BIOL1008 Lecture Notes - Lecture 14: Thoracic Wall, Respiratory Tract, Alveolar Pressure
9 Jun 2018
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Lecture 14
Getting oxygen to the alveoli is a challenge to aerobic function.
RESPIRATORY SYSTEM ANATOMY
The airways
- The layers of tissue in each segment are directly related to
their function.
- The airways deliver gas to the terminal gas exchange areas.
- Each part of the airway system is designed to enable it to
perform specific function.
• Conducting airways: serve to conduct, clean,
warm, and moisten the air
- 1st – 16th divisions: trachea → bronchi→ bronchioles→
terminal bronchioles
- Trachea and bronchi have cartilage in their walls
trachea and bronchi had many ciliated cells and mucous
glands that help protect against foreign material
- Gas movement occurs along pressure gradients that are
generated by changes in lung volume. Changes in lung volume
are generated by changes in thoracic volume.
- The lungs and the thoracic wall are functionally linked.
- Inspiration is an active process, whereas expiration is generally passive
- Bronchioles have smooth muscle in their walls
enables airway caliber to be controlled
elastic tissue in the lung helps hold airways open during expiration
• Exchange airways
- 17th-23rd divisions: terminal bronchioles → alveoli
- alveoli have extremely thin walls
capillary blood pressure is very low
ensures there is adequate time for gas exchange to occur
- minimises fluid leakage from capillaries into surrounding tissue
- At the air-water interface surfactant breaks down surface tension
Gas moves into and out of the lungs along pressure gradients.
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2
Pressure gradients are generated by changes in lung volume.
Changes in lung volume are generated by changes in thoracic volume
- there are no muscles directly attached to the lung
- the lungs and chest wall are functionally linked by
alveolar pressure
subatmospheric intrapleural pressure
surface tension
elastic forces
On inspiration thoracic volume is increased by the inspiratory muscles.
- This stretches the elastic tissue in the lungs and the elastic rib cage.
- At rest expiration is passive using the energy stored during inspiration.
Key points
- The airways deliver gas to the terminal gas exchange areas.
- Each part of the airway system is designed to enable it to perform specific function.
- Gas movement occurs along pressure gradients that are generated by changes in
lung volume. Changes in lung volume are generated by changes in thoracic volume.
- The lungs and the thoracic wall are functionally linked.
- Inspiration is an active process, whereas expiration is generally passive.
Producing speech
Producing a specific sound requires an expiratory airflow of specific pressure and duration
A basic expiratory airflow is produced by elastic recoil of the thoracic wall
We use our inspiratory and expiratory muscles to achieve fine control over the expiratory
airflow.
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3
Key points
- Speech production requires determining
what alveolar pressure is required to produce
the desired sound; determine what
expiratory airflow be generated by
relaxation; and activating inspiratory or
expiratory muscles to produce the necessary
airflow
1. Determine required subglottal pressure
2. Determine relaxation pressure
3. Determine muscular effort required
Airway protection
The larger airways are lined by ciliated cells and have many mucous glands.
The mucociliary escalator removes material from the airways. Its function depends on:
- normal cilia
In the healthy human lung, cilia beat at 12 to 15 Hz moving mucus at 4 to 20
mm/min.
- normal mucous
Cystic fibrosis is caused by mutations in the cystic fibrosis transmembrane
conductance regulator gene.
The gene is responsible for a cell membrane Cl- channel and regulates the
epithelial Na+ channel.
In CF there is increased Na+ absorption and decreased Cl- secretion causing
dehydrated, thickened mucous.
Key points
- The respiratory system is protected by the mucus in the airways which is constantly
being removed by the cilia.
- In cystic fibrosis, the cilia are unable to remove the dehydrated mucus
MOVING OXYGEN INTO THE BLOOD
Lungs are designed to maximise diffusion:
- alveoli have a surface area of 70 – 80 m2
- capillaries have a surface area of about 1000 m2
At every level of the body gas moves across membranes by diffusion so at every level the body
is designed to maximise diffusion.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Getting oxygen to the alveoli is a challenge to aerobic function. The layers of tissue in each segment are directly related to their function. Each part of the airway system is designed to enable it to perform specific function: conducting airways: serve to conduct, clean, warm, and moisten the air. 1st 16th divisions: trachea bronchi bronchioles terminal bronchioles. Trachea and bronchi have cartilage in their walls. Trachea and bronchi had many ciliated cells and mucous glands that help protect against foreign material. Bronchioles have smooth muscle in their walls. Elastic tissue in the lung helps hold airways open during expiration: exchange airways. Ensures there is adequate time for gas exchange to occur. Minimises fluid leakage from capillaries into surrounding tissue. At the air-water interface surfactant breaks down surface tension. Gas moves into and out of the lungs along pressure gradients. Pressure gradients are generated by changes in lung volume.
