Respiration Summary.doc

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Published on 14 May 2012
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SUMMARY: RESPIRATION
Functions of the respiratory system:
-Function of the respiratory zone: gas exchange:
oIn the lungs, we add oxygen to the blood and release carbon dioxide in the
environment.
oIn working cells, oxygen diffuses from blood to ISF to cells, while metabolic
waste products such as carbon dioxide move in the opposite direction.
oTherefore, both respiratory system and CVS work in collaboration to allow
appropriate gas exchange.
-Functions of the conducting airways:
1. Defence against bacterial infection and foreign particles:
The epithelial cells possess cilia and secrete mucous
Foreign particles stick to the mucous and the cilia constantly sweeps the
mucous up into the pharynx.
Tobacco smoking paralyzes the cilia, thus inhibiting this defence
mechanism.
2. Warm and moisten inhaled air
3. Produce sound and speech with the vocal cords
4. Regulation of air flow: smooth muscle around the airways may contract or
relax to alter resistance to air flow.
Anatomy of the respiratory system:
-The respiratory tract:
oAir can enter either by the mouth or the nose
oIf it enters by the nose, it passes through the
nasal septum and the nasal turbinates, which
clean the air of big dust particles.
oAir then passes into the pharynx (common to air
and food), the larynx, and the trachea.
oThe trachea divides into two bronchi, each of
which divides into lobar and segmental bronchi.
oRight main bronchus = 3 lobar bronchi
oLeft main bronchus = 2 lobar bronchi
oThe segmental
bronchi divides
further into
smaller branches
oThe smallest airways without alveoli are the
terminal bronchioles
oSurface of the lungs = visceral pleura
-Subdivisions of the conducting airways and terminal
respiratory units:
oThe airways consist of a series of tubes that
branch and become narrower, shorter and more
numerous as they penetrate into the lungs.
-Conducting and respiratory zones:
oConducting zone:
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Airways from the mouth and nose openings, all the way down to the
terminal bronchioles.
They conduct air from environment to the respiratory zone.
Since they do not participate in gas exchange, they are said to form the
anatomical dead space.
oRespiratory zone:
Characterized by the presence of alveoli in the walls of the airways.
Begins where the terminal bronchioles divide into the respiratory
bronchioles.
Site for gas exchange
Makes most of the lungs
Smallest physiological unit of lungs = acinus (1 respiratory bronchiole)
-Blood supply:
oPulmonary circulation:
Brings mixed
venous blood to
the lungs, allowing
for the blood to get
oxygenated, and
then back to the
heart, where it
enters the systemic
circulation.
Branches from the
pulmonary artery
run with the
airways.
When the alveoli
are reached,
arterioles divide
into a capillary
bed.
oBronchial (systemic)
circulation:
Supplies oxygenated blood to the tracheobronchial tree
Bronchial arteries from the aorta supply the airway walls.
-Alveolar cell types:
oEpithelial cells:
Type I:
Little is known about their specific metabolic activity
Type II:
Produce pulmonary surfactant, a substance that decreases the
surface tension of the alveoli
oEndothelial cells:
Constitute the walls of the pulmonary capillaries
May be as thin as 0,1 micron
oAlveolar macrophages:
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Remove foreign particles that may have escaped the mucocilliary
defence system of the airways.
-Respiratory muscles:
oInspiratory muscles:
Principal:
External intercostals: elevate ribs
Parasternal intercartilaginous: elevate ribs
Diaphragm: dome descend, increasing longitudinal dimension of
chest and elevating lower ribs
Accessory:
Sternocleidomastoid: elevates sternum
Scalenus: elevate and fix upper ribs:
oAnterior
oMiddle
oPosterior
oExpiratory muscles:
Quiet breathing:
Expiration results from passive recoil of lungs
Active breathing:
Internal intercostals, except parasternal intercartilaginous
muscles: depress ribs
Abdominal muscles : depress lower ribs, compress abdominal
contents
oRectus abdominus
oExternal oblique
oInternal oblique
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Document Summary

Functions of the conducting airways: defence against bacterial infection and foreign particles: The epithelial cells possess cilia and secrete mucous. Foreign particles stick to the mucous and the cilia constantly sweeps the mucous up into the pharynx. Subdivisions of the conducting airways and terminal respiratory units: the airways consist of a series of tubes that branch and become narrower, shorter and more numerous as they penetrate into the lungs. Conducting and respiratory zones: conducting zone: Airways from the mouth and nose openings, all the way down to the terminal bronchioles. They conduct air from environment to the respiratory zone. Since they do not participate in gas exchange, they are said to form the anatomical dead space: respiratory zone: Characterized by the presence of alveoli in the walls of the airways. Begins where the terminal bronchioles divide into the respiratory bronchioles. Smallest physiological unit of lungs = acinus (1 respiratory bronchiole)

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