Lymphatic System Flashcards
How much interstitial fluid is collected by the lymphatic system a day?
3 L.
(20L fluid leaves arteriolar ends of capillaries and 17L absorbed back into the venous end - remaining 3L returned to venous system by lymphatic system)
What three things aid the movement of lymph against gravity?
Skeletal muscle contraction
Pressure changes in the thorax during breathing
Pulsation in adjacent arteries
What are diffuse lymphatic tissue?
small concentrations of lymphoid tissue e.g. mucosal associated lymphatic tissue (MALT)
Found in the gastrointestinal tract, skin, lungs, salivary glands
Name three locations of lymphatic nodules
Tonsils (3 - one at back of nose, tongue and throat)
Peters patches - in ilium
Vermiform appendix
What is the function of a lymph node
To filter lymph. Consist of an apparent lymphatic vessel (lymph enters) and an efferent lymphatic vessel (lymph leaves).
Give some examples of locations of lymph nodes
Throat
Arm pits
Groin
What type of cell is abundant in the germinal centre of lymph nodes?
Follicular dendritic cells - bind antigen-antibody complexes. Involved in proliferation on B cells
Lymph nodes contain professional antigen presenting cells, such as…
Macrophages
B cells
(Contain MHC2 on surface)
What is the body’s initial response to an antigen?
Inflammation - mediated by neutrophils and macrophages (may elicit immune response)
What cell types are involved in the immune response?
B cells - humoral - antibody production
T cells - cell mediated - kills infected cells
What is lymphadenopathy?
Enlarged lymph nodes. As the lymph nodes fight infection, germinal centres fill with lymphocytes - causes swelling
What functions does the spleen play?
Immune functions - antigen presentation ny APCs, activation and proliferation of B and T cells and removal of macromolecular antigen from blood (macrophages)
Haemopoietic functions - removal/destruction of old, damaged, abnormal erythrocytes and platelets and retrieval of iron from erythrocytes haemoglobin
If the spleen is removed (splenectomy), what organs/cells take over its function?
Liver and bone marrow take over removal and destruction of ageing erythrocytes.
The spleen may enlarge in response to systemic infections such as
Malaria
Glandular fever
Septicaemia
What is the role of the thymus?
Maturation of bone marrow derived stem cells into immunocompetent T cells
What happens inside a phagocyte after ingestion of a foreign body?
It creates an endoscope which fuses with a lysosome to form a phagosome. Material is degraded in the phagosome then exocytosed.
What two chemical processes are active in phagosome to degrade pathogens?
- oxygen dependent killing mechanisms - production of reactive oxygen and nitrogen species (e.g. superoxides) produce radicals. Act as potent antimicrobials.
- oxygen independent killing mechanisms - lysosomal hydrolases, hydrologic enzymes and lysozyme work to degrade microbes. Also defending form channels in bacterial membranes
What is opsonisation?
Process by which a pathogen is “marked” for destruction by a phagocyte. Involved binging of an opsonin e.g. Antibody to receptor on pathogen membrane (C3b to C3b receptor)
What is complement?
A group of serum proteins that function to:
- promote inflammation
- opsonisation - enhances phagocytosis
- destroys cells - facilitates formation of a membrane attack complex
What can complement be activated by?
Classical pathway: antibody- antigen complex
Alternative pathway: C3b - antigen
Lectin pathway - lectins
What is oedema?
Accumulation of excessive watery fluid in cells, tissues or serous cavities
What is lymphoedema?
Accumulation of large amounts of lymph (swelling) in subcutaneous tissues as a result of obstruction of lymphatic vessels/lymph nodes.
What are starling forces?
Dictate whether reabsorption (into capillary) or filtration (is out of capillary) occurs based on hydrostatic and oncotic pressures in the capillary and interstitial space.
What is hydrostatic pressure?
Pressure that any fluid in a confined space exerts - “pushing water out”
Often higher towards the arteriole and lower towards venous ends
Why is lymphoedema non-pitting?
Because fibroblasts build “storage” for fluid meaning that when you press down there is nowhere for the fluid to move to (cannot leave compartment)
What types of white blood cells are granulcytes?
Neutrophils, basophils and eosinophils
What do natural killer (NK) cells do?
Stimulate apoptosis of virally infected or cancerous cells
What is haemophilia A?
X linked recessive disease - causing lack of clotting factor 8
Where is lymph drained back into blood system?
Right lymphatic duct (drains lymph from upper right area of torso, right arm and head) into internal jugular vein
Larger thoracic duct (drains lymph from rest if the body) into subclavian vein
Where are follicular dendritic cells located and what’s their function?
Located in the germinal centre of lymph nodes/tissues, function in the proliferation of B cells (particularly memory cells)
What happens to the capillaries during inflammation?
Became leaky - allow neutrophils and other proteins to site of infection, cause swelling
What is the innate immune system?
First line of defence
External barriers - skin, mucus membranes, acidic environments
Internal defences - phagocytes, NK cells, antimicrobial proteins
Where are mucous membranes found?
Lining open cavities (respiratory tract, GI tract, urinary tract, reproductive tract)
List three functions of antibodies
Opsonisation
Neutralisation
Agglutination
How do cytotoxic T cells kill infected cells?
Trigger apoptosis
Release perforins
What is the function of helper T cells?
Release cytokines - which trigger other immune cells to divide and also finishes the maturation of B cells
