Download Lymphatic system

Lymph Transport
and Immunity
Lymphatic system

4 main functions
1.
Lymphatic capillaries
1.
2.
absorb excess tissue fluid and return to
bloodstream (homestasis)
In small intestines lacteals absorb fats
(lipoproteins) and take to bloodstream
3. production, maintenance, and distribution of
lymphocytes
4. Defend the body against pathogens
Lymphatic vessels
 Simple squamous epithelium
 Lymph – colorless liquid, mostly water, located inside
lymph vessels
 2 lymphatic ducts
 Thoracic duct – empties all lymph from below thorax
and left side of head and neck, largest
 Right lymphatic duct – returns lymph form right arm
and right side of head and neck
 Edema – swelling due to accumulation of tissue fluid
Lymphatic organs
 Contain lymphocytes (B and T), produced in red bone
marrow and thymus
 Red Bone Marrow – site of stem cells, produce blood
cells
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In adults – in skull, sternum, ribs, clavicle, pelvis,
vertebral column, heads of femur, humerus
B cell production and maturation
 Thymus – largest in children, shrinks as we age
 Contains T-cells that migrate from RBM and mature
 Thymosin - hormone
Secondary lymphatic organs
 Lymph nodes – cleanse lymph
 contains B cells and T cells
 macrophages engulf debris and pathogens
 Spleen – upper left side of abdomen
 Filters blood, removes old and defective cells
 Without, more susceptible to infections
 Tonsils – lymphatic tissue in pharynx
 Cleanse lymph
 Peyer’s patches/vermiform appendix  work in lymphatic system to help to fight pathogens in
intestinal tract
Nonspecific defense - automatic
 Barrier to entry – skin, mucous membranes, ciliate
cells, good bacteria
 Inflammatory response – redness, heat, swelling,
pain

Chronic inflammation precipitates various ills
 Phagocytes and natural killer cells  neutrophils, dendritic cells and macrophages,
 release cytokines that stimulate other WBC’s
 NK – granular lymphocytes, kill virus-infected cells
 Protective proteins – complement and interferons
 Form a membrane attack complex, warns non-infected
cells of possible attack
Specific defenses
 B lymphocytes –
 Give rise to plasma cells that produce
antibodies
 Antibody-mediated immunity
 Produced and mature in bone marrow
 In lymph nodes and spleen
 Recognize antigen and then undergo clonal
selection
 Clonal expansion produces antibody-secreting
plasma cells as well as memory B cells
Antibodies – immunoglobulins (Igs)
 Y shaped, 2 arms – light and heavy based on
polypeptide chain
 Antigen binding sites, particular
 Antigen-antibody reaction = complex, mark
antigen for destruction
 5 different classes
T-cells
 Cell –mediated immunity against virus-
infected cells and cancer cells
 Produced in bone marrow; mature in thymus
 Antigen must be presented in groove of an
MHC protein
 Cytotoxic T cells destroy non-self antigenbearing cells
 Helper T cells secrete cytokines, which
control the immune response
 Helper T cells are host for HIV
Overview of Immunity, p645
 Research has found that invertebrates have
similar non-specific immunity defenses
 Specific defense mechanisms may have only
evolved in vertebrates.
Induced Immunity
 Active immunity – usually induced, long
lasting

Immunization – vaccines – substances that
contain an antigen that results in antibodies for
future protection (B and T memory cells)
 Passive immunity – short lived


given prepared antibodies to combat a
disease
Mother/placenta, Breast feeding, antivenom
Cytokines
 Signaling molecules produced by
lymphocytes
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Regulate WBC formation and function
Interferons and interleukins – used as
immunotherapeutic drugs
All may be used to enhance body’s ability to
recover form disease.
Monoclonal antibodies
 Produced by the same plasma cells (B cells)
 All antibodies are the same type
 Various functions, used in pregnancy tests
and to detect infections
Immunity Side Effects
 Allergies – hypersensitivities to substances
 Tissue rejection – antibodies and cytotoxic T cells
bring about destruction of foreign tissues

Must take immunosuppressive drugs
 Autoimmune diseases – Cytotoxic T cells or
antibodies mistakenly attack the body’s own cells as
if they bear foreign antigens

Myasthenia gravis, multiple sclerosis
 Incompatible blood type – ABO blood system,
antigen on RBC’s and antibody in plasma