• Maintains fluid balance• Protect body from infection and disease

Chapter 21Lymphatic and Immune Systems

Lymphatic Vessels Within Capillary Network

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Lymphatic capillaries weave through blood capillaries.

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• 1.) Fluid recovery– absorbs plasma proteins and fluid from tissues and

returns it to the bloodstream• interference with lymphatic drainage leads to severe edema

– lipid absorption• Lacteals in small intestine absorb dietary lipids

• 2.) Immunity– fluids from all capillary beds are filtered– immune cells stand ready to respond to foreign cells

2 Major Functions of Lymphatic System

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Lymphatic Obstruction

• Elephantiasis- mosquito-borne infection effect the skin to cause it to thicken. Also, the scrotum of men and breasts of women are similarly effected.

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Lymph and Lymphatic Tissue• Lymph

– clear, colorless fluid, similar to plasma• Lymph is like blood in the vascular system• This fluid flows within lymphatic vessels• Lymphatic tissue is specialized connective tissue

that contains lymphocytes

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Route of Lymph Flow• Lymphatic vessels are vein-like, have valves and

go along the course with arteries and veins• Lymphatic vessels permits interstitial fluid to flow

in and out• The flow- Lymphatic capillaries to:• Lymphatic vessels to:• Lymph nodes.• So lymphatic vessels, unlike blood circulation,

don’t have arteries but start with capillaries.

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Valve in a Lymphatic Vessel

• Why valves?

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Lymphatic Drainage

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Lymphatic Drainage of Mammary and Axillary Regions

• Drainage of Right side of the body:• Right lymphatic duct to:• Right subclavian

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Drainage of Thorax

• Drainage of the Left side of the body:• Cisterna Chyli (sis-turn-a ki-lay) to Thoracic Duct

to Left Subclavian vein.

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4 Mechanisms of Lymph Flow• 1.) Moved along by rhythmic contractions of

lymphatic vessels and Cisterna Chyli (“Heart for the lymph”)

• 2.) Flow aided by skeletal muscle pump• 3.) Thoracic pump aids flow from abdominal to

thoracic cavity– Valves prevent backward flow

• 4.) Rapidly flowing bloodstream in subclavian veins, draws lymph into it– Exercise significantly increases lymphatic return

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Lymphatic Cells• T lymphocytes

– Mature in Thymus• B lymphocytes

– Mature in Bone marrow• Secondary lymphatic organs- sites where the B and

T cells carry out the immune response– Lymph nodes– Spleen

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Lymphatic Organs• At well defined anatomical sites. • Lymph nodes

– cervical, axillary and inguinal regions close to surface– thoracic, abdominal and pelvic groups deep in cavities

• Tonsils– guard entrance to pharynx

• Spleen– inferior to diaphragm on the left

• Thymus– behind sternum

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Thymus Gland• Thymus gland is located posterior to the sternal

angle• Thymus gland produces T cells• The thymus may not become atrophied as we age

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Lymph Node• Lymph Nodes- approximately 600 bean shaped

nodes in the body• Lymph nodes - only organs that filter lymph

– reticular tissue cells (like a network of cotton fibers), macrophages phagocytize foreign matter

– lymphocytes respond to antigens– lymphatic nodules-germinal centers for B cell activation

Lymph Node

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Lymphadenopathy• Collective term for all lymph node diseases• Lymphadenitis

– swollen, painful node responding to foreign antigen• Lymph nodes are common sites for metastatic

cancer– swollen, firm and usually painless

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Swollen Lymph nodes• Lymph nodes filter lymph• Foreign substance are trapped• Macrophages destroy by using phagocytosis• Examination of swollen glands:

– Neck- sweep from clavicle on SCM to ear– Axilla- place hand at apex, lower arm– Groin- palpate just below pubic bone by femoral artery

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Differential Diagnosis of Nodes• CANCER• Firm, hard• Non-movable• No fever• Not painful• Diagnosis- neoplasm

• INFECTION• Soft• Movable• Fever• Painful• Diagnosis- swollen lymph nodes

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“Don’t Yank Me!”• Tonsils- aggregation of lymphatic tissue at the ring

of the throat• The tonsils, are strategically positioned to

participate in immune response against foreign substances that are inhaled or ingested.

• Research shows that tonsillectomy is related to respiratory problems

• Appendix- Lymphoid tissue that assists in ______ _________

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Spleen• Largest mass of lymphatic tissue, 5 inch long• 3 Functions-

– Immune function: assists red bone marrow and liver– Clears blood from RBCs and WBCs– Blood storage, platelets are stored

• The spleen- “Mean, bloody and clean”

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Resistance to Disease• Resistance- your body’s ability to ward off disease

– Two Types: – 1.) Nonspecific

• General defense such as skin, mucous membranes, acidity of the stomach

– 2.) Specific (also called Immunity)• Specific defense, produces specific cells (lymphocytes) that

combat particular bugs• results from prior exposure, protects against only a particular

pathogen• immune system

• Susceptibility- the body’s lack of resistance

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Nonspecific Resistance to Disease- External

• Immediate protection against a wide range of pathogens, general not a specific response

• External resistance to disease- passive defense (Barrier- like castle walls, moat- flow)– Barrier: the skin

• toughness of keratin• dry and nutrient-poor• defensins: peptides, from neutrophils attack microbes• lactic acid (acid mantle) is a component of perspiration barrier

– Barrier: gastrointestinal barrier• Leaky gut syndrome is a break in this barrier

– Flow: mucous • stickiness of mucus • lysozyme: enzyme destroys bacterial cell wall

– Flow: cilia, tears, saliva, urine, defecation, vomit, diarrhea, sebum, perspiration, gastric juice, vaginal secretions

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Natural Killer Cells and Phagocytes• Natural killer cells are lymphocytes that kill microbes and

tumor cells– It can mess with the membrane of the bug causing cytolysis or it

can bind to the cell and never get off it’s back• Phagocytes- ingest microbes by 5 processes:

– Chemotaxis- chemical from infection attract phagocytes– Adherence- jumps on the bugs back– Ingestion- pseudopods “hug” the bug– Digestion- from enzymes and lethal oxidants,– Killing

• Two major phagocytes are: Neutrophils, Macrophages

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Inflammation• Defense response from cell damage due to bugs, physical

trauma or chemical agents such as diet– suffix -itis denotes inflammation of specific organs

• Cardinal signs– pain caused by inflammatory chemicals (bradykinin,

prostaglandins) secreted by damaged cells, pressure on nerves– heat caused by hyperemia– redness (erythema) caused by hyperemia ( blood flow)– swelling (edema) caused by capillary permeability and

filtration– “Pa, He Read Swell”

• Diet loaded with refined foods, hydrogenated oils, dairy products can cause subclinical inflammation and disease

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Tissue Repair• Facilitated by hyperemia that provides materials

needed and heat that increases metabolism• Fibrin clot may provide a scaffold for repair• Pain is your normal friend, it tells you to attend!

– it limits use of body part allowing for repair

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Fever• Elevation of core temperature• Most common cause is infection• Defense mechanism: Up to a point fever is

beneficial– promotes interferon activity and phagocytosis– accelerating metabolic rate and tissue repair– inhibiting pathogen reproduction

• How high is too high? Coma and death occurs at 111F- 115F, practically 104-5 degrees is the limit

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Specific Immunity• Immunity is the bodies ability to defend against

specific invaders such as viruses, toxins, bacteria• This system is Antigen (Ags) based- substances

that are recognized as foreign and provoke an immune response

• Immunology- study of the immune response• Immune system principal components- Thymus,

Red Bone Marrow

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Antigens (Bad Guys)• Antigen means Antibody Generator- these guys

stimulate antibodies production, like pollen to an allergic person, usually made of protein

• Two important characteristics:• 1.) Immunogenicity- the ability to provoke an

antibody reaction• 2.) Reactivity- the ability to react with the

antibody it provoked

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Of Bs and Ts• The cells that develop immunocompetence, the

ability to carry out an immune response are B and T cells.

• Both start mostly in the bone marrow, Bs mature in the bone marrow but Ts leave home and go to the thymus to mature

• Both cells acquire antigen receptors that can detect antigens.

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T Cell Doing What It Does Best…

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…Destruction of Cancer Cell

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Immunological Memory• A hallmark of the immune response is memory, this

memory is for the antigen that triggered the response in the past

• Long lasting antibodies “embody” this memory• When you recover from an infection without taking

antibiotic drugs, if at a later time you are infected again by the same bug the response will be swift, so swift that you may not know you were infected

• Vaccination work on the theory that man can induce immunological memory this is called: artificial active immunity

Vacinations- Pros and Cons• Pro- Small Pox• Con- Black Death that swept through Europe in the

14th century killing more than 25 million people, a third of the European population

• Con- Polio vaccine• http://www.hrsa.gov/vaccinecompensation/table.ht

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Antibody Classes• Immuno globulins- glycoprotein antibodies• IgA: Stress decreases, less protection for mucous

membrAnes against bacteria and viruses – Exercise raises levels of Ig A

• IgD: Minor antibody• IgE: Protects against parasites, involved in allErgy• IgG: The Great antibody, most abundant and

protests against bacteria and viruses• IgM: Antibody in blood plasMa (creates ABO

blood type)• In acute infection- IgM, Chronic infection- IgG

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Hypersensitivity (Allergy)• Excessive immune reaction against antigens that most

people can tolerate called allergens• Hypersensitivity- Acute (most common)

– anaphylaxis: IgE (allErgy) mediated, mucus hypersecretion, congestion; hives, watery eyes, runny nose

• Asthma (most common chronic illness in children)– inhaled allergens, bronchiole constriction

• Anaphylactic shock: bronchiolar constriction, dyspnea, vasodilation, shock, death; treatment- epinephrine

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Immunodeficiency Diseases

• Severe Combined Immunodeficiency Disease – hereditary lack of T and B cells– vulnerability to opportunistic

infection

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• AIDS– HIV structure– invades helper T cells, macrophages and dendritic cells

by “tricking” them to internalize viruses by receptor mediated endocytosis

– reverse transcriptase (retrovirus), uses viral RNA as template to synthesize DNA, new DNA inserted into host cell DNA, may be dormant for months to years

Immunodeficiency Diseases

HIV Structure

Comparing cells to bacteria to viruses- If a typical cells was about 2 feet a bacteria would be a speck, if a

bacteria was 2 feet the virus would be a speck.

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AIDS• Signs and symptoms

– early symptoms: flulike chills and fever– progresses to night sweats, fatigue, headache, extreme

weight loss, lymphadenitis– normal T cell count is 600 to 1,200 of blood but in

AIDS it is < 200 – thrush: white patches on mucous membranes may appear– Kaposi sarcoma: cancer originates in endothelial cells of

blood vessels causes purple lesions in skin

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HIV Transmission• Through blood, semen, vaginal secretions, breast

milk, or across the placenta• Most common means of transmission

– sexual intercourse (vaginal, anal, oral)– contaminated blood products– contaminated needles

• Not transmitted by casual contact• Undamaged latex condom is an effective barrier to

HIV especially with the spermicide nonoxynol-9