Comprehensive Study Notes: Respiratory, Urinary, and Fluid/Electrolyte Systems

Chapter 22: The Respiratory System

Overview of the Respiratory System

The respiratory system supplies the body with oxygen and removes carbon dioxide. It is divided into the upper and lower respiratory tracts, each with specialized structures and functions.

• Upper Respiratory System: Includes the nasal cavity, paranasal sinuses, and pharynx.

• Lower Respiratory System: Includes the larynx, trachea, bronchi, and lungs.

The Upper Respiratory System

• Nasal Cavity: Produces mucus, filters, warms, and moistens incoming air.

• Paranasal Sinuses: Lighten the skull and help warm, moisten, and filter air.

• Pharynx: Passageway for air and food, connects nasal cavity to larynx and oral cavity to esophagus, houses tonsils (lymphoid tissue).

The Lower Respiratory System

• Larynx (Voice Box): Houses vocal cords, connects pharynx to trachea, functions as an air passageway and prevents food from entering the lower respiratory tract.

• Trachea: Air passageway that cleans, warms, and moistens incoming air.

• Lungs: House smaller respiratory passages and alveoli, the main sites of gas exchange.

• Bronchial Tree: Branching airways connecting trachea with alveoli, cleans, warms, and moistens air.

• Alveoli: Main sites of gas exchange, lined with pulmonary capillaries. Three cell types: Type I (structure), Type II (produce surfactant), and alveolar macrophages (defense).

Lung Structure and Lobes

• Right Lung: Superior, middle, and inferior lobes; horizontal and oblique fissures.

• Left Lung: Superior and inferior lobes; oblique fissure and cardiac notch.

Breathing and Respiration

Breathing (ventilation) is the process of moving air into and out of the lungs, divided into inspiration and expiration. Respiration refers to the chemical process of using oxygen to produce energy (ATP).

• Inspiration: Air flows into the lungs as lung volume increases and pressure decreases.

• Expiration: Air flows out as lung volume decreases and pressure increases.

Respiratory Pressures and Boyle’s Law

• Atmospheric Pressure (Patm): Pressure exerted by air around the body (760 mmHg at sea level).

• Intrapulmonary Pressure (Ppul): Pressure in alveoli, fluctuates with breathing.

• Intrapleural Pressure (Pip): Pressure in pleural cavity, normally 4 mmHg less than Ppul.

• Transpulmonary Pressure: Difference between Ppul and Pip.

Boyle’s Law: The pressure of a gas varies inversely with its volume: $P_1V_1 = P_2V_2$

Factors Influencing Pulmonary Ventilation

• Airway Resistance: Greater resistance lowers airflow, especially in the conducting zone.

• Alveolar Surface Tension: Surfactant reduces surface tension, preventing alveolar collapse.

• Lung Compliance: Measure of lung expandability; higher compliance means easier expansion.

Respiratory Volumes and Capacities

• Tidal Volume (TV): Air inhaled/exhaled at rest (~500 mL).

• Inspiratory Reserve Volume (IRV): Extra air inhaled after normal inspiration (1900–3100 mL).

• Expiratory Reserve Volume (ERV): Extra air exhaled after normal expiration (700–1200 mL).

• Residual Volume (RV): Air remaining after forced expiration (~1200 mL).

Capacities are combinations of volumes:

• Total Lung Capacity (TLC): $TLC = RV + ERV + TV + IRV$ (~6000 mL)

• Vital Capacity (VC): $VC = TV + IRV + ERV$ (~4800 mL)

• Inspiratory Capacity (IC): $IC = TV + IRV$ (~3600 mL)

• Functional Residual Capacity (FRC): $FRC = ERV + RV$

Gas Exchange and Transport

• External Respiration: O2 diffuses from alveoli to blood; CO2 diffuses from blood to alveoli.

• Internal Respiration: O2 diffuses from blood to tissues; CO2 diffuses from tissues to blood.

• Dalton’s Law: Total pressure of a mixture of gases equals the sum of the partial pressures of each gas.

• Henry’s Law: The amount of gas dissolved in a liquid is proportional to its partial pressure.

	Atmosphere	Alveolar air	Deoxy blood	Oxy blood	Tissue cells
PO2	160	105	40	105	40
PCO2	0.03	40	45	40	45
PN2	597	597	597	597	597

Oxygen and Carbon Dioxide Transport

• Oxygen Transport: 98.5% bound to hemoglobin (Hb), 1.5% dissolved in plasma.

• Hemoglobin: Each molecule binds up to 4 O2 molecules; binding is cooperative (sigmoidal curve).

• Factors Affecting O2 Binding: PO2, temperature, pH, PCO2, and 2,3-BPG.

• Carbon Dioxide Transport: 7–10% dissolved in plasma, ~20% bound to Hb (carbaminohemoglobin), ~70% as bicarbonate ions (HCO3-).

• Bohr Effect: Lower pH (higher H+) decreases Hb affinity for O2.

• Haldane Effect: Deoxygenated Hb binds CO2 more readily.

Buffering and Acid-Base Balance

• Carbonic Acid/Bicarbonate Buffer System: Maintains blood pH near 7.4.

• Equation: $CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons H^+ + HCO_3^-$

• Respiratory Acidosis: Caused by hypoventilation (CO2 retention).

• Respiratory Alkalosis: Caused by hyperventilation (CO2 loss).

Chapter 25: The Urinary System

Kidney Anatomy

• Renal Capsule: Outer covering, protection.

• Cortex: Outer region, contains renal corpuscles and tubules.

• Medulla: Inner region, contains renal pyramids, loops of Henle, and collecting ducts.

• Renal Pelvis: Central collecting region, channels urine to ureter.

Nephron Structure and Function

• Nephron: Functional unit of the kidney, filters blood, reabsorbs needed substances, secretes wastes, regulates fluid/electrolyte balance.

• Renal Corpuscle: Glomerulus (capillary network) + Bowman’s capsule (filtration site).

• Renal Tubule: Proximal convoluted tubule (PCT), loop of Henle, distal convoluted tubule (DCT), collecting duct.

Urine Formation

1. Glomerular Filtration: Plasma filtered from glomerulus into Bowman’s capsule.

2. Tubular Reabsorption: Water, ions, and nutrients reabsorbed from tubules into blood.

3. Tubular Secretion: Additional wastes and ions secreted from blood into tubules.

Regulation of Glomerular Filtration Rate (GFR)

• Autoregulation: Myogenic mechanism and tubuloglomerular feedback (macula densa, JG cells).

• Neuronal Control: Sympathetic nervous system constricts afferent arterioles, reducing GFR.

• Hormonal Control: Renin-angiotensin-aldosterone system (RAAS), ADH, ANP.

Countercurrent Mechanisms

• Countercurrent Multiplier: Loop of Henle creates medullary osmotic gradient for water reabsorption.

• Countercurrent Exchange: Vasa recta preserves medullary gradient.

Hormonal Regulation

• Aldosterone: Increases Na+ reabsorption (and water), increases blood pressure.

• ADH: Increases water reabsorption in collecting duct, concentrates urine.

• ANP: Inhibits Na+ and water reabsorption, lowers blood pressure.

Acid-Base Regulation in the Kidney

• Type A Intercalated Cells: Secrete H+, reabsorb HCO3- (active in acidosis).

• Type B Intercalated Cells: Secrete HCO3-, reabsorb H+ (active in alkalosis).

Chapter 26: Fluid, Electrolyte, and Acid-Base Balance

Fluid and Electrolyte Balance

• Water Intake and Output: Intake must equal output to maintain homeostasis. Regulated by thirst (hypothalamus) and ADH.

• Electrolyte Balance: Mainly Na+ and K+. Aldosterone increases Na+ reabsorption and K+ secretion; ANP opposes these effects.

Acid-Base Balance

• Normal Blood pH: 7.35–7.45. Acidosis: pH < 7.35; Alkalosis: pH > 7.45.

• Regulation Mechanisms: Chemical buffers (bicarbonate system), respiratory system (CO2 exhalation), renal system (H+ secretion, HCO3- reabsorption).

Key Equations:

• Bicarbonate Buffer: $CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons H^+ + HCO_3^-$

• Boyle’s Law: $P_1V_1 = P_2V_2$

Acid-Base Disorders

• Respiratory Acidosis: Hypoventilation, CO2 retention, low pH.

• Respiratory Alkalosis: Hyperventilation, CO2 loss, high pH.

• Metabolic Acidosis: Loss of HCO3- or acid accumulation, low pH.

• Metabolic Alkalosis: Excess HCO3- or acid loss, high pH.

Compensation: If one system fails, the other compensates (lungs or kidneys) to restore pH balance.