Lymphatic System anatomy and physiology

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Lymph

The part of the blood that does not return from body tissue to the capillaries but drains into lymph vessels and is filtered through a series of lymph nodes to remove any foreign material or bacteria. So lymph is basically excess tissue fluid

Lymphatic system

only carries fluid away from the tissues provides a continuous special cleaning of the fluid portion of blood. This process is essential to the body's resistance to disease. The lymph nodes and organs, such as the spleen, tonsils, and thymus, all contain lymphoid tissue, primarily leukocytes that perform important immune functions.

describe the lymphatic vessels

Lymphatic vessels are extensive; every region of the body is supplied richly with lymphatic capillaries, • Lymphatic vessels are very much like vascular vessels; they even have valves
• The movement of lymph within these vessels is dependent upon skeletal muscle contraction—when the muscles contract, lymph is squeezed past a valve that closes, preventing lymph from flowing backward

• This system is a one-way system

o Begins with lymphatic capillaries that lie near blood capillaries
o These lymphatic capillaries take up fluid that exited from, and was not reabsorbed by the blood capillaries
o When the tissue fluid enters the lymphatic vessels, it is called lymph
o The lymphatic capillaries then join to form the lymphatic vessels that merge in the thoracic cavity before entering one of 2 ducts: the thoracic duct or the right lymphatic duct

Thoracic duct:

• The thoracic duct is much larger than the right lymphatic duct
• Serves the lower extremities, abdomen, left arm, and left side of the head and neck
• In the thorax, the left thoracic duct enters the left subclavian vein

Right lymphatic duct

• Smaller than the thoracic duct
• Serves only the right arm and the right side of the head and neck
• Enters the right subclavian vein

Lymphatic organs:

Lymphatic organs contain lymphatic tissue, which consists of many lymphocytes, macrophages, and other cells. The lymphocytes originate from red bone marrow and are carried by the blood to lymph organs. When the body is exposed to microorganisms or foreign substances, the lymphocytes divide and increase in number.

Lymphatic organs consist of

• Tonsils
• Lymph nodes
• Spleen
• Thymus
• Red bone marrow

Tonsils

there are three groups of tonsils- palatine, pharyngeal (also called adenoid when it is enlarged) and lingual; the tonsils provide protection against pathogens and other potentially harmful material entering the nose and mouth. Sometimes the tonsils or adenoids become chronically infected and must be removed. In adults the tonsils decrease in size.

Lymph nodes

these are small, round structures distributed along the various lymph vessels. They are all over the body, but there are three groups which are superficial which are the inguinal nodes in the groin, the axillary nodes in the armpit region, and the cervical nodes of the neck; functions are activation of the immune system and removal (phagocytosis) of microorganisms and foreign substances from the lymph by macrophages

The lymph nodes are filled with?

lymphocytes and macrophages and as lymph passes through the sinuses, it is purified of infectious organisms and any other debris.

Spleen

size of a clenched fist, located in the left upper quadrant of the abdomen just below the diaphragm and behind the stomach; it is the largest lymphatic organ in the body; it is divided into lobules, one red and one white. The red pulp contains RBCs, lymphocytes and macrophages. The white pulp contains only lymphocytes and macrophages

how does the pulps help filter blood

helps to purify the blood that passes through the spleen. The spleen filters blood, destroying microorganisms, foreign substances, and worn out red blood cells; activates the immune system;

how does the spleen function as a reservoir?

holding a small volume of blood; in emergencies, ; can rupture in traumatic injuries causing severe bleeding, shock, and death; if removed (splenectomy), other lymphatic tissue and the liver compensate for its function.

Thymus

bilobed gland, triangular in shape, in superior mediastinum, just beneath the sternum; also an endocrine gland; size depends on age of the individual; grows until puberty, then starts decreasing in size until it may even become difficult to find.

what is produced in the thymus?

large numbers of lymphocytes are produced here, but most degenerate; functions as a site for the processing and maturation of lymphocytes.

Red Bone Marrow

This is the site of origination for all blood cells. In the adult, red bone marrow is found in the bones of the skull, sternum, ribs, clavicle, pelvis, and spinal column, and in the ends of the femur and humerus.

Functions of the lymphatic system:

• Helps maintain fluid balance in the tissues; take up excess tissue fluid and return it to the bloodstream
• Absorbs fats and other substances from the digestive tract
• Is part of the body's defense system; remove microorganisms and other foreign substances

Immunity barrier

• Skin
• Oil glands: secretions have chemicals which weaken or kill bacteria
• Respiratory tract: cilia
• Stomach: acidic pH inhibits growth of many types of bacteria
• Other organs: have bacteria which prevent pathogens from colonizing vulnerable tissues

immunity injury

• Right after injury, capillaries and several tissue cells release histamine (makes vessels dilate and become more permeable)
• Neutrophils and monocytes squeeze through capillary walls to enter tissue fluid where they carry out phagocytosis
• After phagocytosis occurs, an intracellular vacuole is formed
• Inside this vacuole, the bacterium is destroyed
• As the infection is being overcome, some neutrophils die
• The neutrophils, along with the dead tissue, cells, bacteria, and living white blood cells, form pus, a thick, yellowish fluid: the presence of pus indicates that the body is trying to overcome the infection

Protective Proteins:

• Complement system:
o Consists of a number of plasma proteins designated by the letter C and number or letter
o Once a complement protein is activated, it , in turn, activates another protein in a set series of reactions
o Each protein in the series is capable of activating many proteins next in line

o Complement is activated

when pathogens enter the body

Complement proteins form holes in bacterial cell walls and membranes; these

holes allow fluids and salt to enter the bacterial cell until it bursts
o Complement also activates chemicals that attract phagocytes to the site and induce inflammation

Viruse response

When a virus infects a cell, the infected cell produces and secretes interferon

Interferon binds to receptors on the surface of noninfected cells

causing them to prepare for possible attack by producing substances that interfere with viral replication

Interferon is specific to the species:

only human interferon can be used for humans

Specific Defenses

• Immunity usually lasts for a long time
• Immunity is primarily the result of the action of B lymphocytes and T lymphocytes:

lymphocytes

o B stands for bone marrow
o T stands for thymus
o B lymphocytes become plasma cells that produce antibodies

Antibodies are

• Antibodies are proteins capable of combining with and inactivating antigens
• These are secreted into the blood, lymph, and mucus

T lymphocytes do not produce antibodies

These directly attack cells bearing antigens they recognize; other T cells regulate the immune response

Antibody-Mediated Immunity

The cells have receptors which secrete antibodies when there is an invasion from an antigen

• The B cells

• The B cells divide and produce plasma cells which also secrete antibodies against the antigen
• Once there is enough amount of antibodies present in the body, the antigen disappears

Some of the antibodies remain in the blood to become memory B cells

• Some of the antibodies remain in the blood to become memory B cells which are capable of producing the antibody specific to a particular antigen for some time, maybe even a lifetime; so if the same antigen were to attack again, the body would recognize it and begin its invasion
• Defense by B cells is the "antibody-mediated immunity or humoral immunity"

• There are many classes of antibodies with specific functions

o Most belong to the class IgG
o Learn the antibodies

Cell-Mediated Immunity

• T cells are responsible for cell-mediated immunity
• They contain a major histocompatibility protein as a receptor, These contribute to specific tissue and are the ones responsible of making it difficult to transplant tissue from one person to another

helper T cells

stimulate B cells and also release lymphokines (messenger proteins that stimulate the immune system)

As long as T cells are capable of ?

recognizing newly developed changed cells (cancer cells), it releases chemicals that perforate the cell membrane and killing the cell

Active Immunity:

• Provides long-lasting protection against a disease-causing organism
• Develops after an individual is infected with a virus or bacterium or after being artificially immunized

Immunization

• Use of vaccines
o Vaccines are antigens to which the immune system responds
o After it is given, you measure the antibody titer in the blood
o When this titer is high enough, it prevents the disease even if exposed

Passive Immunity

• Occurs when an individual is given antibodies (immunoglobulins) to combat a disease
• It is short-lived
o Example: those passed through placenta which disappear after a few months
o Breast feeding prolongs passive immunity
• Given to people who have been exposed to a disease

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