Fluid/Electrolyte/Acid-Base Balance

Introduction

This study guide covers essential topics in fluid, electrolyte, and acid-base balance, focusing on the respiratory and urinary systems. Understanding these concepts is crucial for maintaining homeostasis in the human body.

The Respiratory System

Functions and Processes of the Respiratory System

• Primary Functions: The respiratory system is responsible for gas exchange, supplying oxygen to the blood and removing carbon dioxide.

• Processes: Pulmonary ventilation (movement of air into and out of the lungs), external respiration (gas exchange between lungs and blood), transport (movement of gases in the blood), and internal respiration (gas exchange between blood and tissues).

• Major Organs: Includes the nose, pharynx, larynx, trachea, bronchi, lungs, and alveoli.

Structures and Functions

• Conducting vs. Respiratory Zone: The conducting zone (nose, pharynx, larynx, trachea, bronchi) transports air; the respiratory zone (respiratory bronchioles, alveolar ducts, alveoli) is where gas exchange occurs.

• Nasal Cavity: Warms, moistens, and filters incoming air.

• Pharynx: Passageway for air and food; aids in vocalization.

• Larynx: Contains vocal cords; involved in sound production.

• Trachea: Windpipe; conducts air to the bronchi.

• Bronchial Tree: Branching system of airways leading to alveoli.

• Alveoli: Site of gas exchange; surrounded by capillaries.

Mechanics of Breathing

• Inspiration and Expiration: Driven by changes in thoracic volume and pressure.

• Boyle's Law: (Pressure and volume are inversely related).

• Intrapulmonary vs. Intrapleural Pressure: Intrapulmonary pressure is within the alveoli; intrapleural pressure is within the pleural cavity and is always lower than atmospheric pressure.

• Airway Resistance, Alveolar Surface Tension, Lung Compliance: Affect the ease of breathing and airflow.

Gas Exchange and Transport

• External Respiration: Exchange of gases between alveoli and blood.

• Internal Respiration: Exchange of gases between blood and tissues.

• Oxygen Transport: Mostly bound to hemoglobin; small amount dissolved in plasma.

• Carbon Dioxide Transport: Dissolved in plasma, bound to hemoglobin, or as bicarbonate ions ().

Control and Regulation

• Brainstem Centers: Medulla and pons regulate respiratory rate and depth.

• Homeostatic Imbalances: Disorders such as hypoxia, hypercapnia, and respiratory acidosis/alkalosis.

The Urinary System

Functions and Importance

• Primary Functions: Removal of metabolic wastes, regulation of blood volume and pressure, electrolyte balance, and acid-base balance.

• Major Organs: Kidneys, ureters, bladder, and urethra.

Kidney Structure and Function

• Nephron: Functional unit of the kidney; responsible for filtration, reabsorption, and secretion.

• Renal Corpuscle: Includes glomerulus and Bowman's capsule; site of filtration.

• Renal Tubules: Proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct.

• Juxtaglomerular Complex (JGA): Regulates blood pressure and filtration rate.

Mechanisms of Urine Formation

• Filtration: Movement of water and solutes from blood into Bowman's capsule.

• Reabsorption: Return of water and solutes from filtrate to blood.

• Secretion: Addition of substances from blood to filtrate.

• Countercurrent Mechanism: Maintains concentration gradient in the medulla for water reabsorption.

Regulation and Homeostasis

• ADH (Antidiuretic Hormone): Increases water reabsorption in the collecting ducts.

• Renin-Angiotensin-Aldosterone System: Regulates blood pressure and sodium balance.

• Acid-Base Balance: Kidneys excrete hydrogen ions and reabsorb bicarbonate to maintain pH.

• Homeostatic Imbalances: Disorders such as dehydration, renal failure, and acid-base disturbances.

Fluid, Electrolyte, and Acid-Base Balance

Fluid Compartments and Movement

• Fluid Compartments: Intracellular fluid (ICF) and extracellular fluid (ECF, including interstitial fluid and plasma).

• Water and Electrolyte Content: ICF is high in potassium and phosphate; ECF is high in sodium and chloride.

• Osmotic and Hydrostatic Pressure: Drive movement of water between compartments.

Electrolytes and Non-Electrolytes

• Electrolytes: Substances that dissociate into ions in solution (e.g., sodium, potassium, calcium).

• Non-Electrolytes: Do not dissociate into ions (e.g., glucose, urea).

Regulation of Fluid and Electrolyte Balance

• Intake and Output: Water intake from food, drink, and metabolism; output via urine, feces, sweat, and respiration.

• ADH and Renin-Angiotensin-Aldosterone: Hormonal control of water and sodium balance.

• Key Electrolytes: Sodium, potassium, calcium, and chloride are tightly regulated.

Acid-Base Balance

• Buffer Systems: Bicarbonate, phosphate, and protein buffers help maintain pH.

• Respiratory Regulation: Lungs remove CO2 to adjust pH.

• Renal Regulation: Kidneys excrete H+ and reabsorb HCO3-.

• Normal Blood pH: 7.35–7.45.

Common Homeostatic Imbalances

• Dehydration: Loss of water exceeds intake.

• Edema: Excess fluid in tissues.

• Acidosis/Alkalosis: pH imbalance due to respiratory or metabolic causes.

Comparison of Fluid Compartments

Key Equations

• Boyle's Law:

• Bicarbonate Buffer Equation:

Additional info: Academic context and definitions have been expanded for clarity and completeness.