Respiratory system

• Respiratory system


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


  • Internal Respiration: Gas exchange between the blood and body cells
  • External Respiration: The breathing process, involving inhalation and exhalation of gases between blood and lungs
• Organs of the respiratory system


  • Nasal passages
  • Pharynx
  • Larynx
  • Trachea
  • Bronchi
  • Lungs
• Upper Respiratory Tract


  • Nose
  • Nasal passages
  • Paranasal sinuses
  • The pharynx
  • The portion of the larynx above the vocal folds
• Lower Respiratory Tract


  • The portion of the larynx below the vocal folds
  • Trachea
  • Bronchi and bronchioles
  • Alveoli
  • Lungs
• Nasal Cavity


  • The nasal cavity is the main route of air entry, and consists of a large irregular cavity divided into two equal passages by a septum
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  • Floor: hard palate (in front and soft on back)
  • Roof: for olfaction (Formed by ethmoid, sphenoid, frontal, nasal bones)
  • Lateral wall: above by orbit and ethmoid sinus, below by maxillary sinus
• Lining of nose

  Ciliated columnar epithelium, with mucus secreting goblet cells
• Openings into nasal cavity


  • Anterior Nares/Nostrils: openings from exterior into the nasal cavity, with nasal hair
  • Posterior Nares: openings from nasal cavity into pharynx
• Paranasal sinuses


  • Maxillary sinus (in lateral walls of nose)
  • Frontal and sphenoid sinus (in roof)
  • Ethmoid sinus (upper part of lateral wall)
• Pharynx


  A tube 13 cm long, extending from base of skull to C6
• Divisions of the pharynx


  • Nasopharynx: behind nasal cavity above soft palate
  • Oropharynx: behind mouth cavity from soft palate to epiglottis
  • Laryngeopharynx: behind larynx from epiglottis to cricoid cartilage
• Parts of the pharynx


  • Nasopharynx: Auditory tubes open into its lateral walls, Adenoids are located on posterior wall
  • Oropharynx: Palatine tonsils are located here
  • Laryngopharynx
• Blood supply of the pharynx


  • Facial artery
  • Facial and internal jugular veins
• Nerve supply of the pharynx


  • Pharyngeal plexus: Parasympathetic (vagus and glossopharyngeal nerve), Sympathetic (Superior cervical ganglia)
• Larynx


  The organ of phonation, 4 cm in length, extending from epiglottis to trachea
• Structures of the larynx

  • Thyroid cartilages meeting in midline in Adam's apple
  • Thyroid cartilages attached inferiorly to cricoid cartilages
  • Epiglottis guarding the inlet of larynx
  • Vocal folds, a pair of folds in laryngeal cavity leaving a fissure between them
• Structures associated with the larynx

  • Superiorly: hyoid bone and root of tongue
  • Inferiorly: continuous with trachea
  • Anteriorly: muscles attached to hyoid bone and neck muscles
  • Posteriorly: laryngopharynx and 3rd to 6th cervical vertebrae
  • Laterally: lobes of thyroid gland
• Cartilages of the larynx


  • 1 thyroid cartilage
  • 1 cricoid cartilage
  • 2 arytenoid cartilages (hyaline cartilages)
  • 1 epiglottis (elastic cartilage)
• Trachea


  A tube of fibro-elastic membrane maintained by C-shaped cartilage, extending from 6th cervical vertebra to the angle of Louis where it divides into 2 bronchi
• Structures associated with the trachea


  • Superiorly: larynx
  • Inferiorly: Right and left bronchi
  • Anteriorly: Isthmus of thyroid gland (upper), Arch of aorta and sternum (lower)
  • Posteriorly: Esophagus separating trachea from vertebral column
  • Laterally: lungs and lobes of thyroid gland
• Layers of the trachea


  • Outer layer: fibrous and elastic tissue enclosing the cartilages
  • Middle layer: Cartilages and bands of smooth muscle
  • Inner layer: Ciliated columnar epithelium, with mucus secreting goblet cells
• Blood supply of the trachea

  • Arterial: Inferior thyroid artery and bronchial arteries
  • Venous: Inferior thyroid veins
• Nerve supply of the trachea


  • Parasympathetic: Recurrent laryngeal nerve
  • Sympathetic: Cervical ganglia
• Lungs


  • Each lung looks like half a cone, with an apex and a base (diaphragmatic surface)
  • Borders: anterior, posterior, inferior
  • Surfaces: costal, mediastinal, diaphragmatic (base)
• Fissures of the lungs


  • Oblique fissure: from 3rd thoracic vertebra to 6th rib
  • Horizontal fissure (only in the right): from 4th costal cartilage to meet oblique fissure
• Broncho-pulmonary segments


  The functional unit of the lung, supplied by a segmental bronchus, pulmonary artery, and pulmonary vein
• Differences between right and left lungs

  • Left lung: Long, narrow with cardiac notch, contains 8 bronchopulmonary segments
  • Right lung: Short, wide with no cardiac notch, contains 10 bronchopulmonary segments, has 3 lobes separated by 2 fissures
• Pulmonary circulation


  • Pulmonary trunk, dividing into right and left pulmonary artery
  • Pulmonary veins
• Pleura


  • A closed sac invaginated from medial side by the lung, with two layers: Visceral (covers the lung) and Parietal (lines chest wall)
• Differences between right and left bronchi

  • Left bronchus: Narrower, longer (4.5 cm), bifurcates after entering the lungs, makes 45 degrees with vertical
  • Right bronchus: Wider, shorter (2.5 cm), bifurcates before entering the lungs, makes 25 degrees with vertical
• Blood supply of the bronchi


  • Bronchial arteries
  • Bronchial veins
• Diaphragm


  Dome shaped muscular structure separating the abdominal and thoracic cavities, forming the floor of the thoracic cavity and the roof of the abdominal cavity
• Diaphragm


  • Consists of a central tendon from which muscle fibres radiate to be attached to the lower ribs and sternum and to the vertebral column by two crura
  • When relaxed, the central tendon is at the level of the 8th thoracic vertebra
  • When contracted, the muscle fibres shorten and the central tendon is pulled downwards to the level of the 9th thoracic vertebra, enlarging the thoracic cavity in length
• Accessory muscles of respiration


  • Sternocleidomastoid muscle
  • Scalene muscle
  • Intercostal muscles
  • Abdominal muscles
• Foreign bodies enter the right bronchus more than the left bronchus