RESPIRATORY SYSTEM

• Respiratory System


  Provides for gas exchange -- intake of oxygen and elimination of carbon dioxide
• Respiration


  Process of gas exchange
• Basic steps of Respiration

  1. Pulmonary ventilation or breathing

  2. External respiration

  3. Internal respiration
• Pulmonary ventilation or breathing


  Mechanical flow of air into and out of the lungs
• External respiration

  Exchange of gases between the air spaces of the lungs and the blood in the pulmonary capillaries. Pulmonary blood gains oxygen and loses carbon dioxide
• Internal respiration


  Exchange of gases between blood and systemic capillaries and tissue cells
• Upper respiratory system

  • Nose
  • Pharynx
  • Associated structures

  
• Lower respiratory system


  • Larynx
  • Trachea
  • Bronchi
  • Lungs
• Nose (external portion)


  • Supporting framework of bone and hyaline cartilage covered with muscle and skin and lined by mucous membrane
  • Septal cartilage, lateral nasal cartilages, alar cartilages, external nares or nostrils
• Nose (internal portion)


  • Large cavity in the anterior aspect of the skull that lies inferior to the nasal bone and superior to the mouth, it also includes muscle and mucous membrane
  • Internal nares (choanae)
  • Nasal cavity
  • Nasal septum (divides nasal cavity)
  • Vestibule
  • Meatuses
• Pharynx


  Funnel shaped tube about 13 cm (5 inches) long, divided into 3 anatomical regions: Nasopharynx, Oropharynx, Laryngopharynx
• Larynx


  Voice box, short passageway that connects laryngopharynx with trachea, lies in the middle of neck anterior to the 4th through 6th vertebra
• Trachea


  Wind pipe, tubular passageway for air that is about 12 cm long and 2.5cm in diameter
• Bronchi


  At the level of 5th thoracic vertebra the trachea divides into right and left primary bronchi, the point where trachea divides is called the CARINA
• Lungs


  • Paired cone shaped organs lying in the thoracic cavity
  • Two layers of serous membrane or pleural membrane enclose and protect each lung: Parietal pleura (superficial layer), Visceral pleura (deep layer)
  • Pleural cavity between the 2 layers contains lubricating fluid
• Alveolus


  • Cup shaped outpouching lined by simple squamous epithelium
  • 2 types of alveolar epithelial cells: Type 1 (main site of gas exchange, simple squamous), Type 2 (septal cells, rounded or cuboidal with microvilli, secrete alveolar fluid, keeps normal moisture of air)
• Pulmonary Ventilation


  Also known as "breathing", process by which gases are exchanged between the atmosphere and lung alveoli
• Inspiration


  1. Breathing in, inhalation

  2. Just before each inspiration, the air pressure in the lungs is equal to the pressure of the atmosphere, which at sea level is about 760 mmhg or 1atm

  3. For air to flow in the lungs the pressure inside the alveoli must become lower than the environment, achieved by increasing the volume of the lung

  
• Muscles of Inspiration


  • Sternocleidomastoid
  • Scalenes
  • External intercostals
  • Diaphragm

  
• Expiration

  1. Breathing out, exhalation

  2. The pressure of the lungs is greater than the pressure of the atmosphere

  3. Passive process: no muscular contractions are involved

  4. Results from elastic recoil of chest wall and lungs

  
• Elastic recoil


  2 inwardly directed forces: recoil of elastic fibers that were stretched during inspiration, inward pull of surface tension due to the film of alveolar fluid
• Muscles of Expiration


  • Internal intercostals
  • External obliques
  • Internal obliques
  • Transversus abdominis
  • Rectus abdominis