The lymphatic system is a vascular network of tubules and ducts that collect, filter, and return lymph to blood circulation. Lymph is a clear fluid that comes from blood plasma, which exits blood vessels at capillary beds. This fluid becomes the interstitial fluid that surrounds cells. Lymph contains water, proteins, salts, lipids, white blood cells, and other substances that must be returned to the blood. The primary functions of the lymphatic system are to drain and return interstitial fluid to the blood, to absorb and return lipids from the digestive system to the blood, and to filter fluid of pathogens, damaged cells, cellular debris, and cancerous cells.
Lymphatic System Structures The major components of the lymphatic system include lymph, lymphatic vessels, and lymphatic organs that contain lymphoid tissues.
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- Lymph Nodes
Lymphatic vessels transport lymph to lymph nodes. These structures filter lymph of pathogens, such as bacteria and viruses. Lymph nodes also filter cellular waste, dead cells, and cancerous cells. Lymph nodes house immune cells called lymphocytes. These cells are necessary for the development of humoral immunity (defense prior to cell infection) and cell mediated immunity (defense after cell infection). Lymph enters a node through afferent lymphatic vessels, filters as it passes through channels in the node called sinuses, and leaves the node through an efferent lymphatic vessel. - Thymus
The thymus gland is the main organ of the lymphatic system. Its primary function is to promote the development of specific cells of the immune system called T-lymphocytes. Once mature, these cells leave the thymus and are transported via blood vessels to the lymph nodes and spleen. T-lymphocytes are responsible for cell mediated immunity, which is an immune response that involves the activation of certain immune cells to fight infection. In addition to immune function, the thymus also produces hormones that promote growth and maturation. - Spleen
The spleen is the largest organ of the lymphatic system. Its primary function is to filter blood of damaged cells, cellular debris, and pathogens. Like the thymus, the spleen houses and aids in the maturation of lymphocytes. Lymphocytes destroy pathogens and dead cells in the blood. The spleen is rich in blood supplied via the splenic artery. The spleen also contains efferent lymphatic vessels, which transport lymph away from the spleen and toward lymph nodes. - Tonsils
Tonsils are arrays of lymphatic tissue located in the upper throat region. Tonsils house lymphocytes and other white blood cells called macrophages. These immune cells protect the digestive tract and lungs from disease causing agents that enter the mouth or nose. - Bone Marrow
Bone marrow is the soft, flexible tissue found inside bone. Bone marrow is responsible for the production of blood cells: red blood cells, white blood cells, and platelets. Bone marrow stem cells play an important role in immunity as they generate lymphocytes. While some white blood cells mature in bone marrow, certain types of lymphocytes migrate to lymphatic organs, such as the spleen and thymus, to mature into fully functioning lymphocytes.
Lymphatic tissue can also be found in other areas of the body, such as the skin, stomach, and small intestines. Lymphatic system structures extend throughout most regions of the body. One notable exception is the central nervous system.
Immunity
“Immunity is the state of sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion.”
The body’s immune system protects against the harmful substances by recognizing and responding to pathogens (antigen). The antigens can be living or non living. Living individual contain antigens on the surface of cells like bacteria, viruses and fungi. Non living substances also act as antigens like toxins, chemicals, drugs, foreign particle etc. Immunity also consists of specific and non specific components. The non specific act as barriers irrespective of antigenic specificity and specific components adapt themselves to each new antigen or disease.
Classification of immunity
There are two major types of immunity that are as follows:
1. Innate immunity:
It is a type of immunity with which a person is born and it is non- specific. It is first lines of defence.they are species dependent. They defenses include secretion of chemical signals, phagocytic activity, antimicrobial substance and fever. The cell include in innate immunity are:
· Neutrophils · Mast cells · Macrophages · Platelets
· Eosinophils · Monocytes · Killer cell
Innate immunity also comes in a protein chemical form, called innate humoral immunity. If an antigen gets past these barriers, it is attacked and destroyed by other parts of the immune system.
E.g.: Cough reflex, Enzymes in tears and skin oils, Mucus, which traps bacteria and small particles, Skin, Stomach acid
2. Adaptive immunity:
The third line of defense is adaptive (acquired) immunity, often called the immune response. This inducible and develops slowly than the innate response. This is specific kind of immunity and has memory, therefore providing long term protection. This occurs with contact of foreign particle (antigen).
It is further divided into different classes depending upon:
A. Naturally acquired immunity:
It is observed when contact with foreign particle was not deliberate and still contact was established.
B. Artificially acquired immunity:
The disease causing agent was deliberately induced in this type of immunity.
E.g. vaccinations
“Immunity is the state of sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion.”
The body’s immune system protects against the harmful substances by recognizing and responding to pathogens (antigen). The antigens can be living or non living. Living individual contain antigens on the surface of cells like bacteria, viruses and fungi. Non living substances also act as antigens like toxins, chemicals, drugs, foreign particle etc. Immunity also consists of specific and non specific components. The non specific act as barriers irrespective of antigenic specificity and specific components adapt themselves to each new antigen or disease.
Classification of immunity
There are two major types of immunity that are as follows:
1. Innate immunity:
It is a type of immunity with which a person is born and it is non- specific. It is first lines of defence.they are species dependent. They defenses include secretion of chemical signals, phagocytic activity, antimicrobial substance and fever. The cell include in innate immunity are:
· Neutrophils · Mast cells · Macrophages · Platelets
· Eosinophils · Monocytes · Killer cell
Innate immunity also comes in a protein chemical form, called innate humoral immunity. If an antigen gets past these barriers, it is attacked and destroyed by other parts of the immune system.
E.g.: Cough reflex, Enzymes in tears and skin oils, Mucus, which traps bacteria and small particles, Skin, Stomach acid
2. Adaptive immunity:
The third line of defense is adaptive (acquired) immunity, often called the immune response. This inducible and develops slowly than the innate response. This is specific kind of immunity and has memory, therefore providing long term protection. This occurs with contact of foreign particle (antigen).
It is further divided into different classes depending upon:
- The contact of foreign particle:
A. Naturally acquired immunity:
It is observed when contact with foreign particle was not deliberate and still contact was established.
B. Artificially acquired immunity:
The disease causing agent was deliberately induced in this type of immunity.
E.g. vaccinations
- The transfer and inducement of immunity:
This is the type of immunity that develops with time and has immunological memory. Therefore on first exposure to the specific pathogen no antibodies were observed and later resistance antibodies develop with second exposure of the pathogens. They develop B cells and T cells in response to the presence of pathogens. Active immunity often shows both cell-mediated and humoral aspects of immunity.
They are subdivided into:
- Naturally acquired active immunity
This type of immunity develops when a person is exposed to live pathogens, which leads to immunological memory (your immune system remembers all the pathogens that have attacked your body so that if you were to catch one of these again you won’t fall ill). It is natural immunity as it is not induced by deliberate exposure. They can be affected by the immunodeficiency and immunosuppression.
- Artificially acquired active immunity
It is induced when the antigens are incorporated in the human body, through vaccines. Vaccine stimulates response, without causing symptoms, against antigens. It usually last for very long time, sometimes lifelong.
B. Passive immunity:
Passive immunity is acquired through transfer of antibodies or activated T-cells from an immune host, and is short lived usually lasting only a few months. It is transfer of readymade antibodies (active immunity) from one individual to another. It provides immediate protection but no memory develops, so a person is likely to be infected by the same pathogens. Passive immunization is used when there is a high risk of infection and insufficient time for the body to develop its own immune response.
They are further subdivided as:
- Naturally acquired passive immunity
It is also known as maternal passive immunity. The antibodies are naturally transferred from mother to fetus during pregnancy. Around the third month of gestation, a mother antibody (MatAB) is passed through placenta (FcRn receptor on placental cells) to the fetus. Passive immunity is also provided through transfer of (IgA) antibodies found in breast milk that are transferred to the gut of the infant, protecting against bacterial infections, until the newborn can synthesize its own antibody. When the baby is between age 6 to 12 months the mothers antibody disappears.
- Artificially acquired passive immunity
Artificially acquired passive immunity is a short-term immunization induced by the transfer of antibodies, which can be administered in several forms; as human or animal blood plasma, as pooled human immunoglobulin for intravenous or intramuscular use, and in the form of monoclonal antibodies. It last only for short period of time.
- The cell involved:
The immunity mediated by the antibodies binding with antigen and ultimately destroying it. It demonstrates immune response using only blood serum. It shows response against bacteria, virus and bacterial toxins. Humoral immunity acts as active immunity when body generates its own antibodies and as passive when antibodies are transferred to other individual.
B. Cell mediated immunity:
It involves the T lymphocytes (helper T-cells and cytotoxic T-cells) only to show immune response. It shows response against virus infected cell, cancer cell, fungi and animal parasites and foreign cells from transplant. It shows active immunity when individuals own T lymphocytes are stimulated and passive immunity when T lymphocytes are induced in the host.
Credists to the owner: http://biology.about.com/od/organsystems/ss/lymphatic-aystem.htm
Credists to the owner: http://www.medilol.com/immunity-and-its-types/
Credists to the owner: http://www.medilol.com/immunity-and-its-types/