Lecture 20
Respiratory System
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Respiratory System Functions
• Gas exchange: Oxygen enters blood and carbon
dioxide leaves
• Regulation of blood pH: Altered by changing
blood carbon dioxide levels
• Voice production: Movement of air past vocal
folds makes sound and speech
• Olfaction: Smell occurs when airborne molecules
drawn into nasal cavity
• Protection: Against microorganisms by preventing
entry and removing them
23-2
Respiratory System Divisions
• Upper tract
– Nose, pharynx and
associated structures
• Lower tract
– Larynx, trachea, bronchi,
lungs
Fig. 25.1
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Nose and Pharynx
Paranasal
sinuses
Nasal conchae
Internal nares
Opening of auditory tube
Nostril
Nasopharynx
Oropharynx
Pharynx
Laryngopharynx
Esophagus
Trachea
• Nose
– External nose
– Nasal cavity
• Functions
–
–
–
–
Passageway for air
Cleans the air
Humidifies, warms air
Smell
Fig. 25.2
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Nose and Pharynx
• Pharynx
Paranasal
sinuses
Nasal conchae
– Common opening for
digestive and
respiratory systems
– Three regions
• Nasopharynx
• Oropharynx
• Laryngopharynx
Internal nares
Opening of auditory tube
Nostril
Nasopharynx
Oropharynx
Pharynx
Laryngopharynx
Esophagus
Trachea
Fig. 25.2
23-5
Larynx
Epiglottis
Epiglottis
Hyoid bone
Hyoid
bone
Fat
Larynx
Thyroid
cartilage
Thyroid
cartilage
Vestibular
ligament
(false vocal
cord)
Cricoid
cartilage
Cricoid
cartilage
Vocal ligament
(true vocal cord)
Tracheal
cartilage
Trachea
(a) Anterior
• Functions
Tracheal
cartilage
(b) Posterior
(c) Midsagittal
Fig. 25.4
– Maintain an open passageway for air movement
– Epiglottis and false vocal cords prevent swallowed material
from moving into larynx
– True vocal folds are primary source of sound production
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Vocal Folds
Fig. 25.5
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Trachea
• Windpipe
– Cartilage rings
– Dense regular
connective tissue
• Divides to form
– Primary bronchi
• Carina
– Most inferior
tracheal cartilage
– Cough reflex
• Trachealis muscle
Fig. 25.7
– Narrows trachea
23-8
Review Question
Which of the following statements about the
trachea is correct?
(a) It is reinforced by circular rings of cartilage
(b) The epithelium does not have mucous glands
(c) It does not alter its diameter
(d) Loose connective tissue connects the bands of
cartilage in the trachea
(e) Paired primary bronchi are at the inferior end
of the trachea
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Lower Respiratory Tract
Two zones based upon function
– Conducting zone
– Respiratory zone
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Lower Respiratory Tract
Conducting Zone
Conducting Zone
– Trachea to
terminal bronchioles
which is ciliated for
removal of debris
– Passageway for air
movement
– Cartilage holds
tube system open
and smooth muscle
controls tube
diameter
Fig. 25.8
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Lower Respiratory Tract
Respiratory
zone
– Respiratory
bronchioles
to alveoli
– Site for gas
exchange
Fig. 25.9
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Points to Remember
• Two major divisions of the respiratory
system: upper tract and lower tract
– Upper tract - warms, moistens and cleans air
(nose and nasal cavity)
– Lower tract - prevention of entrance of food
into lower tract and sound production (larynx),
passageway of air to alveoli for gas exchange
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Questions?
23-14