Lecture Medical assisting: Administrative and clinical procedures with anatomy and physiology (4e) – Chapter 28

Lymphatic Pathways• Lymphatic capillaries – Extend into interstitial spaces – Permeable, thin walls pick up fluid, now lymph – Delivers lymph to lymphatic vessels • Lymphatic vessels –

The Lymphatic and

Immune Systems

Learning Outcomes

28.1 List the pathways and organs of the lymphatic

system and give their locations

28.2 Define lymph and tell how it is circulated in the body

28.3 Define the terms infection, pathogen, and antigen.

28.4 List and describe the nonspecific body defense

mechanisms

28.5 Explain the signs and causes of inflammation

Learning Outcomes (cont.)

28.6 Explain what is meant by body defenses

28.7 Define B cells and T cells and describe their

locations and functions

28.8 Explain the importance of MHC proteins

28.9 List the different types of T cells and describe their

functions

28.10 Explain how antibodies fight infection

Learning Outcomes (cont.)

28.11 List the different types of antibodies and tell how

they differ

28.12 Define complement proteins and give their function

28.13 Explain the difference between the primary immune

response and secondary immune response

28.14 Explain the four different types of acquired

immunities

28.15 Describe the function of a vaccine

Learning Outcomes (cont.)

28.16 Define the terms cancer and carcinogen.

28.17 Describe how cancers are diagnosed and treated

28.18 Explain how cancers are classified

28.19 Describe how allergies develop

28.20 Describe the causes, signs and symptoms, and

treatments of other common immune disorders

– Organs

• Thymus

• Spleen

• Lymph nodes

The Lymphatic System

• Network of

connecting vessels

– Collects fluid (lymph)

between cells and returns it to

bloodstream– Picks up lipids from

digestive organs and transports them to bloodstream

– Functions to defend

the body against pathogens

Lymphatic Pathways

• Lymphatic capillaries

– Extend into interstitial spaces

– Permeable, thin walls pick up fluid, now lymph

– Delivers lymph to lymphatic vessels

• Lymphatic vessels

– Deliver lymph to lymph nodes

• Cells in nodes can remove pathogens from lymph and start an immune response

– Leaves nodes through efferent lymphatic

System

Lymphatic Pathways (cont.)

• Lymphatic trunks

– Receive lymph from efferent lymphatic

vessels – Deliver it to

• Lymphatic collecting ducts

– Thoracic duct

• Left side of head and neck, left arm, left side of thorax, entire abdominopelvic area, and both legs

– Right lymphatic duct

• Right side of head and neck, right arm, and right side of chest

Lymph

System

Tissue Fluid and Lymph

• Interstitial fluid

– Fluid in spaces between cells that has leaked

from blood capillaries and has not been picked up by body cells

– High in nutrients, oxygen, and small proteins

– Becomes lymph

• Pushed through lymphatic vessels by squeezing action of neighboring skeletal muscles and

breathing movement

Back

– Efferent lymphatic

vessels – Lymph from node

Lymph Nodes (cont.)

• More lymph enters than can leave at one time

• Cells in nodes

– Macrophages – digest unwanted pathogens– Lymphocytes – start

an immune response against pathogen

• Nodes can generate some lymphocytes

The Thymus and Spleen

• Thymus

– Soft, bi-lobed organ

– Located just above the heart in the mediastinum

– Large in children, shrinks as we age

– Functions

• Same as lymph nodes

• Also produces lymphocytes

• Produces thymosin – stimulates production of lymphocytes

The Thymus and Spleen (cont.)

• Spleen

– Largest lymphatic organ

– Located in the upper left quadrant of

abdominal cavity – Functions

• Filters blood similarly to lymph nodes

• Removes worn-out red cells

– If removed ( splenectomy ), liver takes over

most of its function

Apply Your Knowledge

What are the lymphatic collecting ducts and

what area do they drain?

ANSWER: The collecting ducts are:

Thoracic duct, which drains the left side of the head

and neck, left arm, left side of thorax, entire

abdominopelvic area, and both legs; and the right

lymphatic duct, which drains the right side of the head

and neck, right arm, and right side of the chest.

Defenses Against Disease

• Infection

– The presence of a

pathogen in or on the body

• Nonspecific defenses

– Species resistance– Mechanical barriers– Chemical barriers

– Phagocytosis

– Fever

– Inflammation

Specific Defenses Against Disease

– Haptens

• Foreign substances too small to start an

immune response by themselves

• Other substances

– Proteins – antibodies and complements

– WBCs – lymphocytes and macrophages

– Lymph system

• Cytokines – assist in immune response regulation

• Monokines – increase

B cell production and stimulate WBC

production

Defenses Against Disease (cont.)

Two major types of lymphocytes

B Cells and T Cells

Recognize antigens in the body

T Cells

 Cell-mediated response

 Bind to antigens on cells and attack them directly

 Secrete lymphokines that

increase T cell production and directly kill cells with antigens

B cells

 Respond to antigens by

becoming plasma cells

 Plasma cells make antibodies

 Memory B cells produce

stronger response with next

exposure to antigen

B cells

 Respond to antigens by

becoming plasma cells

 Plasma cells make antibodies

 Memory B cells produce

stronger response with next

exposure to antigen

Diagram

Defenses Against Disease (cont.)

• T cell activation

– Begins when macrophage ingests and digests

pathogen with antigen on it – Antigens are placed on cell membrane of

macrophage – T cell recognizes and binds to antigen and the

major histocompatibility complex (MHC) on the surface of the macrophage

– Now can divide to form other types of T cells

Defenses Against Disease (cont.)

Defenses Against Disease (cont.)

Apply Your Knowledge

Identify whether each item refers to T cells, B cells, or NK

cells:

_ Primarily target cancer cells

_ Respond to antigens by becoming plasma cells

_ Must be activated to respond to an antigen

_ Bind to antigens on cells and attack them directly

_ Kill on contact

_ Need macrophages and MHC for activation

_ Make antibodies against specific antigen

• Found on B cell membranes

• Thought to control B cell activity

– IgE

• Found with IgA

• Involved in triggering allergic reactions

Antibodies (cont.)

• Actions that occur when antibodies bind to

antigens

– Allow phagocytes to recognize and destroy antigens

– Cause antigens to clump together, causing them to

be destroyed by macrophages – Cover the toxic portions of antigens, making them

harmless– Activate complement

• Group of proteins in serum that attack pathogens by forming holes in them

• Attract macrophages to pathogens and can stimulate inflammation

Apply Your Knowledge

What are the possible actions that occur when

antibodies bind to antigens?

ANSWER: Possible actions include:

 They allow phagocytes to recognize and destroy

Immune Responses and Acquired Immunity

• Primary immune response occurs with first

exposure to antigen

– Slow process

– Memory cells are formed

• Secondary immune response with next exposure

to same antigen

– Quick and carried out by memory cells

– Usually prevents person from developing disease

from the antigen

• Naturally acquired active immunity

– Natural exposure to antigen – having an

illness– Makes antibodies and memory cells

– Long-lasting

• Artificially acquired active immunity

– Injected with pathogen – immunizations or

vaccines– Makes antibodies and memory cells

– Long-lasting

• Naturally acquired passive immunity

– Acquired from mother

• Breast milk

• Placenta

– Short-lived

• Artificially acquired passive immunity

– Injected with antibodies (such as antivenom)

– Short-lived

Apply Your Knowledge

ANSWER: Immunization is an artificially acquired

immunity because a person develops this immunity

by being injected with a pathogen and then making antibodies and memory cells against the pathogen

After you give an immunization to a 2-year-old,

her mother asks you why this will work to

prevent her from getting a disease.

Major Immune System Disorders

• Cancer

– Uncontrolled growth of abnormal cells form

malignant tumors– Factors known to cause cancer are called

carcinogens

– Treatment based on stage

0 – very early; cancer cells localized

I – spread to deeper layers or some in surrounding tissues

II – spread to surrounding tissues but contained in primary site III – spread beyond primary site into nearby areas

IV – spread to other organs Recurrent – reappeared after treatment

Major Immune System Disorders (cont.)

• Allergies

– Immune response to an allergen

– IgE antibodies bind to allergens and stimulate mast cells to release histamine and heparin, triggering allergic response

Major Immune System Disorders (cont.)

– Allergy signs/symptoms

• Inhaled allergens – runny nose, sneezing, coughing, wheezing

• Ingested allergens – nausea, vomiting, diarrhea

• Skin allergens – rashes

• Allergens in blood – most life-threatening; can affect many organs

– Treatment

• Antihistamines, decongestants – OTC or prescription

• Epinephrine for anaphylaxis – vasoconstriction, increasing BP

– Anaphylaxis – life-threatening response

Common Immune System Disorders

Common Immune System Disorders (cont.)

AIDS Development of severe signs and symptoms

caused by HIV as it destroys lymphocytes; leaves immune system weakened and susceptible to other diseases

Chronic fatigue

syndrome (CFS)

Condition of severe tiredness not relieved by rest and not related to other illnesses

Lymphedema Blockage of lymphatic vessels results in tissue

swelling that increases over time

Common Immune System Disorders (cont.)

Mononucleosis “Mono”; highly contagious viral infection spread

through saliva of infected person

Apply Your Knowledge

Matching:

_ Immune response to a substance A CFS

_ Blockage of lymphatic vessels B SLE

_ “Kissing disease” C Cancer

_ “Butterfly” rash on face D Autoimmune disease _ Severe tiredness E Lymphedema

_ Uncontrolled growth of abnormal cells F Mononucleosis

_ Body attacks its own antigens G Allergy

In Summary

28.1 The lymph system is composed of pathways known

as lymph vessels In addition to the lymph vessels, the organs of the lymphatic system include lymph nodes located throughout the body, the thymus in the mediastinum, and the spleen located in the LUQ

28.2 Lymph is the body fluid found between the body’s

cells It circulates through the body via lymphatic capillaries, lymphatic vessels, lymph nodes, lymphatic trunk, collecting ducts, and to the subclavian vein

In Summary (cont.)

28.3 Infection is the presence of a pathogen in or on the

body A pathogen is a disease-causing agent, and antigens are foreign substances within the body that may or may not cause disease

28.4 The nonspecific body defenses include species

resistance, mechanical and chemical barriers, phagocytosis, fever, and inflammation

28.5 Inflammation is the result of injury or infection Signs

are redness, heat, swelling, and pain

In Summary (cont.)

28.6 Specific defenses are immunities or defenses against

very specific antigens

28.7 B and T cells come from the bone marrow, thymus,

lymph nodes, spleen, and the lining of the digestive tract and are found circulating in the blood B cells utilize memory and plasma cells in a process called humoral or antibody-mediated immunity, and T cells bind directly to cell antigens, attacking them directly, producing cell-mediated immunity

In Summary (cont.)

28.8 T cells cannot be activated to produce immunity

without MHC proteins and macrophages

28.9 Activated T cells may form cytotoxic cells which

protect the body against viruses and certain types of cancer Other T cells may become helper T cells, which increase antibody and memory cell and B cell formation and phagocytosis Still other T cells

become memory cells

28.10 Antibodies may work in the following ways:

phagocytosis, antigen clumping, covering (inactivating) toxic portions of antigens, and activating complements

In Summary (cont.)

28.11 Antibodies are also known as immunoglobulins IgA

prevents pathogens from entering the body; IgD controls B cell activity; IgE works with IgA in

triggering allergic reactions; IgG recognizes bacteria, viruses and toxins and activates complements; and IgM binds to antigens on food, bacteria, or

incompatible blood cells IgM also activates complements

In Summary (cont.)

28.12 Complements are serum proteins that attack

pathogens by forming holes in them They also attract macrophages and can stimulate inflammation

28.13 A primary immune response occurs the first time a

person is exposed to an antigen The response is slow and takes several weeks to occur A secondary immune response occurs at the next exposure This response is very quick and may prevent the person from becoming ill

In Summary (cont.)

28.14 The four types of immune response are natural

active immunity, such as when someone becomes ill and develops immunity; artificial active immunity, as when an injection is given against a pathogen,

preventing illness; natural passive immunity occurs when an infant has its mother’s immunity for a short while after birth and through breast-milk; and artificial passive immunity occurs after injection of antibodies such as with an antivenom

In Summary (cont.)

28.15 Vaccines are used to produce artificially acquired

active immunity

28.16 Cancer is defined as the uncontrolled growth of

abnormal cells A carcinogen is an agent that is known to cause cancer

28.17 Cancer diagnoses can come about in many ways,

but often a biopsy confirms the diagnosis

Treatments vary depending on the type and stage of the cancer, but treatment options include surgery, including bone marrow transplants, chemotherapy, and radiation therapy, as well as newer immune therapies

In Summary (cont.)

28.18 Cancers are classified as Stages I−IV and recurrent

Definitions of these stages may be found in Table 28-1

28.19 An allergic reaction is an immune response to a

substance that is not normally considered harmful to the body Allergic reactions can also be an

excessive immune response Allergens are substances that produce an allergic response

In Summary (cont.)

28.20 Diseases and disorders of the immune system

include autoimmune diseases, where the body attacks its own antigens, as well as numerous other diseases, including some cancers, caused by

pathogens, allergens, and other antigens The signs, symptoms and treatments are as numerous and

varied as the diseases Some of the more common diseases and disorders are discussed in the

Pathophysiology section at the end of this chapter

End of Chapter 28

Thought is an inf ection

I n the case of certain thoughts, it becomes an

epidemic

~Wallace Stevens