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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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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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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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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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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?