chapter 23 study guide

• Functions of the respiratory system

  • Supply body with oxygen (O2) and dispose of carbon dioxide (CO2)
  • pH regulation
  • Protect respiratory surfaces from the outside environment
  • Production of sound for speech and other functions
  • Detection of odor (olfactory sense)
  • Assist in returning venous blood to the heart
• "Lines of defense" in the respiratory system

  • Upper respiratory tract: Nasal hairs, nasal mucosa, sneeze reflex, olfactory receptors, paranasal sinuses
  • Lower respiratory tract: Ciliated cells, mucus escalator, alveolar macrophages
• Divisions of the respiratory system

  • Upper respiratory division: Nose, nasal cavity, pharynx, larynx
  • Lower respiratory division: Trachea, bronchi, lungs
• Conducting portion


  Transports and conducts air, includes structures from nasal cavity to terminal bronchioles
• Respiratory portion


  Involved in gas exchange, includes structures from respiratory bronchioles to alveoli
• Respiratory mucosa


  • Mucous membrane lining the conducting portion of the respiratory tract
  • Contains epithelium with mucous-producing goblet cells
  • Underlying connective tissue with large blood vessels
  • Functions include filtering, warming, and moistening air, as well as protection
• Components of the upper respiratory system

  • Nose: Warms, filters, humidifies air, detects odor
  • Nasal cavity: Contains nasal mucosa, nasal hairs, and olfactory receptors
  • Pharynx: Divided into nasopharynx, oropharynx, and laryngopharynx, functions in respiratory and digestive systems
  • Larynx: Functions as the voicebox, contains cartilages, vocal folds, and vestibular folds
• Divisions of the pharynx

  • Nasopharynx: Airway only, contains pharyngeal tonsils and openings to auditory tubes
  • Oropharynx: Common passage for respiratory and digestive systems, contains palatine tonsils
  • Laryngopharynx: Passage to esophagus and larynx, functions in respiratory and digestive systems
• Incomplete rings of cartilage in the larynx

  • Epiglottis: Elastic cartilage, acts as a "guardian of airways" during swallowing
  • Glottis: Opening between vocal folds
  • Vocal folds: Inferior "true vocal cords" responsible for sound production
• Components of the lower respiratory system

  • Larynx: Structure providing open airway, sound production, and routing of food and air
  • Trachea: Cartilaginous tube connecting larynx to bronchi, contains tracheal cartilage and trachealis muscle
  • Bronchi: Branches of trachea leading to lungs, undergo bronchoconstriction and bronchodilation
  • Lungs: Main organs of respiration, contain bronchial tree, alveoli, and respiratory membrane
• Components of the respiratory bronchial tree

  Trachea → Bronchi → Bronchioles → Respiratory bronchioles → Alveolar ducts → Alveolar sacs
• Bronchial tree


  • Proportion of cartilage decreases while smooth muscle increases along the bronchial tree
  • Structures include terminal bronchioles, alveolar ducts, and alveolar sacs surrounded by elastic fibrous tissue
• Cells in the alveoli

  • Type I pneumocytes: Main cells for gas exchange, simple squamous epithelium
  • Type II pneumocytes: Secrete surfactant to reduce surface tension and prevent alveolar collapse
  • Alveolar macrophages (dust cells): Phagocytic cells that remove debris and pathogens
• Respiratory membrane


  • Consists of alveolar epithelial wall, fused basement membrane, and pulmonary endothelial capillary wall
  • Allows for the exchange of oxygen and carbon dioxide between air and blood through diffusion
• Blood supply to/from the lungs

  • Pulmonary arteries: Carry deoxygenated blood from the heart to the lungs for oxygenation
  • Pulmonary veins: Transport oxygenated blood from the lungs back to the heart for distribution to the body
• Pleural membrane


  • Consists of visceral and parietal pleura with pleural fluid in between
  • Provides lubrication and surface tension, which helps maintain lung expansion and prevents lung collapse
• Respiratory functions


  • Pulmonary ventilation: Breathing, involves inhalation and exhalation to exchange air between atmosphere and alveoli
  • External respiration: Exchange of gases between alveoli and blood
  • Internal respiration: Exchange of gases between blood and body tissues
• Pressure differences


  • Atmospheric pressure: Pressure of the air outside the body
  • Intrapulmonary pressure (alveolar pressure): Pressure within the alveoli
  • Intrapleural pressure: Pressure within the pleural cavity
• Airflow during a respiratory cycle

  1. When intrapulmonary pressure is higher than atmospheric pressure, air flows out of the lungs during exhalation

  2. When intrapulmonary pressure is lower than atmospheric pressure, air flows into the lungs during inhalation
• Boyle's Law


  Describes the inverse relationship between volume and pressure of a gas at constant temperature
• Mechanics of breathing


  1. Inhalation: Active process involving contraction of diaphragm and external intercostal muscles, increasing lung volume and decreasing intrapulmonary pressure

  2. Exhalation: Can be passive (relaxation of inspiratory muscles, elastic recoil of lungs) or active (involvement of accessory muscles), decreasing lung volume and increasing intrapulmonary pressure
• Factors influencing pulmonary ventilation

  • Surface tension: Reduced by surfactant, allowing alveoli to expand easily
  • Compliance: Measure of lung and chest wall distensibility
  • Airway resistance: Determined by diameter of airways, affected by bronchoconstriction and bronchodilation
• Respiratory volumes and capacities

  • Tidal volume (VT): Volume of air inhaled or exhaled during normal breathing
  • Inspiratory reserve volume (IRV): Additional air inhaled after a tidal inspiration
  • Expiratory reserve volume (ERV): Additional air exhaled after a tidal expiration
  • Residual volume (RV): Air remaining in the lungs after maximal expiration
  • Inspiratory capacity (IC): Tidal volume plus inspiratory reserve volume
  • Functional residual capacity (FRC): Expiratory reserve volume plus residual volume
  • Vital capacity (VC): Maximum volume of air exhaled after maximal inspiration
  • Total lung capacity (TLC): Sum of all lung volumes
• Factors influencing lung volumes and capacities

  • Age, gender, height, health conditions, and physical activity level
• Spirometer


  Device used to measure lung volumes and capacities by recording airflow and lung volume changes during breathing
• Partial pressure


  Pressure exerted by a specific gas in a mixture of gases
• Dalton's Law


  Total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of individual gases
• Henry's Law


  Amount of gas dissolved in a liquid is directly proportional to the partial pressure of that gas
• Gas exchange


  • External respiration: Exchange of oxygen and carbon dioxide between alveoli and pulmonary capillaries
  • Internal respiration: Exchange of oxygen and carbon dioxide between systemic capillaries and body tissues
• Ventilation-perfusion coupling


  Matching of airflow (ventilation) and blood flow (perfusion) to optimize gas exchange
• Solubility of O2 and CO2

  • O2 is poorly soluble in plasma, most carried by hemoglobin in RBCs
  • CO2 is more soluble in plasma than O2 and can be transported as dissolved CO2, bicarbonate ions, or carbamino compounds
• Hemoglobin structure and function

  • Hemoglobin (Hb): Protein in RBCs that binds oxygen and carbon dioxide
  • Oxyhemoglobin: Hemoglobin bound to oxygen
  • Deoxyhemoglobin: Hemoglobin without oxygen
  • Affinity: Strength of binding between hemoglobin and oxygen
  • Oxygen-hemoglobin saturation curve: Graph showing the relationship between partial pressure of oxygen and hemoglobin saturation
• Factors affecting Hb saturation

  • pH, temperature, PCO2, and H+ concentration affect Hb affinity for oxygen
  • Bohr effect: Decrease in Hb affinity for oxygen in response to increased acidity
  • CO poisoning: Carbon monoxide competes with oxygen for binding sites on hemoglobin, reducing oxygen transport
• Transport and release of CO2

  • HHb: Hemoglobin bound to hydrogen ions
  • Chloride shift: Movement of chloride ions into RBCs to balance the charge as bicarbonate ions move out
  • CarbaminoHb: Hemoglobin bound to carbon dioxide
  • Haldane effect: Deoxygenation of blood increases its ability to carry carbon dioxide
  • In the alveolar capillaries, CO2 is released from bicarbonate ions and carbamino compounds for exhalation
• Local regulation of respiration

  Various factors such as oxygen, carbon dioxide, and pH levels in lung tissue can regulate local blood flow and airway diameter
• Brain respiratory centers


  • Located in the medulla oblongata and pons
  • Medulla controls basic rhythm of breathing
  • Pons regulates respiratory muscles during normal breathing
• Factors affecting breathing


  • Chemoreceptors respond to changes in blood levels of O2, CO2, and pH
  • Central chemoreceptors respond to changes in CSF pH
  • Peripheral chemoreceptors respond to changes in arterial blood O2, CO2, and pH
  • Hypoxia: Low tissue oxygen levels
• Effect of CO2 levels on breathing

  • Increase in CO2 (hypercapnia) stimulates breathing
  • Decrease in CO2 (hypocapnia) depresses breathing
  • Hyperventilation and hypoventilation help restore CO2 levels to normal
• Inflation and deflation reflexes

  • Inflation reflex prevents overinflation of lungs by inhibiting inspiratory neurons
  • Deflation reflex inhibits expiratory neurons to prolong inspiration
• Irritant receptors and proprioreceptors

  • Irritant receptors in airways respond to harmful substances and trigger coughing or bronchoconstriction
  • Proprioreceptors in muscles and joints provide feedback on respiratory rate during physical activity