THE LYMPHATIC SYSTEM

1.4THE LYMPHATIC SYSTEMLearning outcomes..At the end of lesson, you should be able to:Describe the formation interstitial fluid State the composition of interstitial fluidState the importance of interstitial fluidDescribe the fate of interstitial fluidDescribe the structure of the lymphatic systemExplain how the lymphatic system complements the circulatory systemCompare 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 systemThe three parts of the lymphatic system are: The lymph vesselsThe lymph nodesThe lymph fluidThe functions of the system are:Maintains fluid balance within our tissuesTransports fat (an important nutrient) absorbed from the intestine to the bloodstreamIs 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 areaLeft drainage area

Drainage area..Drains lymph from the right side of the head and neckThe right armUpper right quadrant of the body.Lymph from this area flows into the right lymphatic duct.This duct empties the lymph intothe right subclavian vein.

Drains lymph from the left side of the head and neckThe Left arm and the left upper quadrantThe lower trunk and both legsThe cisterna chyli temporarily stores lymph as it moves upward from the lower areas of the body.The thoracic ducttransports lymph upward to the left lymphatic duct.The leftlymphatic duct empties the lymph into the left subclavian vein.Right drainage areaLeft drainage areaWhat 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 capillariesHigh pressure forces water & dissolved substances out into the interstitial spaces The fluid is called interstitial fluid.

Venous end of capillaryBlood absorbs 90% ISF10% of ISF passes back into blood circulatory system as lymph via the lymphatic system.Composition of interstitial fluid (ISF)Similar in composition in blood plasmaDo 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 systemLymph 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.Thoracic duct is the largerst lymphatic vessels in the body

17Cont.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 TransportCollects the ISF and returns it back to the circulatory systemLacteals: lymphatic capillaries in the villi of the illeumAbsorbs fat and fat-soluble vitamins and transport them to the blood circulatory systemLymph nodes:Filter out bacteria and foreign particles (by phagocytes)Lymphocytes in the lymphatic tissues:Produce antibodies (aid destruction of pathogens and the neutralization of toxins)

Comparison of the Cardiovascular and Lymphatic SystemsCardiovascular 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 1.6Compare the contents of blood and lymph.

BLOODSIMILARITIESLYMPHBLOODDIFFERENCESLYMPHGlucose Protein moleculesOxygenWaste materialsErythrocytes LeucocytesPlatelets 1.5Role of the circulatory system in the bodys defence mechanismsLearning outcomes..At the end of lesson, you should be able to..State another function of circulatory system besides transportIdentify the three lines of defence mechanism of body Describe the process of phagocytosisState the meaning of antigen and antibody State the meaning of immunity and immunization Relate antigen and antibody to immunityName and give examples of various Types of immunityState the effects of Human Immunodeficiency virus (HIV) on the bodys defence mechanismDescribe the transmission of HIVSuggest ways to prevent the spread of Acquired Immune Deficiency Syndrome ( AIDS)

H1N1 viruses

Leishmania donovani parasites(photo: CDC)

Cholera bacteria

Bodys defence mechanismHuman 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 defenceSkinActs as a physical barrierMade up of dead keratinized layer which is difficult to penetrateSebaceous glands secrete sebum which contain lysozymes to destroy bacteria

First line of defenceMucous membranesMucus in the nasal cavity trap dust particles and sporesCilia (respiratory tract) sweep the trapped particles to the pharynx.Gastric juices (in stomach) will killed microorganisms that enter the stomach.

Boy with grazed elbow

Crying child

Second line of defenceIf 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 defenceLymphocytes are WBC found in the lymph nodes and in the blood circulatory system.Two types of lymphocytes:T-lymphocytesAttack cells infected by pathogens orProduce certain chemicals to coordinate immune responseB-lymphocytesProduce antibodiesCont.Antibody protein produced by lymphocytes in response to the presence of an antigen.Antigen foreign substance which stimulates the body to produce an immune responseAntibodies 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 immunityImmunity: 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 immunityAcquired Passive Immunity Inherited natural immunity: inherited by individual through the placenta or mothers milk.

vaccine: when the vaccine injected into a persons body, lymphocytes in the body produce antibodies to fight against particular antigen.

47Active natural immunityActive natural acquired immunity: acquired after a person recovers from an infection. Eg; measles or chickenpox.

Natural active immunityActive artificial immunityActive artificial acquired immunity: Eg; vaccine (contains killed or weakened antigens). Active because the a/bodies produced by the body itselfArtificial because it is obtained through vaccination. the process is known as immunisation.

Artificial active immunity

Passive immunityPassive natural immunity: when a/bodies from the mother transported across the placenta to the foetus. Lasts for a few months.Passive artificial immunity: injecting serum containing a specific a/bodies prepared from human/animals blood.

Apssive natural immunity- temporary. Cannot last for several weeks/ months bcos the foreign a/bodies break down in the body n not replaced.

52Passive artificial immunityUsually used to treat patient with serious ill. Eg: rabies, tetanus or snake bitesGive temporary immunity.

Difference between passive and active immunity

Assignment 1.6Describe the process of phagocytosis. Drawing will help you to get marks. (10 marks)Name and give examples of various types of immunity. (10 marks)Artificial passive immunity

Human Immunodeficiency Virus (HIV)- Effects on the bodys defence mechanismAIDS (acquired immune deficiency syndrome) is caused by HIV.HIV infects the helper T-cells (important to activate other lymphocytes in the bodys defence mechanisms against disease).Once infected, it takes a long incubation period before the symptoms appear.A persons 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: Kaposis sarcomaHIV also affect the nervous system. A patient will suffered malfunction nervous system.

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HIV

Kaposis sarcomaTransmission of HIVThere are several possible ways in which the virus can enter.Having sex with an infected partnerInjection-drug users who share needles or syringes that are contaminated with blood from an infected person.Women can transmit HIV to their babies during pregnancy or birth, when infected maternal cells enter the baby's circulation, or through breastfeeding.HIV can be spread in health-care settings through accidental needle sticks or contact with contaminated fluids.

Transmission of HIVTransfusion of contaminated blood or blood components. 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.Despite significant efforts, there is no effective vaccine against HIV

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Ways to prevent the spread of AIDSAbstain 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.

661.6Appreciating a healthy cardiovascular systemLearning 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 smokingPoor diet and nutritionPhysical inactivityOverweight and obesityHigh blood pressureHigh blood cholesterolDiabetesHigh alcohol consumptionAtherosclerosis

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.