unifying concepts of animal respiration cells using cellular respiration need a steady supply of...
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UNIFYING CONCEPTS OF ANIMAL RESPIRATION• Cells using cellular respiration need a steady supply of
oxygen and must continuously dispose of CO2
• The respiratory system promotes this gas exchange.
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Environment
Cell
Glucose Oxygen Water EnergyCellular
respiration Carbondioxide
C6H12O66 O2 6 CO2 6 H2O ATP
CO2O2
The Human Respiratory System
• Gas exchange occurs at the respiratory surface within the lungs
– A large, moist internal surface folded into the body
– open to the air only through narrow tubes
– The circulatory system transports gases between the respiratory surface (alveoli) and the rest of the body
Lungs(localized
internal organs)
Model of a pair of human lungs
The Human Respiratory System
• The human respiratory system has three phases of gas exchange:
1. breathing, the ventilation of the lungs by alternate
inhalation and exhalation,
2. transport of oxygen from the lungs to the rest of the body via the circulatory system, and
3. diffusion of oxygen from the blood and release of CO2 into the blood by cells of the body.
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Figure 23.UN02
Pulmonaryarteries
CO2
O2-rich blood
O2
PulmonaryveinsPulmonary circuit
O2-poor blood
Capillaries
Systemic circuit
Heart
Capillaries
Aorta
Arteries
Arterioles
Venaecavae
Veins
Venules
The Human Respiratory System
• The human respiratory system:
- has a series of passageways that carry air into and out of the lungs
- It warms & moistens the air moving through it
- It is lined by epithelial cells:
• mucus traps dust and microorganisms
• cilia sweep mucus up toward pharynx
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Air
Nostrils – into nasal cavity
Mouth – into oral cavity
Pharynx
Air filtered by hairs & mucusAir warmed & humidified
common chamber for air & food
Esophagus food to stomach
Larynx (voice box)
Trachea (windpipe)Flexible tube with walls reinforced reinforced
with semicircular bands of stiff with semicircular bands of stiff hyaline cartilagehyaline cartilage
Muscles in the voice box stretch vocal
chords & exhalation passes air over them to produce sounds
Human respiratory system
TracheaBronchus(to right lung)
In the lungs
In the lung the bronchi branch into numerous, even smaller
tubes called bronchioles
Bronchioles
BronchiolesLead to alveoli (pl.)
(air sacs)
(to left lung) Bronchus
Gas exchange
Figure 23.19a
Larynx (voice box)
Trachea (windpipe)
(a) Overview of the human respiratory system
Pharynx
Right lung
Bronchus
Bronchiole
Diaphragm
EsophagusNasal cavity
Left lung
Heart
Figure 23.19b
(b) The structure of alveoli (air sacs) 1.5 to 2.5 million are packed into each lung
Bronchiole
Bloodcapillaries
Fromheart
Toheart
Alveoli
O2-richblood
O2-poorblood
O2
CO2
• Respiratory surface is thin and moist & allows for rapid diffusion
- AlveoliAlveoli: simple : simple squamous epitheliumsquamous epithelium
- Pulmonary Pulmonary capillariescapillaries: simple : simple squamous epithelium squamous epithelium
• Pulmonary capillaries surround alveoli
frompulmonaryartery
alveolarmembrane
respiratorymembrane
to pulmonary vein
(air) CO2
O2
capillary
fluid
Oxygen diffusesinto red blood cells
Carbon dioxidediffuses into alveolus
Gas exchange between alveoli and capillaries
Gases can dissolve & diffuse between the lungs and the circulatory system
Lungs
• Lungs are protected within an airtight chest cavity
• The chest cavity is bound by:
– neck muscles & connective tissue on the top
– muscular thin diaphragm on the bottom
• The rib cage surrounds and protects the lungs
Taking a Breath
• Breathing is the alternating process of inhalation and exhalation.
• During inhalation
– upward movement of the ribs
– downward movement of the diaphragm (contraction)
– volume of the lungs increases/chest is expanded
– Air pressure in lungs drops below air pressure of atmosphere
• Air moves into the lungs by negative pressure breathing (air moves from high to low pressure)
Taking a Breath
• Automatic exhalation of air occurs when muscles that cause inhalation are relaxed and the chest cavity is restricted
– inward movement of the ribs
– upward movement of the diaphragm
– the volume of the lungs decreases
– air pressure in the lungs increases
– air moves out of the respiratory system
Figure 23.20
Inhalation(Air pressure is higher in
atmosphere than in lungs.)
Exhalation(Air pressure is lower in
atmosphere than in lungs.)
Diaphragmrelaxes(moves up)
Diaphragmcontracts(movesdown)
Rib cageexpands asrib musclescontract
Rib cage getssmaller asrib musclesrelax
Airinhaled
Airexhaled
Lung
• Breathing can be controlled
– consciously, as you deliberately take a breath, or
– unconsciously
• Breathing control centers in the brain stem
– automatically control breathing most of the time
– regulate breathing rate in response to CO2 levels in the blood
Taking a Breath
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Figure 23.21-3
CO2 levels in theblood rise as aresult of exercise.
Brain
Breathing controlcenters in the brainmonitor the rising CO2 levels in the blood.
Breathing controlcenters
Nerve signals trigger contraction of muscles to increase breathingrate and depth.
Rib musclesDiaphragm
1
2
3
Signals a need for more oxygen
The Role of Hemoglobin in Gas Transport
• The human respiratory system
– takes in O2
– expels CO2, but
– relies on the circulatory system to shuttle these gases between the lungs and the body’s cells.
AlveolusAir spaces
Capillariesof lung
Tissuecapillaries
CO2-rich,
O2-poor
blood
O2-rich,
CO2-poor
blood
O2 in
inhaled airCO2 in
exhaled air
CO2 O2
Tissue cells throughout body
CO2 O2
Heart
O2
CO
2
O 2CO2
Interstitialfluid
• Oxygen does not readily dissolve in blood.
– Solution: Oxygen is carried in hemoglobin molecules within red blood cells
The Role of Hemoglobin in Gas Transport
Hemegroup
Ironatom
Polypeptide chain
O2 loadedin lungs
O2 unloadedin tissues
O2
O2
How Smoking Affects the Lungs
• Breathing exposes your respiratory tissues to potentially damaging chemicals
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• Tobacco smoke
– damages the cells that line the bronchi and trachea
– interferes with the normal cleansing mechanism of the respiratory system: more toxin-laden smoke particles reach & damage the lungs’ alveoli
• Smoking
– kills half of all people who smoke, about 440,000 Americans every year,
– causes 90% of all lung cancer (one of the deadliest forms of cancer), and
How Smoking Affects the Lungs
(a) Healthy lung (nonsmoker) (b) Cancerous lung (smoker)