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GAS EXCHANGE
The Human Respiratory System
Are the human lungs identical?
No, the right lung is shorter than the left by 1 inch; however,
its total capacity is greater. The right lung has three lobes, the
left lung has two. The maximum capacity of the lung averages
about 6,500 cubic centimeters (cc) or 1.7 gallons (6.4 liters).
A. Respiration - has two definitions
1) The release of energy from nutrients
2) The Gas Exchange of Oxygen and Carbon Dioxide
between the organism and the environment.
Respiratory Surface Requirements:
1) surface must be thin walled so that diffusion across it
can occur rapidly
2) surface must be moist because the Oxygen and
Carbon-Dioxide must be in a solution
3) surface must be in contact with a source of Oxygen
that exists in the surroundings
4) surface must be in contact w/ the transport system
that carries dissolved materials to & from the cells of the
organism
a) SKIN is respiratory surface which must be kept moist
for oxygen to dissolve in & diffuse across the skin
b) skin secretes mucus which facilitates the diffusion of
gases into & out of blood
c) hemoglobin- respiratory pigment proteins in blood
that increases oxygen & carbon dioxide carrying
capacity
Human Respiratory System
a) alveoli
(respiratory surface) in the lungs are thin, moist, internal
gas exchange surface
b) hemoglobin aids in the transport of oxygen
THE FLOW OF AIR
Nasal Cavity
The nasal cavity is exposed to the air through the
nostrils which is lined with a ciliated mucous
membrane which filters, warms, and moistens the air.
Pharynx
The pharynx is the area in which the oral cavity & nasal
cavity meet. Food is prevented from entering the trachea
by the epiglottis
Trachea
The trachea is kept open by rings of cartilage. The
ciliated mucous membrane which lines the trachea traps
microscopic particles & sweeps them toward the
bronchi. Deposits from cigarette smoke & other
atmospheric pollutants may interfere with the action of
cilia.
Bronchi
The 2 major subdivisions of the trachea are the bronchi.
The bronchi are lined with mucous membrane & ringed
with cartilage. Each bronchus extends into a lung where
it subdivides many times forming progressively smaller
bronchioles.
Bronchioles
Bronchioles are lined with mucous membrane but lack
cartilage rings and no cilia present. Tiny bronchioles
terminate with the alveoli.
Alveoli
Alveoli are the functional units for gas exchange. They
are thin, moist, & surrounded by capillaries. In humans,
oxyhemoglobin is in highest concentration in the
capillaries of alveoli.
Lung
Each bronchus with its bronchioles and alveoli is called
a lung.
PHASES of HUMAN RESPIRATION
1. Breathing:
bringing air into & out of lungs
(2 PHASES)
Inhalation (inspiration)1. diaphragm pulled down
Active phase
2. ribs pulled up & out
3. (-) pressure causes air to fill lungs
Exhalation (expiration)1. diaphragm relaxes, comes up
Passive phase
2. ribs relax, drop down & in
3. (+) pressure forces air out of lungs
Breathing rate is affected by carbon dioxide level (NOT the
AMOUNT of OXYGEN) in blood & its affect on the
respiratory center of the brain. Also, the acidity of the blood
(caused by lactic acid) stimulates the respiratory center.
2. External Respiration:
exchange of gases between air & blood in the alveoli
3. Circulation:
bringing respiratory gases to different parts of body
4. Internal Respiration
exchange of oxygen for carbon dioxide between blood & body
cells
DISEASES of RESPIRATORY SYSTEM
1. Asthma
- severe allergic reaction that constricts bronchioles
2. Bronchitisinflammation of bronchial tubes
3. Emphysema
- lungs lose elasticity, shortness of breath
4. Pneumoniafluid in alveoli
5. Lung Cancer
- tumors form in lungs
* Smokers are at greater risk for # 2, 3, & 5 *
2. Why does the human voice sound so strange after
breathing helium?
Since the speed of sound in helium is nearly three times the
speed of sound in air, the pitch of the human voice becomes
correspondingly higher.