Lymphatic and Immune System

Lymphatic and Immune System

High School

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Learning Objectives

• Define the lymphatic system and its primary functions in the body.

• Identify the key structures and organs of the lymphatic system.

• Differentiate between the innate and adaptive immune responses.

• Describe the mechanism of the inflammatory response.

• Recognize examples of immunological disorders like autoimmune diseases and lymphoma.

Key Vocabulary

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Lymph

The fluid in lymphatic vessels, containing water, plasma proteins, and crucial white blood cells for immunity.

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Lymph Nodes

These are small, oval-shaped organs that filter out foreign particles and store many lymphocytes.

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Spleen

The largest lymphatic organ that filters lymph, stores lymphocytes, and recycles our old red blood cells.

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Innate Immunity

The body’s immediate, non-specific defense system activated when it encounters any foreign pathogen.

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Antigens

These are protein or sugar tags on cell membranes used to identify if cells are self or non-self.

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Lymphocytes

These are the main white blood cells of lymph, which include B cells and T cells.

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What is the Lymphatic System?

• It is a network that moves a fluid called lymph into the bloodstream.

• It returns excess fluid from tissues to the blood, preventing swelling.

• Special vessels in the small intestine absorb and transport digested fats.

• It produces white blood cells (lymphocytes) that help fight infection.

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Multiple Choice

Which of the following are the three primary functions of the lymphatic system?

• Fluid balance, fat absorption, and immunity.

• Nerve transmission, muscle contraction, and breathing.

• Blood circulation, hormone production, and digestion.

• Filtering blood, producing urine, and storing bile.

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Structures of the Lymphatic System

• Lymphatic capillaries collect interstitial fluid, which then flows into larger lymphatic vessels.

• ​These vessels form a one-way network with valves to guide the lymph flow.

• Small, oval lymph nodes act as filters, removing bacteria from the traveling lymph.

• Packed with lymphocytes, these nodes are key centers for fighting bodily infections.

Multiple Choice

What is the main purpose of valves within lymphatic vessels?

• To ensure lymph flows in a single direction toward the heart.

• To filter out foreign particles and cancer cells.

• To speed up the transport of lymph throughout the body.

• To allow interstitial fluid to enter the vessel.

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Key Lymphatic Organs

• The spleen’s white pulp manages immunity, while its red pulp recycles red blood cells.

• The thymus is an organ where important immune cells, called T-cells, mature.

• Tonsils are tissues in the throat that trap pathogens from your mouth or nose.

• MALT and GALT are lymphatic tissues that protect the body’s mucosa and gut.

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Multiple Choice

Which part of the spleen is responsible for degrading and recycling old red blood cells?

• The White Pulp

• The Red Pulp

• The B-zone

• The T-zone

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What is Lymph and How Does It Flow?

• Lymph forms from fluid that leaks out of blood capillaries into your tissues.

• It contains water, proteins, fats, and white blood cells called lymphocytes.

• The lymphatic system has no pump; muscle contractions push lymph along the vessels.

• Valves ensure one-way flow, and lymph returns to the blood via two large ducts.

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Multiple Choice

How is lymph moved throughout the body without a central pump?

• By the pressure created from the heart pumping blood.

• By the contraction of skeletal muscles around the vessels.

• By the continuous production of new lymph in the capillaries.

• By gravity pulling the fluid downwards.

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The Immune Function

B Cells

• B cells are produced and fully mature within the red bone marrow.

• When activated, they create antibodies which are proteins that neutralize specific pathogens.

• Some B cells develop into memory cells for long-lasting immunity from future infections.

T Cells

• T cells are produced in the bone marrow but travel to the thymus to mature.

• They directly attack the body's own infected cells or help activate other immune cells.

• Like B cells, some T cells also become memory cells to create a faster response.

Multiple Choice

Where do B cells and T cells originate before they mature and learn to fight infections?

• In the thymus gland.

• In the lymph nodes.

• In the spleen's white pulp.

• In the red bone marrow from stem cells.

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Innate Immunity and Inflammatory Response

• The innate immune system is the body's immediate defense, including skin/mucus.

• If pathogens enter, a cellular inflammatory response begins, releasing mediators.

• Histamines increase local blood flow, and cytokines help immune cells multiply.

• Prostaglandins cause swelling and clotting; NSAIDs work by blocking them.

Multiple Choice

During an inflammatory response, what is the role of histamines?

• To act as a physical barrier against pathogens.

• To increase blood circulation to the site of injury.

• To promote the proliferation of immune cells.

• To help in the formation of blood clots.

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Bridging Innate and Adaptive Immunity

• The innate and adaptive immune systems are linked by Antigen-Presenting Cells (APCs).

• An antigen is a part of a pathogen that triggers an immune response.

• APCs like macrophages engulf pathogens and display the pathogen’s antigen on their surface.

• This '''flag''' activates T cells and B cells to target the specific invader.

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Multiple Choice

What is the primary role of Antigen-Presenting Cells (APCs)?

• To produce antibodies against specific pathogens.

• To directly destroy pathogens by releasing histamine.

• To display a pathogen's antigen to activate the adaptive immune response.

• To form a physical barrier like skin or mucus.

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Immunological Disorders

• Autoimmune disorders occur when the immune system attacks the body's own tissues.

• ​In Crohn's disease, it attacks the digestive system; in Addison's, the adrenal glands.

• Hodgkin's Lymphoma is a cancer of the immune system causing enlarged lymph nodes.

• Artificial acquired immunity is developed from vaccinations that train your immune system.

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Solved Example 1
A patient with Hodgkin's Lymphoma has a 90% five-year survival rate. If a group of 200 patients is diagnosed, how many are expected to survive for five years?

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Step 1: Analyze and Sketch the Problem

• Goal: Calculate the number of patients expected to survive.

• Knowns: Total patients = 200; Survival rate = 90%.

• Unknown: Number of survivors.

• Formula: Survivors = Total Patients × (Survival Rate / 100).

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Solved Example 1
A patient with Hodgkin's Lymphoma has a 90% five-year survival rate. If a group of 200 patients is diagnosed, how many are expected to survive for five years?

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Step 2: Solve for the Unknown

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Solved Example 1
A patient with Hodgkin's Lymphoma has a 90% five-year survival rate. If a group of 200 patients is diagnosed, how many are expected to survive for five years?

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Step 3: Evaluate the Answer

• To verify, divide the number of survivors by the total patients: 180 / 200 = 0.90.

• Converting this back to a percentage gives 90%, which matches the given survival rate. The answer is reasonable.

Multiple Choice

Which of the following is an example of an autoimmune disorder where the immune system attacks the digestive system?

• Hodgkin's Lymphoma

• Addison's disease

• Crohn's disease

• Artificial acquired immunity

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Common Misconceptions about the Lymphatic System

Misconception	Correction
The lymphatic system is a closed loop.	It's a one-way system that returns fluid to the blood.
Lymph is pumped by the heart.	Lymph is moved by muscle contractions and breathing.
Lymph nodes produce lymphocytes.	Lymph nodes filter lymph; lymphocytes are made in bone marrow.
Swollen lymph nodes always indicate a serious disease.	Swelling is a normal response to infection.

Multiple Choice

Based on its function, which lymphatic organ is primarily responsible for the maturation of T-cells?

• Thymus

• Lymph Nodes

• Tonsils

• Spleen

Multiple Choice

How does the lymphatic system directly support the function of the digestive system?

• By producing stomach acid to break down food.

• By absorbing and transporting fats and fatty acids from the small intestine.

• By filtering waste products from the liver.

• By moving food through the intestines via muscle contractions.

Multiple Choice

A person has a severe blockage in their Thoracic Duct. What is a likely consequence of this condition?

• Swelling (edema) in the legs and the left arm.

• An inability to produce B-cells and T-cells.

• A significant decrease in the recycling of red blood cells.

• Swelling (edema) in only the right arm and right side of the head.

Multiple Choice

If a new virus had a mutation that made its antigens invisible to Antigen-Presenting Cells (APCs), how would this impact the overall immune response?

• The adaptive immune response would not be activated, preventing the production of specific antibodies.

• The innate immune response, including inflammation, would be unable to start.

• The body's physical barriers, like skin, would immediately fail.

• The circulation of lymph would stop completely throughout the body.

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Summary

• The lymphatic system balances fluid, absorbs fats, and helps the immune system.

• Key structures include lymph vessels, nodes, the spleen, and the thymus.

• Lymph flows in one direction and is moved by muscle contractions.

• The innate immune system provides the body's rapid, first-line defense.

• The adaptive immune system uses B cells and T cells for a targeted response.

• APCs link the innate and adaptive systems by presenting antigens.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

• 1

• 2

• 3

• 4