What does the lymphatic system consist of? (4)
Lymphatic vessels, lymph, lymphatic tissue, lymphatic organs
In what direction does the lymphatic system carry fluid?
Lymphatic vessels carry fluid in one direction only – away from the tissues
Where are immune cells produced within the lymphatic system?
Tissues and organs - lymph nodes, thymus, tonsils, spleen, and red bone marrow
What are the three functions of the lymphatic system?
- Maintenance of fluid balance
- the absorption of fat
- immunity
Explain the function of the maintenance of fluid balance
Fluid continually seeps out of capillaries into surrounding tissues. The capillaries reabsorb about 85% of the fluid and return it to the bloodstream
What is the function of absorption of fats in the lymphatic system?
Specialized lymphatic vessels in the small intestines absorb fats and fat-soluble vitamins
What is the function of immunity in the lymphatic system?
Lymph nodes and other lymphatic organs filter lymph to remove microorganisms and foreign particles
What is lymph?
A clear, colourless fluid similar to plasma but with a lower protein content
Why do lymphatic vessels have thin walls and valves?
To prevent backflow
What type of cells comprise the lymphatic vessel walls?
A thin layer of epithelial cells
How does fluid enter lymphatic vessels?
Between the overlapping epithelial cells
What anchors vessels to surrounding cells that prevents them from collapsing soon?
Protein filaments
What forms the basis of lymphatic fluid?
Tissue fluid left behind after capillary exchange
In which lymphatic organ do T cells mature?
Thymus
Where do lymphatic blood vessels originate?
In tissue spaces as microscopic, sacs within a bed of blood capillaries
The vessels converge to form larger and larger vessels. Periodically, the vessels empty into lymph nodes. What happens in the lymph nodes?
Immune cells phagocytize bacteria
What helps to aid or propel the lymph towards the bloodstream?
Rhythmic contractions of the lymphatic vessels
Contraction of skeletal muscles
What are the two collecting ducts of the lymphatic system?
The right lymphatic duct and the thoracic duct
The right lymphatic duct drains lymph from which parts of the body into which vein?
From the upper right quadrant of the body into the right subclavian vein
The thoracic duct drains lymph from which parts of the body into which vein?
The rest of the body into the left subclavian vein
Is red bone marrow a primary or secondary lymphatic organ and what is its role?
Primary – provide a location for B and T lymphocytes to mature
Is the thymus a primary or secondary lymphatic organs and what is its role?
Primary – provide a location for B and T lymphocytes to mature
Are lymph nodes a primary or secondary lymphatic organ and what is its role?
Secondary – contain lymphocytes that have matured in either the red bone marrow or thymus
Are the tonsils and spleen a primary or secondary lymphatic organ?
Secondary
Where are the tonsils found, and why are they found in these particular locations?
Back of the throat - guard against pathogens entering the body through the nose or throat
What tonsils are most prone to becoming infected?
Palatine tonsils
How does the thymus help to the mature the immature T lymphocytes?
Inside the thymus, the cells are protected from antigens in the blood, giving them a chance to divide and mature
What is the role of lymph nodes?
Cleanse lymoh, also serve as sites for final maturation of some types of lymphocytes and monocytes
Where is the spleen found?
Upper left quadrant of the abdomen, just inferior to the diaphragm
What are the four functions of the spleen?
- immunity
- Destruction of old red blood cells
- Blood storage
- Hematopoiesis
*Explain the three lines of defence of the immune system
First: External barriers (such as skin & mucous membranes)
Second: Nonspecific immunity - Launch the production of phagocytic white blood cells and triggering inflammation and fever
Third: Specific immunity - This occurs when the body retains a memory of a pathogen after defeating it
What are the mechanisms of non-specific immunity?
- Phagocytosis
- Antimicrobial proteins
- Natural killer cells
- Inflammation
- Fever
What is the role of phagocytes?
Cells whose sole job is to ingest and destroy microorganisms and other small particles
What are the most important phagocytes?
Neutrophils and macrophages
Where are neutrophils found?
They roam the body, seeking out bacteria
Monocytes in the connective tissue grow several times larger and transform into macrophages. Where do macrophages congregate?
In areas where microbial invasion is likely to occur: the alveolus of the lungs, Liver, nerve tissue, bone, and the spleen
How are neutrophils summoned to an infection?
By a chemical released from inflamed cells – chemotaxis
*Two types of proteins help provide nonspecific resistance against bacterial and viral invasion. What are they?
Interferons and the complement system
*How do interferons prevent virus replication?
Cells produce interferons (alert), bind to receptors of neighboring cells, enzymes are produced within the cells that prevent the virus from replicating
*How do complement proteins work to destroy bacteria?
Circulates in the blood stream in an inactive form, waiting to assist in the immune response.
Once reaction begins, it continues as a cascade of chemical reactions, with one complement protein activating the next
What are natural killer cells and their function?
- Unique group of lymphocytes
- Roam the body
- Use several methods to destroy cells - by the secretion of chemicals that cause the cell to die and break apart (lysis)
Words ending in “itis” denote
Inflammation
How is a fever beneficial?
- Promotes the activity of interferon
- High body temperature stops the reproduction of bacteria and viruses
In the first stage of the normal sequence of events during a fever - As neutrophils and macrophages phagocytize bacteria, they secrete…
a fever producing substance called a pyrogen
Specific immunity uses what two mechanisms?
- Cellular (cell-mediated) immunity
- Humoral (antibody-mediated) immunity
What is an important white blood cell that travels throughout the bloodstream seeking out bacteria?
Neutrophils
What is an important white blood cell that remains fixed and strategic areas?
Macrophages
What is the white blood cell that ingest microorganisms?
Phagocytes
What is the sac formed around a microorganism when it’s ingested by a phagocyte?
Phagosome
**How does cellular (cell-mediated) immunity work?
Aims to destroy foreign cells or host cells that have become infected with a pathogen
**How does humoral (antibody-mediated) immunity work?
Focusses on pathogens outside the host cells, sends out antibodies to ”mark” a pathogen for later distruction
*What are the three classes that lymphocytes fall into?
- Natural killer cells
- T lymphocytes
- B lymphocytes
*Where are T cells (Or T lymphocytes) made?
Develop from stem cells in red bone marrow
*Where do the T cells mature?
Thymus gland
*Where are B cells made, and where do they mature?
Begin life as stem cells in red bone marrow. Unlike T cells, B cells remain in bone marrow until they are fully mature
Where are antibodies found?
Plasma and body secretions
Antibodies consist of chains of protein joined in a way that resembles a ”Y” or “T”. What does the unique shape at the end of each arm of the Y allow?
Allows each antibody to combine with a specific antigen
What is an antigen?
Any molecule that triggers an immune response
Why is nonspecific immunity not an acquired immunity?
Because it’s present from birth
*What is active immunity, and how long does it last?
When the body makes its own antibodies or T cells.
It is permanent, or at least long lasting
*What is passive immunity?
When immunity results from injection of antibodies from another person or animal
How long does passive immunity last, and why?
Only a few months. The body doesn’t develop a memory for the pathogen
*How does natural active immunity happen? provide an example
Occurs when the body produces antibodies or T cells after being exposed to a particular antigen.
Ex. You become ill with measles, body produces antibodies to the particular virus, making you immune
*How does artificial active immunity happen?
Results when the body makes T cells and antibodies against a disease as a result of a vaccination.
(Such as tetanus or influenza)
*How does natural passive immunity happen?
Results when a fetus acquires antibodies from the mother through the placenta, or when a baby acquires them through breastfeeding
*How does artificial passive immunity happen?
Involves obtaining serum from a person or animal that has produced antibodies against a certain pathogen and then injecting it into someone else.
(Typically used in emergencies for the treatment of rabies and botulism)
Cellular immunity destroys pathogen’s that exist within a cell. What are the three classes of T cells that it uses to accomplish this?
Cytotoxic T cells
Helper T cells
Memory T cells
*What is the role of cytotoxic T cells?
Carry out the attack
Also called killer T cells
*What is the role of helper T cells?
Play a supportive role in helping attack
By secreting a chemical interleukin, which attracts neutrophils, natural killer cells, and macrophages
*What is the role of memory T cells?
Remember the pathogen in case of future invasion
*What is Humoral immunity?
Focusses on the pathogens outside the cell. Uses antibodies to mark antigen for later destruction
In an allergic reaction, if the allergen links two antibodies, what do the mast cells release?
Histamine
