1 Respiratory system L1 Faisal I. Mohammed, MD, PhD University of Jordan

2 Recognize the Functions of the respiratory system. Understand Mechanism of Inspiration and Expiration. Recognize Surface tension and role of Surfactant. Understand Pressure and Volume Changes During Breathing.

I. Pulmonary ventilation * 1.Mechanisms of pulmonary ventilation 2.Indexes of pulmonary ventilation function II. Pulmonary gas exchange and Tissue gas exchange 1. Principles of gas exchange * 2. Pulmonary gas exchange * 3. Tissue gas exchange III. Gas transport in the Blood 1. Transport forms of oxygen and carbon dioxide in the blood 2. Oxygen transport * 3. Carbon dioxide transport * IV. Respiratory Regulation 1. Respiratory centers and formation of respiratory rhythm 2. Reflex regulation of respiration * V. Role of the lungs in regulation of acid-base balance The objectives will be met through

Overview of lung function and structure Lung Functions Lungs are a site for gas exchange with the external environment. Regulate acid-base balance. Lungs have a defense mechanism. Lungs are a blood reservoir. Serve a biosynthetic function (Angiotensin II, surfactant)

Respiratory component element  Respiration is the exchange of gas between the body and the environment.  External respiration : the exchange of gases between pulmonary blood and the external environment, which involves not only diffusion across the lung capillaries （ pulmonary gas exchange, but also the bulk movement of gases in and out of the lungs (pulmonary ventilation).  Internal respiration : the exchange of gases between the tissue cells and the systemic capillaries. The diffusion of gases between the interstitial fluid and the cytoplasm.  Gas transport in the blood : physical solvation and chemical constitution.

6 Structures of the Respiratory System University of Jordan

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Respiratory Zone Region of gas exchange between air and blood. Includes respiratory bronchioles and alveolar sacs. Must contain alveoli.

Conducting Zone All the structures air passes through before reaching the respiratory zone. Warms and humidifies inspired air. Filters and cleans:  Mucus secreted to trap particles in the inspired air.  Mucus moved by cilia to be expectorated. Insert fig. 16.5

10 Microscopic Anatomy of Lobule of Lungs University of Jordan

11 Alveoli  Cup-shaped outpouching  Alveolar sac – 2 or more alveoli sharing a common opening  2 types of alveolar epithelial cells Type I alveolar cells – form nearly continuous lining, more numerous than type II, main site of gas exchange Type II alveolar cells (septal cells) – free surfaces contain microvilli, secrete alveolar fluid (surfactant reduces tendency to collapse) University of Jordan

12 Components of Alveolus University of Jordan

Pneumocytes I and pneumocytes II

14 Pulmonary ventilation Respiration (gas exchange) steps 1. Pulmonary ventilation/ breathing Inhalation and exhalation Exchange of air between atmosphere and alveoli 2. External (pulmonary) respiration Exchange of gases between alveoli and blood 3. Internal (tissue) respiration Exchange of gases between systemic capillaries and tissue cells Supplies cellular respiration (makes ATP) University of Jordan

15 Inhalation/ inspiration  Pressure inside alveoli lust become lower than atmospheric pressure for air to flow into lungs 760 millimeters of mercury (mmHg) or 1 atmosphere (1 atm)  Achieved by increasing size of lungs Boyle’s Law – pressure of a gas in a closed container is inversely proportional to the volume of the container  Inhalation – lungs must expand, increasing lung volume, decreasing pressure below atmospheric pressure University of Jordan

16 Boyle’s Law University of Jordan

17 Inhalation Inhalation is active – Contraction of  Diaphragm – most important muscle of inhalation Flattens, lowering dome when contracted Responsible for 75% of air entering lungs during normal quiet breathing  External intercostals Contraction elevates ribs 25% of air entering lungs during normal quiet breathing  Accessory muscles for deep, forceful inhalation When thorax expands, parietal and visceral pleurae adhere tightly due to subatmospheric pressure and surface tension – pulled along with expanding thorax As lung volume increases, alveolar (intrapulmonic) pressure drops University of Jordan

18 Exhalation/ expiration  Pressure in lungs greater than atmospheric pressure  Normally passive – muscle relax instead of contract Based on elastic recoil of chest wall and lungs from elastic fibers and surface tension of alveolar fluid Diaphragm relaxes and become dome shaped External intercostals relax and ribs drop down  Exhalation only active during forceful breathing University of Jordan

Diaphragm is the main muscle of inspiration Dome-shaped

Inspiration

Expiration

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25 Thank You University of Jordan