THE RESPIRATORY SYSTEM

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

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

O RGANIZATION OF THE RESPIRATORY SYSTEM Upper Respiratory System – Nose, nasal cavity, paranasal sinuses, and pharynx Lower Respiratory System – Larynx, Trachea, Bronchi, Bronchioles, Alveoli

N OSE, NASAL CAVITY, PARANASAL SINUSES Nose - Primary passageway for air entering the respiratory system Nose is 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

P HARYNX ( THROAT ) Chamber shared by the digestive and respiratory systems The pharnyx is divided into the nasopharynx, oropharynx, and laryngopharynx 1. Nasopharynx – superior portion of pharynx 2. Oropharynx – oris/mouth; extends between the soft palate and the base of the tongue at the level of the hyoid bone 3. Laryngopharynx – inferior part of pharynx; entrance to larynx and esophagus

L ARYNX ( 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)

T RACHEA ( 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 (most likely site for a lodged object) supplies the right lung, left bronchus supplies the left lung

LUNGS Soft, spongy, cone shaped organs in the thoracic cavity Separated medially by the heart and the mediastinum; enclosed by the diaphragm and the thoracic cage 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) – small passageways that lead to the alveoli At the end of each bronchiole are groups of microscopic structures called alveoli (thin-walled air sacs covered with capillaries)

B REATHING – VENTILATION Movement of air from outside the body into the bronchial trees and alveoli Inspiration – inhalation Expiration – exhalation

M ECHANICS OF BREATHING Inspiration (inhalation):  The size of the thoracic cavity increases when the diaphragm moves downward  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 pulls air in through the nose or mouth  Air continues to move into the lungs until it equals atmospheric pressure

M ECHANICS OF BREATHING Expiration (exhalation):  When we breathe out, the diaphragm moves upward, forcing the chest cavity to get smaller  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 of the nose and mouth to equalize the pressure inside and outside the lungs

R ESPIRATION With each inhalation, air fills a large portion of the millions of alveoli (air sacs) Diffusion – oxygen moves from the alveoli to the blood through the capillaries lining the alveolar walls Once oxygen is in the bloodstream it gets picked up by the hemoglobin in red blood cells This oxygen rich blood flows back to the heart, which pumps it through the arteries to your body Carbon dioxide moves out of the cells into the capillaries and blood rich in carbon dioxide returns to the heart via the veins From the heart, this blood is pumped to the lungs, where carbon dioxide passes into the alveoli to be exhaled

L UNGS AND RESPIRATORY PROBLEMS Asthma – chronic inflammatory lung disease that causes airways to tighten and narrow Emphysema – lungs produce an excessive amount of mucus and the alveoli become damaged (caused by long-term smoking) Bronchitis – membranes lining the bronchial tubes become inflamed and an excessive amount of mucus is produced; a bad cough develops to get rid of the mucus

R ESPIRATORY SYSTEM D ISORDERS / DISEASES 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 bacterial infections (average predicted age of survival = 37 years) Atelectasis – complete or partial collapse of a lung or lobe of a lung; develops when the alveoli within the lung become deflated; caused by a blockage of the air passages, by pressure on the outside of the lung (injury), lung tumor, inhaled object Apnea – temporary absence or cessation of breathing; can cause decreased oxygen levels in the body (infant apnea and sleep apnea)

R ESPIRATION 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

R ESPIRATORY 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)

R ESPIRATORY 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 Spirometer testing is useful for evaluating losses in respiratory functioning and respiratory illnesses (pneumonia & emphysema)