Organs of the Respiratory system
• Nose
• Pharynx
• Larynx
• Trachea
• Bronchi
• Lungs
• alveoli
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
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
• 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
cords
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
Lungs
✓ Occupy most of the thoracic
✓ cavity
• Apex is near the clavicle (superior portion)
• Base rests on the diaphragm (inferior
portion)
✓ Each lung is divided into lobes by fissures
• Left lung – two lobes
• Right lung – three lobes
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
✓ Secondary bronchi
✓ Tertiary bronchi
✓ Bronchioli
✓ Terminal
✓ bronchioli
Respiratory Zone
Structure
• Respiratory bronchioli
• Alveolar duct
• Alveoli
Site of gas exchange
Alveoli
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
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
bloodstream
✓ 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
Inspiration
• Diaphragm and intercostal muscles
contract
• The size of the thoracic cavity increases
• External air is pulled into the lungs due to
an increase in intrapulmonary volume
Exhalation
• Largely a passive process which depends
on natural lung elasticity
• As muscles relax, air is pushed out of the
lungs
• Forced expiration can occur mostly by
contracting internal intercostal muscles
to depress the rib cage
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
actions
Examples
• 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
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