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Chapter 18/19

SC1223D Chapter Notes - Chapter 18/19: Nasal Cavity, Nasal Septum, Mucous Membrane


Department
Science
Course Code
SC1223D
Professor
James Brinson
Chapter
18/19

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CHAPTER 19: RESPIRATORY SYSTEM
19.1 Overview of the Respiratory System
(page 731)
The respiratory system includes the passages
that transport
air to and from the lungs and the air sacs in
which gas
exchanges occur.
a. Respiration is the entire process by which
gases are
exchanged between the atmosphere and the
body cells.
b. Respiration is necessary because cells require
oxygen to
extract maximal energy from nutrient molecules
and release
carbon dioxide, a metabolic waste.
19.2 Organs of the Respiratory System (page
731)
The respiratory system is divided into two tracts.
The upper
respiratory tract includes the nose, nasal cavity,
sinuses,
and pharynx; the lower respiratory tract includes
the larynx,
trachea, bronchial tree, and lungs.
1. Nose
a. Bone and cartilage support the nose.
b. Nostrils provide entrances for air.
2. Nasal cavity
a. The nasal cavity is a space posterior to the
nose.
b. The nasal septum divides it medially
c. Nasal conchae divide the cavity into
passageways and
help increase the surface area of the mucous
membrane.
d. Mucous membrane cleans, warms, and
moistens
incoming air.
e. Particles trapped in the mucus are carried to
the
pharynx by ciliary action and are swallowed.
3. Sinuses
a. Sinuses are spaces in the bones of the skull
that open
into the nasal cavity.
b. They are lined with mucous membrane that is
continuous with the lining of the nasal cavity.
4. Pharynx
a. The pharynx is posterior to the mouth,
between the
nasal cavity and the larynx.
b. It provides a common passage for air and
food.
c. It aids in creating vocal sounds.
5. Larynx
a. The larynx is an enlargement at the top of the
trachea.
b. It is a passageway for air and helps prevent
foreign
objects from entering the trachea.
c. It is composed of muscles and cartilages;
some of these
cartilages are single, whereas others are paired.
d. It contains the vocal cords, which produce
sounds by
vibrating as air passes over them.
(1) The pitch of a sound is related to the tension
on
the cords.
(2) The intensity of a sound is related to the
force of
the air passing over the cords.
e. The epiglottis helps prevent food and liquid
from
entering the trachea.
6. Trachea
a. The trachea extends into the thoracic cavity
anterior to
the esophagus.
b. It divides into the right and left main bronchi.
c. The mucous lining continues to clean
incoming air.
d. Incomplete cartilaginous rings support the
wall.

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7. Bronchial tree
a. The bronchial tree consists of branched air
passages
that connect the trachea to the air sacs.
b. The branches of the bronchial tree include
main
bronchi, lobar bronchi, segmental bronchi,
intralobular bronchioles, terminal bronchioles,
respiratory bronchioles, alveolar ducts, alveolar
sacs, and alveoli.
c. Structure of the respiratory tubes
(1) As tubes branch, the amount of cartilage in
the
walls decreases, and the muscular layer persists
to the ends of the respiratory bronchioles.
(2) Elastic fibers in the walls aid breathing.
(3) The epithelial lining changes from
pseudostratified
and ciliated to cuboidal and then to simple
squamous as the tubes become progressively
smaller.
d. Functions of the respiratory tubes and alveoli
include
distribution of air and exchange of gases
between the
alveolar air and the blood.
8. Lungs
a. The left and right lungs are separated by the
mediastinum and are enclosed by the
diaphragm and
the thoracic cage.
b. The visceral pleura is attached to the surface
of the
lungs; parietal pleura lines the thoracic cavity.
c. The right lung has three lobes, and the left
lung has two.
d. Each lobe is composed of lobules that contain
alveolar
ducts, alveolar sacs, alveoli, nerves, blood
vessels,
lymphatic vessels, and connective tissues.
19.3 Breathing Mechanism (page 741)
Inspiration and expiration movements are
accompanied
by changes in the size of the thoracic cavity. One
inspiration
followed by one expiration is a respiratory cycle.
1. Inspiration
a. Atmospheric pressure forces air into the
lungs.
b. Inspiration occurs when the intra-alveolar
pressure is
reduced.
c. The intra-alveolar pressure is reduced when
the
diaphragm moves downward and the thoracic
cage
moves upward and outward.
d. Surface tension holding the pleural
membranes
together aids lung expansion.
e. Surfactant reduces surface tension in the
alveoli.
2. Expiration
a. The forces of expiration come from the elastic
recoil of
tissues and from surface tension in the alveoli.
b. Expiration can be aided by thoracic and
abdominal
wall muscles that pull the thoracic cage
downward and
inward and compress the abdominal organs
inward and
upward.
3. Respiratory air volumes and capacities
a. The amount of air that moves in or out during
a
respiratory cycle is the tidal volume.
b. Additional air that can be inhaled is the
inspiratory
reserve volume; additional air that can be
exhaled is
the expiratory reserve volume.
c. Residual air remains in the lungs and is mixed
with
newly inhaled air.
d. The residual volume is difficult to measure.
e. The vital capacity is the maximum amount of
air
a person can exhale after taking the deepest
breath
possible.
f. The inspiratory capacity is the maximum
volume of
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air a person can inhale following exhalation of
the tidal
volume.
g. The functional residual capacity is the volume
of air
that remains in the lungs following the
exhalation of the
tidal volume.
h. The total lung capacity is equal to the vital
capacity
plus the residual volume.
i. Air in the anatomic and alveolar dead spaces is
not
available for gas exchange.
4. Alveolar ventilation
a. Minute ventilation is tidal volume multiplied
by
breathing rate.
b. Alveolar ventilation rate is the physiologic
dead
space subtracted from the tidal volume
multiplied by
breathing rate.
c. The alveolar ventilation rate is a major factor
affecting
gas exchange between the alveolar air and the
blood.
5. Nonrespiratory air movements
a. Nonrespiratory air movements are air
movements other
than breathing.
b. They include coughing, sneezing, laughing,
crying,
hiccupping, and yawning.
19.4 C ontrol of Breathing (page 750)
Normal breathing is rhythmic and involuntary,
although the
respiratory muscles can be controlled
voluntarily.
1. Respiratory areas
a. The respiratory areas are in the brainstem and
include
parts of the medulla oblongata and pons.
b. The medullary respiratory center includes two
groups of neurons.
(1) The ventral respiratory group provides the
basic
rhythm of breathing.
(2) The dorsal respiratory group stimulates
inspiratory
muscles and processes sensory information
regarding the respiratory system. It may play a
role
in certain cardiopulmonary reflexes.
c. The pontine respiratory group may contribute
to the
rhythm of breathing by limiting inspiration.
2. Partial pressure
a. The partial pressure of a gas is determined by
the
concentration of that gas in a mixture of gases
or the
concentration of gas dissolved in a liquid.
b. The partial pressure of a gas dissolved in a
liquid equals
the partial pressure of that gas in the air with
which the
liquid has equilibrated.
3. Factors affecting breathing.
a. Chemicals, lung tissue stretching, and
emotional state
affect breathing.
b. Chemosensitive areas (central
chemoreceptors) are
associated with the respiratory center.
(1) CO2 combines with water to form carbonic
acid,
which, in turn, releases hydrogen ions in the
CSF.
(2) Stimulation of these areas increases alveolar
ventilation.
c. Peripheral chemoreceptors are in the carotid
bodies
and aortic bodies of certain arteries.
(1) These chemoreceptors sense low oxygen
levels as
well as excess hydrogen ions.
(2) When oxygen levels are low or blood pH
drops,
alveolar ventilation increases.
d. Stretching the lung tissues triggers an inflation
reflex.
(1) This reflex reduces the duration of
inspiratory
movements.
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