Week 6 - The Lymphatic System Flashcards
Give an overview of the lymphatic system
Comprosed of several structures and organs:
1. Lymphatic tissue
2. Bone marrow
3. Lymph
4. Lymphatic vessels
Protects us against disease
Lymphoid cells respond to: Environmental pathogens, toxins, Abnormal body cells such as cancers.
What are some pathogens that cause disease?
Viruses (Bacteriophage, Simian Virus, Epstein Barr Virus)
Bacteria ( E.coli, S. aureus)
Parasites (Schistosome)
Fungi (Candidiasis)
What are the 4 parts of the lymphatic system?
Lymph (fluid) - Similar to plasma w out plasma proteins
Lymphatic Vessels (lymphatics) - Carry lymph from peripheral tissues to venous system.
Lymphoid tissues and lymphoid organs
Lymphoid cells (Lymphocytes, phagocytes)
List the main functions of the lymphatic system
- To produce, maintain, and distribute lymphocytes.
- Return of fluid and solutes from peripheral tissues to blood
- Distribution of hormones, nutrients and waste products from tissue of origin to circulation.
Describe how production and distribution of lymphocytes occurs.
Prod: Occurs in - Lymphoid tissues (e.g tonsils)
Lymphoid organs (e.g spleen)
Red bone marrow
Dist: Travels through lymphatic vessels and capillaries - Detects problems, travels into site of injury or infection.
Describe Lymphatic vessels and capillaries
Lymphatic vessels begin as lymphatic capillaries, which are closed on one end.
Lymphatic capillaries are located between cells of many tissues
Lymphatic capillaries merge to form lymphatic vessels, which have thin wallls and many valves.
Whats the difference between lymphatic vessels and blood capillaries??
Lymph start as blind pockets rather than tubes, have larger diameters, thinner walls and flat or irregular in section.
what are Lymph trunks and ducts?
From the lymph vessels, lymph passes through lymph nodes and then into lymph trunks. - Lymph trunks include the lumbar, intestinal, bronchomediastinal, subclavian and jugular trunks.
Lymph truks then merge to form either the thoracic duct or the right lymphatic duct.
What are some Circulating Lymphocytes?
T Cells: thymus dependent
B cells: bone marrow-derived
NK cells: natural killer cells - also bone marrow derived.
What are the primary and secondary lymphatic organs and tissues?
Primary: Red bone marrow
Thymus
Secondary: Lymph nodes
Spleen
Lymphoid Nodules
Whats the difference between lymph organs and lymphoid nodules?
Lymph organs (lymph nodes, thymus, spleen) are separated from surrounding tissues by a fibrous capsule
Lymphoid nodules = bundle of lymphoid tissue without fibrous capsule. e.g tonsils, appendix, digestive system.
Describe Lymph node circulation in relation to afferent lymphatics
Flows though lymph node in a network of sinuses:
- from subscapular space: contains macrophages and dendritic cells
- through outer cortex: contains B cells w germinl centers
- through deep cortex: dominated by T cells
- Through the core (medulla): contains B cells and plasma cells, organized into medullary cords
- Finally, into hilum and efferent lymphatics.
what is the function of the lymph node?
A filter: purifies lymph before return to venous circulation
Removes: Debris, Pathogens, 99% of antigens.
How are the lymph nodes distributed accross the body?
Lymph nodes of gut, trachea, lungs and thoracic duct - Protect against pathogens in digestive and respiratory systems.
Lymph nodes (Glands) - at groin and base of neck, swell in response to inflammation
Lymphadenopathy - chronic or excessive enlargement of lymph nodes may indicate infections, endocrine disorders, or cancer.
Non-specific vs specific immunity
Non-specific: Block or attack any potential pathogen, present from birth, no memory.
Specific: Identify, attack and develop immunity to a specific antigen. Aquired in response to antigens
What are the 7 non-specific defense categories? (7NSDC)
- Physical barriers
- Phagocytic cells
- Immunological surveillance (NK cells)
- Interferons (antiviral)
- Complement system
- Inflammation
- Fever
Describe 1. Physical barriers (7NSDC)
Eyes: 1. Washing by tears
2. Lysozyme
Respiratory tract: 1. Mucus
2. Ciliated Epithelium
3. Antibody
4. Phagocytosis
Skin: 1. Anatomic barrier - sweat, sebum
2. Antimicrobial secretions; lactic acid, free fatty acids.
3. Low pH (GS)
4. commensal microbes
Digestive tract: 1. Stomach acidity
2. Normal flora
3. Intestine-Alkaline pH
4. Mechanical flushing
5. Enzymes e.g lysozyme
6.Bacteriocins (colons)
Genitourinary tract: 1. Washing by urine
2. Acidity of urine
3. Lysozyme
4. Vaginal lactic acid
Describe 2. Phagocytosis and antigen presentation (7NSDC)
Classes of phagocytes:
Microphages - Neutrophils and eisonophils, leave the bloodstream, enter peripheral tissues to fight infections.
Macrophages - Large phagocytic cells derived from monocytes
Distributes throughout body, make up monocyte-macrophage system. May be fixed or free.
Phagocytic cells remove debris and pathogens.
Activated Macrophages respond by:
Engulfing pathogens and destroying them w lysosomal enzymes
Binding to pathogen so other cells can destroy it
Destroying pathogen by releasing toxic chemicals into interstitial fluid.
Describe 3. Immunological Surveilance by NK cells (7NSDC)
- Recognition and adhesion
- Realignment of golgi apparatus
- Secretion of perforin
- Lysis of abnormal cell
Describe 4. Interferons (anti-viral) (7NSDC)
Non-specific response to viral infections
Interferons = proteins (cytokines) released by activated lymphocytes and macrophages
Three types of interferons:
Alpha-interferons - Produced by leukocytes, stimulate NK cells
Beta-interferons - Secreted by fibrocytes, slow inflammation
Gamma-interferons - secreted by T cells and NK cells, stimulate macrophage activity.
Describe 5. Complement system
Enhances ability of antibodies and phagocytic cells to clear pathogens from an organism.
Complement cascade - 11 complement (C) proteins (C1 to C11), complement antibody action. A chain reaction (cascade)
2 pathways of activation:
classical pathway (fast)
alternate pathway (slow)
Conversion of inactive protein (C3) to active form (C3b)
forms pores in bacterial cell wall (membrane attack complex, MAC)
Destruction of bacteria
Effects of complement activation:
1. attraction of phagocytes
2. enhancement of phagocytosis by opsonisation
3. stimulation of inflammation
4. destruction of target cell membrane (MAC)
Describe 6. Inflammation and tissue repair (7NSDC)
Response to tissue damage:
Inc Blood flow
Mast cells release histamine
Phagocytes (neutrophils) move to site
Neutrophils remove debris
Clot formation/removal of debris
Activation of fibrinogen
Tissue repair
Describe 7. Fever (7NSDC)
Inc body temp due to release of pyrogens. (any material that causes hypothalamus to raise body temp.)
- Mobilises defenses
- Accelerates repair
- Inhibits pathogens
What is specific immunity?
Acquired upon exposure to specific antigens.
Memory,specificity, tolerance.
Two main divisions:
1. Cell-mediated immunity (T-Cells) - T cells only recognise fragments of antigenic proteins that are processed and presented in a certain way (i.e via MHC)
2. Humoral (or antibody-mediated) immunity(B cells)
B cells can recognise and bind to antigens in lymph, interstitial fluid, or blood plasma.
What are MHC proteins?
Used to distinguish self and non-self
Class I: On all nucleated cells
Class II: On antigen-presenting cells (APCs). And lymphocytes
How does specific immune system recognise antigens?
Either Free living - exogenous
or Inside host cells - Endogenous
White blood cells differentiate self antigens expressed on the cell surface from non-self antigens presented on the cell surface.
What are the three types of T-Cells
Cytotoxic T-cells: cell mediated immunity, destroy virally infewcted cells
Helper T cells: stimulate function of T cells and B cells
Suppressor (regulatory) T cells: inhibit function of T cells and B cells.
Look at the slides for a lot of stuff.
What are the 5 types of antibodies
IgG (80% of all antibody, placental transfer)
IgA (glandular secretions, e.g mucus, saliva, breastmilk, tears, sweat.
IgM
IgD
IgE
Look at table 22.3
