Anatomy & Physiology II: Study Guide for the Respiratory System, Urinary System, and Fluid, Electrolyte, and Acid-Base Balance

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Chapter 22: The Respiratory System

Overview of the Respiratory System

The respiratory system is responsible for gas exchange, supplying oxygen to the blood and removing carbon dioxide. It works closely with the circulatory system to maintain homeostasis.

Functions: Gas exchange, olfaction, sound production, and regulation of blood pH.
Relationship with Circulatory System: Oxygen is transported from the lungs to tissues, and carbon dioxide is carried from tissues to the lungs for exhalation.

Processes of Respiration

Pulmonary Ventilation: Movement of air into and out of the lungs (breathing).
External Respiration: Gas exchange between alveoli and blood.
Transport of Respiratory Gases: Movement of O2 and CO2 in the blood.
Internal Respiration: Gas exchange between blood and tissues.

Each process involves both the respiratory and circulatory systems.

Anatomy of the Respiratory System

Upper Respiratory Tract: Nose, nasal cavity, pharynx (nasopharynx, oropharynx, laryngopharynx).
Lower Respiratory Tract: Larynx, trachea, bronchi, bronchioles, alveoli.
Conducting Zone: Passages that carry air to the respiratory zone (nose to terminal bronchioles).
Respiratory Zone: Sites of gas exchange (respiratory bronchioles, alveolar ducts, alveoli).

Airflow Pathway

Nasal cavity → pharynx → larynx → trachea → bronchi → bronchioles → terminal bronchioles → respiratory bronchioles → alveolar ducts → alveolar sacs → alveoli

Histology and Structural Changes

Olfactory Mucosa: Contains olfactory epithelium for smell.
Respiratory Mucosa: Pseudostratified ciliated columnar epithelium with goblet cells; lines most of the respiratory tract.
Epithelium Changes: Becomes thinner and less ciliated as airways branch; cartilage decreases, smooth muscle increases.
Alveoli: Lined by simple squamous epithelium (type I cells) and cuboidal type II cells (produce surfactant).

Alveolar Structure and Function

Type I Alveolar Cells: Form the respiratory membrane for gas exchange.
Type II Alveolar Cells: Secrete surfactant to reduce surface tension.
Alveolar Macrophages: Remove debris and pathogens.
Alveolar Pores: Equalize air pressure between alveoli.

Pleura and Lung Mechanics

Visceral Pleura: Covers the lungs.
Parietal Pleura: Lines the thoracic cavity.
Pleural Cavity: Contains fluid to reduce friction and assist lung expansion/recoil.

Pressure Relationships and Ventilation

Atmospheric Pressure (Patm): Pressure of air outside the body.
Intrapulmonary Pressure (Ppul): Pressure within alveoli; fluctuates with breathing.
Intrapleural Pressure (Pip): Pressure within pleural cavity; always negative relative to Ppul.
Transpulmonary Pressure: Difference between Ppul and Pip; keeps lungs inflated.
Boyle’s Law: (Pressure and volume are inversely related in a closed system.)

Muscles of Breathing

Inspiration: Diaphragm and external intercostal muscles contract.
Forced Inspiration: Accessory muscles (scalenes, sternocleidomastoid) assist.
Expiration: Normally passive; forced expiration uses internal intercostals and abdominal muscles.

Factors Affecting Pulmonary Ventilation

Airway Resistance: Inverse relationship with airflow; greatest in medium-sized bronchi.
Alveolar Surface Tension: Reduced by surfactant; prevents alveolar collapse.
Lung Compliance: Ease of lung expansion; decreased by fibrosis, low surfactant, or reduced thoracic flexibility.

Lung Volumes and Capacities

Volume/Capacity	Definition
Tidal Volume (TV)	Air inhaled/exhaled in one breath (~500 mL)
Inspiratory Reserve Volume (IRV)	Extra air inhaled after normal inspiration
Expiratory Reserve Volume (ERV)	Extra air exhaled after normal expiration
Residual Volume (RV)	Air remaining after maximal exhalation
Vital Capacity (VC)	TV + IRV + ERV
Total Lung Capacity (TLC)	VC + RV

Gas Laws and Gas Exchange

Dalton’s Law: Total pressure of a gas mixture equals the sum of partial pressures of each gas.
Henry’s Law: Amount of gas dissolved in a liquid is proportional to its partial pressure and solubility.
CO2 is more soluble in plasma than O2.

External and Internal Respiration

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.
Ventilation-Perfusion Coupling: Blood flow and airflow are matched for efficient gas exchange.

Transport of Gases in Blood

Oxygen: 98.5% bound to hemoglobin, 1.5% dissolved in plasma.
Hemoglobin Saturation Influences: Partial pressure of O2, temperature, pH, PCO2, BPG.
Bohr Effect: Increased CO2 or decreased pH reduces hemoglobin’s O2 affinity.
Carbon Dioxide: Transported as bicarbonate (70%), bound to hemoglobin (23%), dissolved in plasma (7%).
Chloride Shift: Exchange of Cl- and HCO3- across RBC membrane to maintain charge balance.
Haldane Effect: Deoxygenated blood can carry more CO2.

Control of Respiration

Medullary Centers: Ventral and dorsal respiratory groups control rhythm and integration.
Pontine Centers: Modify and fine-tune breathing patterns.
Chemical Factors: CO2 is the most potent regulator; sensed by central and peripheral chemoreceptors.
Hering-Breuer Reflex: Inflation reflex prevents over-inflation of lungs.

Chapter 25: The Urinary System

Functions and Anatomy of the Urinary System

Functions: Removal of metabolic wastes, regulation of blood volume and pressure, electrolyte and acid-base balance, hormone production.
Organs: Kidneys, ureters, urinary bladder, urethra.
Kidney Location: Retroperitoneal (behind the peritoneum), surrounded by renal fascia, adipose capsule, and renal capsule.

Internal Structure of the Kidney

Three Regions: Cortex (outer), medulla (pyramids), pelvis (collects urine).
Urine Flow: Nephron → collecting duct → minor calyx → major calyx → renal pelvis → ureter.

Nephron Structure and Function

Nephron: Functional unit of the kidney; filters blood and forms urine.
Renal Corpuscle: Glomerulus (capillary tuft) + glomerular (Bowman’s) capsule.
Filtrate: Fluid filtered from blood; becomes urine after leaving collecting ducts.
Collecting Ducts: Principal cells (water/salt balance), intercalated cells (acid-base balance).

Nephron Capillary Beds

Glomerulus: Filtration; high pressure due to afferent arteriole being wider than efferent.
Peritubular Capillaries: Reabsorption and secretion around cortical nephrons.
Vasa Recta: Concentration of urine in juxtamedullary nephrons.

Juxtaglomerular Complex

Components: Macula densa (sense NaCl), granular cells (release renin), extraglomerular mesangial cells (communication).
Function: Regulates blood pressure and filtration rate.

Urine Formation Processes

Glomerular Filtration: Non-selective, passive process; occurs in renal corpuscle.
Tubular Reabsorption: Selective; returns substances to blood (mostly in proximal tubule).
Tubular Secretion: Selective; removes substances from blood to tubule (mainly in distal tubule and collecting duct).

Filtration Membrane and Pressures

Filtration Membrane: Fenestrated endothelium, basement membrane, podocyte foot processes.
Allows: Water, glucose, amino acids, nitrogenous wastes; blocks cells and large proteins.
Net Filtration Pressure (NFP): Where HP_g = glomerular hydrostatic pressure, OP_g = glomerular osmotic pressure, HP_c = capsular hydrostatic pressure.

Glomerular Filtration Rate (GFR) Regulation

Intrinsic Controls: Renal autoregulation (myogenic mechanism, tubuloglomerular feedback).
Extrinsic Controls: Neural (sympathetic) and hormonal (renin-angiotensin-aldosterone system).

Hormonal Regulation

ADH: Increases water reabsorption in collecting ducts.
Aldosterone: Increases Na+ reabsorption in distal tubule and collecting duct.
ANP: Inhibits Na+ reabsorption, lowers blood pressure.
Parathyroid Hormone: Increases Ca2+ reabsorption.

Countercurrent Mechanisms

Countercurrent Multiplier: Loop of Henle; creates medullary osmotic gradient.
Countercurrent Exchanger: Vasa recta; preserves gradient.
Urea Recycling: Contributes to medullary gradient.

Urine Transport, Storage, and Elimination

Ureters: Move urine via peristalsis.
Urinary Bladder: Detrusor muscle contracts for urination.
Sphincters: Internal (involuntary), external (voluntary).
Micturition: Requires relaxation of sphincters and contraction of detrusor muscle.

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

Body Fluid Compartments

Solvent: Water; Solute: Dissolved substances (electrolytes, nonelectrolytes).
Two Main Compartments: Intracellular fluid (ICF, ~2/3), extracellular fluid (ECF, ~1/3; includes plasma and interstitial fluid).

Electrolytes vs. Nonelectrolytes

Electrolytes: Dissociate into ions in water; greater osmotic power (e.g., Na+, K+, Cl-).
Nonelectrolytes: Do not dissociate (e.g., glucose, urea).

Major Electrolytes

Compartment	Cations	Anions
ECF	Na+	Cl-, HCO3-
ICF	K+, Mg2+	HPO42-, proteins

Water Movement and Balance

Osmosis: Water moves along osmotic gradients; increased osmolality draws water in, decreased osmolality causes water to leave.
Fluid Exchange: Plasma ↔ IF (across capillary walls); IF ↔ ICF (across plasma membrane).
Water Balance: Intake = output; metabolic water is produced by cellular respiration; insensible loss via skin/lungs.
Normal Body Osmolality: ~300 mOsm/kg.

Regulation of Water and Electrolyte Balance

Thirst Mechanism: Driven by osmoreceptors in hypothalamus.
ADH: Increases water reabsorption; triggered by high osmolality, low blood volume, or low blood pressure.
Abnormalities: Dehydration, hypotonic hydration, edema.

Sodium, Potassium, and Calcium Regulation

Sodium: Central to ECF volume and osmotic balance; regulated by renin-angiotensin-aldosterone, ANP, and baroreceptors.
Potassium: Important for membrane potential; regulated in collecting ducts, influenced by aldosterone and H+ levels.
Calcium and Phosphate: Regulated by parathyroid hormone.

Acid-Base Balance

Normal pH: 7.35–7.45; Acidosis: <7.35; Alkalosis: >7.45.
Causes of pH Change: Metabolism, diet.
Regulation Mechanisms (in order): 1) Chemical buffers (not covered), 2) Respiratory system, 3) Renal system.
Respiratory Regulation: CO2 exhalation adjusts blood pH.
Renal Regulation: Kidneys excrete or reabsorb H+ and HCO3-.