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Respiratory System

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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

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The Respiratory System

• During inspiration or inhalation, air is conducted toward the lungs.

• During expiration or exhalation, air is conducted away from the lungs.

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The Respiratory System

• The respiratory system works with the cardiovascular system to accomplish respiration.– Breathing.– External respiration.– Internal respiration.– Cellular respiration.

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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.

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The Respiratory Tract

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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.

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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.

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The Path of Air

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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.

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Placement of the Vocal Cords

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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.

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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.

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Gas Exchange in the Lungs

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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).

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Respiratory Volumes

– Vital CapacityExpiration 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.

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Vital Capacity

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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.

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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.

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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.

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Inspiration Versus Expiration

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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.

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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.

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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.

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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.

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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.

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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.

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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

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