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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

what are data colletion method in community diagnodis
loice Reply
50 prefix and surfix
Martha Reply
why arteries deeper than veins?!
Cismaan Reply
arteries colour of blood is deeper than that of vein because its blood contains oxygen which is adhered to haemoglobin(a protein which gives the blood its red color) , while vein contains deoxygenated blood(blood without oxygen)
As we know, vein carries used blood to the heart. when we say used blood, we mean to say, blood that its content(oxygen and other nutrients) has been used up.
Arteries are deeper b'cuz they need to be protected.......If they are ruptured they cannot form clot and repair themselves.... Moreover, the pressure of blood is too high for the artery to form the clot and repair itself....... Hence, Arteries are deeper than veins........
Than u all. Special thanks too AMEL JEELANI.
You're welcome......
Thanks all
describe the location of the macula densa and explain its role in the regulation of renin secretion and in tubuglomerular feedback
mwamba Reply
its located near the vascular pole of the glomurelus also regulate blood pressure and the filtration rate of glomurelus
what are the three methods of data collection used during a community diagnosis
Interviews. Questionnaires and Surveys. Observations.
Describe two early induced responses and what pathogens they affect
olivia Reply
what are pathogens
pathogens are disease-causing agents/organisms
pathogen are the causative of disease
thank you sister
What are organelles
The are little organs found in cells of living things... Eg gogi apparatus
what is anatomy
Linda Reply
is the study of the structures of the body and how they relates to each other
Anatomy is the study of the structures of body parts and how they relates to each other
is the study of the structure of the body and how they relates to each other
what are the difference between Pacinian corpuscle and cutaneous vascular plexus?
thivya Reply
what are membranous epithelial tissues
Naa Reply
they are the lining and covering epithelial tissues which cover body surfaces and line cavities... they're grouped into simple and stratified according to the number of layers and squamous, cuboidal and columnar according to their shape
what is an acina
acina is known to be the basic functional unit of the lungs .(singular:- acinus) this is where the alveoli(the gaseous exchange site) is found...
what happens to the unfertilized egg
the study of tissues is called
Scandy Reply
microscopic or histology anatomy
What specific types of biological macromolecules do living things require and why?
Marieland Reply
what is partial pressure?
Tariq Reply
it is the pressure exerted by mixture of gases...
What is the Important of studying anatomy and philosophy
Michael Reply
because to know the mechanisms of our body
to discover the regional structural of human body based on physically and also biochemically.
how many region do we have in human body
nsofor Reply
head thorax abdomen and many kind of...
what is principal ponatine nucleas
Human body can be divided into different regions on the basis of: 1. Systems: e.g. digestive system, respiratory system, excretory system etc.. 2. Parts: e.g. head, thorax, neck, upper limbs, lower limbs etc..
we have 9 region in d human body
what is systematic anatomy?
nsofor Reply
it is the anatomy or study of a certain body system for example the digestive system. or respiratory system.
It is a group of structure that work together to perform a unique function..

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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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