Download 1 Organisation of resp syst

Mikel Egaña
Trinity College Dublin
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings.
Respiratory System. Lecture 1.
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Respiratory System. Lecture 1.
•  General function: to obtain O2 for use by the body’s cells
and to eliminate the CO2 the body cells produce
•  Encompasses two separate but related processes:
–  Internal respiration
•  Oxidative phosphorylation
–  External respiration
•  Exchange of oxygen and carbon dioxide
between atmosphere and body tissues
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Cellular respiration
Refers to metabolic processes carried out within
the mitochondria, which use O2 and produce CO2,
while deriving energy from nutrient molecules
Respiratory System. Lecture 1.
1.  Pulmonary ventilation (movement of air into lungs and out)
2.  Exchange O2 & CO2 between lungs (alveoli) and blood
(pulmonary capillaries) by diffusion
3.  Transportation of O2 & CO2 between lungs and tissues
4.  Exchange O2 & CO2 between blood and body tissues by
diffusion across systemic (tissue) capillaries
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Respiratory System. Lecture 1.
•  Short term regulation of pH (acid-base balance)
•  Enabling speech, singing, and other vocalizations
•  Help in defense against pathogens in the airways
•  Removes, modifies, activates, or inactivates various
materials passing through the pulmonary circulation
•  Eliminates heat and water
•  Assist venous return
•  Nose serves as the organ of smell
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Respiratory System. Lecture 1.
Air passages of the head and neck
• 
Nasal cavity (nose)
• 
Oral cavity
• 
Pharynx (common passageway for respiratory
and digestive systems)
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Conducting zone
(anatomical dead
space)
Airways from pharynx to
lungs
• Larynx
• Conducting zone
• Respiratory zone
Respiratory zone
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Conducting
zone
(anatomical
dead space)
Respiratory
zone
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•  Trachea
•  Bronchi
•  Secondary bronchi
–  Right side - 3 (to 3 lobes of right lung)
–  Left side - 2 (to 2 lobes of left lung)
•  Tertiary,...Bronchi
–  20-23 orders of branching
Up to 8 million tubules!!
•  Bronchioles
–  Less than 1 mm diameter
–  No cartilage, risk of collapse. To prevent:
walls of elastic fibers
•  Terminal bronchioles
Respiratory System. Lecture 1.
•  Air passageway
–  150 mL volume = dead space volume
•  Increase air temperature to body temperature
•  Humidify air
• 
• 
• 
Goblet cells – secret mucus
and traps foreign particles
Ciliated cells – propel the
mucus up the glotis to be
swallowed or expelled
Process: Mucus escalator
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•  Respiratory bronchioles
•  Alveolar ducts
•  Alveolar sacs
•  Alveoli
Respiratory System. Lecture 1.
•  Exchange of gases between air and blood
by diffusion
•  Respiratory membrane
–  Epithelial cells of alveoli
–  Endothelial cells of capillary
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Respiratory System. Lecture 1.
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Alveoli = site of gas exchange
300 million alveoli/lung (tennis court
size):facilitate gas exchange.
Rich blood supply- capillaries form
sheet over alveoli
Pores of Kohn permit airflow between
adjacent alveoli (collateral ventilation)
3 cell types:
– 
Type I alveolar cells –
- Make up wall of alveoli, single layer epithelial cells
– 
Type II alveolar cells –
- Secrete surfactant
- Reduces surface tension in alveolar walls
- Helps prevent alveolar collapse
– 
Alveolar macrophages
Removes foreign particles
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• 
Barrier for diffusion
–  Alveoli: Type 1 cells + basement membrane
–  Capillaries: Endothelial cells + basement membrane
• 
0.2 microns thick
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- Pleural sac around
each lung
- Side attached to
chest: parietal pleura
- Side attached to lung:
visceral pleura
- Intrapleural space
filled with intrapleural
fluid
Volume = 15 mL
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