Respiratory System

• Respiratory System


  The system responsible for bringing oxygen into the body and removing carbon dioxide
• Respiration


  The process of releasing water vapour and other gases of the body through metabolic reactions
• Breathing


  The life-sustaining process in which gases are exchanged between the body and the outside atmosphere
• Structural components of the respiratory system

  • Upper respiratory system
  • Lower respiratory system
• Upper respiratory system


  • Nasal cavity
  • Pharynx
  • Larynx
• Lower respiratory system


  • Trachea
  • Bronchi
  • Lungs
• Supporting Structures


  • Thoracic cage
  • Muscles of breathing including the diaphragm and accessory muscles
• Functions of the Respiratory System

  • Bring oxygen from the atmosphere into the bloodstream and remove carbon dioxide
  • Regulate blood pH
  • Contains receptors for the sense of smell
  • Filter, warm, and moisten inspired air
  • Produce sounds
  • Remove water and heat in exhaled air
• Describe the structure and functions of the nose, pharynx, larynx, trachea, bronchi, bronchioles, and lungs

  1. The conducting zone

  2. The respiratory zone
• Functions of the Upper Respiratory Tract

  • Heating or cooling inspired gases to body temperature
  • Filtering particles from the inspired gases
  • Humidifying inspired gases to a relative humidity of 100%
  • Providing for the sense of smell, or olfaction
  • Producing sounds, or phonation
  • Ventilating, or conducting, the gas down to the lower airways
• The nose


  • External portion made of cartilage and skin, lined with mucous membrane
  • Nasal cavity separated into right and left halves by the nasal septum
  • Contains the vestibular, olfactory, and respiratory regions
• The pharynx


  • Funnel-shaped tube posterior to the nasal and oral cavities
  • Composed of skeletal muscle and lined with mucous membrane
  • Functions as a passageway for air and food, a resonating chamber for speech sounds, and houses the tonsils
  • Divided into the nasopharynx, oropharynx, and laryngopharynx
• The larynx


  • Connects the pharynx and trachea, helps conduct air through the respiratory tract, contains the vocal cords which vibrate to produce sound
  • Protects the trachea from aspirated food by the epiglottis closing over the entrance to the larynx during swallowing
• Larynx


  • Contains the thyroid cartilage (Adam's apple), the epiglottis, the cricoid cartilage, arytenoid cartilages, false vocal cords, and true vocal cords
• The trachea


  • Extends from the larynx to the primary bronchi, composed of smooth muscle and C-shaped rings of cartilage, lined with pseudostratified ciliated columnar epithelium
  • Bifurcates at the level of vertebrae T4-5 into the right and left main bronchi, the site of bifurcation is called the carina
• Bronchi and Bronchioles


  • Right and left main bronchi divide into lobar bronchi, which continue to branch into segmental bronchi and then bronchioles
  • Bronchioles have less cartilage than the trachea and bronchi, their walls are mainly smooth muscle and elastic fibres, still have a lining of ciliated epithelium
  • Bronchioles branch into terminal bronchioles, the arrangement is known as the bronchial tree
• The Lungs


  • Paired organs in the thoracic cavity enclosed by the pleural membrane
  • Right lung has 3 lobes, left lung has 2 lobes
  • Each lobe consists of lobules containing lymphatic vessels, arterioles, venules, terminal bronchioles, respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli
  • Gaseous exchange (O2 and CO2) occurs across the respiratory membrane
• Structure of an Alveolus

  • Small sacs surrounded by capillaries, adapted for efficient gaseous exchange
  • Walls are only one cell thick, with specialized squamous cells
  • Capillaries are very close to the alveolar walls, decreasing the diffusion distance
  • Type I cells represent the gas exchange surface, type II cells act as "caretakers" and produce surfactant
• Pulmonary Ventilation


  1. Inhalation occurs when the pressure inside the lungs is less than atmospheric pressure

  2. Exhalation occurs when the pressure inside the lungs is greater than atmospheric pressure

  3. Contraction and relaxation of skeletal muscles create the air pressure changes that power breathing
• Pulmonary Ventilation


  • The diaphragm contracts when it receives nerve impulses, the SCMs, scalenes, and pectoralis minors contribute to forced inhalation
  • External intercostals participate in relaxed inhalation, forced exhalation involves contraction of the internal intercostals, external oblique, internal oblique, transverse abdominis, and rectus abdominis
• Type II cell


  Acts as the "caretaker" of the alveolar compartment, responds to damage of the vulnerable type I cell by dividing and acting as a progenitor cell for both type I and type II cells, synthesises, stores and releases pulmonary surfactant
• Pulmonary ventilation


  1. Flow of air between the atmosphere and the lungs, occurs due to differences in air pressure

  2. We inhale when the pressure inside the lungs is less than the atmospheric air pressure

  3. We exhale when the pressure inside the lungs is greater than the atmospheric air pressure

  4. Contraction and relaxation of skeletal muscles create the air pressure changes that power breathing
• Diaphragm


  • Contracts when it receives nerve impulses from the phrenic nerves
  • SCMs, scalenes, and pectoralis minors contribute to forced inhalation
  • External intercostal m. participate in relax inhalation
  • Forced exhalation involves contraction of the internal intercostals, external oblique, internal oblique, transverse abdominis, and rectus abdominis
• Lung volumes


  Volume of gas in the lungs at a given time during the respiratory cycle, measures the amount of air for one function (such as inhalation or exhalation)
• Lung capacities


  Derived from a summation of different lung volumes, the average total lung capacity of an adult human male is about 6 litres of air
• Lung volumes measurement


  • Tidal volume
  • Inspiratory reserve volume
  • Expiratory reserve volume
• Spirometry


  An apparatus for measuring the volume of air inspired and expired by the lungs
• Tidal volume is the volume that enters and leaves with each breath, from a normal quiet inspiration to a normal quiet expiration, about 0.5 L
• Inspiratory reserve volume is the extra volume that can be inspired above tidal volume, from normal quiet inspiration to maximum inspiration, about 2.5 L
• Expiratory reserve volume is the extra volume that can be expired below tidal volume, from normal quiet expiration to maximum expiration, about 1.5 L
• Residual volume/reserve volume is the volume remaining after maximum expiration, about 1.5 L
• Partial pressure


  The pressure of a specific gas in a mixture
• External respiration


  Exchange of gases between alveolar air and pulmonary blood capillaries
• Internal respiration


  Exchange of gases between systemic tissue capillaries and systemic tissue cells
• About 98.5 percent of blood O2 is bound to hemoglobin in red blood cells
• Carbon dioxide is transported in three ways: About 7 % is dissolved in plasma, 23 % combines with the globin of hemoglobin, and 70 % is converted to bicarbonate ions (HCO3–)
• Respiratory center


  The medullary respiratory center in the medulla oblongata, and the pontine respiratory group in the pons
• Carbon dioxide influences on respiratory rate


  The brainstem detects increased carbon dioxide and increases the respiratory rate to eliminate the excess
• Blood oxygen is the secondary influencer on respiratory rate


  An abnormally low blood pH increases the respiratory rate
• Exercise and the respiratory system

  1. The abrupt increase in ventilation at the start of exercise is due to neural changes that send excitatory impulses to the inspiratory area in the medulla oblongata

  2. The more gradual increase in ventilation during moderate exercise is due to chemical and physical changes in the bloodstream