The Respiratory System

• What are the main skeletal structures involved in respiration?

  • Thoracic cage
  • Ribs (12 pairs):
  • Sternum
  • Thoracic vertebrae (T1-T12)
• What is the thoracic cage composed of?

  • Sternum
  • Ribs
  • Thoracic vertebrae
• What are the ribs composed of?

  • True ribs (1-7) directly attached to the sternum
  • False ribs (8-10) attach indirectly via the costal cartilage
  • Floating ribs (11-12) do not attach to the sternum

  
• What is the sternum composed of?

  • Manubrium body
  • Xiphoid process

  
• How does the thoracic cage contribute to breathing?

  • Provides a rigid yet flexible structure for lung expansion and contraction.
  • Ribs move via costovertebral and costotransverse joints, allowing changes in thoracic volume.
  • Protects vital organs (lungs, heart) while permitting movement.
• What are the key soft tissue structures in the thorax involved in breathing?

  • Diaphragm: Primary muscle of respiration.
  • Intercostal muscles: External, internal, and innermost layers assist rib movement.
  • Pleura: Parietal and visceral layers reduce friction during lung expansion.
  • Lung tissue: Expands and recoils with changes in thoracic volume.
• Describe the role of the diaphragm in inspiration and expiration.

  • Inspiration: Contracts and moves downward, increasing thoracic volume and decreasing pressure, allowing air to enter.
  • Expiration: Relaxes and moves upward, decreasing thoracic volume and increasing pressure, pushing air out.
• What are the intercostal muscles, and how do they aid in respiration?

  • External intercostals: Elevate ribs during inspiration (increase thoracic volume).
  • Internal intercostals: Depress ribs during forced expiration (decrease thoracic volume).
  • Innermost intercostals: Assist internal intercostals.

  
• Explain the process of inspiration in terms of skeletal and soft tissue movement.

  • Diaphragm contracts → Moves downward.
  • External intercostals contract → Ribs move upward and outward.
  • Thoracic volume increases, intrapulmonary pressure decreases → Air flows in.
• Explain the process of expiration in terms of skeletal and soft tissue movement.

  • Diaphragm relaxes → Moves upward.
  • External intercostals relax → Ribs move downward and inward.
  • Thoracic volume decreases, intrapulmonary pressure increases → Air flows out.
  • Forced expiration uses internal intercostals and abdominal muscles.
• What are the two types of rib movements in breathing?

  • Pump-handle movement (upper ribs 1-6): Ribs move anteriorly and superiorly, increasing anteroposterior diameter of the thoracic cavity.
  • Bucket-handle movement (lower ribs 7-10): Ribs move laterally and superiorly, increasing transverse diameter of the thoracic cavity.
• How does the pleura contribute to breathing?

  • Parietal pleura: Lines the thoracic cavity and diaphragm.
  • Visceral pleura: Covers the lungs.
  • Pleural fluid: Reduces friction and creates surface tension, ensuring the lungs follow chest wall movement.
• What nerves control the diaphragm and intercostal muscles?

  • Diaphragm: Controlled by the phrenic nerve (C3-C5).
  • Intercostal muscles: Controlled by intercostal nerves (T1-T11).
• What are the two main divisions of the respiratory system?

  1. Upper respiratory tract – Includes the nose, nasal cavity, sinuses, pharynx, and larynx.
  2. Lower respiratory tract – Includes the trachea, bronchi, bronchioles, and lungs.
• What are the functions of the upper respiratory tract?

  • Air filtration (removes dust, pathogens)
  • Humidification (adds moisture to inhaled air)
  • Warming of air (regulates temperature before reaching lungs)
  • Resonance for speech
  • Olfaction (sense of smell via olfactory receptors)
• What are the functions of the lower respiratory tract?

  • Conducts air to the alveoli (gas exchange sites)
  • Gas exchange (oxygen and carbon dioxide diffusion in alveoli)
  • Regulation of airway resistance (bronchoconstriction and bronchodilation)
  • Mucociliary clearance (removes debris via cilia and mucus)
• What are the structures of the upper respiratory tract?

  • Nose and nasal cavity – Filters, warms, and humidifies air.
  • Paranasal sinuses – Air-filled spaces that reduce skull weight and produce mucus.
  • Pharynx (throat) – Common pathway for air and food, divided into nasopharynx, oropharynx, and laryngopharynx.
  • Larynx (voice box) – Contains vocal cords; involved in sound production and airway protection.
• What are the structures of the lower respiratory tract?

  1. Trachea (windpipe) – A cartilaginous tube that conducts air to the bronchi.
  2. Bronchi – The trachea divides into right and left primary bronchi, further branching into secondary and tertiary bronchi.
  3. Bronchioles – Smaller airways leading to alveoli, lacking cartilage but containing smooth muscle.
  4. Alveoli – Tiny air sacs where gas exchange occurs via diffusion.
• What is the function of the nasal cavity?

  • Warms, humidifies, and filters incoming air.
  • Contains olfactory receptors for the sense of smell.
  • Has mucous membranes and cilia to trap debris and pathogens.
• What is the role of the pharynx in respiration?

  • Acts as a passageway for air and food.
  • Connects nasal and oral cavities to the larynx and oesophagus.
  • Divided into three regions:
  • Nasopharynx – Air passage only.
  • Oropharynx – Common for air and food.
  • Laryngopharynx – Leads to larynx (air) and oesophagus (food).
• What is the function of the larynx?

  • Houses the vocal cords, producing sound.
  • Prevents food from entering the trachea (via the epiglottis).
  • Allows the passage of air between the pharynx and trachea.
• What is the trachea and its function?

  • A cartilaginous tube that conducts air from the larynx to the bronchi.
  • Contains C-shaped cartilage rings that provide structural support.
  • Lined with ciliated epithelium and goblet cells for mucus secretion and debris clearance.
• What are bronchi and bronchioles?

  • Large airways branching from the trachea into right and left primary bronchi, which further divide into secondary (lobar) and tertiary (segmental) bronchi.
  • Bronchioles: Smaller, cartilage-free airways that regulate airflow through smooth muscle contraction and relaxation.
• What are alveoli and their function?

  • Alveoli are microscopic air sacs where gas exchange occurs.
  • Surrounded by capillaries for oxygen (O₂) and carbon dioxide (CO₂) exchange.
  • Contain Type I pneumocytes (gas exchange) and Type II pneumocytes (surfactant production to prevent collapse).
• What are the protective mechanisms of the respiratory system?

  • Nasal hairs and mucus trap dust and pathogens.
  • Cilia in the airway move mucus and debris upwards (mucociliary clearance).
  • Epiglottis prevents food from entering the airway.
  • Alveolar macrophages ingest pathogens in alveoli.
• What are the paranasal sinuses?

  • Air-filled cavities within the bones of the skull and face that are lined with mucous membranes.
  • Connected to the nasal cavity and serve functions such as humidifying air, reducing skull weight, and enhancing voice resonance.
• Name the four paired paranasal sinuses

  • Frontal sinus
  • Maxillary sinus
  • Ethmoidal sinuses
  • Sphenoidal sinus

  
• Where is the frontal sinus located?

  • Located in the frontal bone, superior to the orbits (above the eyes).
  • Drains into the middle meatus of the nasal cavity via the frontonasal duct.
• What is the largest of the paranasal sinuses, and where is it located?

  • The maxillary sinuses are the largest paranasal sinuses.
  • Located in the maxilla (cheekbones), inferior to the orbits.
  • Drain into the middle meatus via the semilunar hiatus.
• What is unique about the drainage of the maxillary sinus?

  The maxillary sinus drains superiorly into the middle meatus, making drainage less efficient, which predisposes it to infections (sinusitis).
• Where are the ethmoidal sinuses located?

  • Found within the ethmoid bone, between the nasal cavity and the orbits.
  • Consist of anterior, middle, and posterior air cells.
  • Drain into the middle meatus (anterior and middle cells) and superior meatus (posterior cells).
• Where is the sphenoidal sinus located?

  • Located within the body of the sphenoid bone, posterior to the nasal cavity.
  • Drains into the sphenoethmoidal recess, which is above the superior nasal concha.
• How do the paranasal sinuses contribute to respiratory function?

  • Humidify and warm inhaled air.
  • Reduce skull weight.
  • Enhance voice resonance.
  • Provide some degree of protection against facial trauma.
• What are the three divisions of the pharynx?

  • Nasopharynx
  • Oropharynx
  • Laryngopharynx
• Where is the nasopharynx located?

  • The nasopharynx is the uppermost part of the pharynx.
  • It is located posterior to the nasal cavity and above the soft palate.
• What are the key features of the nasopharynx?

  • Lined with ciliated pseudostratified columnar epithelium (respiratory epithelium).
  • Contains the pharyngeal tonsils (adenoids) on the posterior wall.
  • Connected to the middle ear via the auditory (Eustachian) tubes, which help equalise pressure.
• What is the function of the nasopharynx?

  • Acts as an air passageway between the nasal cavity and oropharynx.
  • Filters, warms, and humidifies air before it enters the lower respiratory tract.
  • The Eustachian tubes regulate middle ear pressure.
• Where is the oropharynx located?

  • The oropharynx is the middle part of the pharynx.
  • It is located posterior to the oral cavity, extending from the soft palate to the upper border of the epiglottis.
• What are the key features of the oropharynx?

  • Lined with non-keratinised stratified squamous epithelium, which protects against mechanical stress.
  • Contains the palatine tonsils (on lateral walls) and lingual tonsils (at the base of the tongue).
  • Shared by both the respiratory and digestive systems.
• What is the function of the oropharynx?

  • Serves as a passageway for both air and food.
  • Plays a role in swallowing (deglutition).
  • Involved in immune defence via the tonsils.