Respiration Part 1
Dr. Ashfaq Bukhari
Assistant Professor, Physiology
RAKCOMS
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Objectives
At the of the lecture, students will be able to:
o 1.o During inspiration the lungs are stretched
o Compliance is measure of effort that has to go into stretching
or distending the lungs
o Volume change per unit of pressure change across the lungs
o The less compliant the lungs are, the more work is required
to produce a given degree of inflation
o Decreased by factors such as pulmonary fibrosis
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Lung Compliance Diagram
Elastic Forces of the Lungs
o Characteristics of the compliance diagrams are determined by
2 elastic forces:
- Elastic properties of the lung tissue itself (fairly straight
forward).16
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oPleural fluid produced by pleural
membranes
-Acts as lubricant
-Helps hold parietal and visceral pleural
membranes together
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Ventilation
o Movement of air into and out of lungs
o Air moves from area of higher pressure to
area of lower pressure
o Pressure is inversely related to volume
Inspiration
o Diaphragm and intercostals muscles contract
o Diaphragm moves inferiorly and flattens during contraction,
causing height of thoracic cavity to increase
o Intercostals contraction lifts the ribcage and thrusts sternum
forward, increasing anterioposterior and lateral dimensions
(circumference)
o Lungs adhere tightly to the thorax walls (due to surface
tension of fluid between pleural membranes), they are
stretched to the new, larger size of the thorax.4
An Overview of Key Steps in Respiration
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Respiration can be divided into
four major functional events
o Ventilation: Movement of air into and out of
lungs
o Gas exchange between air in lungs and blood
o Transport of oxygen and carbon dioxide in the
blood
o Internal respiration: Gas exchange between
the blood and tissues
Respiratory System Functions
o Gas exchange: Oxygen enters blood and carbon dioxide leaves
o Regulation of blood pH: Altered by changing blood carbon dioxide levels
o Voice production: Movement of air past vocal folds makes sound and speech
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ANATOMY OF THE RESPIRATORY
TRACT
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Respiratory System Divisions
o Upper Airway
- Nose, pharynx,
larynx and
associated
structures
o Lower Airway
- trachea, bronchi,
lungs
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Conducting Zone
o All the structures air
passes through before
reaching the
respiratory zone.BLOOD SUPPLY TO THE LUNG
o Two separate blood supplies:
o Pulmonary circulation
o Bronchial circulation
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Pulmonary circulation
o Brings deoxygenated blood from the right ventricle to the gas-
exchange units
o At the gas-exchanging units, oxygen is picked up and carbon dioxide
is removed from the blood
o The oxygenated blood returned to the left atrium for distribution to
the rest of the body
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Bronchial circulation
oArise from the aorta
oProvides nourishments to the lung
parenchyma
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MUSCLES OF RESPIRATION
oInspiratory muscle:
oDiaphragm and Abdominal breathing
oexternal intercostal muscle and thoracic breathing
oaccessory muscle of inspiration
oExpiratory muscle
orelax during normal breathing
oInternal intercostal muscle
oMuscles of the abdominal wall
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Thoracic Walls and Muscles of Respiration
Breathing Rate
oAt rest: 10-20 breaths / minute
oDuring exercise: 40 - 45 at maximum
exercise in adults
oWhat about Kids?o Normally this is a passive process, but if passageways are
narrowed due to spasms of bronchioles (asthma) or clogged
with mucus/fluid (bronchitis/pneumonia), it becomes an
active process, using intercostal muscles to help depress rib
cage and abdominal muscles to help squeeze air out of lungs.o As inspiratory muscles relax and resume normal resting length, rib
cage descends and lungs recoil.o Includes
respiratory
bronchioles
and alveolar
sacs.o 2.o 3.