Lymphatic System
Chapter 22 - BIO 100
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– Lymphatic system
• Functions
– Return excess tissue fluid to bloodstream
– Defense against disease
• Lymphatic vessels – a one-way system
– Begins with capillaries in tissues
– Fluid inside is lymph
» Water, nutrients, electrolytes
» Cell products like hormones
Lymphatic vessels
– Lymphatic capillaries merge to form vessels
– Vessels merge and empty into ducts
• Thoracic duct-empties
Vessel structure
– Small and larage vessels
• Similar to veins, with valves to prevent backflow
• Skeletal muscles “pump” lymph
Edema
– Accumulation of tissue fluid
– Occurs if not enough drainage, or too much produced
– Can cause tissue damage and death
Lymphatic organs
– Contain lymphocytes
• Produced in thymus and bone marrow
• Antibodies (B Lymphocytes)
• Cellular immunity (T lymphocytes)
– Primary lymphatic organs
• Red bone marrow where stem cells produce blood cells
• The Primary lymphatic organs include:
– The Thymus
• Between trachea and sternum above the heart
• Shrinks with age
• Divided into 2 lobules
• Produces hormones – Thymosin
• The Secondary lymphatic organs include
– The Spleen - upper left side of abdomen
• Lymph nodes
• Located along lymphatic vessels
• Nodules connective tissue & packed with B and T lymphocytes
• Lymph filters through nodules
– Macrophages phagocytize pathogens and debris
• Lymph nodes named for location
– Inguinal nodes - groin
– Axillary nodes - armpit
– Cervical nodes - neck
Defense Barriers
• Skin
– Most organism don survive well
– Lack the needed water & nutrients
– Presence of oil and sweat –
• Contain lactic acid that inhibits bacterial/fungal growth
– Shedding of skin
• Mucous memebranes
– Harbor bacteria but possess effective defenses
– Contain antibacterial enzymes
– Traps debris & organisms that enter mouth or nose
– Cilia sweep mucus and microbes out of the body
– Expelled via coughing, sneezing or swallowing
Nonspecific specific defenses
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Inflammatory reaction
• Initiated by chemical agents or pathogens
• The 4 classic signs:
Redness, Heat, Swelling, Pain
– Signs due to capillary changes – release of Histamine
• Inflammatory Response
– Army of phagocyte (natural killers) to destroy microbes by engulfing or
digesting them
• Neutrophils, Monocytes (blood)
• Dendritic cells (skin)
• Macrophages (tissues)
– Isolate the infection
– Fever – slows down microbe production
– Inflammation – released histamines from damaged cells.
• Inflammatory Response
– Phagocytes enfulf microbes, debris, damaged cells
– Each phagocyte can only eat few microbes and then it dies.
– In severe tissue damage or wounds, the surrounding fluid will turn into
pus.
– Pus- dead phagocytes and debris
– Fever – macrophages release chemicals into the bloodstream
• Hypothalamus of the brain raises the thermostat
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Active immunity
Response to vaccination
• Monitored by antibody titre
• After first exposure, one gets primary response
• Booster response
– Boosts the titre to high level
• Active immunity depends on memory T and B cells
• Passive immunity
– Comes from prepared antibodies
– Not produced by individual’s body
– Temporary immunity used to prevent illness
Immunity side effects
• Allergies
– Hypersensitivities to allergens
– Immediate allergic response
• occurs within seconds
• Hay fever- reaction in mucous membranes of nose/eyes
• Asthma- reaction occurs in small airways
• Anaphylactic shock
– Allergen enters bloodstream
– Life-threatening
– Epinephrine can delay reaction
• Antigens – the invader
– large complex molecules that are recognize as foreign body
• Antibodies – the army, interact with the antigens
– Are produce by B-cells and T-cells
• Blood-type reactions
– ABO system
• Based on presence or absence of A and B antigens on RBC’s
– If A present- blood is type A
– If B present- blood is type B
– If both resent- blood is type AB
– If neither is present- blood is type O
– Transfusions
• Must consider recipient’s antibodies and donor’s antigens to prevent
agglutination and transfusion reaction
• Type O is universal donor
– Neither anti-A nor anti-B antibodies
• Type AB is universal recipient
– Neither A nor B antigens
Blood-type reactions
Rh system
– Antigen present- Rh positive
– Antigen absent- Rh negative
• Significant in pregnancy
– Rh neg mom pregnant with Rh pos baby
– If baby’s cells leak into mother’s bloodstream, she forms anti-Rh antibodies
» Attack baby’s RBC’s- hemolytic disease of newborn
» Can affect subsequent Rh pos pregnancies
– Pevent by giving Rh neg mom anti-Rh immunoglobulins in an injection
Diseases of the immune system
– Autoimmune diseases
• Cytotoxic T cells or antibodies attack body’s cells
• No cures available; it is only controlled with drugs
Examples:
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Myasthenia gravis - neuromuscular junctions do not work
Multiple sclerosis -myelin sheath of neurons break down
Systemic lupus erythematosis - many systemic signs
Rheumatoid arthritis - affects joints
Immunodeficiency diseases
• Immune system unable to protect against disease
• Can be congenital from defect in lymphocyte formation
• Can be infectious- HIV
• Severe combined immunodeficiency disease-both T cells and B
cells affected