1. Lecture 20
Respiratory System

2. 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

3. Respiratory System Divisions
Upper tract
Nose, pharynx and associated structures
Lower tract
Larynx, trachea, bronchi, lungs
Fig. 25.1

4. Nose and Pharynx Nose External nose Nasal cavity Functions
Paranasal
sinuses
Nasal conchae
Internal nares
Opening of auditory tube
Nostril
Nasopharynx
Oropharynx
Pharynx
Laryngopharynx
Esophagus
Nose
External nose
Nasal cavity
Functions
Passageway for air
Cleans the air
Humidifies, warms air
Smell
Trachea
Fig. 25.2

5. Nose and Pharynx Pharynx
Paranasal
sinuses
Pharynx
Common opening for digestive and respiratory systems
Three regions
Nasopharynx
Oropharynx
Laryngopharynx
Nasal conchae
Internal nares
Opening of auditory tube
Nostril
Nasopharynx
Oropharynx
Pharynx
Laryngopharynx
Esophagus
Trachea
Fig. 25.2

6. Larynx Functions Maintain an open passageway for air movement
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
Tracheal
cartilage
(b) Posterior
(c) Midsagittal
(a) Anterior
Fig. 25.4
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

7. Vocal Folds
Fig. 25.5

8. Trachea Windpipe Divides to form Carina Trachealis muscle
Cartilage rings
Dense regular connective tissue
Divides to form
Primary bronchi
Carina
Most inferior tracheal cartilage
Cough reflex
Trachealis muscle
Narrows trachea
Fig. 25.7

9. Review Question
Which of the following statements about the trachea is correct?
It is reinforced by circular rings of cartilage
The epithelium does not have mucous glands
It does not alter its diameter
Loose connective tissue connects the bands of cartilage in the trachea
Paired primary bronchi are at the inferior end of the trachea

10. Lower Respiratory Tract
Two zones based upon function
Conducting zone
Respiratory zone

11. Lower Respiratory Tract 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

12. Lower Respiratory Tract
Respiratory zone
Respiratory bronchioles to alveoli
Site for gas exchange
Fig. 25.9

13. 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

14. Questions?