Chapter 22
Respiratory System
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.
Slide 1
Introduction
• The respiratory system is primarily concerned
with the delivery of oxygen to every cell in the
body and the elimination of carbon dioxide.
Slide 2
Structures: Organs
of the Respiratory System
• The respiratory system consists of the upper
and lower respiratory tracts.
• Nose and Nasal Cavities
– The nose and nasal cavities warm and humidify
inhaled air.
– Olfactory receptors are located in the nose.
– The nasal cavities receive drainage from the
paranasal sinuses and tear ducts.
Slide 3
Structures: Organs
of the Respiratory System - cont’d
• Pharynx (throat)
– The nasopharynx forms a passage for air only.
– The oropharynx and laryngopharynx form
passageways for both air and food.
Slide 4
Structures: Organs
of the Respiratory System - cont’d
• Larynx (voicebox)
– The larynx is a passage for air.
– The epiglottis is the uppermost cartilage and
covers the larynx during swallowing.
Slide 5
Structures: Organs
of the Respiratory System - cont’d
• Trachea (windpipe)
– Bifurcates into the right and left bronchi.
– C-shaped rings of cartilage keeps the
trachea open.
Slide 6
Structures: Organs
of the Respiratory System - cont’d
• Bronchial Tree
– The bronchial tree contains the bronchi, bronchioles,
and alveoli.
– The bronchioles determine the radius of the
respiratory air passages and therefore affect the
amount of air that can enter the alveoli.
– The alveoli are tiny, grapelike air sacs surrounded by
pulmonary capillaries.
– Gas exchange occurs across the thin walls of the
alveoli.
Slide 7
Structures: Organs
of the Respiratory System - cont’d
• Lungs
– The right lung has three lobes, and the left lung
has only two lobes.
– The lungs contain the structures of the lower
respiratory tract.
Slide 8
Structures: Organs
of the Respiratory System - cont’d
• Pleural Membranes
– The serous membranes in the chest cavity are the
parietal pleura and the visceral pleura.
– Serous fluid between the pleural membranes
prevents friction.
– For the lungs to remain expanded, pressure in the
intrapleural space must be negative.
Slide 9
Respiratory Function
• Respiration includes three steps: ventilation,
exchange of respiratory gases, and transport
of respiratory gases in the blood.
– Ventilation (Breathing)
• The two phases of ventilation are inhalation and
exhalation.
• Ventilation occurs in response to changes in the
thoracic volume (Boyle’s law).
Slide 10
Respiratory Function - cont’d
– Respiration includes three steps—cont’d
– Ventilation (Breathing)—cont’d
• Thoracic volume changes because of the contraction and
relaxation of the respiratory muscles.
• The phrenic and intercostal nerves are motor nerves that
supply the diaphragm and the intercostal muscles.
• Inhalation is an active process (ATP used is used during
muscle contraction). Unforced exhalation is passive
(no ATP used).
Slide 11
Respiratory Function - cont’d
• Respiration includes three steps—cont’d
– Exchange of Gases
• Exchange of respiratory gases occurs by diffusion across
the alveoli and pulmonary capillaries.
• Oxygen diffuses from the air in the alveoli into the
blood while CO2 diffuses from the blood into the
alveoli.
• At the cellular layer, oxygen diffuses from the capillaries
to the cells. Carbon dioxide diffuses from the cells into
the capillaries where it is transported to the lungs for
excretion.
Slide 12
Respiratory Function - cont’d
– Respiration includes three steps—cont’d
– Transport of Gases in the Blood
• Most of the oxygen is transported by the red blood cell
(oxyhemoglobin).
• The blood transports most
carbon dioxide in the form
–
3
of bicarbonate ion (HCO ).
Slide 13
Respiratory Function - cont’d
• Amounts of Air
– Pulmonary Volumes
• Refers to the amounts of air moved into and out of the
lungs.
• Pulmonary volumes are illustrated in Figure 22-10 and
summarized in Table 22-1.
Slide 14
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.
Slide 15
Respiratory Function - cont’d
• Amounts of Air—cont’d
– Vital Capacity and Anatomic Dead Space
• Lung capacities are combinations of pulmonary
volumes.
• Vital capacity is the amount of air that can be exhaled
after a maximal inhalation.
• Anatomic dead space refers to air remaining in the
large conducting passageways that is unavailable for
gas exchange: ~150 ml of air.
Slide 16
Respiratory Function - cont’d
• Control of Breathing
– Neural control of breathing
• The respiratory center is located in the brain stem.
• The medullary respiratory center contains inspiratory
and expiratory neurons. Nerve impulses travel along
the phrenic and intercostal nerves to the muscles of
respiration.
• The pneumotaxic center and the apneustic center are
in the pons. These centers help control the medullary
respiratory center to produce a normal breathing
pattern.
Slide 17
Respiratory Function - cont’d
• Control of Breathing—cont’d
– Neural control of breathing—cont’d
• Two other areas of the brain can affect respirations: the
hypothalamus and the cerebral cortex.
– Chemical control of respiration
• Central chemoreceptors are stimulated by carbon
dioxide (Pco2) and [H+].
• Peripheral chemoreceptors are sensitive to low
concentrations of oxygen and increased hydrogen ion
concentration in the blood.
Slide 18