<< Chapter < Page Chapter >> Page >
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

explain respiratory centers
Tharshana Reply
which enzyme help in excretion of bile
Sakshi Reply
how conversion of Beta-carotiene into vitamin-A takes place
Sakshi
best reference books for anatomy pls suggest that
Sakshi
what is gross anatomy
Saroj Reply
The study of large structure of the body
Mablean
what is scrotum
Dakshit Reply
a bag of skin near the penis which contains the testicles
Mablean
hi
Sardar
its me Sardar from kpk pakistan
Sardar
Why are you on my digits
Mablean
hi
Kryme
how does it work?
Uriah Reply
I want to know the fertilization process in human
Nana Reply
Which plane divides the body into right and left parts
Kaeze
sagittal plane
Irvin
Thank you
Kaeze
Homestatic regulations usually involves a (n) _ that detects a particular stimulus, and a(n) _that respond to the stimulus by communicating with a (n) _whose activity has an effect on the same stimulus.
Kaeze
A cell is producing proteins to be transported out of that cell. They will be processed on ribosomes that are
Kaeze
what are diseases in the bood
Azoyenime Reply
Haemophilia
Aliyu
right hypochondriac rision how meain word
Ganesh Reply
Diabetes insipidus or diabetes mellitus would most likely be indicated by ________.
Ganesh
oral cavity how miean
Ganesh Reply
oral cavity how mean what
Suresh
seems to me every one is here a doctor and worse part is that even they donot know what to ask.
Muhammad
they know what to ask the problem is how to ask it.too much broken english.
George
dear George ongeche I think if they ask these kind questions and telling themselves as HCPs or medical student's .these are the basic ones go ask something more interesting .
Muhammad
what is blood red
Ahmad Reply
what is human anatomy?
Arpita Reply
tell me what is human anatomy?
Arpita
what is Openstax?
Arpita
arpita jana I think it's not the forum to ask such basic question...
Muhammad
study of structure of an object in this case human body.
Suresh
what are deferent between trasemicacid and vitamin k
Ubah Reply
This medication is used to treat heavy bleeding during your menstrual period. Tranexamic acid works by slowing the breakdown of blood clots, which helps to prevent prolonged bleeding. It belongs to a class of drugs known as antifibrinolytics
Muhammad
jj
John
In the body, vitamin K plays a major role in blood clotting. So it is used to reverse the effects of “blood thinning” medications when too much is given; to prevent clotting problems in newborns who don’t have enough vitamin K; and to treat bleeding caused by medications including salicylates, sulfo
Muhammad
Vitamin K plays a key role in helping the blood clot, preventing excessive bleeding. Unlike many other vitamins, vitamin K is not typically used as a dietary supplement. Vitamin K is actually a group of compounds. The most important of these compounds appears to be vitamin K1 and vitamin K2. Vitami
Muhammad
how much tha total vertebrea bone
Muhammad
26 vertebrea bone
Bhumi
wathe is blood function
dhena Reply
Blood, fluid that transports oxygen and nutrients to the cells and carries away carbon dioxide and other waste products. ... It is a tissue because it is a collection of similar specialized cells that serve particular functions. These cells are suspended in a liquid matrix (plasma), which makes the 
Ashiish
how tissue carries waste matrial
Nadeem
how many bone in human body?
Islam Reply
what is endocrin? plese help many people.
Islam
206
Nadeem
heart layers
Suresh
endoceime is the inner layer of heart
pandit
What is buffer?
Peer Reply
a buffer is a solution that resists a chemical change.
George
Yup it also balances the solutions
Peer

Get the best Anatomy & Physiology course in your pocket!





Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Anatomy & Physiology' conversation and receive update notifications?

Ask