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Respiratory system Full details

Organs of the Respiratory system

• Nose
• Pharynx
• Larynx
• Trachea
• Bronchi
• Lungs
• alveoli

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Function of the Respiratory System

✓ Oversees gas exchanges between the blood and external environment
✓ Exchange of gases takes place within the lungs in the alveoli
✓ Passage ways to the lungs purify, warm, and humidify the incoming air.

The Nose

✓ The only externally visible part of the
respiratory system
✓ Air enters the nose through the external
nares (nostrils)
✓ The interior of the nose consists of a nasal cavity divided by a nasal septum
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Anatomy of the Nasal Cavity

✓ Olfactory receptors are located in the mucosa on the superior surface
✓ The rest of the cavity is lined with respiratory mucosa
            • Moistens air
            • Traps incoming foreign particles
✓ Lateral walls have projections called conchae
            • Increases surface area
            • Increases air turbulence within the nasal cavity
✓  The nasal cavity is separated from the
oral cavity by the palate
           •Anterior hard palate (bone)
           •Posterior soft palate (muscle)

Paranasal Sinuses

✓ Cavities within bones surrounding
the nasal cavity
           • Frontal bone
           • Sphenoid bone
           • Ethmoid bone
           • Maxillary bone

Pharynx (Throat)

✓ Auditory tubes enter the nasopharynx
✓ Tonsils of the pharynx
         • Pharyngeal tonsil (adenoids) in the
         • nasopharynx
         • Palatine tonsils in the oropharynx
         • Lingual tonsils at the base of the tongue

Larynx (Voice Box)

✓ Routes for air and food into proper channels
✓ Plays a role in speech.
✓ Made of eight rigid hyaline
✓ cartilages and a spoon-shaped flap of elastic cartilage (epiglottis)

Structures of the Larynx

✓ Thyroid
✓ cartilage
             • Largest hyaline cartilage
             • Protrudes anteriorly (Adam’s apple)
✓ Epiglottis
             • Superior opening of the larynx
             • Routes food to the larynx and air toward the trachea

Structures of the Larynx

✓ Vocal cords (vocal folds)
             • Vibrate with expelled air to create sound (speech)
✓ Glottis – opening between vocal

Trachea (Windpipe)

✓ Connects larynx with
✓ bronchi 
✓ Lined with ciliated mucosa
           • Beat continuously in the opposite direction of incoming air
          • Expel mucus loaded with dust and other
debris away from lungs
✓ Walls are reinforced with C-shaped
hyaline cartilage

Primary Bronchi

✓ Formed by division of the trachea
✓ Enters the lung at the hilus (medial depression)
✓ Right bronchus is wider, shorter,and straighter than left
✓ Bronchi subdivide into smaller
and smaller branches


✓ Occupy most of the thoracic
✓ cavity
     • Apex is near the clavicle (superior portion)
                 • Base rests on the diaphragm (inferior
✓ Each lung is divided into lobes by fissures
                • Left lung – two lobes
                • Right lung – three lobes
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Coverings of the Lungs

✓ Pulmonary (visceral) pleura covers the
lung surface
✓ Parietal pleura lines the walls of the
thoracic cavity
✓ Pleural fluid fills the area between layers of pleura to allow gliding

Respiratory Tree Divisions

✓ Primary bronchi
✓ Secondary bronchi
✓ Tertiary bronchi
✓ Bronchioli
✓ Terminal
✓ bronchioli

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Respiratory Zone

• Respiratory bronchioli
• Alveolar duct
• Alveoli
Site of gas exchange


Structure of alveoli

• Alveolar duct
• Alveolar sac
• Alveolus
✓ Gas exchange takes place within the alveoli
in the respiratory membrane

Respiratory Membrane (Air-Blood Barrier)

✓ Thin squamous epithelial layer
lining alveolar walls
✓ Pulmonary capillaries cover external
surfaces of alveoli
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Gas Exchange

✓ Gas crosses the respiratory membrane
by diffusion
       • Oxygen enters the blood
       • Carbon dioxide enters the alveoli
✓ Macrophages add protection
✓ Surfactant coats gas-exposed
✓ alveolar surfaces

Events of Respiration

✓ Pulmonary ventilation – moving air in
and out of the lungs
✓ External respiration – gas exchange
between pulmonary blood and alveoli
✓ Respiratory gas transport – transport
of oxygen and carbon dioxide via the
✓ Internal respiration – gas exchange
between blood and tissue cells in

systemic capillaries Mechanics of Breathing (Pulmonary Ventilation)

• Two phases
✓ Inspiration – flow of air into lung
✓ Expiration – air leaving lung


• Diaphragm and intercostal muscles
• The size of the thoracic cavity increases
• External air is pulled into the lungs due to
an increase in intrapulmonary volume
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• Largely a passive process which depends
on natural lung elasticity
• As muscles relax, air is pushed out of the
• Forced expiration can occur mostly by
contracting internal intercostal muscles
to depress the rib cage
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Pressure Differences in the Thoracic Cavity

• Normal pressure within the pleural space is always negative (intrapleural pressure)
• Differences in lung and pleural space pressures keep lungs from collapsing

Nonrespiratory Air Movements

✓ Can be caused by reflexes or voluntary


• Cough and sneeze – clears lungs of debris
• Laughing
• Crying
• Yawn
• Hiccup

Respiratory Volumes and Capacities

✓ Normal breathing moves about 500 ml of air
with each breath (tidal volume [TV]) Many factors that affect respiratory capacity
• A person’s size
• Sex
• Age
• Physical condition
✓ Residual volume of air – after exhalation,
… about 1200 ml of air remains in the lungs

Respiratory Volumes and Capacities

✓ Inspiratory reserve volume (IRV)
       • Amount of air that can be taken in forcibly over the tidal volume
      • Usually between 2100 and 3200 ml
✓ Expiratory reserve volume (ERV)
      • Amount of air that can be forcibly exhaled
      • Approximately 1200 ml

Respiratory Volumes and Capacities

✓ Residual volume
      • Air remaining in lung after expiration
      • About 1200 ml