Thank you for your most interesting question. My findings (and some
previous knowledge on this topic) confirm that plasma/lymph and
seawater are almost identical, in terms of ionic composition, yet
differ slightly in osmotic pressure. Also, plasma contains proteins
and organic substances not found in sea water. Here are the sources
that support these findings :
ChemLab - Chemistry 3-5 - Analysis of Seawater - Introduction
It is generally believed that life evolved in the oceans, and living
organisms reflect this aquatic past both by a high overall water
content (50% for trees, 65% for people, 99.7% for jelly fish) and by
an elaborate biochemistry established in salt solutions. These
solutions contain the same ions that were brought from the seas by the
first amphibians. Thus, perhaps it is not surprising that there is a
striking resemblance between the ionic composition of seawater and
that of human blood plasma, one of the solvent systems for human
"Human blood plasma has an osmotic pressure of about 290 mOsm and
water from the open ocean has an osmotic pressure of about 1010 mOsm.
This indicates that there is much more salt in sea water than in human
blood plasma and also that there is less pure water in a liter of sea
water than in a liter of plasma."
Blood - The River of Life
"Plasma is a pale yellowish fluid with a total volume of 2-3 liters in
a normal adult.
Its contents are :
Inorganic Ions 0.9%
Organic Substances 1.1% "
Spa Massage Alliance - Portal
"French scientist René Quinton devoted much of his life's work to the
study of seawater and in 1906 published L'eau de Mer, Milieu Organic
("Sea Water, Organic Medium"), which demonstrated the chemical
similarity between blood plasma and seawater. Quinton's colleague
Claude Bernard discovered that the body is comprised of 70 percent
water. Working from Bernard's findings regarding the makeup of blood,
intracellular fluid and lymphatic fluid in the body, Quinton stated in
1897 that the human system is analogous to the systems found among
marine life: "In the internal environment of our system, and only
there we find the same mineral make-up, the same physiognomy, as that
of sea water [sic]." "
"From this notion that seawater is a complete mineral source came
multiple ideas of the healing powers of seawater. Quinton's study
indicated that seawater and human plasma are almost identical in their
composition of mineral salts, proteins and various other elements.
Quinton also established that human cells could continue to live in
seawater, while they break down and disintegrate almost instantly in
any other medium."
As to the second part of your question, you are correct in that there
is no difference between Plasma, Lymph and the Interstitial fluids,
other than where these fluids can be found. Here is the information :
Classification of body fluids :
- body fluids
2.a. blood (plasma)
2.b. interstitial fluids
2.b.i. occupies spaces between cells
2.b.ii. moves in lymph vessels as lymph
HordeNet at The University of Akron
"Comparison of Body Fluids. The fluids of the body are located inside
tissue cells (intracellular fluid) or outside tissue cells
(extracellular fluid). Volumetrically, most of the extracellular
fluids are of two types: blood and interstitial fluid. The latter is
the fluid that occupies spaces between cells and moves in the lymph
vessel. Other extracellular body fluids that occur in smaller amounts
are urine, digestive juices, and cerebrospinal fluid. Chemically,
blood (plasma) and interstitial fluid (including lymph) are similar.
intracellular fluid is chemically different from the extracellular
==== OTHER INFORMATION ====
Detailed composition of seawater
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Hope that answers your question. Have a good day!