Download Respiration

BIO 238
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 Body cells require
 Constant supply of oxygen
 Constant removal of carbon dioxide
 Both respiratory and cardiovascular systems
contribute to fulfilling this requirement
 Respiration is the overall process of gas
exchange between atmosphere and body
cells
 Respiration involves four events
Movement of air in and out of the lungs, which is call
ventilation
1. External respiration


Gas exchange between air and blood in lungs by
diffusion
O2 from Air
CO2 from blood
2. Transport of gases between lungs and body cells
(cardiovascular system)
3. Internal respiration


Gas exchange between blood and body cells by
diffusion
O2 from blood
CO2 from cells
Organs of the Respiratory System
 Subdivisions
 Upper respiratory
system

Portion not located in
the thorax
 Lower respiratory
system

Portion located in the
thorax
Alveoli
 Alveoli
 ~300 million per lung
 Surface area ~75m2, holding ~6,000ml of air
 Site of respiratory gas exchange
 Filled with watery fluid to aid diffusion

Surfactant prevents alveolar collapse during exhalation
 Reduces attraction between water molecules
Breathing
 Process that exchanges air between atmosphere
and alveoli
 Air moves along a pressure gradient
 Air moves from high pressure region to low pressure
region
 Three important breathing pressures
1.



2.

3.



Atmospheric pressure
Pressure of air surrounding earth
760 mmHg at sea level
Decreases at higher elevations
Intra-alveolar (intrapulmonary) pressure
Air pressure within the lungs
Intrapleural pressure
Pressure within the pleural cavity
Normally 756 mmHg
Called “negative pressure”


Keeps lungs pressed against thorax walls during breathing
If it equals atmosphere pressure, lungs would collapse
 Inspiration
 Process of breathing air into lungs
 Air pressure in lungs must be reduced to less then
atmospheric air pressure
 Begins with muscle contraction

Diaphragm
 Contraction pulls the
diaphragm downward and
flattens it

External intercostal
muscles
 Contraction lifts the ribs
upward and outward

Contractions increase
volume of thoracic cavity
Air moves into lungs

 Expiration
 Diaphragm and external intercostal muscles relax



Thoracic cavity and lungs to return to normal size
Aided by abundant elastic tissue in lungs and thoracic
wall
Air is pushed out until intra-alveolar pressure and
atmospheric pressure are equalized
 Forceful expiration

Contraction of internal intercostal muscles


Contraction of abdominal muscles


Pull ribs down and inward
Force abdominal viscera and lungs upward
Further decreases volume of lungs

Increases air pressure in lungs, causing more air to
flow out
Respiratory Volumes
 Average adult: 10 to 20 quiet breathing cycles per
minute
 Breathing cycle: one inspiration followed by one
expiration
 Volume of air inhaled during quiet or forceful
breathing cycle varies
 Size, age, sex, physical condition
 Volumes 80% or less than normal average indicate
respiratory disease
 Spirometers are used to determine respiratory
volumes
 Produces a spirogram, a graphic record of air
volumes being exchanged
Respiratory Center
 Control is through neurons of the respiratory
center
 Located in both the medulla and the pons of the
brain stem
 Many other factors can also influence breathing
Factors That Influence Breathing
• Chemicals
– Important chemical factors include
• CO2
• H+ ions (formed from ↑ levels of CO2)
• O2
– Chemoreceptors detect changes in these
chemicals
• Respiratory center
• Carotid bodies
• Aortic Bodies
 Inflation Reflex
 Stretch reflex that prevents over inflation of the
lungs
 Higher Brain Centers
 Voluntarily generated
 When a person chooses to alter the normal pattern of quiet
breathing
 Limited in their control
 Involuntary impulses
 Emotional experiences and chronic pain increase breathing
rate
 Sudden emotional experience, sharp pain, or sudden cold
stimulus can cause apnea
 Body Temperature
 Increase temperature, increase breathing rate
 Decrease temperature, decrease breathing rate
Disorders of the Respiratory System
 Disorders are grouped into
 Inflammatory disorders
 Noninflammatory disorders
Inflammatory Disorders
 Chronic obstructive pulmonary disease (COPD)
 Long-term obstruction


Chronic bronchitis
Emphysema
 Bronchitis
 Inflammation of bronchi accompanied by excessive
mucus production partially obstructing air flow
 Acute bronchitis: viral or bacterial infection
 Chronic bronchitis: chronic asthmatics and
smokers
 Emphysema
 Due to long term exposure to airborne irritants
 Effects


Large spaces form when alveoli rupture
Air blocked in alveoli due to excess mucus production
 Reduces respiratory surface area and impairs gas
exchange
 Asthma
 Characterized by wheezing and dyspnea (difficult
breathing)
 Due to contraction of bronchiole smooth muscle
 Causes


Allergic reactions
Hypersensitivity to pathogens infecting the bronchial tree
 Common cold
 Viral infections
 Involves rhinitis, laryngitis, sinusitis
 Causes excessive mucus production, sneezing,
and congestion
 Influenza
 Caused by flu virus
 Symptoms include fever, chills, headache, muscle
aches
 True influenza viruses do not infect the digestive
system – there is not such thing as a “stomach flu.”
 Laryngitis
 Inflammation of mucus membrane of the larynx
 Thickens the vocal cords, deepening the voice
 Caused by viruses and bacteria
 Rhinitis
 Inflammation of mucus membrane in nasal cavity
 Main symptom is increased mucus secretion
 Causes can be viral, bacterial, or allergens
 Sinusitis
 Inflammation of the sinuses
 Symptoms include increased mucus secretion and
pressure in sinuses
 Causes can be viral, bacterial, or allergens
 Pleurisy
 Inflammation of pleural membranes
 Can have two effects


Decreases serous fluid production,
 Causes sharp pains during breathing
Increase serous fluid production,
 Causes increase in pressure on lungs
 Impairs their expansion
 Pneumonia
 Acute inflammation of alveoli caused by virus or
bacteria
 Alveoli become filled with fluid, pathogens, and
WBCs
 Reduces gas exchange space, resulting in low
blood oxygen levels
 Tuberculosis
 Inflammation caused by bacteria Mycobacterium
tuberculosis
 Transmitted by inhaling the bacteria
 Destroyed lung tissue is replaced by fibrous
connective tissue


Reduces lung elasticity
Retards gas exchange
 Effective medical therapies are available
Noninflammatory Disorders
 Lung cancer
 Due to long term exposure to irritants, such as
cigarette smoke
 Metastasizes rapidly and spreads quickly to other
body areas
 Treatments include surgery and anti-cancer therapy
 Pulmonary edema
 Accumulation of fluid in the lungs

Due to excessive fluid passing from blood into alveoli
 Symptoms include labored breathing and
suffocation feeling
 Treatments include oxygen therapy, diuretics, and
mechanical ventilation
 Pulmonary embolism
 Blood clot or gas bubble that blocks a pulmonary
artery and


Prevents blood from reaching that lung portion
No gas exchange possible in affected area
 Massive embolism can cause a cardiac arrest
 Respiratory distress syndrome (RDS)
 Disease of newborn infants, usually those
prematurely born
 Due to insufficient surfactant production in alveoli

Causes alveolar collapse
 Without surfactant, alveoli collapse after every
expiration

Requires a lot of energy to perform each inhalation