Outline • The Respiratory Tract • The Nose • The Pharynx • The Larynx • The Bronchial Tree • The Lungs • Gas Exchange • Mechanisms of Breathing • Inspiration and Expiration • Respiration and Health
The Respiratory System • During inspiration or inhalation, air is conducted toward the lungs. • During expiration or exhalation, air is conducted away from the lungs.
The Respiratory System • The respiratory system works with the cardiovascular system to accomplish respiration. • Breathing. • External respiration. • Internal respiration. • Cellular respiration.
The Respiratory Tract • As air moves towards the lungs it is cleansed, warmed, and moistened. • As air moves out during expiration, it cools and deposits moisture on the lining of the trachea and the nose.
The Nose • The nose contains two nasal cavities that empty into the nasopharynx. • Tear glands drain into the nasal cavities. • Auditory tubes lead from the nasopharynx to the middle ears.
The Pharynx • The pharynx is a funnel-shaped passageway that connects the nasal and oral cavities to the larynx. • Three sections. • Nasopharynx - Nasal cavities open above soft palate. • Oropharynx - Oral cavity opens. • Laryngopharynx - Opens into the larynx.
The Larynx • The larynx serves as a passageway for air between the pharynx and the trachea. • When food is swallowed, the larynx moves against the epiglottis preventing food from passing into the larynx. • The larynx houses the vocal cords which are stretched across the glottis. • The trachea is a tube connecting the larynx to the primary bronchi.
The Bronchial Tree • The trachea divides into left and right primary bronchi which eventually branch into secondary bronchi and then into bronchioles. • Each bronchiole leads to an elongated space enclosed by alveoli.
The Lungs • The lungs lie on either side of the heart within the thoracic cavity. • Right lung has three lobes and the left lung has two lobes. • Each lobe is divided into lobules, further divided into bronchioles serving many alveoli.
Mechanism of Breathing • Respiratory Volumes • Tidal volume is the amount of air that moves in and out with each breath. • Vital capacity is the maximum amount of air that can be moved out in a single breath. • Inspiration can be increased by expanding the chest (inspiratory reserve volume).
Respiratory Volumes • Vital Capacity • Expiration can be increased by contracting the abdominal and thoracic muscles (expiratory reserve volume). • Residual volume is the air remaining in the lungs after deep exhalation.
Inspiration and Expiration • Ventilation • Normally there is a continuous column of air from the pharynx to the alveoli. • Lungs lie within sealed thoracic cavity. • Rib cage forms top and side of the cavity, while the diaphragm forms the floor. • Lungs are enclosed by two membranes, pleura.
Inspiration • A respiratory center is located in the medulla oblongata and triggers inspiration. • Inspiration is the active phase of breathing. • The diaphragm and the rib muscles contract, intrapleural pressure decreases, the lungs expand, and air rushes in. • Creation of a partial vacuum in the alveoli causes air to enter the lungs.
Expiration • When the respiratory center stops sending signals to the diaphragm and the rib cage, the diaphragm relaxes. • Abdominal organs press up against the diaphragm, and the rib cage moves down and inward. • Expiration is usually passive as the diaphragm and external intercostal muscles are relaxed.
Gas Exchanges in the Body • External respiration refers to gas exchange between air in the alveoli and blood in the pulmonary capillaries. • Blood entering the pulmonary capillaries has a higher partial pressure of carbon dioxide than atmospheric air. • Carbon dioxide diffuses out of the blood into the lungs. • The pressure pattern is the reverse for oxygen.
Internal Respiration • Internal respiration refers to gas exchange between the blood in systemic capillaries and the tissue fluid. • Oxygen diffuses out of the blood into the tissue because the partial pressure of oxygen of tissue fluid is lower than that of blood.
Binding Capacity of Hemoglobin • Binding capacity of hemoglobin varies according to the environmental conditions in the lungs and tissues. • If the binding capacity of hemoglobin is high, hemoglobin will be saturated with oxygen. • The binding capacity of hemoglobin for oxygen is affected by the partial pressure of oxygen, temperature, and pH.
Respiration and Health • Upper Respiratory Tract Infections • Sinusitus - Infection of cranial sinuses. • Otitis Media - Bacterial infection of middle ear. • Tonsillitis - Inflammation and enlargement of tonsils. • Laryngitis - Infection of larynx with hoarseness and inability to talk.
Respiration and Health • Lower Respiratory Tract Infections • Acute bronchitis - Infection of primary and secondary bronchi. • Pneumonia - Viral or bacterial infection of the lungs. • Pulmonary tuberculosis - Tubercle bacillus bacterium.
Respiration and Health • Restrictive pulmonary disorders - Vital capacity is reduced because lungs have lost elasticity. • Pulmonary fibrosis. • Obstructive pulmonary disorders - Air does not flow freely in the airways. • Chronic bronchitis. • Emphysema. • Asthma. • Lung cancer.
Review • The Respiratory Tract • The Nose • The Pharynx • The Larynx • The Bronchial Tree • The Lungs • Gas Exchange • Mechanisms of Breathing • Inspiration and Expiration • Respiration and Health