What is the function of lymphatic vessels?
Function of the Lymphatic System. Mingled among the blood capillaries throughout your body is another network of tiny, thin-walled vessels called lymphatic capillaries. Lymphatic capillaries are designed to pick up the fluid that leaks into your tissues from your bloodstream and return it to your circulatory system
What is lymph?
Lymph is the fluid that circulates throughout the lymphatic system. The lymph is formed when the interstitial fluid (the fluid which lies in the interstices of all body tissues) is collected through lymph capillaries
Name the two large lymphatic ducts into which the lymphatic trunks empty.
There are two lymph ducts in the body: the right lymph duct and the thoracic duct.
The lymph trunks drain into the lymph ducts, which in turn return lymph to the blood by emptying into the respective subclavian veins.
Describe the drainage of the right lymphatic duct and the thoracic duct.
The right lymphatic duct drains lymph from the right upper limb, right side of thorax and right halves of head and neck. The thoracic duct drains lymph into the circulatory system at the left brachiocephalic vein between the left subclavian and left internal jugular veins
When the lymph vessels are blocked or unable to carry lymph fluid away from the tissues, localized swelling (lymphedema) is the result. Lymphedema most often affects a single arm or leg, but in uncommon situations both limbs are affected
Identify the three main classes of lymphocytes
There are three main types of lymphocytes: B cells, T cells, and natural killer cells. Two of these types of lymphocytes are critical for specific immune responses. They are B lymphocytes (B cells) and T lymphocytes (T cells).
Which cells are responsible for antibody-mediated immunity?
B cells develop from bone marrow stem cells in adults. When B cells become activated due to the presence of a particular antigen, they create antibodies that are specific to that specific antigen. Antibodies are specialized proteins that travel thorough the bloodstream and are found in bodily fluids. Antibodies are critical to humoral immunity as this type of immunity relies on the circulation of antibodies in bodily fluids and blood serum to identify and counteract antigens.
Which tissues are involved in lymphopoiesis?
The red bone marrow, thymus, and peripheral lymphoid tissues are involved in lymphopoiesis.
Name the lymphoid tissue that protects epithelia lining the digestive, respiratory, urinary, and reproductive tracts.
Mucosa-Associated Lymphoid Tissue (MALT)
Define tonsils, and name the three types of tonsils
Tonsils are collections of lymphoid tissue facing into the aerodigestive tract. The set of lymphatic tissue known as Waldeyer’s tonsillar ring includes the adenoid tonsil, two tubal tonsils, two palatine tonsils, and the lingual tonsil.
Describe the functions of the spleen.
The spleen serves two major functions in humans. First, it plays an important role in adaptive immunity; groups of B and T lymphocytes reside in the spleen. These white blood cells produce antibodies, fight bacteria and viruses and destroy infected cells.
Second, the spleen holds a third of the body’s platelets in reserve. If a person suffers an internal hemorrhage, the spleen releases these platelets into the circulation
How does the integumentary system protect the body?
The skin helps protect our body’s internal structures from physical, chemical, biological, radiological, and thermal damage as well as damage from starvation and malnutrition.
Identify the types of phagocytes in the body, and differentiate between fixed macrophages and free macrophages.
The body’s phagocytes are neutrophils, eosinophils, and macrophages. Fixed macrophages are scattered among connective tissues and do not move; free macrophages are mobile and reach injury sites by migrating through adjacent tissues or traveling in the bloodstream.
Chemotaxis is phagocyte movement in response to attraction to or repulsion from chemical stimuli.
Describe antigen presentation.
Antigen presentation occurs when an antigen-glycoprotein, or antigen-MHC prtein, combination capable of activating T cells appears in a plasma membrane (typically that of a macrophage). T cells sensitive to this antigen are activated if they contact the antigen on the plasma membrane of the antigen-presenting cell.
Which cells can be activated by direct contact with virus-infected cells?
Cytotoxic T cells and NK cells can be activated by direct contact with virus-infected cells.
Which cells produce antibodies?
Plasma cells produce antibodies.
Describe the structure of an antibody.
An antibody molecule consists of two parallel pairs of polypeptide chains: a pair of long, heavy chains and a pair of short, light chains. Each chain contains both constant segments and variable segments. The constant segments of the heavy chains form the base of the antibody molecule; the free tips of the two variable segments form the antigen binding sites.
Describe the ways that antigen-antibody complexes can destroy target antigens
Antibodies, also called immunoglobulins, are proteins manufactured by the body that help fight against foreign substances called antigens. When an antigen enters the body, it stimulates the immune system to produce antibodies. (The immune system is the body’s natural defense system.) The antibodies attach, or bind, themselves to the antigen and inactivate it.
Every healthy adult’s body has small amounts of thousands of different antibodies. Each one is highly specialized to recognize just one kind of foreign substance. Antibody molecules are typically Y-shaped, with a binding site on each arm of the Y. The binding sites of each antibody, in turn, have a specific shape. Only antigens that match this shape will fit into them. The role of antibodies is to bind with antigens and inactivate them so that other bodily processes can take over, destroy, and remove the foreign substances from the body.
The Lymphatic system consists of what two semi-independent parts
Lymphoid tissues and organs
Lymphatic System functions
Transports escaped fluids back to the blood
Plays essential roles in body defence and resistance to disease
What pressures force fluid out of the blood at the arterial ends of the capillary beds
Hydrostatic and osmotic pressures force fluid out of the blood at the arterial ends of the capillary beds
Properties of lymphatic vessels
Have large diameters and thin walls
Overlapping endothelial cells in lymphatic capillaries act as one-way valves to push fluid only towards heart
Low pressure in lymphatic capillaries
Function of the spleen
Filters blood rather than lymph
Destroys bacteria, viruses and other debris
Destroys worn out RBC (RBC graveyard) and recycles some products:
Iron returns to blood for Hb
RBC goes to liver for bile
Superficial and deep lymphatics converge to form:
Larger vessels, lymphatic trunks, which empty into two collecting vessels
Thoracic duct & Right lymphatic duct
Describe Lymphodema’s causes and symptoms
Caused by blocked lymphatic drainage (usually affects limbs; can affect other areas)
Interstitial fluid accumulates
Causes swollen and distended areas
Lymph may contain these harmful materials that then can enter the lymphatic vessels:
Defence cells within lymph nodes include:
Macrophages - engulf and destroy foreign substances
Lymphocytes - provide immune response to antigens
T-lymphocytes (T cells)
B-lymphocytes (B cells)
NK Cells (Cytotoxic lymphocyte)
Large clusters of lymphatic nodes are found three main regions of the body:
Cervical – head and neck
Axillary – under arm (often associated with breast cancer)
Inguinal – located in groin
Describe tonsils and explain their functions
Small masses of lymphoid tissue around the pharynx
Trap and remove bacteria and other foreign materials
Describe Peyer’s Patch and it’s fuctions
Found in the wall of the SI
Resemble tonsils in structure
Capture and destroy bacteria leaving the intestine
Describe Thymus and it’s function
Located in upper mediastinum thoracic cavity
Functions at peak levels only during childhood – shrinks by puberty
Site of T-cell maturation
Define Lymphopoiesis and the organs it involves
Lymphopoiesis = Lymphocyte production
Red bone marrow
Peripheral lymphoid tissues
Define Thymosin and its relationship to Lymphopoiesis
Size and secretory abilities of thymus declines with age
Correlated with increased susceptibility to disease
Stimulates maturation of T cells
Reenter bloodstream when near mature and travel to:
Red bone marrow & Peripheral tissues
Account for 20–40 % of circulating leukocytes
Circulating lymphocytes are a small fraction of total lymphocyte population (i.e. most are fixed in tissues)
Three classes of lymphocytes
The body has two defence systems for foreign materials
Innate (nonspecific) defence system
Adaptive (specific) defence system
specific resistance to disease
Characteristics of Innate defence system (nonspecific defence system) includes
Does not distinguish one type of pathogen from another (response is the same regardless of invading agent)
Present at birth (innate) and responds immediately
Characteristics of Adaptive defence system (specific defence system) include ……………
Specific defence is required for each type of invader
This system must be primed / exposed to the foreign substance (which is called an antigen) therefore much slower to respond