The Respiratory System
System Overview
• Includes tubes that
remove particles from
incoming air and transport
air in and out of the lungs
• Microscopic air sacs for
gas exchange
• Organs include:
• Nose, nasal cavity, and
paranasal sinuses
• Pharynx
• Larynx
• Trachea
• Bronchial tree
• Lungs
Steps of Respiration
•
1.
2.
3.
4.
Respiration = the
process of gas exchange
between the atmosphere
and body cells
Ventilation
External Respiration:
Gas exchange between
blood and air in lungs
Gas transport between
lungs and body cells
Internal Respiration:
Gas exchange between
blood and body cells
Upper and Lower Respiratory
Tracts
• Upper
Respiratory Tract
• Organs located
outside the
thorax
• Lower
Respiratory Tract
• Organs located
within the thorax
The Nose
• Supported by bone
and cartilage
• Nostrils
• Nasal cavity
• Nasal septum
• Nasal conchae
• Support mucous
membranes
• Pseudostratified
columnar epithelium
and goblet cells
• Extensive network of
blood vessels to warm
air
Paranasal Sinuses
• Air-filled spaces
within:
•
•
•
•
Maxillary bones
Frontal bone
Ethmoid bone
Sphenoid bone
• Reduce skull weight
• Resonance
chambers
Pharynx
• Behind the oral
cavity and between
the nasal cavity and
the larynx
• Passageway for
food and air
• Helps produce
speech
Larynx
• Enlargement at the top
of the trachea and below
the pharynx
• Conducts air in and out
of the trachea
• Prevents foreign objects
from entering trachea
• Houses vocal cords
• Epiglottis
Vocal Cords
• Horizontal folds of muscle
and CT with a mucous
membrane covering
• False vocal cords
• True vocal cords
• Speech is formed by
changing the shape of the
pharynx and oral cavity
• Words formed by the tongue
and lips
• Loudness
• Pitch
• Glottis
Trachea
• AKA windpipe
• Extends in front of the
esophagus and into the
thoracic cavity
• Splits into left and right
bronchi
• Ciliated epithelium and
goblet cells
• Filters incoming air
• Sweeps particles out into
pharynx
• 20 hyaline cartilage rings
Bronchial Tree
• Branched airways
leading from trachea to
lungs
• Structurally similar to
trachea with less
cartilage
• Mucous membranes
filter incoming air and
distribute air to alveoli
Passage of Air Though the Bronchial Tree
• Primary bronchi 
secondary bronchi
 bronchioles 
alveolar ducts 
alveoli
Lungs
• Soft, spongy, coneshaped organs in
thoracic cavity
• Lungs separated by the
heart
• Enclosed by thoracic
cage and diaphragm
• Suspended from bronchi
and some large blood
vessels
• Right lung (3 lobes) is
larger than left (2 lobes)
• Visceral pleura
Breathing
•
•
Breathing consists of 2 processes:
1. Inspiration (inhalation)
2. Expiration (exhalation)
Air moves into the lungs because of
atmospheric pressure.
• When lung pressure is lower than
atmospheric pressure because of
diaphragm and intercostal
muscle contractions 
inspiration
• When muscles relax and lungs
and thoracic cage return to
normal size  expiration
Control of Breathing
• Controlled by the
respiratory center of the
medulla oblongata and
the pons
• May also be affected by
• Chemicals in body fluids
(CO2, H+, O2)
• Degree to which lung
tissue stretches
• Emotional state
• Hyperventilation