Transcript Reading Part 2: The Respiratory System

Maintenance of the Human Body
Part 3: The Respiratory System
Concepts: chapter 24
The respiratory system
 Body cells continually use O2 & produce CO2
as a waste product.
 Respiratory system moves these 2 gases.
 Consists of:
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Nose
Pharynx
Larynx
Trachea
Bronchi
Lungs
The respiratory system—structures
 Nose fxns to filter & moisten air. Also
receptors for smell.
 Pharynx is posterior to nasal & oral cavities.
It’s a passageway for air, food, voice
resonance, houses tonsils.
 Larynx connects pharynx with trachea. Walls
are composed of cartilage.
The respiratory system—structures
The respiratory system—structures
 Trachea is reinforced with C-shaped hyaline
cartilage. Goes from larynx to level of 5th
thoracic vertebrae. Then it branches.
 Bronchi are the 2 tubes that enter the right &
left lung.
The respiratory system—structures
 Trachea primary bronchi  secondary
bronchi  tertiary bronchi  bronchioles 
terminal bronchioles
The respiratory system—structures
 Lungs are covered in double layer called
pleural membrane. Consists of:
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Parietal pleura
Visceral pleura
Pleural cavity is in btwn
 These membranes help to reduce friction.
The respiratory system—structures
 Each lung has a hilum which is the region
through which the bronchi, pulmonary blood
vessels, lymphatic vessels & nerves enter
and exit.
 Right lung is slightly larger.
It has 3 lobes. Left has 2.
The respiratory system—structures
 At the end of each terminal bronchiole are
clusters of alveoli.
 Alveoli have very thin, moist walls that are
closely associated with capillaries.
 The walls also have “dust cells” which are
phagocytic immune cells.
The respiratory system—ventilation
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Respiration = the process of gas exchange.
There are 3 parts:
1. Pulmonary—inhalation & exhalation
2. External—exchange btwn alveoli &
capillaries (O2 in to blood, CO2 out)
3. Internal—exchange btwn blood & tissue
cells (O2 into tissue cells, CO2 out)
The respiratory system—ventilation
 Inhalation
Diaphragm contracts & flattens.
 Intercostal myo’s contract & raise rib cage.
(these first two actually occur at the same time)
 Volume of the thoracic cavity increases, so
pressure inside decreases.
 Air moves in b/c pressure inside lungs is less
than air pressure.
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The respiratory system—ventilation
The respiratory system—ventilation
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Diaphragm decends ~1cm during relaxed
breathing & ~10 cm during strenuous
breathing.
Accessory myo’s can elevate sternum & upper
ribs to increase thoracic volume even more.
The respiratory system—ventilation
 Exhalation
 Usually a passive process.
 There is elastic recoil of the thoracic
structures—they tend to spring back after
being stretched.
 Diaphragm relaxes & rises.
 Intercostal myo’s relax & rib cage lowers.
 Thoracic cavity space decreases, air is forced
out.
Lung volumes
The respiratory system—gas exchange
 Gases diffuse in & out of
alveoli & vessels based on
pressure differences.
 If oxygen has higher partial
pressure in alveoli than in
capillaries, it will diffuse into
capillaries. The opposite is
also true.
The respiratory system—gas exchange
 Oxygen doesn’t dissolve well in water.
 It must be carried in red blood cells by the
protein hemoglobin.
 The higher the partial pressure of O2, the
more saturated Hb is.
The respiratory system—gas exchange
 pH can also affect the affinity of Hb for
oxygen.
 Exercising tissues produce several metabolic
acids.
 What does that do to Hb’s ability to “let go” of
the oxygen so it can diffuse into active
tissues?
The respiratory system—gas exchange
The respiratory system—gas exchange
 CO2 is transported
differently.
 Some is dissolved in
blood plasma (non
cellular part of blood)
 A little more is
transported on Hb
 Most is transported
as bicarbonate ion.
The respiratory system—control
 Cortical influences
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Cerebral cortex has connections with the
respiratory center in medulla oblongata.
You can voluntarily change your breathing
pattern.
Limited by build up of CO2 & H+.
The respiratory system—control
 Chemoreceptor regulation
 Chemoreceptors can sense changes in certain
chemicals.
 An increase in CO2 causes a decrease in pH.
 Chemoreceptors detect this.
 Respiratory center sends signals to myo of
inhalation & exhalation.
 Breathing rate & depth is increased.
The respiratory system—control
 Other factors affect respiration:
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Emotional anxiety ↑ rate
Temperature
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↑Temp  ↑ rate
Sudden ↓temp temporary apnea
Pain—brief apnea, then rate ↑
Airway irritationapnea followed by cough or
sneeze.
The end…