Lymphatic System

Lymphatic System

High School

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Learning Objectives

• Describe the main structure and functions of the lymphatic system.

• Explain how lymph is formed and transported throughout the body.

• Identify the major organs of the lymphatic system and their roles in immunity.

• Understand the lymphatic system's role in the cardiovascular, digestive, and immune systems.

• Recognize key diseases and disorders associated with the lymphatic system.

Key Vocabulary

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Lymph

A clear, watery fluid with white blood cells that circulates in the lymphatic system to remove waste.

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Lymphocytes

A type of white blood cell, like B and T cells, essential for the adaptive immune system.

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Chyle

A milky fluid full of fatty acids, made in the small intestine and moved by lymphatic vessels.

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Lymph Nodes

Small, bean-shaped organs that filter lymph, store lymphocytes, and are key sites for immune defense.

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Spleen

The largest lymphatic organ, it filters pathogens from blood, stores blood, and destroys old red blood cells.

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The Lymphatic System

• It is a network of tissues and organs that removes toxins.

• The system is a key part of your body's immune defenses.

• It moves a fluid called lymph throughout the body.

• It's a one-way system that drains into the bloodstream.

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Multiple Choice

What are the primary components of the lymphatic system and in which direction does lymph flow?

• Nerves and spinal fluid; it flows from the brain to the body.

• Arteries and veins; it flows in a circular, closed loop.

• Blood vessels and red blood cells; it flows away from the heart.

• Lymph, lymphocytes, and vessels; it flows in a single direction toward the chest.

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Lymph: Formation and Composition

• Fluid from blood becomes interstitial fluid, which surrounds and nourishes body cells.

• Tiny lymph capillaries absorb this interstitial fluid, which is now called lymph.

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

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Solved Example 1
If 20 liters of blood plasma circulate through the capillaries and 10% of this fluid becomes interstitial fluid, what is the volume of interstitial fluid formed in milliliters?

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Step 1: Analyze and Sketch the Problem

• Goal: Calculate the volume of interstitial fluid formed.

• Knowns: Total plasma volume = 20 L; Percentage that becomes interstitial fluid = 10%.

• Unknown: Volume of interstitial fluid in mL.

• Formula: Interstitial Fluid Volume = Total Plasma Volume × Percentage.

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Solved Example 1
If 20 liters of blood plasma circulate through the capillaries and 10% of this fluid becomes interstitial fluid, what is the volume of interstitial fluid formed in milliliters?

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Step 2: Solve for the Unknown

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Solved Example 1
If 20 liters of blood plasma circulate through the capillaries and 10% of this fluid becomes interstitial fluid, what is the volume of interstitial fluid formed in milliliters?

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Step 3: Evaluate the Answer

• The volume of interstitial fluid is 2000 mL.

• This makes sense, as 10% of 20 liters is 2 liters, which equals 2000 milliliters. The answer is reasonable and the units are correct.

Multiple Choice

How is lymph formed and what is its main cellular component?

• It is absorbed in the lungs and is primarily composed of platelets.

• It forms from interstitial fluid that enters lymph capillaries, and its main cellular components are lymphocytes.

• It is filtered from saliva and its main cells are epithelial cells.

• It is produced in the heart and its main cells are red blood cells.

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How Is Lymph Transported?

Movement of Lymph

• Lymph moves through a network of tubes called lymphatic vessels.

• These vessels have one-way valves that prevent the backward flow of lymph.

• Movement is aided by vessel contractions and pressure from surrounding skeletal muscles.

Lymphatic Drainage

• The Right Lymphatic Duct drains the upper right side of the body.

• The much larger Thoracic Duct is responsible for draining the rest of the body.

• From these ducts, lymph is returned to the bloodstream through the subclavian veins.

Multiple Choice

Which duct drains lymph from the legs, and what mechanism prevents the backflow of lymph in the vessels?

• Right Lymphatic Duct; one-way valves.

• Thoracic Duct; pressure from the heart.

• Right Lymphatic Duct; pressure from the heart.

• Thoracic Duct; one-way valves.

Functions of the Lymphatic System

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Cardiovascular Function

• The system collects excess fluid from the body's tissues.

• This fluid is then returned to the bloodstream.

• This helps maintain normal blood volume and pressure levels.

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Digestive Function

• Special vessels in the small intestine absorb fatty acids.

• These vessels are known as lacteals in the system.

• This creates a fatty fluid called chyle for transport.

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Immune Function

• This system is central to the body's immune defense.

• It circulates key immune cells called lymphocytes (B and T cells).

• These cells provide an adaptive immune response against specific pathogens.

Multiple Choice

Which function of the lymphatic system involves the absorption of fatty acids from the small intestine?

• Respiratory Function

• Cardiovascular Function

• Digestive Function

• Immune Function

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The Origin of Lymphocytes

Common Origin

• All lymphocytes, B cells and T cells, start from stem cells in the red bone marrow.

• These are a type of white blood cell in the adaptive immune system.

• They learn to tell the difference between the body's own cells and foreign invaders.

Maturation Paths

• B cells mature in the bone marrow, where they are made.

• T cells, however, travel from the bone marrow to the thymus gland to mature.

• This is why they are called T cells, which stands for thymus cells.

Multiple Choice

Where do T lymphocytes mature?

• In the thymus gland

• In the lymph nodes

• In the red bone marrow

• In the spleen

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Organs: Lymph Nodes and Tonsils

Lymph Nodes

• These are small, bean-shaped organs that filter lymph fluid and trap foreign particles.

• They contain immune cells that activate an adaptive immune response; swollen nodes indicate an infection.

• Key groups include Cervical (neck), Axillary (armpits), and Inguinal (groin) nodes.

Tonsils

• These are specialized lymph nodes in the throat that trap germs from the mouth and nose.

• The three types are the Palatine tonsils, Pharyngeal tonsils (adenoids), and Lingual tonsils.

• They are located in the pharynx, near the nasal cavity, and at the back of the tongue.

Multiple Choice

A doctor finds swollen lymph nodes in a patient's armpit. Which group of lymph nodes is affected, and what is their primary function?

• Palatine tonsils; their function is to filter air.

• Axillary nodes; their function is to filter lymph.

• Cervical nodes; their function is to filter blood.

• Inguinal nodes; their function is to produce saliva.

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Spleen and Thymus: Key Lymphatic Organs

Spleen

• The spleen is the largest lymphatic organ, located in the upper left side of your abdomen.

• It filters pathogens directly from the blood, unlike lymph nodes which filter lymph fluid.

• It also stores extra blood and is responsible for destroying old or damaged red blood cells.

Thymus

• The thymus is a gland in the chest where important immune cells called T lymphocytes mature.

• It is part of the lymphatic and immune systems, as well as the endocrine system.

• The thymus is largest in children and begins to shrink after puberty, continuing into adulthood.

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Solved Example 3
If the spleen filters 1.5 liters of blood per minute and removes 500,000 pathogens per liter, how many pathogens are removed from the blood in 5 minutes?

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Step 1: Analyze and Sketch the Problem

• Goal: Calculate the total number of pathogens removed by the spleen in 5 minutes.

• Knowns: Blood filtration rate = 1.5 L/min, Pathogen concentration = 500,000 pathogens/L, Time = 5 minutes.

• Unknown: Total pathogens removed.

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Solved Example 3
If the spleen filters 1.5 liters of blood per minute and removes 500,000 pathogens per liter, how many pathogens are removed from the blood in 5 minutes?

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Step 2: Solve for the Unknown

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Solved Example 3
If the spleen filters 1.5 liters of blood per minute and removes 500,000 pathogens per liter, how many pathogens are removed from the blood in 5 minutes?

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Step 3: Evaluate the Answer

• The spleen filters 7.5 liters in 5 minutes. At a concentration of 500,000 pathogens per liter, this equals 3,750,000 pathogens. The units (L and L/min, min) cancel correctly to give the number of pathogens.

• The answer is reasonable.

Multiple Choice

What is the primary difference between the filtering function of the spleen and that of lymph nodes?

• The spleen matures B cells, while lymph nodes mature T cells.

• The spleen creates red blood cells, while lymph nodes destroy them.

• The spleen filters pathogens from blood, while lymph nodes filter pathogens from lymph.

• The spleen filters lymph, while lymph nodes filter blood.

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Related Diseases and Disorders

Immune System Disorders

• ​The lymphatic system's dysfunction is linked to several diseases that affect overall health and immunity.

• ​​Hodgkin's Lymphoma is an immune system cancer that enlarges lymph nodes, often causing fever and weight loss.

• ​In autoimmune disorders like Crohn's disease, the immune system mistakenly attacks the body’s own healthy tissues.

Acquired Immunity

• ​Artificial acquired immunity is intentionally gained through methods like vaccination.

• ​​Vaccines prompt the immune system to build a defense against a pathogen without causing the disease.

• ​This process creates a defense system for future protection against that specific pathogen.

Multiple Choice

What is Hodgkin's Lymphoma?

• Immunity acquired through a vaccination.

• A condition where the spleen enlarges due to infection.

• An autoimmune disorder that attacks the digestive system.

• A cancer of the immune system characterized by enlarged, non-tender lymph nodes.

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Common Misconceptions About the Lymphatic System

Misconception	Correction
The lymphatic system is a closed loop, like the cardiovascular system.	It is a one-way system transporting lymph from tissues to the chest.
The heart is responsible for pumping lymph throughout the body.	Lymph is moved by vessel and skeletal muscle contractions.
The spleen's main job is to filter lymph.	The spleen filters blood, while lymph nodes filter lymph.
Lymphocytes are just one type of cell.	Lymphocytes include B cells and T cells, which have different roles.

Multiple Choice

Why would a doctor check for swollen cervical (neck) lymph nodes if a patient complains of a sore throat?

• Because the neck nodes filter lymph from the throat area, and swelling indicates an active immune response to infection there.

• Because the cervical nodes are responsible for producing T-cells to fight the infection.

• Because all lymph is returned to the neck area.

• Because the thymus is located in the neck and swells during infection.

Multiple Choice

Based on their functions, what is the key difference between the fluid filtered by the spleen and the fluid filtered by the tonsils?

• The spleen filters chyle from the intestines, while the tonsils filter blood.

• The spleen filters interstitial fluid, while the tonsils filter chyle.

• The spleen filters lymph from the lower body, while the tonsils filter lymph from the head.

• The spleen filters blood, while the tonsils filter lymph from the throat.

Multiple Choice

A patient has a severe blockage in their thoracic duct. What is the most likely and immediate consequence throughout their body?

• Fluid would accumulate in the right arm and right side of the head.

• The maturation of T cells would stop.

• Fluid (lymph) would build up in the legs, left arm, and abdomen, as it cannot be returned to the bloodstream.

• The patient would be unable to absorb fatty acids from their diet.

Multiple Choice

Analyze the relationship between the lymphatic system's digestive function and the cardiovascular system. How does the former support the latter?

• The lymphatic system produces red blood cells, which are then used by the cardiovascular system.

• The lymphatic system returns excess fluid, which helps the cardiovascular system absorb nutrients.

• The lymphatic system filters blood for the cardiovascular system.

• The lymphatic system absorbs fats into chyle and delivers them to the bloodstream for transport and processing, which the blood vessels cannot absorb directly.

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Summary

• The lymphatic system is a one-way network essential for immune defense.

• It circulates lymphocytes, such as B cells and T cells, for immunity.

• Lymph is moved by muscle contractions and filtered by organs like lymph nodes.

• The system returns fluid to the blood and helps your body absorb fats.

Poll

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