1.4

THE LYMPHATIC SYSTEM

Learning outcomes..

At the end of lesson, you should be able to: Describe the formation interstitial fluid State the composition of interstitial fluid State the importance of interstitial fluid Describe the fate of interstitial fluid Describe the structure of the lymphatic system Explain how the lymphatic system complements the

circulatory system Compare the content of blood, interstitial fluid and lymph Predict what will happen if interstitial fluid fails to return to

the circulatory system Conceptualize the relationship between the lymphatic

system and circulatory system

Lymphatic system

The three parts of the lymphatic system are: The lymph vessels The lymph nodes The lymph fluid

The functions of the system are: Maintains fluid balance within our tissues Transports fat (an important nutrient) absorbed from

the intestine to the bloodstream Is a vital part of the immune system as it removes

microorganisms and other disease-causing substances from body tissues.

The human lymphatic

system

Lymph capillary

Lymph node

Lymph vessels begin as small closed end tubes found in the spaces between cells within tissue.

After the tissue fluid enters the lymph capillaries (the smallest vessels) it is referred to as fluid.

Lymph capillaries merge to form larger lymph ducts.

lymph

Drainage area..

Right drainage area Left drainage area

Drainage area..

Drains lymph from the right side of the head and neck

The right arm Upper right quadrant of the

body. Lymph from this area flows

into the right lymphatic duct.

This duct empties the lymph into the right subclavian vein.

Drains lymph from the left side of the head and neck

The Left arm and the left upper quadrant

The lower trunk and both legs

The cisterna chyli temporarily stores lymph as it moves upward from the lower areas of the body.

The thoracic duct transports lymph upward to the left lymphatic duct.

The left lymphatic duct empties the lymph into the left subclavian vein.

Right drainage area Left drainage area

What is going to happen to the lymph fluid?

Back to the blood to become plasma again.

Do you still remember how the interstitial fluid (ISF) is formed?

Arterial end of capillaries• High pressure forces water &

dissolved substances out into the interstitial spaces

• The fluid is called interstitial fluid.

Venous end of capillary• Blood absorbs 90% ISF• 10% of ISF passes back into blood

circulatory system as lymph via the lymphatic system.

Composition of interstitial fluid (ISF) Similar in composition in blood plasma Do not have erythrocytes, platelet and

large protein molecules. Consists of a water solvent containing

amino acids, sugars, fatty acids, coenzymes, hormones, neurotransmitters, salts, as well as waste products from the cells.

Importance of interstitial fluid (ISF)

It forms the internal environment of the body.

Bathes the cells and supplies them with oxygen and nutrients.

Waste products such as CO2 and urea diffuse out from the cells into interstitial fluid.

Keep the body within normal range range homeostatic process.

How the lymphatic system complements the circulatory system

Lymph travels through the lymphatic vessels by the contraction on the surrounding skeletal muscles.

Lymph flow in one direction. One end of the vessel is closed and back

flow is prevented by valves present in the larger vessels.

Smaller lymphatic vessels join to form larger vessels.

The vessels from the left side of the body, the alimentary canal and the right side of the lower part of the body flow into the thoracic duct.

Cont.

It carries lymph to the left subclavian vein and back to the bloodstream.

Right lymphatic duct transport lymphs from the right side of the head and chest into the right subclavian vein.

Role of Lymphatic System in Transport

1. Collects the ISF and returns it back to the circulatory system

2. Lacteals: lymphatic capillaries in the villi of the illeum Absorbs fat and fat-soluble vitamins and transport

them to the blood circulatory system

3. Lymph nodes: Filter out bacteria and foreign particles (by

phagocytes)

4. Lymphocytes in the lymphatic tissues: Produce antibodies (aid destruction of pathogens

and the neutralization of toxins)

Comparison of the Cardiovascular and Lymphatic Systems

Cardiovascular System(Blood)

Lymphatic System(Lymph)

Blood is responsible for collecting and distributing oxygen, nutrients and hormones to the tissues of entire body.

Lymph is responsible for collecting and removing waste products left behind in the tissues.

Blood flows in a closed continuous loop throughout the body via the arteries, capillaries, and veins.

Lymph flows in an open circuit from the tissues into lymphatic vessels. Once within these vessels, lymph flows in only one direction.

Blood is pumped. The heart pumps blood into the arteries that carry it to all of the body. Veins return blood from all parts of the body to the heart.

Lymph is not pumped. It passively flows from the tissues into the lymph capillaries. Flow within the lymphatic vessels is aided by other body movements such as deep breathing and the action of nearby muscles and blood vessels.

Blood consists of the liquid plasma that transports the red and white blood cells and platelets.

Lymph that has been filtered and is ready to return to the cardiovascular system is a clear or milky white fluid.

Blood is visible and damage to blood vessels causes obvious signs such as bleeding or bruising.

Lymph is invisible and damage to the lymphatic system is difficult to detect until swelling occurs.

Blood is filtered by the kidneys. All blood flows through the kidneys where waste products and excess fluids are removed. Necessary fluids are returned to the cardiovascular circulation.

Lymph is filtered by lymph nodes located throughout the body. These nodes remove some fluid and debris. They also kill pathogens and some cancer cells.

Blood vessel damage or insufficiency produces swelling that containing low-protein fluid.

Lymphatic vessel damage or insufficiency produces swelling containing protein-rich fluid.

Assignment 1.6

1. Compare the contents of blood and lymph.BLOOD SIMILARITIES LYMPH

BLOOD DIFFERENCES LYMPH

Glucose

Protein molecules

Oxygen

Waste materials

Erythrocytes

Leucocytes

Platelets

1.5

Role of the circulatory system in the body’s defence mechanisms

Learning outcomes..

At the end of lesson, you should be able to.. State another function of circulatory system besides

transport Identify the three lines of defence mechanism of body Describe the process of phagocytosis State the meaning of antigen and antibody State the meaning of immunity and immunization Relate antigen and antibody to immunity Name and give examples of various Types of immunity State the effects of Human Immunodeficiency virus

(HIV) on the body’s defence mechanism Describe the transmission of HIV Suggest ways to prevent the spread of Acquired Immune

Deficiency Syndrome ( AIDS)

H1N1 viruses

Leishmania donovani parasites(photo: CDC)

Cholera bacteria

Body’s defence mechanism

Human bodies have three lines of defence against pathogens. First line of defence (skin, mucous

membrane) Second line of defence (phagocytes) Third line of defence (lymphocytes)

First line of defence Skin

Acts as a physical barrier Made up of dead keratinized

layer which is difficult to penetrate

Sebaceous glands secrete sebum which contain lysozymes to destroy bacteria

First line of defence

Mucous membranes Mucus in the nasal cavity trap dust

particles and spores Cilia (respiratory tract) sweep the trapped

particles to the pharynx. Gastric juices (in stomach) will killed

microorganisms that enter the stomach.

Second line of defence

If the pathogens are able to get past the first line of defence, for example, through a cut in your skin, and an infection develops, the second line of defence becomes active.

Some WBC such as neutrophils act as phagocytes. They are attracted by the chemicals produced at the sites of infection.

The phagocytes move towards the pathogens and engulf them by phagocytosis.

Third line of defence

Lymphocytes are WBC found in the lymph nodes and in the blood circulatory system.

Two types of lymphocytes: T-lymphocytes

Attack cells infected by pathogens or Produce certain chemicals to coordinate

immune response B-lymphocytes

Produce antibodies

Cont.

Antibody – protein produced by lymphocytes in response to the presence of an antigen.

Antigen – foreign substance which stimulates the body to produce an immune response

Antibodies are specific in action and promote the destruction of antigens in different ways.

After an infection, some lymphocytes remain in the body as memory cells.

Memory lymphocytes help to defend the body against further infection by the same antigen.

Types of immunity

Immunity: the ability of an organism to defend itself against infection by pathogens.

Types of immunity: Active immunity (natural & artificial) Passive immunity (natural & artificial)

Immunisation: the process by which an individual's immune system becomes fortified against an agent (known as the immunogen).

Types of immunityImmunity

ActiveOwn antibodies

Natural

Exposure to

infectious agent

Artificial

Immunization

PassiveReady-made antibodies

Natural

Maternal antibodi

es

Artificial

Antibodies from other

sources

Acquired Passive Immunity

Inherited natural immunity: inherited by individual through the placenta or mother’s milk.

Active natural immunity

Active natural acquired immunity: acquired after a person recovers from an infection.

Eg; measles or chickenpox.

Natu

ral act

ive im

munit

y

Active artificial immunity

Active artificial acquired immunity:

Eg; vaccine (contains killed or weakened antigens).

Active because the a/bodies produced by the body itself

Artificial because it is obtained through vaccination. the process is known as immunisation.

Art

ifici

al act

ive

imm

un

ity

Passive immunity

1. Passive natural immunity: when a/bodies from the mother transported across the placenta to the foetus. Lasts for a few months.

2. Passive artificial immunity: injecting serum containing a specific a/bodies prepared from human/animal’s blood.

Passive artificial immunity

Usually used to treat patient with serious ill. Eg: rabies, tetanus or snake bites

Give temporary immunity.

Difference between passive and active immunity

Assignment 1.6

1. Describe the process of phagocytosis. Drawing will help you to get marks. (10 marks)

2. Name and give examples of various types of immunity. (10 marks)

Art

ifici

al p

ass

ive im

mun

ity

Human Immunodeficiency Virus (HIV)- Effects on the body’s defence mechanism

AIDS (acquired immune deficiency syndrome) is caused by HIV.

HIV infects the helper T-cells (important to activate other lymphocytes in the body’s defence mechanisms against disease).

Once infected, it takes a long incubation period before the symptoms appear.

A person’s immune system gradually decrease in function and tend to get infected by secondary infection such as pneumonia, meningitis and fungal diseases.

He/she may develop a cancer. Eg: Kaposi’s sarcoma

HIV

Kaposi’s sarcoma

Transmission of HIV

There are several possible ways in which the virus can enter.

1. Having sex with an infected partner2. Injection-drug users who share needles or syringes

that are contaminated with blood from an infected person.

3. Women can transmit HIV to their babies during pregnancy or birth, when infected maternal cells enter the baby's circulation, or through breastfeeding.

4. HIV can be spread in health-care settings through accidental needle sticks or contact with contaminated fluids.

Transmission of HIV

5. Transfusion of contaminated blood or blood components.

6. The virus does not spread through casual contact such as preparing food, sharing towels and bedding, or via swimming pools, telephones, or toilet seats. The virus is also unlikely to be spread by contact with saliva, unless it is contaminated with blood.

Ways to prevent the spread of AIDS

Abstain from sex. Use a condom in other situations. Do not share needles or inject illicit drugs. If you work in a health-care field, follow

recommended guidelines for protecting yourself against needle sticks and exposure to contaminated fluids.

If you have engaged in risky behaviors, get tested to see if you have HIV.

Strict screening of blood before transfusion. Awareness campaign and counseling.

1.6

Appreciating a healthy cardiovascular system

Learning outcomes..

At the end of lesson, you should be able to: Select and practice suitable ways to

maintain a healthy cardiovascular system.

Risk factors for cardiovascular diseases (CVD)

Cardiovascular diseases share risk factors with other major diseases. Tobacco smoking Poor diet and nutrition Physical inactivity Overweight and obesity High blood pressure High blood cholesterol Diabetes High alcohol consumption

Atherosclerosis

How to take care of healthy cardiovascular system?

Follow a well-balanced diet that is low in saturated fats, cholesterol and salt.

Maintain a healthy weight to reduce stress on the heart, blood vessels, and lymph vessels.

Participate in regular aerobic exercise for at least 30 minutes three to four times per week.

Avoid the use of tobacco products and exposure to secondhand tobacco smoke.

Avoid illegal drugs including stimulants, marijuana and ecstasy.