Body Fluids

Body Fluids

1. Fluid Classification:

The human body is composed of fluids, mainly intracellular fluid and extracellular fluid.

• Intracellular Fluid (ICF): Located inside cells, accounting for approximately 2/3 of the total body fluid volume. Intracellular fluid is separated from extracellular fluid by the cell membrane.

• Extracellular Fluid (ECF): Located outside cells, accounting for approximately 1/3 of the total body fluid volume. It includes:

• Plasma: The liquid component of blood, light yellow in color, accounting for about 5% of body weight. Plasma has a composition similar to interstitial fluid but contains more protein (three times higher). Important proteins in plasma include albumin, alpha 1,2, beta 1,2, and fibrinogen.

• Interstitial Fluid: Fluid located in the spaces between cells, accounting for about 15% of body weight.

• Lymph: Interstitial fluid flowing into the lymphatic system.

2. Composition and Functions of Extracellular Fluids:

• Plasma:

• Contains plasma proteins with functions:

• Create colloid osmotic pressure to retain water in blood vessels.

• Regulate acid-base balance.

• Serve as a reservoir of amino acids for cells.

• Participate in blood clotting.

• Participate in body defense.

• Act as carriers.

• Lymph:

• Contains an average protein concentration of 2g%.

• Contains many lymphocytes.

• Functions:

• Collect waste products from cells.

• Transport fat from the small intestine to the liver.

• Participate in immunity.

3. Exchange of Substances Between Extracellular Fluid and Cells:

The exchange of substances between extracellular fluid and cells depends on several factors:

• Colloid Osmotic Pressure of Plasma: Normally around 28mmHg, it pulls water and solutes from interstitial fluid into the bloodstream.

• Capillary Pressure (Blood Pressure): Normally around 30mmHg at the beginning of the arterioles and 10mmHg at the end of the venules, it pushes water and solutes in plasma out of the blood vessels into the interstitial fluid.

• Interstitial Fluid Pressure: Varies depending on body position, can be positive or negative.

• Positive pressure pushes water and solutes from the interstitial fluid into the blood vessels.

• Negative pressure pushes water and solutes from the blood vessels into the interstitial fluid.

• Colloid Osmotic Pressure of Interstitial Fluid: Normally around 8mmHg, it pulls water from capillaries into the interstitial space.

4. Lymph Flow:

Normal lymph flow in a resting person is 120ml/hour. Factors affecting lymph flow:

• Interstitial Fluid Pressure: Increased interstitial fluid pressure increases lymph flow.

• Lymph Pumps: Lymphatic capillaries have the ability to contract due to myosin and actin in the endothelial cells of the lymphatic vessels.

5. Cerebrospinal Fluid:

• Fluid contained in the cavities of the brain and spinal cord.

• Colorless, specific gravity 1005, almost no protein, cells, has a Na+ concentration similar to plasma, Cl- ions are 15% higher, K+ ions are 40% lower, and glucose is 30% lower.

• Normal cerebrospinal fluid pressure:

• Lying down: 100-200mmH2O.

• Sitting: 200mmH2O.

• Functions:

• Cushions brain tissue.

• Adapts to changes in skull volume.

• Exchanges nutrients for the nervous system.

6. Blood-Cerebrospinal Fluid and Blood-Brain Barriers:

• Separates blood from cerebrospinal fluid, blood from brain fluid.

• Highly permeable to water, CO2, O2, and lipid-soluble substances, anesthetics.

• Less permeable to Na+, Cl- ions, impermeable to proteins and other organic substances.

7. Intraocular Fluid:

• Fluid located in the eye socket, has a certain pressure to maintain the rigidity of the eyeball.

• Secreted by the ciliary body.

• Normal intraocular pressure: 15mmHg.

• Intraocular pressure in glaucoma: 60-70mmHg.

8. Role of Water in Body Fluids:

• Water is the most important component of body fluids, accounting for 45-75% of body weight.

• Water percentage is lower in obese individuals and women compared to men.

9. Notes:

• The lymphatic system is one of the important pathways for absorbing nutrients, especially fat.

• Red blood cells are not present in interstitial fluid.

Note: This information is compiled from the provided content. More information may be needed to create a more complete article.