Chapter 19

Chapter 19: Respiratory System Overview

19.1 Overview of the Respiratory System

  • Respiratory System Functions:

    • Specialized for intake of oxygen and expelling carbon dioxide.

    • Composed of passages that filter, moisten, and warm incoming air, transporting it to the lungs and microscopic air sacs for gas exchange.

    • Produces vocal sounds and aids in the sense of smell.

    • Regulates blood pH.

  • Respiration Defined:

    • Process of exchanging gases between atmosphere and body cells.

    • Oxygen is essential for energy production.

    • Key events in respiration:

      • External respiration: Breathing (ventilation) for gas exchange in lungs.

      • Internal respiration: Gas transport in blood and exchange with tissues.

      • Cellular respiration: ATP production in mitochondria, utilizing oxygen and releasing carbon dioxide.

19.2 Organs of the Respiratory System

  • Divided into Two Tracts:

    • Upper Respiratory Tract:

      • Nose, nasal cavity, sinuses, pharynx, and larynx.

    • Lower Respiratory Tract:

      • Trachea, bronchial tree, and lungs.

19.3 Parts of the Respiratory System

  • Illustrated view of the respiratory structures, including sinuses and cavities that aid in air conduction and protection against pathogens.

19.4 Nose and Nasal Cavity

  • Nose:

    • Nostrils provide entry and exit for air, protected by internal hairs.

  • Nasal Cavity:

    • Hollow space behind the nose, divided by the nasal septum.

    • Contains conchae that increase surface area and passageways.

    • Contains olfactory receptors and is lined with mucous membrane.

    • Goblet cells produce mucous.

    • Mucus traps dust; cilia move mucus toward pharynx.

19.8 Sinuses

  • Functionality of Sinuses:

    • Air-filled spaces that reduce skull weight and resonate voice.

    • Continuous mucous membranes with the nasal cavity; sinusitis can occur if blockages happen.

19.12 Pharynx (throat)

  • Space behind nasal cavity, oral cavity, and larynx functioning in both air and food passage.

  • Divided into three parts: nasopharynx, oropharynx, laryngopharynx.

19.13 Larynx

  • Connects to trachea and contains vocal cords.

  • Comprised of cartilages: thyroid (Adam’s apple), cricoid (floating), and epiglottic (covers trachea when eating or drinking) (largest).

    True and False Vocal Cords

  • false: close airway during swallowing (upper folds)

  • true: vocal sounds (lower folds)

19.17 Trachea (windpipe)

  • Flexible cylindrical tube extending to upper bronchi

  • Contains rings of cartilage preventing collapse and lined with ciliated mucous membrane.

19.20 Bronchial Tree

  • Comprises branched airways leading from trachea into lungs.

    • Divisions: Right/left main bronchi → lobar bronchi → segmental bronchi → bronchioles → alveoli, which are sites of gas exchange.

19.27 Lungs

  • Soft, spongy organs located in the thoracic cavity, separated by mediastinum, containing pleura layers.

    • Right lung: 3 lobes; Left lung: 2 lobes.

  • Hilum: The region where blood vessels, bronchi, and nerves enter and exit the lungs, playing a crucial role in pulmonary function.

  • Pleura: Double layered serous membrane surrounding lungs

  • visceral pleura: inner layer of serous membrane; attached to surface of lung

  • parietal pleura: outer layer of serous membrane; lines thoracic cavity

  • pleural cavity: space between visceral and parietal pleura

19.32 Breathing Mechanism

  • Breathing Actions:

    • Inspiration: movement of air into lungs. (active)

    • Normal resting inspiration: diaphragm and external and intercostal muscles enlarge the size of the thoracic cavity

    • Maximal forced/deep inspiration: uses pectoralis minors, sternocleidomastoids, and scalenes

    • Expiration: movement of air out of lungs. (passive)

    • elastic recoil: tissue returning to original shaped (relaxation)

  • Respiratory Volumes and Capacities:

  • Tidal Volume (TV): the amount of air inhaled or exhaled during normal breathing.

  • Inspiratory Reserve Volume (IRV): the additional air that can be inhaled after a normal inhalation.

  • Expiratory Reserve Volume (ERV): the additional air that can be exhaled after a normal exhalation.

  • Residual Volume (RV): the amount of air remaining in the lungs after a forced exhalation.

  • Vital Capacity (VC): the total amount of air that can be exhaled after a maximal inhalation, calculated as TV + IRV + ERV.

19.70 Alveolar Gas Exchange

  • Alveoli are the primary site for gas exchange, allowing diffusion of oxygen into blood and carbon dioxide out.

    Dead Air Spaces

  • Anatomic dead space: the portion of the respiratory system that does not participate in gas exchange, including the trachea and bronchi. (NOT ALVEOLI)

  • Alveolar dead space: the volume of air in the alveoli that is not involved in gas exchange due to poor perfusion or blockage, leading to ineffective ventilation.

  • Physiologic dead space: the sum of anatomic and alveolar dead spaces, representing the total volume of air that does not contribute to effective gas exchange in the lungs.

Main respiratory areas:

  • Medulla oblongata: Responsible for the basic rhythm of breathing and involuntary control of respiration.

  • Pontine respiratory groups (Pons): Modulates the rhythm of breathing and coordinates transitions between inhalation and exhalation.

    Medullary respiratory center:

  • Ventral respiratory group: sets basic rhythm of breathing

  • Dorsal respiratory group: modifies activities of ventral group

    Factors affecting breathing

  • low plasma PO2 - chemoreceptors in carotid and aortic bodies stimulated

  • high plasma PCO2 - chemosensitive areas of the respiratory center stimulated

  • high cerebrospinal fluid - decreases plasma PCO2

  • PCO2: as PCO2 increases, so does the amount of O2 released from oxyhemoglobin

  • pH of blood: as blood pH decreases, the amount of O2 released from oxyhemoglobin increases

  • bicarbonate ion - buffer that helps maintain pH balance in the blood by neutralizing excess acids.