Body Fluids and Water Movement

Body Fluids and Fluid Compartments

• The human body's internal environment is an aqueous solution.
• Water is the primary solvent, containing dissolved substances called solutes.
• Solutes include proteins, carbohydrates, and electrolytes.
• Electrolytes are minerals with a charge, such as sodium (Na+), chloride (Cl-), potassium (K+), and calcium (Ca++).

Water Movement in the Human Body

• Osmosis is the movement of water across membranes, driven by osmotic gradients.
• Water moves from areas of lower solute concentration (higher water concentration) to areas of higher solute concentration (lower water concentration).
• This balance of solutes and water inside and outside cells is crucial for proper function.
• Angiotensin II stimulates thirst and aldosterone increases sodium and water reabsorption by the kidneys to maintain this balance.

Dehydration

• Dehydration results from inadequate fluid intake or excessive fluid loss, possibly due to sweating, diarrhea, vomiting, or hemorrhage.
• It leads to reduced water for metabolic reactions, decreased blood pressure, and potential shock.
• Severe dehydration (>10% total body water loss) is a medical emergency, requiring rapid rehydration orally or intravenously.

Diuresis

• Diuresis is the production of high urinary volumes, usually occurring with excessive water intake.
• Diuretic medications increase urine output, decreasing blood volume and pressure, often used to treat hypertension and heart failure.
• Alcohol acts as a diuretic by inhibiting ADH release.

Diagnosing pH Imbalances

• Arterial blood gas (ABG) testing is used to diagnose pH imbalances.
• ABG provides pH, partial pressure of carbon dioxide (pCO2), and bicarbonate levels.
• pH determines acidosis or alkalosis.
• pCO2 indicates respiratory causes, while bicarbonate indicates metabolic causes.

Systemic Routes of Fluid Gain and Loss

• Kidney: A well-hydrated person excretes 1 to 2 L urine daily.
• Skin: Skin loss is approximately 300 mL daily, increased with respiratory rate, depth, or dry climates.
• Gastrointestinal Tract (GIT): Loss is about 100 to 200 mL daily, with most reabsorbed into the bloodstream. Diarrhea and intestinal fistulas can lead to significant fluid losses.

Tonicity

• Tonicity refers to the ability of solutes to create an osmotic force that drives water movement between compartments.
• It is often described in relation to sodium chloride (NaCl) content.
• Hypertonic solutions have a higher NaCl concentration, causing water to move from the ICF to ECF.
• Hypotonic solutions have a lower NaCl concentration, causing water to move from ECF to ICF.

Osmolality and Osmolarity

• Osmolality: The concentration of milliosmoles (measuring osmotic pressure) of solute per kilogram of solvent, expressed as mosm/kg.
• Osmolality can be increased by factors like dehydration or free water loss, and decreased by factors like fluid volume excess.

Sodium (Na+)

• Primary functions include maintaining fluid balance, nerve transmission, muscle contraction, and blood pressure regulation.
• Sodium is a major electrolyte, crucial for fluid balance.
• The Renin-Angiotensin-Aldosterone System (RAAS) regulates sodium levels.

Food Sources of Sodium

• Table Salt: The greatest source of sodium.
• Processed Meats: High in sodium due to preservatives and flavoring.
• Soy Sauce: Very salty.
• Pickled and Pickled Products: Contain significant amounts of brine.
• Seafood: Some types have higher sodium content.
• Barbecue Sauce: Can be high in sodium.
• Frozen Meals: Many are high in sodium.
• Processed Cheese: Generally higher in sodium than natural cheese.

Potassium (K+)

• Potassium acts as a counterpart to sodium.
• It is essential for nerve impulse transmission, muscle contraction, and maintaining heart rhythm.
• Potassium deficiency (hypokalemia) can lead to muscle weakness, spasms, tingling, numbness, arrhythmias, and other symptoms.
• Potassium excess (hyperkalemia) can cause muscle weakness, paralysis, and cardiac issues.

Syndromes Associated with Potassium Imbalance

• Cushing Syndrome: Can cause hypokalemia.
• Fanconi Syndrome: Can cause hypokalemia.
• Bartter Syndrome: Can cause hypokalemia.

Explore the complexities of body fluids, including the role of water as a solvent and the importance of solutes such as electrolytes. Learn about osmosis, fluid balance, and the physiological consequences of dehydration. This quiz will test your understanding of the human body's internal environment and its mechanisms.