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By the end of this section, you will be able to:
  • Explain the importance of water in the body
  • Contrast the composition of the intracellular fluid with that of the extracellular fluid
  • Explain the importance of protein channels in the movement of solutes
  • Identify the causes and symptoms of edema

The chemical reactions of life take place in aqueous solutions. The dissolved substances in a solution are called solutes. In the human body, solutes vary in different parts of the body, but may include proteins—including those that transport lipids, carbohydrates, and, very importantly, electrolytes. Often in medicine, a mineral dissociated from a salt that carries an electrical charge (an ion) is called and electrolyte. For instance, sodium ions (Na + ) and chloride ions (Cl - ) are often referred to as electrolytes.

In the body, water moves through semi-permeable membranes of cells and from one compartment of the body to another by a process called osmosis. Osmosis is basically the diffusion of water from regions of higher concentration to regions of lower concentration, along an osmotic gradient across a semi-permeable membrane. As a result, water will move into and out of cells and tissues, depending on the relative concentrations of the water and solutes found there. An appropriate balance of solutes inside and outside of cells must be maintained to ensure normal function.

Body water content

Human beings are mostly water, ranging from about 75 percent of body mass in infants to about 50–60 percent in adult men and women, to as low as 45 percent in old age. The percent of body water changes with development, because the proportions of the body given over to each organ and to muscles, fat, bone, and other tissues change from infancy to adulthood ( [link] ). Your brain and kidneys have the highest proportions of water, which composes 80–85 percent of their masses. In contrast, teeth have the lowest proportion of water, at 8–10 percent.

Water content of the body’s organs and tissues

This illustration shows a silhouette of a human body  with various organs highlighted. The percent of water contained in each organ is given. The brain typically contains 80% to 85% water, teeth contain 8% to 10% water, a single lung contains 75% to 80% water, the heart contains 75% to 80% water, the bones contain 20% to 25% water, the liver contains 70% to 75% water, the kidneys contain 80% to 85% water, the skin contains 70% to 75% water and the muscles also contain 70% to 75% water.
Water content varies in different body organs and tissues, from as little as 8 percent in the teeth to as much as 85 percent in the brain.

Fluid compartments

Body fluids can be discussed in terms of their specific fluid compartment    , a location that is largely separate from another compartment by some form of a physical barrier. The intracellular fluid (ICF)    compartment is the system that includes all fluid enclosed in cells by their plasma membranes. Extracellular fluid (ECF) surrounds all cells in the body. Extracellular fluid has two primary constituents: the fluid component of the blood (called plasma) and the interstitial fluid (IF)    that surrounds all cells not in the blood ( [link] ).

Fluid compartments in the human body

This diagram shows a small blood vessel surrounded by several body cells. The fluid between the body cells is the interstitial fluid (IF), which is a type of extracellular fluid (ECF). The fluid in the blood vessel is also an example of extracellular fluid. The fluid in the cytoplasm of each body cell is intracellular fluid, or ICF.
The intracellular fluid (ICF) is the fluid within cells. The interstitial fluid (IF) is part of the extracellular fluid (ECF) between the cells. Blood plasma is the second part of the ECF. Materials travel between cells and the plasma in capillaries through the IF.

Intracellular fluid

The ICF lies within cells and is the principal component of the cytosol/cytoplasm. The ICF makes up about 60 percent of the total water in the human body, and in an average-size adult male, the ICF accounts for about 25 liters (seven gallons) of fluid ( [link] ). This fluid volume tends to be very stable, because the amount of water in living cells is closely regulated. If the amount of water inside a cell falls to a value that is too low, the cytosol becomes too concentrated with solutes to carry on normal cellular activities; if too much water enters a cell, the cell may burst and be destroyed.

Questions & Answers

Hi Be Home Be safe , how are things doing hope all is well
Natarajan Reply
3 longitudinal bands of smooth muscles found in large intestines
Jamia
what's is sutures
Nimeshka Reply
what would I like to know
Roy Reply
anything u can tell me
Roy
anatomy mins
Manish
when two or more bones meet.
Joseph
Joints
Anita
I am interested in learning but it is a little threatening corona virus covid 19
Samnang Reply
I don't know about Corona virus
Vicky
what would you like to know?
Mbasa
what is a peripheral protien
Ayesha Reply
actually its located in between the lipid layer, it does not specify if it's closer to the inside or the outside of the cell
Justin
It is protein found in lipid bilayer but found attached with Cytoplasm aspect
Jamal
what are the collection of blood.?
sunshine Reply
Effect of exercise on different body systems?
Rania Reply
what is ambroylogy
kashif Reply
embryology..is the biological studing of embryos
Ava
I know biological study but embryology mean any pic, example?
kashif
https://upload.wikimedia.org/wikipedia/commons/b/b6/Comparative_embryology_of_the_vertebrates%3B_with_2057_drawings_and_photos._grouped_as_380_illus_%281953%29_%2820482505100%29.jpg
Ava
I like to learn about medical and more
Samnang
what is the function of the blood
Yolanda Reply
Transporting of oxygen,fighting against germs, forms clotting ,distribution of nutrients and minerals through out the body ,
Nimco
Transportation of gases such as oxygen and water blance and carrei metabolites to the exit organ and Acid base equilibrium and clotting blood and Immune
Jamal
What are Gross and microscopicAnatomy
Waiswa Reply
study of the internal structures of a human being
Niyi
gross anatomy is the study of body parts that can be seen with our naked eyes while micro anatomy involves the study of body parts that cannot be seen with our naked eyes but with the aid of a microscope
Oppong
gross means examination of specimen or tissue with bare (unaided ) eye while microscopic means examination of same with the help of microscope
Jamia
what is physiology
Waiswa Reply
what are blood pressure
Waiswa
physiology is the study of the normal functions of organs
Romaissaa
Blood pressure is a when systolic phase is 190 and diastolic phase 90.
Rahma
systolic phase is 180.not 190
Manish
explain the anatomy of the human heart
Maia Reply
is the scientific study of the body structure ie like structure very small which can be only observed.
Waiswa
where can I find the muscle organization
Taonga Reply
what is the physiology?
Josoph Reply
the study of functioning of body organs
Muskan
In other words... Physiology is the study of normal function within living creatures. It is a sub-section of biology, covering a range of topics that include organs, anatomy, cells, biological compounds, and how they all interact to make life possible.
Young
which part of the heart supply blood to all parts of the body
Waiswa
left heart supply all the body.
Rahma
what analysisof an anatomy
Waiswa
Okay thanks distinguish between blood pressure and body organs
Waiswa
branch of anatomy which deal with the life process and function
MT
how oxygen and carbondioxide are transported in the body.
riddon Reply
Through the lungs as we inhale oxygen it diffuses into the alveoli while carbon dioxide diffuses out of the blood and from our bodies
Angel
from lungs o2 diffuses into blood capillaries from where it is bound to heam part of hb there after it is transported to different parts of body ...co2 that is produced during respiration in cells gets transported to lungs from lungs it gets exhalated
Jamia
o2 is mainly transported by hb present in blood while co2 is transported main as bicarbonate.. detailed topics
Malik

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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