The immune system and the lymphatic system help each other out (Kent, 2000).
The lymphatic system is made up of two semi-independent parts; a network of lymphatic vessels and many lymphoid tissues and organs within the body (Kent, 2000).
The lymphatic system is a filter and drainage system that controls the fluid balance within the body (Kent, 2000).
During blood circulation, blood plasma seeps into tissue by means of the thin capillary walls (Encyclopædia Britannica, 2017). Blood plasma that escapes is referred to as interstitial or extracellular fluid. This fluid carries all the nutrients needed by tissue cells and removes waste product (Encyclopædia Britannica, 2017).
The walls of the capillaries are selectively permeable to many components of the blood plasma such as glucose and mineral ions (Encyclopædia Britannica, 2017). These nutrients in the tissue are low in concentration and diffuse from the plasma (Encyclopædia Britannica, 2017). Any of this fluid that’s left behind is removed from the tissue by the lymphatic vessels and returned into the blood (Encyclopædia Britannica, 2017). Not all fluid returns to the blood capillaries though some enters the lymph capillaries (Kent, 2000).
Molecules that are too big to pass through the lymph capillaries have the ability to enter the lymph system at tiny valves in their walls (Kent, 2000). The movement of liquid is done by compression caused by body movement and backflow is stopped by valves (Kent, 2000). Whereas the lymphoid organs accommodate phagocytic cells and lymphocytes, they have a vital job in the bodies defence mechanisms and resistance to disease. (Kent 2000). Lymphocytes are white blood cells that are produced by the lymphatic system in the lymph nodes they help defend the body from infection by engulfing and secreting antibodies to destroying the foreign particles (Kent, 2000). If invaders are present in the circulation, they will eventually have to pass the lymph nodes where B lymphocytes (B cells) and T lymphocytes (T cells) lie and wait (Kent, 2000). The cells activate when they come into contact with an alien antigen that matches their receptors on the Major histocompatibility complex (MHC), this is known as antigen presentation (Kent, 2000).Antigens can be ‘self or no self’ meaning it could be a pathogen or a self-cell (Kent, 2000).Antibodies are proteins called immunoglobulin (Kent, 2000).
The lymphatic system is split into two; the primary lymphoid organs, this is where B and T cell maturation occurs, and the secondary lymphoid organs, these additionally differentiate the lymphocytes (Encyclopædia Britannica, 2017).
Primary lymphoid organs Secondary lymphoid organs
Bone Marrow Spleen
Fetal liver Peyers patches
(Encyclopædia Britannica, 2017).
Figure 1. The Lymphatic system (Kent 2000)
The key parts of the lymphatic system and describe their role.
Lymph nodes are the sites where white blood cells circulate in the lymphatic system patrolling all the vessels and the ducts, they are in lymph fluid searching for invaders and pathogens (Kent, 2000). When this happens, you can feel the immune response by it swelling (Kent, 2000). White blood cells also search for damaged cells or host cells (Kent, 2000). They should destroy these hosts cells as it could be compromised by a virus or our own cells that have gone rogue (Kent, 2000). In mitosis to ensure this doesn’t happen check points are in place to prevent our own cells going rogue (Kent 2000)
The tonsils make a ring around the lymphatic tissue surrounding the entrance to the pharynx, they are swellings of the mucosa (Spellman, 2007). The cilia within them collect and remove pathogens entering the pharynx where it be food or inhaled (Spellman, 2007).
Adenoids are located at the back of the nasal cavity, they protect the lungs from pathogens getting into the body through the nose in the same way (Spellman, 2007).
The thymus secrets the hormones Thymopoietin and Thymosin resulting in T lymphocytes being able to work against specific pathogens in the immune system (Spellman, 2007). Differentiation of T cells happen in the thymus (Spellman, 2007).
Cervical lymph nodes when a pathogen is detected it becomes swollen inflamed (Spellman, 2007).
Right lymph duct drains lymph from the upper right of the body (Spellman, 2007).
Thoracic duct drains lymph from everywhere else (Spellman, 2007).
The spleen filters out toxins and filters your red blood cells (Kent, 2000). Red blood cells can live up to 100-120 days, after this you don’t want them in your blood stream they are not as effective as transported oxygen around your body or carbon dioxide (Kent, 2000). The spleens job is to filter out red blood cells that have exceeded 120 days (kent 2000). If your spleen gets damaged or removed due to an injury your body can still function, but your filtration system won’t be as efficient (Kent, 2000). If the spleen ruptures, because it holds a residual volume of blood, your more at risk of rapid intensive bleeding (kent 2000).
Peyers patches are big isolated clusters of lymphoid follicles located in the small intestine (Spellman, 2007).They prevent pathogens from penetrating the intestinal wall and produce memory lymphocytes to be able to have long term immunity (Spellman, 2007).
Appendix release some mucus into the large intestine (Encyclopedia Britannica, 2018). Leukocytes are introduced to antigens within the gastrointestinal tract by the appendix (Encyclopedia Britannica, 2018).
Inguinal lymph nodes filter lymph from the legs before the lymph heads toward the thoracic duct (Spellman, 2007).
In the bone marrow B cells mature and are tested, any that bind to with self-proteins in the bone marrow undergo apoptosis, deactivated then killed (Spellman, 2007).
Lymphocytes originate from stem cells within the bone marrow. It constantly renews red blood cells (Spellman, 2007).
Popliteal lymph nodes filter and balance the blood supply to the lower part of body
Part B (assessment criterion 3.2)
Q2 What are the different types of Leukocytes and how does their structure and function differ?
Leukocytes are white blood cells that are present in the non-specific immune system (Brooker, 2008). They patrol our lymphatic system and the blood, there method of transport is they are carried around by our circulatory system (Brooker, 2008).
Leukocytes are split into Argranular and Granular.
Granular Leukocytes Argranula Leukocytes
Argranular leukocytes do not have visible cytoplasmic granules and the nuclei is special or kidney shaped. Whereas granular leukocytes have lobed nuclei and have a membrane bound cytoplasmic granules that stain easily
Neutrophils have a complex nucleus which is lobulated shape, it’s easy from looking at it to mistake it has more than one nucleus (Brooker, 2008). Neutrophils are the majority of leukocytes in the body (Brooker, 2008). They go around in the blood searching for their primary target (Brooker, 2008). At the point when the body sends out a chemical substance showing that a microorganism is endeavouring to enter, the neutrophils are the initial ones to touch base at the site (Brooker, 2008). By engrossing them they kill the invaders (Brooker, 2008). The discharge present in infections is comprised of these neutrophils that in this process have died (Brooker, 2008). Neutrophils cause the inflammatory and fever response (Brooker, 2008).
Basophils have a bilobed nucleus. Basophils can have a big impact once activated but only account for a small number of leukocytes in the body (Brooker, 2008). They are in charge of the hypersensitive responses that reason a few people to have asthma attacks, struggle to breath, swelling, and hives (Brooker, 2008). Despite the fact that these indications are not nice, it is the body’s reaction to particular trespassers (Brooker, 2008). Basophils recognize these intruders in the body and make antibodies that assist in destruction of their foreign substances (Brooker, 2008). They additionally call different leukocytes to come help in the battle (Brooker, 2008). Basophils store histamine and heparin (Brooker, 2008).
Eosinophils have a bilobed nucleus. Eosinophils trap trespassers, disturbing foreign bodies, and taking part in the hypersensitive responses (Brooker, 2008). In comparison to other leukocytes they don’t need to know what the specific invader is before they kill (Brooker, 2008). Any intruder that has the potential to cause harm, the eosinophils distinguish them and attack them (Brooker, 2008). When large parasitic worms or large parasites are detected the Eosinophils affixes to the worm and secrets a solution that will kill it (Brooker, 2008).
Monocytes have a kidney shaped nucleus they come from the bone marrow (Marieb, 2017). Monocytes are phagocytes that circulate the blood then develop into macrophages in the tissue (Marieb, 2017).
Lymphocytes have a spherical nucleus. Lymphocytes attack immune response by direct cell attack or via antibodies (Marieb, 2017).T lymphocytes (T cells) work in the immune response by working directly against infected cells (Marieb, 2017).B lymphocytes (B cells) give rise to plasma cells these make antibodies known as immunoglobulins that are released into the blood (Marieb, 2017).
Macrophages surround and engulf pathogens and dead cells they also alert other immune system cells of a problem (Marieb, 2017). Macrophages cause the inflammatory and fever response (Marieb, 2017). If a macrophage comes into contact with and phagocytoses a microbe, the macrophage will secrete a protein named interleukin-1 (Marieb, 2017).Interleukin glycoproteins will be transports in the blood stream to the hypothalamus in the brain (Marieb, 2017).The hypothalamus will then raise the body’s core temperature by resetting the body’s core temperature to a higher temperature resulting in a fever (Marieb, 2017).
Mast cells release chemical alarms that alert other immune cells to invaders (Marieb, 2017). They are accountable for the majority of allergic and inflammatory response (Marieb, 2017).
Natural killer cells can lyse and killer cancer cells and virus infected body cells before the adaptive immune system is activated (Marieb, 2017).Natural killer cells do not directly attack pathogens alternatively they attacked cells that have become infected by creating a hole in the plasma membrane, enabling water into the cell making it swell then enforcing them to undergo apoptosis (Marieb, 2017). Natural killer cells cause the inflammatory and fever response (Marieb, 2017).
Q3 How do macrophages activate helper T cells?
The innate responses will decide the type of effector cell a helper T cell will develop into (Alberts et al., 2018). T cells are non-antibody producing lymphocytes that make up the cell-mediated arm of adaptive immunity (Alberts et al., 2018).
Infected cells fibrocytes by antigens. These foreign body antigens combine with MHC II and this will form the MHC II antigen complex (Alberts et al., 2018). Once it has been formed it will be expressed on the surface of the cell (Alberts et al., 2018). The MHC II antigens complex is going to be recognised by the T cell receptors on the T helper cells, this is the first signa (Alberts et al., 2018).
The second signal is the costimulatory signal its occurs when by the interaction of B7 and CD28 take place (Alberts et al., 2018). When both these signals have interacted, it will lead to activation of cytotoxic T cells and helper T cells (Alberts et al., 2018). Helper T cells are now able to produce cytokines, whereas the cytotoxic T cells recognise and kill the infected cell (Alberts et al., 2018).
Interleukin 1 is secreted by activated macrophages it promotes inflammation and the activation of T cells (Marieb, 2017).
Interleukin 2 is secreted by T cells, they stimulate proliferation of T cells and activates natural killer cells (Marieb, 2017).
Q4 What role does a B cell play during the invasion of a pathogenic bacterium?
B cells oversee the humoral immune system. In the bone marrow B cells become immunocompetent and self-tolerant (Marieb, 2017). The B cell clones itself they can become memory cells or plasma cells (Marieb, 2017). B cells learn to recognise harmful microbes that have invaded the body before, enabling them to produce anti bodies specific to the invaders antigen that will surround the pathogen and tag it for destruction by other immune cells (Marieb, 2017).
Part C (assessment criterion 3.3)
For each of the immunity categories below, provide an explanation of what components they encompass and how they act to defend the body against infection.
Natural is happening in our own body and artificial is external being given with a needle
(Bbc.co.uk, 2018). Active means able to produce antibodies ourselves and passive is where we are not producing our own cells and need assistance to do so someone else is doing it for us (Bbc.co.uk, 2018).
(i) Natural active immunity
Clinical infection means you show symptoms of a disease when a person is exposed to the disease then their body produces the antibodies and specialised lymphocytes themselves (Bbc.co.uk, 2018). by themselves. When antigens enter the body, microbes cause the person to catch the disease, however some people can have a subclinical infection meaning they have already developed antibodies against the pathogen but already immune (Bbc.co.uk, 2018). The pathogen has entered their system, but their immune system has fought it off and won but didn’t present with any symptoms (Bbc.co.uk, 2018).
(ii) Artificial active immunity
Antigens are given by vaccines (Bbc.co.uk, 2018). It’s where vaccines and cells are being put into our body that are going to be recognised as antigens (Bbc.co.uk, 2018). The body is having an active response itself by producing antibodies and specialised lymphocytes but its artificial as the antibodies initially came from outside of the body (Bbc.co.uk, 2018).
(iii) Natural passive immunity
We are not able to produce antibodies ourselves and we are getting from our mother in some way via the blood in the placenta or breastmilk (Bbc.co.uk, 2018). Babies don’t produce any of their own antibodies, so the mother passes her antibodies on to the baby (Bbc.co.uk, 2018).
(iv) Artificial passive immunity
Its artificial so it comes from outside the body an injection of immunoglobulin is in injected which is serum containing antibodies this is used when you need an instant reaction and boost of antibodies and can’t afford to wait for the body to produce its own (Bbc.co.uk, 2018). As a result, the body does not produce any antibodies (Bbc.co.uk, 2018).