Lymphatic system Flashcards
(35 cards)
What is the lymphatic system
Is our built in (innate) defence against pathogens
What does the lymphatic system consist of
-Lymphatic tissue
-Lymph
-Lymphatic vessels
-Lymphoid cells
What are lymphoid cells
Are a type of white blood cell that respond to environmental pathogens (viruses, bacteria, fungi, parasites), toxins and abnormal body cells like cancers
What are the main functions of the lymphatic system
Main: To produce, maintain and distribute lymphocytes
Other:
Returns fluids and solutes to the blood
Distribute hormones, nutrients and waste from their tissues of origin into circualtion
Where does lymphocyte production and distribution occur
Lymphocyte production occurs in the lymphoid tissues (tonsils), lymphoid organs (spleen) and red bone marrow
Lymphatic distribution travels through lymphatic vessels and capillaries to detect problems and then travel to the site of injury/infection.
What are the three main circulating lymphocytes, and what do they do
T (Thymus) cells = involved in cell mediated immunity
B cells = involved in antibody mediated immunity
NK cells = involved in immunological survailence
What happens at primary lymphatic organs
Where immune cells become immunocompetent. This is where they are produced and mature
E.g. Thymus and bone marrow (T and B cells)
What happens at the secondary lymphatic organs
Lymphocytes encounter antigens and are activated, leading to their proliferation and differentiation into effector and memory cells
e.g. lymph nodes or lymphoid nodules
What are the two secondary lymphatic nodules
Lymph Nodes = are small bean like structures that aid in the immune system. They filter the substances travelling in the lymphatic fluid and contain white blood cells
Lymphoid nodules = Are small, localized collections of lymphoid tissue, often found within lymph nodes themselves. Often found within the digestive system.
Whats the difference between lymph nodes and lymphoid nodules
Nodes (organs) are separated from the surrounding tissues by a fibrous capsule, and nodules are bundles of lymphoid tissue without the capsule, like the tonsils and appendix.
What is lymph
Is a clear watery fluid that circulates within the lymphatic system. It collects excess fluid from tissues, absorbs fat from the digestive system and transports white blood cells
Where do you find lymph nodes, and how are they distributed
are located in clusters along the vessel’s lymph travels through. More common at sites like neck, armpit, chest and groin
Nodes of the gut (protect against pathogens in digestive and respiratory system)
Nodes (glands) = swell in response to inflammation
How does lymph travel through nodes
Afferent lymphatic vessels — lymph enters the lymph node here.
Subcapsular sinus (or subscapular space) — the lymph first enters this space beneath the capsule.
Outer cortex — lymph flows through this region containing mainly B cells organized in follicles.
Deep cortex (paracortex) — rich in T cells, lymph passes through here next.
Medullary sinus (medulla) — lymph then moves into the medullary cords and sinuses.
Efferent lymphatic vessels — lymph exits the node here at the hilum.
What does lymph nodes do
Are a filter, that purifies lymph before it returns to venous circulation by removing debris, pathogens and 99% of antigens
What is lymphodenopathy
Is the chronic/excessive enlargement of lymph nodes, This can indicate infections, endocrine disorders or cancer.
What are the two divisions of the immune system
Non specific = Block/attack potential pathogens, are present from birth and dont include memory
Specific = Identify, attack and develop immunity to a specific antigen and are acquired with memory cells
What are examples of Physical barriers in non specific defence (5)
Eyes (tears and lysozyme)
Respirtory tract (mucus)
Skin (autonomic barrier and low pH)
Digestive tract (stomach acidity )
Genitourinary tract (washing by urine, acidity)
What are the 7 non specific defences
Physical barriers
Phaegocytes
NK cells
Complementary systems
Interferons
INflammation and tissue repair
Fevers
What do phagocytes do
They engulf and destroy bacteria, viruses, fungi, and other foreign invaders, as well as dead cells and debris.
Can be:
Micro or macrophages
Micro = leave the blood stream to fight infections
Macro = Distributed throughout the body
What do NK cells do
Lymphocyte involved in immunological surveillance. They destroy virally infected cells and cancer cells without requiring prior activation, via a rapid response
What are interferons
Are a nonspecific response to viral infections. They are proteins (cytokines) released by activated lymphocytes and macrophages. Once produced they increase the resistance of a cell to viral infection and slow down the spread of disease,
Can be alpha, beta or gamma
What are complementary systems in the non specific defences
Consists of C proteins that complement the ability of antibodies and phagocytic cells to clear pathogens.
They attract phagocytes, enhance phagocytosis, stimulate inflammation, destroy the target cell membrane.
Role of inflammation and tissue repair in nonspecific defence
In response to tissue damage:
- increases blood flow,
- release of histamine from mast cells,
- phagocytes move to site
-neutrophils remove debris - formation of a clot
- activation of fibrinogen, which all leads to TISSUE REPAIR
What is the role of fevers in non specific defences
Increase the body temperature due to the release of pyrogens, which mobilises defences, accelerates repair and inhibits pathogens.
