deficiency syndrome.
9. You can get infected with HIV through unprotected sex, sharing needles and
blood transfusion.
10. You can get infected with HIV if you share food and personal things with an
HIV-infected person.

12
 Correct Statement Incorrect Statement

Compare your answers with those in the Answer Key on page 26.

Let’s Learn

Acquired Immune Deficiency Syndrome (AIDS)

Let us now learn about what medical experts call the “health threat of the
century.” AIDS is a specific group of diseases that result from the reduction of the
immunity of the body. This means that it attacks the lymphatic system, specifically,
the T lymphocytes or T cells. This is brought on by a virus called human
immunodeficiency virus (HIV).
HIV is transmitted through the following means:
♦ unprotected sex with an infected person
♦ sharing needles or syringes for drug injection with someone who is infected
with the virus
♦ transfusion of infected blood
The three modes of transmission listed above are the only means by which one
can get infected with HIV. You can’t get infected through mosquito and animal bites,
because the virus lives only in humans. You can’t also get the virus by hugging an
infected person or by sharing his or her food and personal things. Nor can you get it in
swimming pools—the chemicals in pools are strong enough to kill the virus.
However, women infected with HIV can pass on the virus to their unborn
children. They can also transmit the virus to their babies through breastfeeding.
Hence, if a woman is HIV-positive (infected with HIV), she is discouraged from
getting pregnant.

13
 If a person is infected with HIV, this does not mean that he or she will develop
AIDS, but it is highly probable that he or she will. Some HIV-positive people can go
for more than ten years without developing AIDS. However, once their T cell count
becomes lower than 200 cells per cubic milliliter of blood and they develop an
infection, they are considered to have AIDS already.
AIDS causes death because as HIV multiplies inside the body, it attacks and kills
the T cells. This slows down the ability of the body to fight infection caused by
bacteria, viruses and other foreign materials. Thus, the patient becomes prone to all
sorts of infections, and these infections are the ones that eventually lead to the
patient’s death. Among these infections are pneumonia, Kaposi’s sarcoma (a type of
skin cancer), and meningitis (an infection of the fluids in the brain). Without the T
cells to fight the organisms that cause the infection, the infection worsens until the
patient dies.

Let’s Review

Let’s see if you now have a clearer understanding of AIDS. Answer the following:
1. Tell the difference between AIDS and HIV.
________________________________________________________________
_________________________________________________________________
_________________________________________________________________

2. Name the ways by which HIV is transmitted.

________________________________________________________________
_________________________________________________________________
_________________________________________________________________

Compare your answers with those in the Answer Key on page 27.

14
 Let’s Learn

Here are some more diseases and disorders that affect the lymphatic system.
Edema
Mrs. Castro was a 56-year-old teacher. She had been having heart problems for a
long time. One day, she noticed that both of her legs were swollen and heavy. She
went to the doctor, who told her that she was suffering from heart failure. Her legs
swelled because of edema, a symptom of heart failure. She was given medicine to
relieve the swelling in her legs and to improve her blood circulation.

Edema is a swelling on the body caused by the accumulation of fluid in the

body tissues. It results from the inability of the lymphatic system to perform the
task of draining the body’s fluids. It can also be brought on by various diseases
and disorders, such as heart failure, kidney malfunction and varicose veins.
Lymphangitis and Lymphadenitis
Carlo, a 16-year-old boy, woke up one day to find that his legs were painfully
swollen. He remembered that he stepped on a sharp object a week before, but did not
do anything about it. Afterwards he developed a fever which lasted for days. He was
brought to a hospital, where he was diagnosed to have lymphangitis.

Lymphangitis and lymphadenitis are complications that result from infections

caused by bacteria.

15
 Lymphangitis is the inflammation of the lymphatic vessels that results from
infection by streptococci and staphylococci, two common bacteria. These bacteria are
usually transmitted through insect or animal bites. Lymphadenitis, on the other hand,
involves inflammation of the lymph nodes. This may occur if the nodes are
overwhelmed by bacteria, viruses, fungi or other organisms, infection then develops
within the nodes. Both lymphangitis and lymphadenitis should be treated immediately
(usually with antibiotics). Otherwise, the infection could spread to the bloodstream
and cause death.

Lymphoma
Alice was a 35-year- old housewife. One day, she noticed that there was a lump
on the left side of her neck. She dismissed it as a swollen lymph node and hoped it
would disappear on its own. However, the node kept on growing. She also began to
feel constantly tired and started losing weight. She consulted a doctor, who told her to
undergo a biopsy. Biopsy involves getting a tissue sample and studying it under a
microscope. The result of the biopsy revealed something Alice did not expect: She
had lymphoma.

Lymphoma is a cancer of the lymphatic system. The most common type of

lymphoma is non-Hodgkins lymphoma. In this type of disease, cells in the
lymphatic system become abnormal. They divide and grow without any order or
control. This disease can start anywhere in the body. Its most common symptom is a
painless swelling of the lymph nodes in the neck, under arm or groin. Lymphoma
patients usually undergo chemotherapy and radiation therapy. Some even have to
undergo surgery.

16
Elephantiasis
Juan is an abaca farmer, who often wades in dirty water because of his work. One
day, he noticed that his left leg was swollen. The swelling got worse until his entire
lower left extremity swelled. He was diagnosed to be suffering from elephantiasis.

Elephantiasis is an abnormal enlargement of any part of the body caused by the

obstruction of the lymphatic vessels in the affected area. This disease commonly
affects the leg and scrotum.
In tropical countries like ours, elephantiasis is normally caused by filariasis, an
infestation of certain parasitic round worms called Wuchereria bancrofti. These tiny
worms are introduced into the body by many types of mosquitoes. These parasites
search out the lymph nodes and lymph vessels, where they absorb nutrients. Abaca
plantations are often infested with these parasites, hence workers are advised to wear
boots and protective clothing. Recovery from filariasis is possible, but elephantiasis
itself cannot be cured.

Let’s See What You Have Learned

Answer the following:

1. Differentiate lymphadenitis from lymphangitis.
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________

17
 2. What is AIDS?
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________

Compare your answers with those in the Answer Key on page 27. If you answered
both questions correctly, good work! You have learned a lot about the diseases that
affect the lymphatic system.
If you were not able to answer both questions correctly you should study the
lesson again. Review them and try to answer the questions again. Afterwards, you may
proceed to the next lesson.

Let’s Remember

♦ The lymphatic system is prone to many kinds of diseases. Among these are
AIDS, edema, lymphangitis, lymphadenitis, lymphoma and elephantiasis.
♦ AIDS is a group of infections that occur due to the reduction of the body’s
immunity. It is caused by HIV, a virus that attacks the lymphatic system,
specifically the T cells.
♦ Edema is a swelling in the body caused by a buildup of fluid in the body
tissues.
♦ Lymphangitis is an inflammation of the lymphatic vessels that results from
infection by streptococci and staphylococci.
♦ Lymphadenitis is an inflammation of the lymph nodes that occurs if the
nodes are overwhelmed by bacteria and other organisms.
♦ Lymphoma is a cancer of the lymphatic system, the most common type of
which is non-Hodgkin’s lymphoma.
♦ Elephantiasis is an abnormal enlargement of any part of the body caused by
the obstruction of the lymphatic vessels. It is usually caused by the
infestation of roundworms that are transmitted through mosquito bites.

18
 LESSON 3

Taking Care of the Lymphatic System

In the previous lesson, you learned about some diseases that can affect your
lymphatic system. To prevent these diseases from occurring, it is very important for
you to learn how to take care of your lymphatic system.
In this lesson, you will learn how to take good care of the lymphatic system.

Let’s Try This

How well do you take care of your lymphatic system? Find out by answering the
set of questions below.
1. Do you have a well-balanced diet, that is, do you eat plenty of fruits and
vegetables and less high-fat foods such as meat, eggs and butter? Yes No
2. Do you avoid a lot of salty foods? Yes No
3. Do you try to maintain your normal weight? Yes No
4. Do you clean your wounds and scratches with soap and water? Yes No
5. Do you go to the doctor regularly for a checkup? Yes No
6. Do you exercise regularly? Yes No
7. Do you get enough sleep and rest? Yes No
8. Do you protect yourself from mosquito and animal bites? Yes No
9. Do you practice safe sex? Yes No
Did you answer Yes to all of the questions? If you did, that means that you are
taking care of your lymphatic system very well. If you answered No to some of the
questions, that means you need a change of habits. Read on to find out how you can
take care of your lymphatic system and prevent yourself from getting sick.

19
 Let’s Learn

There are some ways by which you can take care of your lymphatic system.

Avoid acquiring and spreading Practice safe sex in order to

infections. Cover your nose when prevent AIDS. Be faithful to your
you sneeze and your mouth when partner to spare yourselves the
you cough. danger of getting infected with HIV.

Avoid illegal drugs. Drug Avoid infection. Clean your

dependents, especially those who wounds and scratches thoroughly to
share needles, tend to get infected prevent inflammation of the
with HIV. lymphatic vessels.

20
 Check regularly for any lump in Avoid prolonged standing and
your armpit, on your neck and around other activities that can impede lymph
your groin. Seek medical attention drainage.
immediately if you detect any lump.

Eat nutritious foods such as fruits Exercise regularly to keep

and vegetables to keep your lymphatic your lymphatic system healthy.
system healthy. Avoid eating salty foods Make sure also that you get
because having too much salt in the enough sleep and rest.
body can cause you to retain fluids in
your tissues.

21
 Wear rubber boots and protective Maintain proper hygiene.
clothing when working in farms to
avoid contact with filariasis-causing
organisms.

Let’s Think About This

After studying some of the guidelines on how to take care of the lymphatic
system, examine yourself. Are you observing the proper habits and methods to protect
your lymphatic system? Remember, protect your lymphatic system and it will protect
you.

Let’s See What You Have Learned

Which of the following practices are good for your lymphatic system? Put a
check on the line before the number of the correct practice.
____ 1. eating junk foods
____ 2. taking a bath regularly
____ 3. covering the nose and mouth when sneezing
____ 4. having multiple sexual partners
____ 5. exercising regularly
____ 6. eating plenty of salted nuts, daing and tinapa
____ 7. cleaning wounds and scratches thoroughly
____ 8. going to the doctor regularly for a checkup

22
 ____ 9. ignoring painless lumps on the neck, armpits and groin
____ 10. protecting oneself from mosquito and animal bites

Compare your answers with those in the Answer Key on page 27.

Let’s Remember

♦ There are many ways by which you can take care of your lymphatic system.
Among these are: avoiding catching and spreading infections, practicing safe
sex, avoiding illegal drugs, cleaning wounds and scratches thoroughly,
checking regularly for lumps in the armpits, neck and groin, avoiding
activities that can impede lymph drainage, eating nutritious foods, avoiding
salty foods, exercising regularly, protecting yourself from mosquito bites
and maintaining proper hygiene.
You have now reached the end of the module. Congratulations! Did you enjoy
studying this module? Did you learn a lot from it? The following is a summary of its
main points to help you remember them better.

Let’s Sum Up

♦ The lymphatic system serves to maintain fluid balance in the body and fight
off infections.
♦ The lymphatic system is composed of the lymphatic vessels, lymph nodes
and lymphoid organs. The infection-fighting components of this organ
system are the lymphocytes, specifically the T lymphocytes and B
lymphocytes.
♦ Many diseases and disorders can affect the lymphatic system. Among these
are AIDS, edema, lymphangitis, lymphadenitis, lymphoma and elephantiasis.
♦ You can take care of your lymphatic system by observing proper hygiene,
protecting yourself against infection and eating nutritious foods.

23
 What Have You Learned?

Fill in the blanks.

1. Once the fluid in the interstitial spaces enters the lymphatic vessels, it is
called _________.
2. ___________ become swollen when there is an infection in the body.
3. The _________ is an organ where lymphocytes mature and develop into T
lymphocytes.
4. The three parts of the lymphatic system are the ______________,
______________ and _________________.
5. The most common type of lymphoma is ___________________.
6. ____________ may be brought on by such diseases as heart failure.
7. AIDS stands for ___________________________________.
8. __________ foods can cause the body tissues to retain more fluid.
9. Lymphangitis and lymphadenitis are two diseases that result from infections
caused by ______________.
10. B lymphocytes produce ___________ that attach themselves to antigens.
Compare your answers with those in the Answer Key on page 27.
If your score is:
8 – 10 Well done! You learned a lot from this module. Keep up the
good work.
4 – 7 Good! You only need to review the parts you missed.
0 – 3 You should study the module again.

24
 Answer Key

A. Let’s See What You Already Know (page 2)

1. a. lymphatic vessels
b. lymph nodes
c. lymphoid organs
2. a. maintains fluid balance in the body
b. maintains immunity
3. a. lymphangitis
b. lymphadenitis
(Other possible answers: AIDS, lymphoma, elephantiasis, edema)
4. a. Proper hygiene
b. Avoiding infections
c. Regular consultation with the doctor
d. Checking regularly for palpable masses in the body
5. a. bacteria
b. viruses
(Other possible answers: parasites such as tiny worms, fungi)

B. Lesson 1
Let’s Think About This (page 4 )
(Answers will depend on the learner’s perception. The following are the
expected answers, however.)
1. Ben got sick because he probably got infected by bacteria or viruses
in the mud and river he played in.
2. Ben got well because his immune system fought the microorganisms
that caused the infection in his body.

25
 Let’s Review ( page 8)

Similarities Differences

They both circulate fluids throughout The ciculatory system circulates

the body. blood while the lymphatic system
circulates lymph.

Blood circulates through the pumping

action of the heart; lymph circulates
without any organ to pump it.

Both circulating fluids pass through a Blood passes through veins, arteries,
series of tubes. and capillaries: lymph passes
through lymphatic vessels.

Let’s See What You Have Learned (pages 10-11)

1. e 6. a
2. h 7. i
3. j 8. f
4. g 9. c
5. b 10. d

C. Lesson 2
Let’s Try This (page 13)

Corrrect Statement Incorrect Statement

3 1
6 2
7 4
8 5
9 10

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 Let’s Review (page 14)
1. AIDS is a group of diseases that result from the reduced immunity of
the body; HIV is the virus that causes AIDS.
2. HIV is transmitted through (a) unprotected sex, (b) sharing needles in
injecting drugs and (c) blood transfusion.
Let’s See What You Have Learned (pages 17-18)
1. Lymphadenitis refers to the inflammation of the lymph node, while
lymphangitis refers to the inflammation of lymph vessels.
2. AIDS stands for Acquired Immune Deficiency Syndrome. It is
caused by HIV, a virus that attacks the T cells of the lymphatic system
and causes immunity to fail. This leads to many infectious and
diseases.

D. Lesson 3
Let’s See What You Have Learned (pages 22-23)
The following numbers should be checked: 2, 3, 5, 7, 8, 10.

E. What Have You Learned (page 24)

1. lymph
2. Lymph nodes
3. thymus
4. lymphatic vessels; lymph nodes; lymphoid organs
5. non-Hodgkin’s lymphoma
6. Edema
7. acquired immune deficiency syndrome
8. Salty
9. bacteria
10. antibodies

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 Glossary

AIDS Stands for acquired immune deficiency syndrome; a group of infections

that attack the body as a result of the reduction of the body’s immunity.
Biopsy A test conducted on whether a patient has cancer or not by taking a
sample of the body tissues and studying it.
Edema A swelling in the body caused by the accumulation of fluid in the body
tissues.
Elephantiasis An abnormal enlargement of any part of the body caused by the
obstruction of the lymphatic vessels.
Immunity The ability of the body to fight off infections.
Infection The presence of harmful microorganisms and other foreign materials
in the body.
Inflammation A condition characterized by redness, heat, swelling and pain; a
reaction of the body to the presence of infection.
Interstitial spaces The spaces between cells in the tissues of the body.
Lymphadenitis An inflammation of the lymph nodes.
Lymphangitis An inflammation of lymphatic vessels.
Lymph nodes Part of the lymphatic system that filter lymph as it passes before
it returns to the bloodstream.
Lymphoma A cancer of the lymphatic system.
Lymphocyte A type of white blood cell found in the lymph and the parts of the
lymphatic system.
Spleen A lymphoid organ; filters the blood that passes through it.
Thymus An organ found high above the abdomen; where lymphocytes mature and
develop.

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 References

Junqiera, I.,C.J. Carneiro, and R. Kelly. Basic Histology. 6th ed . U.S.A.:

Appleton and Lange Prentice Hall, 1989.
Rischer, C. and T. Easton. Focus on Human Biology. 2nd ed . U.S.A.: Harper
Collins College Publishers, 1995.
Van de Graaf, K. and Stuart I.F. Forx. Concepts of Human Anatomy and
Physiology. 2nd ed. Iowa: WM Brown Publishers, 1985.

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