Chemical composition of the body BODY FLUID BODY

Chemical composition of the body

BODY FLUID BODY- FLUID COMPARTMENTS Water is by far the major component of the fluids in the body. Water accounts for about 60% of normal body weight

Total body water (TBW) Volume = 42 L 60% body weight EXTRACELLULAR FLUID (ECF) (Internal Environment) Volume =14 L 1/3 TBW INTRACELLULAR FLUID VOLUME= 28 L 2/3 TBW INTERSTITAL FLUID VOLUME = 11 L 80% OF ECF PLASMA VOLUME = 3 L 20% OF ECF

The body fluids are enclosed in compartments. 1. Extracellular fluid exists in two location a. Intercellular fluid (interstitial fluid) Approximately 80% of the extracellular fluid surrounds all the body's cells exept the blood cells. It lies between`cells. b. Plasma It is the fluid protein of the blood, in which the various blood cells are suspended. 20% of extracellular fluid is plasma.

2. Intracellular fluid All the fluid inside a cell – in other words, cytosol plus the fluid inside all the organelles, including the nucleus.

Two-thirds of the body water is intracellular. There is continuous exchanges between plasma and interstitial fluid, concentrations of dissolved substances are virtually identical in the two fluids, except for protein concentration. With this major exception – higher protein concentration in plasma than in interstitial fluid – the entire extracellular fluid may be considered to have a homogeneous composition.

In contrast, the composition of the extracellular fluid is very different from that in the intracellular fluid, the fluid inside the cells. The differing composition of the compartments reflect the activities of the barriers separating them. The fluid in the body are enclosed in compartments The volumes of the body – fluid compartments are summarized in figure in terms of water.

�Atoms The units of matter that form all chemical substances are called atoms. the smallest atom, is hydrogen. Each type of atom - carbon , oxygen , hydrogen , and so on – is called chemical element. A one – or two letter symbol is used as a shorthand identification for each element. Although slightly more than 100 elements exist in the universe , only 24 are known to be essential for the structure and function of the human body.

Essential elements in the body symblo element Major elements: 99. 3% of total atoms H(63%) Hydrogen O(26%) Oxygen C(9%) Carbon N(1%) Nitrogen Mineral elements: 0. 7% of total atoms Ca Calcium P Phosphorus K (Latin kalium) Potassium S Sulfur Na Sodium Cl Chlorine Mg magnesium

Trace elements : less than 0. 01% of total atoms Fe (latin ferrum) I Cu (latin cuproum) Z Mn Co Cr Se Mo F Sn Si v Iron Iodine Copper Zinc Manganese Cobalt Chromium Selenium Molybdenum Fluorine Tin Silicon vanadium

Atoms are composed of three subatomic particles : Positive protons and neutral neutrons , both located in the nucleus , and negative electrons revolving around the nucleus. �The atomic number the number is the number of protons in an atom, and because atoms electrically neutral , it is also equal to the number of electrons.

�The atomic weight of an atom is the ratio of the atom's mass relative to that of a carbon – 12 atom. for example a hydrogen atom has an atomic weight of 1 indicating that it has one – twelfth the mass of a carbon atom. �molecules are formed by linking atoms together. The molecular weight of a molecule is the sum of the atomic weight of all its atoms. When an atom gains or loses one or more electrons, it acquires a net electric charge and becomes an ion.

�Substances dissolved in a liquid are solutes, and the liquid in which they are dissolved is the solvent. Water is the most abundant solvent in the body. �Substances that release a hydrogen ion in solution are called acids.

�Those that accept a hydrogen ion are bases. The acidity of a solution is determined by its free hydrogen – ion concentration, the greater the acidity.

�The PH of solution is the negative logarithm of the hydrogen – ion concentration. As the acidity of a solution increases, the PH decreases. Acid solutions have a PH less than 7. 0 whereas alkaline solutions have a PH greater than 7. 0.

�Carbohydrates are composed of carbon , hydrogen , and oxygen in the proportion Cn(H 2 O)n. Carbohydrates are soluble in water. The most abundant monosaccharide in the body is glucose (C 6 H 12 O 6) , which is stored in cells in the form of polysaccharide glycogen.

�Lipids are insoluble in water. They could be: Triacylglycerol , Phospholipids , or Steroids. �Proteins, macromolecules composed primarily of carbon, hydrogen, and nitrogen , are polymers of different amino acids.