Transcript Respiratory System

Respiratory System
Exercises 36 and 37
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Respiration
• Entire process of exchanging gases
between the atmosphere and body cells is
called respiration.
• Breathing or ventilation – moving air in
and out of the lungs
• External respiration – exchange of gases
between the air in the lungs and the blood.
• Internal respiration – exchange of gases
between the blood and body cells.
• Cellular respiration – use of O2and
2
production of CO2 by cells of the body
Organs of the Respiratory System:
• Two parts or tracts:
• Upper respiratory tract (URT) – nose,
nasal cavity, sinuses and pharynx
• Lower respiratory tract – larynx, trachea,
bronchial tree, and lungs
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Pharynx
• Muscular tube lined by mucous membrane
• Nasopharynx –
– Respiration – lined with pseudostratified ciliated
columnar epithelium
• Oropharynx and Laryngopharynx
– digestion and respiration
– Nonkeratinized stratified squamous epithelium
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Larynx
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Connects pharynx and trachea
Passage of air in and out of lungs
Prevents foreign objects entering trachea
Contains vocal cord – speech
Muscle and 9 cartilages connected by
elastic tissue
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Thyroid cartilage
• “Adam’s Apple”
• In female more rounded – shorter front to
back – shorter vocal cords
• In male more “V” shaped – longer front to
back – longer vocal cords
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• Cricoid cartilage – inferior to thyroid cartilage.
Marks end of larynx
• Epiglottic cartilage – elastic cartilage
– Attaches to thyroid cartilage and supports epiglottis
• Arytenoid cartilages and
• Corniculate cartilages serve as sites for
muscles that regulate tension on vocal cords
and aid in closing larynx during swallowing
• Cuneiform cartilages in mucous membrane –
stiffen soft tissue
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Vocal cords
• Two sets of muscle and connective tissue
covered by mucous membrane
• Upper are “false vocal cords” –close off glottis
to keep food out
• Lower are true vocal cords – sound produced
when air forced across them.
• Pitch changed by amount of tension – modified
by resonating chambers, and position of lips,
mouth and tongue
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Trachea
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“windpipe”
Extends from larynx to primary bronchi (T5)
Smooth muscle – trachealis muscle
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Open end of C posterior to allow esophagus to
expand in
• Lined with pseudostratifed ciliated columnar
epithelium
• Ridge – carina – most sensitive areas for
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triggering cough reflex
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Bronchial Tree
• Right and left primary bronchi
– Right bronchus shorter, wider, more vertical
• Secondary or lobar bronchi
– 3 branches on right ; 2 on left
• Tertiary or segmental bronchi
– 10 branches on right; 8 on left
• Bronchi lined with pseudostratified ciliated
columnar epithelium
• Held open by complete rings of cartilage
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Lungs
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Separated by mediastinum
Pleural membranes
Right has 3 lobes and two fissures, shorter
Left has 2 lobes and one fissure, cardiac
notch
• Apex, base, hilum
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Pulmonary ventilation
• Air moves depending on a pressure
gradient
• Before inspiration, pressure in lungs =
pressure of atmosphere = 760 mm Hg
• Inspiration increases the size of the
thoracic cavity and ↓ pressure .
• Diaphragm is the most important muscle
of inspiration.- 75 % of air
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• Diaphragm is innervated by the phrenic
nerve.
• Decreases pressure 1-3 mm Hg
• Moves 500 ml of air
• External intercostals also contract – move
ribs up and sternum forward
• Strenuous breathing –
sternocleidomastoid, scalenes, and
pectoralis minor
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Expiration
• Passive process – the diaphragm and
external intercostals relax. Elastic recoil of
stretched elastic fibers and surface tension
of the liquid in the lungs decreases the
lung volume and increases the pressure,
forcing air out of the lungs.
• Forced expiration involves contraction of
the internal intercostal and abdominal
muscles.
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Lung volumes
• Clinically, respiration = one inhalation and
one exhalation – respiratory cycle
• Adult breathes about 12 X/ min.
• Air volumes can be measured with a
spirometer.
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Lung volumes
• Tidal volume – air moved by one
respiration, about 500 ml.
• Inspiratory reserve volume – additional air
taken in during maximal inhalation
• Expiratory reserve volume – additional air
expired during forced exhalation.
• Residual volume – amount of air left in
alveoli after forced expiration that keeps
them inflated.
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Respiratory capacities
• Inspirational capacity – tidal vol. +
inspiratory reserve volume
• Functional residual – residual volume +
expir. res. vol.
• Vital capacity - inspir. Res. + tidal vol.+
expir. Res.
• Total lung capacity – sum of all volumes
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Other lung volumes
• Anatomic dead space – due to conducting
parts of system
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Regulation of the Respiratory
Center
• Respirations can be modified by factors from
inside and outside the brain.
• Chemical influences:
– Central chemoreceptors in medulla oblongata
– Sensitive to changes in conc. of CO2 and pH
– CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3carbon +
dioxide
water
carbonic hydrogen bicarbonate
acid
ion
ion
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Peripheral Chemoreceptors
• Carotid bodies and aortic bodies
• Stimulated by oxygen concentration
decrease
• Send impulses to respiratory centers, and
breathing increases
• Not triggered until O2 is very low (50 mm
Hg)
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