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Q: Is Blood An Organ? ( Answered,   6 Comments )
Subject: Is Blood An Organ?
Category: Health
Asked by: currentcontacts-ga
List Price: $10.00
Posted: 06 Sep 2005 16:52 PDT
Expires: 06 Oct 2005 16:52 PDT
Question ID: 564993
I am trying to argue what I believe is a fact that blood is indeed an
organ and being so would make it the largest organ in the body - even
larger then the skin. it seams alot of people including some doctors
disagree with this

medical referances to this would be helpfull

Request for Question Clarification by easterangel-ga on 06 Sep 2005 18:23 PDT

I was able to find only one medical website that states categorically
that the blood is an organ.

Will this be ok with you?


Clarification of Question by currentcontacts-ga on 06 Sep 2005 19:36 PDT
does it just mention that it is a organ or does it explain why it is considered one?

Request for Question Clarification by easterangel-ga on 06 Sep 2005 22:14 PDT
It explains in brief why the blood and for example the heart is
considered an organ. But again only briefly and in general terms and
not discussed technically.

Will this be ok?


Request for Question Clarification by easterangel-ga on 07 Sep 2005 06:46 PDT
In connection with borisshah-ga's comments, the source I found does
not say about blood as the largest organ but it does mention it as an

Subject: Re: Is Blood An Organ?
Answered By: crabcakes-ga on 08 Sep 2005 00:37 PDT
Hello Currentcontacts,

   Such an interesting question! Arguably, blood can be considered an
organ, or a body fluid. I found blood described as both, but overall,
blood is not popularly considered to be an organ.

Organ: ?Biology. A differentiated part of an organism, such as an eye,
wing, or leaf, that performs a specific function.?

?Part of a living thing, distinct from the other parts, that is
adapted for a specific function. Organs are made up of tissues and are
grouped into systems, such as the digestive system.?

?a fully differentiated structural and functional unit in an animal
that is specialized for some particular function?

?Organ systems
·	circulatory system
·	digestive system
·	endocrine system
·	immune system
·	integumentary system
·	lymphatic system
·	muscular system
·	nervous system
·	reproductive system
·	respiratory system
·	skeletal system
·	urinary system

?Circulatory system
The bodily system consisting of the heart, blood vessels, and blood
that circulates blood throughout the body, delivers nutrients and
other essential materials to cells, and removes waste products. Also
called cardiovascular system.? ?circulatory system, group of organs
that transport blood and the substances it carries to and from all
parts of the body. The circulatory system can be considered as
composed of two parts: the systemic circulation, which serves the body
as a whole except for the lungs, and the pulmonary circulation, which
carries the blood to and from the lungs. The organs of circulatory
system consist of vessels that carry the blood and a muscular pump,
the heart, that drives the blood.?

a.	?·  The fluid consisting of plasma, blood cells, and platelets that
is circulated by the heart through the vertebrate vascular system,
carrying oxygen and nutrients to and waste materials away from all
body tissues.
b.	A functionally similar fluid in animals other than vertebrates.
c.	The juice or sap of certain plants.
·  A vital or animating force; lifeblood.
·  One of the four humors of ancient and medieval physiology,
identified with the blood found in blood vessels, and thought to cause

?Because it contains living cells, blood is alive. Red blood cells and
white blood cells are responsible for nourishing and cleansing the
body. Since the cells are alive, they too need nourishment. Vitamins
and Minerals keep the blood healthy. The blood cells have a definite
life cycle, just as all living organisms do.?

?Blood: The familiar red fluid in the body that contains white and red
blood cells, platelets, proteins, and other elements. The blood is
transported throughout the body by the circulatory system. Blood
functions in two directions: arterial and venous. Arterial blood is
the means by which oxygen and nutrients are transported to tissues
while venous blood is the means by which carbon dioxide and metabolic
by-products are transported to the lungs and kidneys, respectively,
for removal from the body.?

?(1) the various structures may be separately considered?systematic
anatomy; or (2) the organs and tissues may be studied in relation to
one another?topographical or regional anatomy.?

? SYSTEMATIC ANATOMY.?The various systems of which the human body is
composed are grouped under the following headings:
1.	Osteology?the bony system or skeleton. 
2.	Syndesmology?the articulations or joints. 
3.	Myology?the muscles. With the description of the muscles it is
convenient to include that of the fascić which are so intimately
connected with them.
4.	Angiology?the vascular system, comprising the heart, blood vessels,
lymphatic vessels, and lymph glands.
5.	Neurology?the nervous system. The organs of sense may be included
in this system.
6.	Splanchnology?the visceral system. Topographically the viscera form
two groups, viz., the thoracic viscera and the abdomino-pelvic
viscera. The heart, a thoracic viscus, is best considered with the
vascular system. The rest of the viscera may be grouped according to
their functions: (a) the respiratory apparatus; (b) the digestive
apparatus; and (c) the urogenital apparatus. Strictly speaking, the
third subgroup should include only such components of the urogenital
apparatus as are included within the abdomino-pelvic cavity, but it is
convenient to study under this heading certain parts which lie in
relation to the surface of the body, e. g., the testes and the
external organs of generation.?
Gray?s Anatomy, lists the heart, the blood vessels, th elympatic
vessels, and lymph glands as making up the vascular system. Blood is
not mentioned.

These sites say ?NO?

Organs of the body
?Appendix, Bladder, Brain, Gallbladder, Female genitals, Heart,
Kidneys, Large intestine, Liver, Lungs, Male genitals, Pancreas, Skin,
Spleen, Small intestine, Stomach, Voice box?

<haematology> Considered a circulating tissue composed of a fluid
portion (plasma) with suspended formed elements (red blood cells,
white blood cells, platelets).
Arterial blood is the means by which oxygen and nutrients are
transported to tissues, venous blood is the means by which carbon
dioxide and metabolic by-products are transported for excretion.?
?1 : the fluid that circulates in the heart, arteries, capillaries,
and veins of a vertebrate animal carrying nourishment and oxygen to
and bringing away waste products from all parts of the body
2 : a fluid of an invertebrate comparable to blood?

See the organs in their places:

Organ: : a differentiated structure (as a heart or kidney) consisting
of cells and tissues and performing some specific function in an

These sites say ?YES?
Blood, the sticky red fluid three times thicker than water, is the
body's transport system, circulating continuously throughout its
intricate network of veins, arteries and capillaries. One small drop
contains 250 million cells.

Cells group together in the body to form tissues - a collection of
similar cells that group together to perform a specialized function. 
There are 4 primary tissue types in the human body: epithelial tissue,
connective tissue, muscle tissue and nerve tissue.?

Organs are the next level of organization in the body.  An organ is a
structure that contains at least two different types of tissue
functioning together for a common purpose.  There are many different
organs in the body: the liver, kidneys, heart, even your skin is an

No other organ travels the body. Blood passes through the heart
(organ), to the lung (organ), to the kidneys (organ), to the liver
(organ), to the brain (organ), to the genitals (organ), the
intestines(organ), skin (organ), etc.

The adult human body contains about 5 quarts of blood, while skin
accounts for 15 percent of body weight. Skin still wins as the largest
organ regardless! 

While blood may technically meet the criteria of being an organ, it is
generally not considered an organ. I do not consider blood to be an
organ. Organs are fairly stationary, while blood circulates, cleans,
oxygenates, carries wastes, hormones, vitamins, lipids, electrolytes,
and minerals. When we get another?s blood, it is called a transfusion,
not an organ transplant. In autopsy reports, organs are weighed and
noted on the report. Blood is not.

There you go! I hope this has adequately answered your question. If
not, please request an Answer Clarification, before rating this
answer. This will enable me to assist you further, if possible.

Regards, Crabcakes

Search Terms
Organs + body
Blood definition
Organs definition
Blood + organ
Subject: Re: Is Blood An Organ?
From: borisshah-ga on 07 Sep 2005 04:29 PDT
Hi There.

You would be completely wrong. The skin is the largest organ of our
body bar none. I don't know how you came up with your theory but the
fact is that blood is made up of many different components like plasma
and platelets so you cannot just lump all of them in one category:
Subject: Re: Is Blood An Organ?
From: neilzero-ga on 07 Sep 2005 20:34 PDT
There are good reasons to regard the skin as an organ. If you regard
blood as an organ, you should possibly also consider several other
types of bodily fluids organs. I generally reject the borisshah line
of reasoning.   Neil
Subject: Re: Is Blood An Organ?
From: truthindian-ga on 11 Sep 2005 03:37 PDT
good question.
Subject: Re: Is Blood An Organ?
From: linezolid-ga on 12 Sep 2005 09:10 PDT
Questions like this do not, generally speaking, have a right or wrong
answer.  It is a matter of how the different parts of the body are
defined.  Statements like "blood is not an organ because it moves", or
"blood is not an organ because we don't call it a transplant when we
get someone else's blood" are meaningless.  In the final analysis, an
organ is something that is convenient to define as an organ for
whatever purpose we have.  Since we are medical scientists (for the
purposes of this discussion), we define blood in a convenient way for
us.  If we were alchemists, we would define it as a humour, and lump
it in with bile and so on.

Crabcakes list of different levels of organization of bodliy parts is
of great relevance here:  tissues are groups of similar cells, organs
are groups of tissues that function together (but often have multiple
autonomous functions), and organ systems are groups of organs that
function together.  Blood is composed of many different components,
including cells from widely different origins and of widely varying
functions, as well as proteins, water, and inorganic molecules and
ions.  Certainly this is a substance much more complicated than what
one would generally regard as a tissue.

Blood's multiple functions make it also difficult to define as
something MORE than an organ: an organ system.  Generally speaking, an
organ system is something that is defined as such because we perceive
it to have an overall functional similarity between its parts.  There
are problems with this, of course.  The nervous system and the
endocrine system both have multiple functions, and in fact they
overlap on almost all of their functions.  Their structures are
likewise similar, and most (if not all) neurotransmitters are also
hormones (and vice versa).  It might make sense to define these as one
organ system: the neurendocrine system, as some have suggested.  But
current consensus is that they are more managable when considered as
separate systems.

Blood's functions overlap many organ systems.  Blood has immune
functions, for example (T cells, B cells, globulins, and so on).  It
has endocrine functions (in that it carries hormones from point A to
point B).  It has functions that are unique to it, as in the transport
of oxygen, carbon dioxide, and other nutrients and waste products.

It is probably best (as in most convenient) to consider blood an
organ, rather than a tissue (it is too complicated) or an organ system
(its functions are too diverse).  This categorization is the most
common one amongst medical scientists.  Blood transfusions are,
incidently, considered organ transplants, and the same considerations
are necessary when transplanting blood as other organs.  Skin is
heavier than blood, and thus, regardless of what blood is, skin is the
largest organ.

Subject: Re: Is Blood An Organ?
From: crabcakes-ga on 12 Sep 2005 12:53 PDT
Linezolid makes some good points, but a blood transfusion is not
considered an organ transplant. To transfuse blood, only group and
type is tested, along with antibody screening. For organ
transplantation, one need to match HLA and histocompatibility
antigens. Organ transplant patients must take anti-rejection drugs
such as FK506 and cyclosporine. Patients receiving blood transfusions
do not.
Subject: Re: Is Blood An Organ?
From: linezolid-ga on 12 Sep 2005 15:40 PDT
"HLA and histocompatibility antigens" are in fact one and the same
thing; they are found on all nucleated cells.  As red blood cells are
not nucleated, they do not have HLA antigens and testing for them is
irrelevant when transfusing RBCs.  White blood cells are nucleated,
and thus can provoke immune responses (which are generally clinically
insignificant --- this is only important in people who have or are
about to undergo bone marrow transplantation; in these cases, the RBCs
are irradiated to destroy any WBCs that may be present).

The process known as the "type and screen" is one that checks the
donor and receiver of blood for immune compatibility.  Assuming that
there is no mistake or rare antigen present, there is little or no
immune response against the donated blood.  Thus immunosupression with
drugs such as those mentioned by Crabcakes (as well as plain old
prednisone), is unnecessary.  If a transfusion reaction takes place
for any reason (mistake, rare antigen), then the transfusion is
stopped, and immunosupressive therapy (prednisone) is instituted, just
as would be done in the case of transplant rejection.

The issues involved with blood transfusion and organ transplantation
are one and the same.  To consider them different processes is to make
an artifical distinction.  Blood transfusion is the most common, and
generally speaking the safest form of organ transplantation.


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