1 Human Physiology-I (PHSL 205) Lab
12th Lab
Hakami,Hana A- 2010/2011
Recording Respiratory
Movements
Prepared by;
Hakami, Hana A
Viewed by;
Dr.Naseem Siddiqui
2 Human Physiology-I (PHSL 205) Lab
12th Lab
Hakami,Hana A- 2010/2011
Recording Respiratory Movements
Introduction :
Mechanics of Pulmonary Ventilation
Pulmonary ventilation: refers to the movement of air in and out
of the lungs during breathing.
Alveolar gas concentrations are kept at the required level by
continuous alternation between expiration, which expels O2-depleted
and CO2-loaded gas, and inspiration, which replaces this with normal
air.
The necessary flow of gas is driven by pressure gradients
generated by the movements of the chest wall and diaphragm.
Relevant structures
Air enters the nose and is drawn through the nasopharynx into
the larynx. It passes through the glottis before entering the trachea,
which divides into the right and left main bronchi going to the two
lungs.
The airways continue to branch, decreasing in diameter. Bronchi,
which have cartilage in their walls, lead into bronchioles which do not
collapsible.
The airways finally terminate in grape-like collections of alveoli,
the main site of gas exchange
Bronchi and bronchioles contain smooth muscle and the airways
are lined by mucus-secreting cells within a ciliated epithelium. These
have important protective functions.
The alveoli have a thin epithelial wall and are covered on their
inner surface by a narrow layer of alveolar fluid.
Pulmonary connective tissue contains a large amount of elastic
tissue which is stretched beyond its passive resting length at normal lung
volume and, therefore, generates tension.
3 Human Physiology-I (PHSL 205) Lab
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Hakami,Hana A- 2010/2011
Two lungs: Principal organs of respiration
Right lung: Three lobes
Left lung: Two lobes
The lungs lie within the thoracic cavity. The outer surface of the
lung is covered by a membrane known as the visceral or pulmonary
pleura, and this is separated from the parietal pleura, which lines the
inside of the thoracic cavity, by the thin layer of pleural fluid filling the
intra pleural space.
This is sometimes called a potential space, since it contains liquid
rather than gas. Liquids cannot be easily expanded or compressed,So the
two layers of pleura normally remain tightly adherent to one another.
The outer surface of the lung is forced to follow the movements of
the diaphragm and chest wall so that lung volume increases and
decreases as thoracic volume changes.
Muscles of Respiration:
Inspiration is an active process in which the thoracic volume is
increased by the action of the relevant muscles.
The dome of the diaphragm is pulled down during diaphragmatic
contraction, thereby increasing the vertical height of the thoracic cavity.
This is augmented by contraction of the external intercostal
muscles between the ribs, which raises them into a more horizontal
position, increasing the width of the thorax from front to back.
Accessory muscles in the neck, including sternocleidomastoid and
scalenus, may also be used during maximal inspiration to elevate the
sternum and first two ribs.
The intercostal muscles are innervated by intercostals nerves
from the thoracic spinal cord but the diaphragm is innervated by the
phrenic nerves,which arise from cervical spinal nerve roots 3,4 and 5
before descending through the thorax to their destination.
4 Human Physiology-I (PHSL 205) Lab
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Hakami,Hana A- 2010/2011
Because of this, high cervical cord damage is likely to be fatal,
since repiration ceases.
Lower level spinal injuries may leave a patient handicapped
without being immediately life-threatening.
Quiet expiration is passive and relies on elastic recoil of the
stretched lungs as the inspiratory muscles relax.
During forced expiration by contraction of the abdominal muscles,
which increases the intra-abdominal pressure forcing the diaphragm
upwards, and of the internal intercostals, which actively pull the ribs
downwards.
Protocol of Recording Respiratory Movements
Required Equipment
A computer system - Chart software - Power supply (PowerLab) Respiratory belt transducer - Finger pulse transducer - Medium-sized
paper bag
Procedures
Set up and equipment calibration
1. Locate Chart on the computer and start the software.
2. Fasten the respiratory belt around the upper abdomen of a
volunteer, as shown in the figure . The transducer should be at the
front of the body, level with the navel, and the belt should fit
snugly.
5 Human Physiology-I (PHSL 205) Lab
12th Lab
Hakami,Hana A- 2010/2011
3. Connect the BNC plug on the respiratory belt transducer cable to
the BNC connector for Input 1 on the front of the PowerLab .
4. Turn on the program and ask the volunteer to take deep, strong
breaths and observe the signal on the software.
5. Study the results.
Note:
*The respiratory belt transducer can be used over clothing, and it
doesn’t matter whether the volunteer is sitting or standing, as long as
they are comfortable (note that this is quite a long exercise). Because
everyone’s breathing patterns differ, the position of the transducer may
need to be changed to get the best signal.
**You can study variations in heart rate during breathing by connection
the BNC plug on one end of the finger as next figure.