• 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

• 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, it bathes the

cells…

• 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 of Mammary and Axillary Regions

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Lymphatic Cells (WBC’s)

• Macrophages– Large WBC’S that eat invaders

• T lymphocytes– Mature in Thymus

• B lymphocytes– Mature in Bone marrow

• Memory cells– Specialized B & T lymphocytes that recognize a

pathogen (invader) after it has been encountered and react with a quick response

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Lymphatic Organs

• Organs of the immune system • 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 (above the heart)

• Thymus gland produces T cells

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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 (eat) foreign matter– lymphocytes respond to antigens

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Swollen Lymph nodes

• Lymph nodes filter lymph• Common site for metastatic cancer• 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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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.

• Most common reason for tonsillectomy today is apnea

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

– Immune function: filters blood for antibody covered invaders

– Recycles old & damaged blood cells– Stores blood to prevent shock

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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

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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: the skin

• toughness of keratin• dry and nutrient-poor• lactic acid (acid mantle) is a component of perspiration barrier

– Barrier: gastrointestinal 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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Nonspecific Resistance to Disease- Internal

• Natural killer cells: lymphocytes & Phagocytes • Fever

– Can kill or prevent invader from reproducing– How high is too high? Coma and death occurs at 111F- 115F,

practically 104-5 degrees is the limit

• Inflammation– suffix -itis denotes inflammation of specific organs– Pain, heat, redness, swelling– Increased blood flow, temp & WBC’s leaking out

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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 based- substances that are recognized as foreign and provoke an immune response

• Immunology- study of the immune response

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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

• Antibodies are proteins designed by the immune system to lock onto a specific part of an invader and mark it for destruction. They are specific to a particular invader.

Primary & Secondary Immune Response

• Primary Response– Primary response happens the first time a pathogen is

encountered. It takes 5-7 days to mount a specific response (antibodies), so the illness will last 7 – 10 days.

• Secondary Response– Secondary response occurs at each subsequent

encounter with that pathogen. Memory cells will trigger immediate response to the antigens, so that the person may not even feel ill.

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Active & Passive Immunity

• Active Immunity– A result of actually encountering the antigen– Can happen by getting the disease or by vaccination– Vaccination exposes the body to a weakened or killed

version of the disease

• Passive Immunity– Receiving antibodies from another person– Mother’s milk– “blood serum” – antibodies filtered from another

person’s blood23

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Hypersensitivity (Allergy)

• Excessive immune reaction against antigens that most people can tolerate called allergens

• Hypersensitivity- Acute (most common)– anaphylaxis: 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 – One disease that has been

successfully treated with genetic engineering

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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

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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