Respiratory

Respiratory System Study Guide

Did You Know?

  1. The right lung is slightly larger than the left lung.

  2. The surface area of the lungs is approximately the same size as a tennis court.

  3. A sneeze travels faster than a cough, at speeds of 100 miles per hour compared to 60 miles per hour, respectively.

  4. A person at rest breathes about 12 to 15 times a minute, which totals at least 17,000 breaths a day, amounting to over 6 million breaths per year.

Outline of the Respiratory System

Organs and Structures of the Respiratory System

  • Conducting Zone
      - Divided into two zones

  • Lungs
      - Includes respiratory zone

  • Blood Supply & Pleural Linings

  • Neural Innervation

Functions of the Respiratory System

  1. Transport of Gases

  2. Process of Breathing (Ventilation)
        - Includes inspiration and expiration

  3. Gas Exchange

  4. Atmospheric Pressure

  5. Intra-alveolar Pressure

  6. Intrapleural Pressure

  7. Transpulmonary Pressure

  8. Regulation by pons and medulla

  9. Requires understanding of peripheral and central chemoreceptors

Respiratory Functions

Main Functions

  1. Gas Exchange
       - Deliver oxygen to tissues throughout the body.
       - Remove carbon dioxide from tissues throughout the body.

  2. Non-respiratory Functions
       - Regulation of acid-base balance in the blood.
       - Vocalization (sound production).
       - Defense against pathogens (e.g., through mucociliary escalator).
       - Route for heat loss and water loss.
       - Enhances venous return.
       - Activates plasma proteins.

Anatomy of the Respiratory System

  • The flowchart illustrates airflow through the respiratory system.

  • Upper Respiratory Tract includes:
      - Conducting trachea.
      - Bronchi (lobar and segmental).

  • Lower Respiratory Tract includes:
      - Alveolar ducts and sacs.

Anatomical Features of the Zones

  1. As air flows from the trachea to the alveoli:
       - Diameter of Airways: Gradually narrows.
       - Amount of Cartilage: Decreases as one moves down the tract.
       - Smooth Muscle: Increases in the respiratory zone.

  2. The amount of cilia decreases as the diameter of airways decreases.

  3. Zones with cilia typically contain goblet cells, which secrete mucus.

Respiratory Zone and Alveoli

  • Alveolar Pores: Facilitate gas exchange.

  • Composed of:
      1. Respiratory bronchioles
      2. Alveolar ducts
      3. Alveolar sacs
      4. Alveolus (plural: alveoli)

Anatomy of Alveoli

  • Three Cell Types and Functions:
      1. Type I Alveolar Cells: Comprise the walls for gas exchange.
      2. Type II Alveolar Cells: Surfactant-secreting cells.
      3. Macrophages: Engulf invaders.

  • The Respiratory Membrane consists of:
      - Type I alveolar cells.
      - Capillary endothelium.

  • Gas Exchange:
      - Oxygen moves into the capillaries from the alveoli via simple diffusion.
      - Carbon dioxide moves into the alveoli from the capillaries.

Importance of Surfactant

  • Surfactant is a phospholipoprotein secreted from Type II Alveolar Cells.

  • Water molecules have strong surface tension due to hydrogen bonding.

  • Without surfactant, alveoli tend to collapse due to high surface tension.

  • Surfactant is amphipathic, disrupting cohesive forces, preventing alveolar collapse.

Respiratory Pressures

Boyle's Law

  • Concept: The pressure of a gas is inversely proportional to its volume.

  • Mathematical Expression:
    PimesV=extconstantP imes V = ext{constant}

  • In a closed container, increasing the volume leads to decreased pressure and vice versa.

Pleural Pressures at Rest

  • At sea level and at rest:
      - Patm (atmospheric pressure) = Pip (intrapleural pressure) < Palv (intra-alveolar pressure).

  • Under normal circumstances, the relationship is:
    ext{Pip} < ext{Palv} < ext{Patm} .

  • Goals:
      - Maintain lung inflation against elastic recoil tendency.

Pneumothorax

  • Defined as collapsed lung due to an equalization of pressures: Pip = Palv = Patm.

  • Treatment involves restoring negative pressure through procedures such as needle decompression.

Forces for Air Flow

  • Air flow is driven by pressure gradients:
      1. Flow = Patm - Palv.
      2. R = Resistance, influenced by airway radius and mucus presence.

  • Bronchoconstriction decreases radius, increasing resistance and reducing flow.

  • Bronchodilation increases radius, decreasing resistance and increasing flow.

Determinants of Intra-Alveolar Pressure

  1. During Expiration:
       - Increase volume in the alveoli causes a drop in intra-alveolar pressure, forcing air out.

  2. During Inspiration:
       - Decrease in volume in the alveoli causes pressure to drop, allowing air to rush in.

Breathing Phases

Quiet Breathing (Eupnea)

  • Inspiration: Air intake involves muscle contraction (forced).

  • Expiration: Primarily a passive process, involving muscle relaxation.

Forced Breathing (Hyperpnea)

  • Involves the active contraction of accessory muscles, increasing airflow above resting levels.

  • Inspiration and Expiration Steps:
      - Active inhalation includes diaphragm and intercostal muscles.
      - Active exhalation includes abdominal and intercostal muscle contractions.

Respiratory Volumes and Capacities

  1. Spirometry: Technique for measuring lung volumes.

  2. Volumes Include:
       - Tidal Volume (TV): Amount of air during normal breath (avg. 500 ml).
       - Inspiratory Reserve Volume (IRV): Extra air that can be inhaled (avg. 3000 ml).
       - Expiratory Reserve Volume (ERV): Extra air that can be exhaled (avg. 1000 ml).
       - Residual Volume (RV): Air remaining after max expiration (avg. 1200 ml).

  3. Capacities Include:
       - Inspiratory Capacity (IC): Maximum air following resting expiration (avg. 3500 ml).
       - Vital Capacity (VC): Max air expelled after max inspiration (avg. 4500 ml).
       - Total Lung Capacity (TLC): Air in lungs after max inhale (avg. 5700 ml).
       - Functional Residual Capacity (FRC): Remaining air after tidal expiration (avg. 2200 ml).

Outline Structure of Respiratory System Continued

  • Includes further details on the structure of blood circulation (Pulmonary vs. Systemic).

  • Concepts of partial pressures (Dalton's Law) are addressed, including blood transport mechanisms for gases.

Transport of Gases in the Blood

Erythrocytes & Hemoglobin

  • Red blood cells, filled with hemoglobin, are the primary transport units of oxygen.

  • Structure:
      - Each hemoglobin molecule can bind four oxygen molecules (one per heme group).

Oxygen and Carbon Dioxide Handling by Hemoglobin

  • Oxygen loading and unloading are critical for gas exchange:
      - Oxyhemoglobin: Hemoglobin bound to oxygen.
      - Deoxyhemoglobin: Hemoglobin released from oxygen.

  • CO2 binds to hemoglobin to form carbaminohemoglobin primarily in tissues, aiding in CO2 transport back to the lungs.

This concludes the study guide for the respiratory system, providing comprehensive insights into anatomy, physiology, and function of respiratory processes. Review specifics of lung volumes, capacities, pressure dynamics, neural control, and gas exchange to solidify understanding of this critical system.