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Anatomy of the lymphatic system

The left panel shows a female human body, and the entire lymphatic system is shown. The right panel shows magnified images of the thymus and the lymph node. All the major parts in the lymphatic system are labeled.
Lymphatic vessels in the arms and legs convey lymph to the larger lymphatic vessels in the torso.

Lymphatic capillaries

In the small intestine, lymphatic capillaries called lacteals are critical for the transport of dietary fats and fat-soluble vitamins to the bloodstream. These fats are abosorbed lacteals and form a milky fluid called chyle    . The chyle then travels through the lymphatic system, eventually entering the liver and then the bloodstream.

The organization of immune function

The immune system is a collection of barriers, cells, and proteins that interact and communicate with each other in extraordinarily complex ways to combat pathogens . A pathogen is anything that can make one sick when it enters the body. The modern model of immune function is organized into three phases based on the timing of their effects. The three phases consist of the following:

  • Barrier defenses such as the skin are also referred to as mechanical defenses that act instantly to prevent pathogens from invading the body tissues.
  • The rapid, but nonspecific innate immune response    , consists of a variety of specialized cells and chemicals.
  • The slower but more specific and effective adaptive immune response    , involves many cell types and chemicals, but is primarily controlled by white blood cells (leukocytes) known as lymphocytes    , which help control immune responses.

The cells of the blood, including all those involved in the immune response are made in the bone marrow. Hematopoietic tissue contains stem cells that produce the blood cells. ( [link] ). Hematopoietic stem cells are present throughout adulthood to replace those lost to age or function. These cells produce the all the classes of white blood cells that are involved in the function of the the immune system. These cells can be divided into three classes based on function:

  • Phagocytic cells also called phagocytes, ingest pathogens to destroy them
  • Lymphocytes specifically coordinate the activities of adaptive immunity
  • Cells containing cytoplasmic granules, which help regulate immune responses against parasites and viruses

Hematopoietic system of the bone marrow

This flowchart shows the steps in which a multipotential hematopoietic stem cell differentiates into the different cell types in blood.
All the cells of the immune response as well as of the blood arise by differentiation from hematopoietic stem cells. Platelets are cell fragments involved in the clotting of blood.

Lymphocytes: b cells, t cells, plasma cells, and natural killer cells

As stated above, lymphocytes are the primary cells of adaptive immune responses ( [link] ). The two basic types of lymphocytes, B cells and T cells, start out as identical cells with a large central nucleus surrounded by a thin layer of cytoplasm. As they develop they start to change and become distinguished from each other by their surface protein markers as well as by the molecules they secrete. While B cells mature in red bone marrow and T cells mature in the thymus, they both initially develop from bone marrow. T cells migrate from bone marrow to the thymus gland where they further mature. B cells and T cells are found in many parts of the body, circulating in the bloodstream and lymph, and residing in the spleen and lymph nodes, which will be described later in this section. The human body contains approximately 10 12 lymphocytes.

B cells

B cells    are immune cells that function primarily by producing antibodies. An antibody    is any of the group of proteins that binds specifically to pathogen-(think viruses, bacteria, etc.). An antigen    is a chemical structure on the surface of a pathogen that binds to T or B lymphocyte antigen receptors. Once activated by binding to antigen, B cells change into plasma cells .

T cells

The T cell    , on the other hand, does not secrete antibodies but performs a variety of functions in the adaptive immune response. Different T cell types have the ability to either secrete substances that communicate with other cells of the adaptive immune system or destroy cells infected with pathogens. The roles of T and B lymphocytes in the adaptive immune response will be discussed further in this chapter.

Plasma cells

When a B cell discovers a pathogen, it creates plasma cells. When a signal from the B cell occurs the plasma cell    creates the antibodies that attack the pathogen.

Natural killer cells

A fourth important lymphocyte is the natural killer cell, a participant in the innate immune response. A natural killer cell (NK)    is a circulating blood cell that contains cytotoxic (cell-killing) chemicals. These chemicals destroy the invading cells, literally causing the cell membrane to burst. It shares this mechanism with the cytotoxic T cells of the adaptive immune response. NK cells are among the body’s first lines of defense against viruses and certain types of cancer.

Lymphocytes
Type of lymphocyte Primary function
B lymphocyte Generates diverse antibodies
T lymphocyte Secretes chemical messengers
Plasma cell Secretes antibodies
NK cell Destroys virally infected cells

Chapter review

The lymphatic system is a series of vessels, ducts, and trunks that remove interstitial fluid from the tissues and return it the blood. The lymphatics are also used to transport dietary lipids and cells of the immune system. Cells of the immune system all come from the hematopoietic system of the bone marrow. Primary lymphoid organs, the bone marrow and thymus gland, are the locations where lymphocytes of the adaptive immune system proliferate and mature. Secondary lymphoid organs are site in which mature lymphocytes congregate to mount immune responses. Many immune system cells use the lymphatic and circulatory systems for transport throughout the body to search for and then protect against pathogens.

Questions & Answers

what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
How can I make nanorobot?
Lily
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
how can I make nanorobot?
Lily
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
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Source:  OpenStax, Mrs. browne's immune modules. OpenStax CNX. Apr 27, 2015 Download for free at https://legacy.cnx.org/content/col11783/1.1
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