Respiratory System

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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 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.

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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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