1. THE RESPIRATORY SYSTEM

2. FUNCTIONS OF THE RESPIRATORY SYSTEM
Transports air into the lungs and facilitates the diffusion of oxygen into the blood stream
Receives carbon dioxide from the blood and exhales it

3. Organs of the Respiratory system
Nose
Pharynx
Larynx
Trachea
Bronchi
Lungs - alveoli
Figure 13.1
Slide 13.1
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

4. Organization of the respiratory system
Upper Respiratory System – Nose, nasal cavity, paranasal sinuses, and pharynx
Lower Respiratory System – Larynx, Trachea, Bronchi, Bronchioles, Alveoli

5. Nose, nasal cavity, paranasal sinuses
Primary passageway for air entering the respiratory system
The only externally visible part of the respiratory system
The maxillary, nasal, frontal, ethmoid, and sphenoid bones form the lateral and superior walls of the nasal cavity
The mucous secretions produced in the paranasal sinuses keep the nasal cavity moist and clean

6. Pharynx (throat)
Chamber shared by the digestive and respiratory systems
The pharnyx is divided into the nasopharynx, oropharynx, and laryngopharynx
Nasopharynx – superior portion of pharynx
Oropharynx – oris/mouth; extends between the soft palate and the base of the tongue at the level of the hyoid bone
Laryngopharynx – inferior part of pharynx; entrance to larynx and esophagus

7. Larynx (voicebox)
Cartilaginous structure that surrounds and protects the glottis (narrow opening where inhaled air leaves the pharynx and enters larynx)
Epiglottis – superior to the glottis; composed of elastic cartilage; during swallowing the larynx is elevated and the epiglottis folds back over the glottis, preventing the entry of both liquids and food into the respiratory tract
Sound production - air passing through the glottis vibrates the vocal folds and produces sound waves (phonation)

8. Trachea (windpipe) Tough, flexible tube
Transports air between the larynx and primary bronchi
Cilia and mucus protect the respiratory tree by trapping inhaled debris and sweeping it toward the pharynx, where it is removed through coughing or swallowing
Branches within the mediastinum, giving rise to the right and left primary bronchi
Right bronchus supplies the right lung, left bronchus supplies the left lung

9. LUNGS Air moves into the lungs through the trachea (windpipe)
The trachea branches out into two bronchi (main airways that reach into each lung)
Bronchioles (network of tubes) brings air closer to the site of external respiration
At the end of each bronchiole are groups of microscopic structures called alveoli (thin-walled air sacs covered with capillaries)
Gas exchange takes place as oxygen and carbon dioxide spread across the walls of the capillaries and alveoli

10. Lungs
Figure 13.4b
Slide 13.12b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

11. Respiration
Pulmonary ventilation – air must move into and out of the lungs so that the gases in the alveoli are refreshed
External respiration – gas exchange (oxygen loading and carbon dioxide unloading) between the blood and alveoli
Respiratory gas transport – oxygen and carbon dioxide must be transported to and from the lungs and cells of the body via the blood
Internal respiration – gas exchanges must be made between the blood and cells at capillaries

12. Mechanics of breathing
Inspiration:
The size of the thoracic cavity increases when the diaphragm and external intercostals contract
As the volume within the lungs increases, the gases within the lungs spread out
This results in a decrease of gas pressure and produces a partial vacuum (pressure less than atmospheric pressure) which sucks air into the lungs
Air continues to move into the lungs until it equals atmospheric pressure

13. Mechanics of breathing
Expiration:
As the inspiratory muscles relax, the rib cage descends and the lungs recoil
As volume decreases, the gases inside the lungs are forced more closely together, and the pressure rises to a point higher than atmospheric pressure
This causes the gases to flow out to equalize the pressure inside and outside the lungs

14. Respiratory volumes and capacities
Many factors affect respiratory capacity – size, sex, age, and physical condition
Normal quiet breathing moves approx. 500ml of air into and out of the lungs with each breath (tidal volume)
The amount of air that can be taken in above the tidal volume is the inspiratory reserve volume (IRV)
The amount of air that can be forcibly exhaled after a tidal expiration is the expiratory reserve volume (ERV)
Residual volume – amount of air that still remains in the lungs after expiration (allows for gas exchange to go on continuously between breaths)

15. Respiratory volumes and capacities
Vital capacity = TV + IRV + ERV
Dead space volume – air that enters and remains in the passageways and never reaches the alveoli
Spirometer – measures respiratory capacities
Spirometer testing is useful for evaluating losses in respiratory functioning and respiratory illnesses (pneumonia & emphysema)

16. Respiratory system Disorders/diseases
Atelectasis – “collapsed lung”; caused by a blockage of the air passages or by pressure on the outside of the lung
Apnea – temporary absence or cessation of breathing; can cause decreased oxygen levels in the body
Emphysema – chronic, progressive condition; destruction of alveolar surfaces and inadequate surface area for oxygen and carbon dioxide exchange
Cystic Fibrosis – most common lethal inherited disease; respiratory mucus is extremely dense and cannot be transported by the respiratory defense system which leads to frequent infections (average predicted age of survival = 37 years)