NAPP - Week 6

• Respiratory system


  The set of organs that allows a person to breathe and exchange oxygen and carbon dioxide throughout the body

  
• Respiratory system


  • Integrated system of organs involved in the intake and exchange of oxygen and carbon dioxide between the body and the environment, including the nasal passages, larynx, trachea, bronchial tubes, and lungs

  
• Two major tasks of the respiratory system

  • Exchanging air between the body and the outside environment (external respiration)
  • Bringing oxygen to the cells and removing carbon dioxide from them (internal respiration)
• Respiratory system


  • Supplies the body with oxygen and disposes of carbon dioxide
  • Filters inspired air
  • Produces sound
  • Contains receptors for smell
  • Rids the body of some excess water and heat
  • Helps regulate blood pH

  
• Breathing (pulmonary ventilation)

  Consists of two cyclic phases: Inhalation (inspiration) - draws gases into the lungs, Exhalation (expiration) - forces gases out of the lungs

  
• Nose and nasal cavities


  • External nares - opening to exterior, Internal nares - opening to pharynx, Nasal conchae - folds in the mucous membrane that increase air turbulence and ensure most air contacts the mucous membranes

  
• Functions of the nose and nasal cavities

  Provides an airway for respiration, Moistens and warms entering air, Filters and cleans inspired air, Resonating chamber for speech, Detects odors in the air stream

  
• Pharynx


  Common space used by both the respiratory and digestive systems, Commonly called the throat, Originates posterior to the nasal and oral cavities and extends inferiorly near the level of the bifurcation of the larynx and esophagus, Common pathway for both air and food, Walls are lined by a mucosa and contain skeletal muscles that are primarily used for swallowing, Flexible lateral walls are distensible in order to force swallowed food into the esophagus
• Three sections of the pharynx

  • Nasopharynx - contains the pharyngeal tonsils (adenoids) which aid in the body's immune defense
  • Oropharynx - back portion of the mouth that contains the palatine tonsils which aid in the body's immune defense
  • Laryngopharynx - bottom section of the pharynx where the respiratory tract divides into the esophagus and the larynx

  
• Larynx


  Voice box, a short, somewhat cylindrical airway that ends in the trachea, Prevents swallowed materials from entering the lower respiratory tract, Conducts air into the lower respiratory tract, Produces sounds, Supported by a framework of nine pieces of cartilage (three individual pieces and three cartilage pairs) that are held in place by ligaments and muscles

  
• Trachea


  A flexible tube also called the windpipe, Extends through the mediastinum and lies anterior to the esophagus and inferior to the larynx, Cartilage rings reinforce and provide rigidity to the tracheal wall to ensure that the trachea remains open at all times, At the level of the sternal angle, the trachea bifurcates into two smaller tubes, called the right and left primary bronchi, Each primary bronchus projects laterally toward each lung

  
• Lungs


  • Each lung has a conical shape with a wide, concave base resting upon the muscular diaphragm, The superior region called the apex projects superiorly to a point that is slightly superior and posterior to the clavicle, Both lungs are bordered by the thoracic wall anteriorly, laterally, and posteriorly, and supported by the rib cage, Toward the midline, the lungs are separated from each other by the mediastinum, The relatively broad, rounded surface in contact with the thoracic wall is called the costal surface of the lung, Left lung is divided into 2 lobes by an oblique fissure and is smaller than the right lung, Right lung is divided into 3 lobes by oblique and horizontal fissures and is located more superiorly in the body due to the liver on the right side

  
• Pleura


  The outer surface of each lung is tightly covered by the visceral pleura, while the internal thoracic walls, the lateral surfaces of the mediastinum, and the superior surface of the diaphragm are lined by the parietal pleura, The parietal and visceral pleural layers are continuous at the hilus of each lung, The potential space between the serous membrane layers is a pleural cavity, The pleural membranes produce a thin, serous pleural fluid that circulates in the pleural cavity and acts as a lubricant, ensuring minimal friction during breathing, Pleural effusion is pleuritis with too much fluid

  
• How lungs work

  Air enters lungs through bronchi, Alveoli are where gas exchange takes place between air and blood, Oxygen from fresh air in alveoli diffuses into blood in capillaries, Carbon dioxide from blood in capillaries diffuses into air in alveoli and is then breathed out

  
• Breathing

  Lungs are sealed in pleural membranes inside the chest cavity, During inhalation, the diaphragm contracts and the rib cage rises up, expanding the volume of the chest cavity and creating a partial vacuum that draws air into the lungs, During exhalation, the rib cage lowers and the diaphragm relaxes, decreasing the volume of the chest cavity and pushing air out of the lungs

  
• Normal breathing

  • Inspiration is an active process, expiration is a passive process, The thoracic cage and lungs increase and decrease in size during inspiration and expiration respectively, Different muscles and pressures help facilitate these movements
• Respiratory muscles


  • Primary inspiratory muscles: Diaphragm, External intercostals
  • Primary expiratory muscles: Internal intercostals
  • Accessory inspiratory muscles: Sternomastoid, Scalene, Elevator of scapulae, Anterior serrate, Pectorals
  • Accessory expiratory muscles: Abdominal muscles

  
• Movement of thoracic cage and lungs during inspiration

  Thoracic lid (sternal first pair of ribs) moves upward, Upper costal series (2-6th pairs of ribs) move upward and outward, Lower costal series (7-10th pairs of ribs) also increase diameter, Diaphragm contracts and moves downward, Increasing the volume of the thoracic cavity and drawing air into the lungs

  
• Mechanics of breathing: Inspiration and Expiration

  1. Inspiration: Diaphragm and intercostal muscles contract, Diaphragm moves downwards increasing volume of thoracic cavity, Intercostal muscles pull ribs up expanding rib cage and further increasing volume

  2. Expiration: Diaphragm and intercostal muscles relax, Thoracic cavity returns to original volume, Increasing air pressure and pushing air out of lungs
• Thoracic cage

  • Increasing transverse diameter
  • Lower costal series (7-10th pair of ribs) increases diameter similar to upper series
  • 11th and 12th pair does not take part in respiration

  
• Diaphragm


  • During inspiration, contraction moves it upward and flattens it, increasing diameter of thoracic cage
• Lungs


  • During inspiration, increase in size of thoracic cage creates negative pressure in thoracic cavity, causing expansion of lungs

  
• Mechanics of Breathing: Inspiration and Expiration

  1. Diaphragm and intercostal muscles contract, diaphragm moves downwards increasing thoracic cavity volume

  2. Intercostal muscles pull ribs up, expanding rib cage and further increasing volume

  3. During expiration, diaphragm and intercostal muscles relax, returning thoracic cavity to original volume, increasing air pressure in lungs and forcing air out

  
• This increase of volume lowers the air pressure in the alveoli to below atmospheric pressure, causing air to rush in through the respiratory tract and into the alveoli (negative pressure breathing)

  
• Nonrespiratory air movements


  • Coughing
  • Sneezing
  • Sighing
  • Yawning
  • Sobbing
  • Crying
  • Laughing
  • Hiccupping
  • Valsalva maneuver
• Tidal volume (VT)


  The volume of one breath
• Minute ventilation (MV)


  The total volume of air inhaled and exhaled each minute
• Spirometer is the apparatus commonly used to measure the volume of air exchanged during breathing and the respiratory rate

  
• Lung Volumes

  • Tidal Volume
  • Inspiratory Reserve Volume
  • Expiratory Reserve Volume
  • Residual Volume/Reserve Volume
• Lung Capacities

  • Total Lung Capacity
  • Vital Capacity
  • Inspiratory Capacity
  • Functional Residual Capacity

  
• External respiration (pulmonary gas exchange) occurs in the lungs, while internal respiration (systemic gas exchange) occurs in tissues throughout the body

  
• Regulation of Respiration

  • Nervous/Neural Mechanism
  • Chemical Mechanism
• Respiratory Centres

  • Medullar Centers (Inspiratory, Expiratory)
  • Pontine Centers (Pneumotaxic, Apneustic)

  
• Inspiratory Center


  Concerned with inspiration, receives sensory impulses from peripheral receptors
• Expiratory Center


  Inactive during quiet breathing, becomes active during forced breathing or when inspiratory center is inhibited
• Pneumotaxic Center


  Controls the medullary respiratory centers, particularly the inspiratory center, increasing respiratory rate by reducing inspiration duration

  
• Respiratory center


  • Ata
  • Anterior and lateral to inspiratory center
  • Also called the Ventral group of respiratory neurons

  
• Respiratory center

  1. Neurons form nucleus ambiguus anteriorly

  2. Neurons form nucleus retroambiguous posteriorly
• Inspiratory center


  • Active during quiet breathing
  • Expiratory center inactive
• Expiratory center


  • Active during forced breathing
  • Active when inspiratory center is inhibited
  • Passive process during quiet breathing due to recoiling of thoracic cage and lungs