Download Unit 5 Respiratory System Outline

Mader
Inquiry into Life, Thirteenth Edition
Chapter Outline
CHAPTER 15: RESPIRATORY SYSTEM
15.1 The Respiratory System
The primary function of the respiratory system is to allow oxygen from the air to enter the blood
and carbon dioxide from the blood to exit into the air. Inspiration is breathing in and expiration is
breathing out.
The Respiratory Tract
As air moves into the airways of the respiratory tract, it is cleansed, warmed, and
moistened.
The Nose
The nose is part of the upper respiratory tract. Air enters the nose, which is lined
with mucous membranes and contains odor receptors.
The Pharynx
The pharynx is part of the respiratory as well as the digestive system.
The Larynx
The larynx is a cartilaginous structure between the pharynx and the trachea. It is
called the voice box because it houses the vocal cords.
The Trachea
The trachea connects the larynx to the primary bronchi. It is held open by Cshaped cartilaginous rings. It is lined with a mucosa that contains cilia for
sweeping mucus and debris toward the pharynx.
The Bronchial Tree
The trachea divides into right and left primary bronchi that lead into the right
and left lungs. The bronchi branch into secondary bronchi that lead to
bronchioles. Each bronchiole leads to an air sac called an alveolus.
The Lungs
The lungs consist of portions of the bronchial tree leading to the alveoli. Each
alveolus is surrounded by an extensive capillary network where gas exchange
occurs.
15.2 Mechanism of Breathing
During ventilation, air first moves into the lungs from the nose or mouth and then moves out of
the lungs.
Respiratory Volumes
Normally the amount of air that moves into and out of the lungs during each breath is
much less than the maximum amount that can be inhaled or exhaled.
Inspiration and Expiration
There is a continuous column of air from the pharynx to the alveoli. The lungs lie within
the sealed-off thoracic cavity and adhere to the thoracic wall by way of the pleura.
Inspiration
Inspiration is the active phase of ventilation. The diaphragm lowers and the
external intercostal muscles move the rib cage upward and outward. The volume
of the thoracic cavity is larger than it was before and air rushes into the lungs.
Expiration
Expiration is the passive phase of breathing and no effort is required to bring it
about.
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Control of Ventilation
Normally adults have a breathing rate of 12–20 ventilations per minute. The
rhythm of ventilation is controlled by a respiratory center in the medulla
oblongata of the brain.
Chemical Input
The respiratory center is sensitive to the levels of carbon dioxide and
hydrogen ions in the blood.
15.3 Gas Exchanges in the Body
Respiration includes not only the exchange of gases in the lungs but the exchanges of gases in the
tissues. The principle of diffusion governs whether oxygen or carbon dioxide enters or leaves the
blood in the lungs and in the tissues.
External Respiration
External respiration refers to the exchange of gases between air in the alveoli and blood
in the pulmonary capillaries.
Internal Respiration
Internal respiration refers to the exchange of gases between the blood in systemic
capillaries and the tissue fluid.
15.4 Disorders of the Respiratory System
Disorders of the Upper Respiratory Tract
The upper respiratory tract consists of the nasal cavities, the pharynx, and the larynx.
The Common Cold
Most “colds” are relatively mild infections of the upper respiratory tract.
Pharyngitis, Tonsillitis, and Laryngitis
These disorders are caused by inflammation of the pharynx, tonsils, and larynx,
respectively.
Sinusitis
Sinusitis is an inflammation of the cranial sinuses.
Otitis Media
Otitis media is an inflammation of the middle ear. Although not part of the
respiratory tract, the middle ear can become infected from a nasal infection
through the eustachian tubes.
Disorders of the Lower Respiratory Tract
Disorders of the Trachea and Bronchi
One of the most life-threatening disorders that affects the trachea is choking.
Acute bronchitis is an inflammation of the primary and secondary bronchi. In
chronic bronchitis, the airways are inflamed and filled with mucus. Asthma is a
disease of the bronchi and bronchioles due to an unusual sensitivity to specific
irritants.
Diseases of the Lungs
Pneumonia is a viral or bacterial infection of the lungs in which the bronchi or
alveoli fill with fluid. Tuberculosis is caused by a bacterial infection.
Emphysema is a chronic and incurable disorder in which the alveoli are distended
and their walls damaged. Cystic fibrosis is a genetic lung disease. Lung cancer
is correlated with smoking.
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