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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
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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
• Nose– External nose
– Nasal cavity
• Functions– Passageway for air
– Cleans the air
– Humidifies, warms air
– Smell
Fig. 25.2
Pharynx
Nasal conchae
Nostril
Internal nares
Opening of auditory tube
Nasopharynx
Oropharynx
Laryngopharynx
Esophagus
Trachea
Paranasal sinuses
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23-5
Nose and Pharynx
• Pharynx– Common opening for
digestive and respiratory systems
– Three regions• Nasopharynx
• Oropharynx
• Laryngopharynx Fig. 25.2
Pharynx
Nasal conchae
Nostril
Internal nares
Opening of auditory tube
Nasopharynx
Oropharynx
Laryngopharynx
Esophagus
Trachea
Paranasal sinuses
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Larynx
• Functions– 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
Fig. 25.4
Hyoid bone
Epiglottis
Hyoidbone
Thyroidcartilage
Cricoidcartilage
Trachealcartilage
Larynx
Trachea
(a) Anterior(b) Posterior (c) Midsagittal
Epiglottis
Cricoidcartilage
Thyroidcartilage
Vocal ligament(true vocal cord)
Vestibularligament(false vocalcord)
Fat
Trachealcartilage
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Vocal Folds
Fig. 25.5
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23-8
Trachea• Windpipe
– Cartilage rings– Dense regular
connective tissue
• Divides to form– Primary bronchi
• Carina– Most inferior
tracheal cartilage– Cough reflex
• Trachealis muscle– Narrows tracheaFig. 25.7
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23-9
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 TractConducting Zone
Fig. 25.8
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
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Lower Respiratory Tract
Respiratory zone– Respiratory
bronchioles to alveoli
– Site for gas exchange
Fig. 25.9
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23-13
Points to RememberPoints 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?