RESPIRATION
CHAPTER 24
TYPES OF RESPIRATORY SYSTEMS
• Respiration is the uptake of oxygen and the
simultaneous release of carbon dioxide.
• Most primitive animal phyla obtain oxygen
directly from their environments through diffusion.
• More advanced phyla have specific respiratory
organs:
• Gills, tracheae, and lungs
GAS EXCHANGE IN ANIMALS
CO2
O2
CO2
Body wall
O2
Gill
Fish
Flatworm
Tracheoles
Gill filament
Blood vessels
Trachea
O2
Mammalian lung
Blood vessels
Trachea
Spiracles
CO2
O2
CO2
O2
Alveoli
CO2
Terrestrial arthropod
Spiracle
Mammal
RESPIRATION IN AQUATIC
VERTEBRATES
• Water always moves past a fish’s gills in one
direction.
Gill raker
Gill arch
Gill raker
Gill arch
Lamellae with
capillary networks
Gill filaments
Water
Artery
Water
Water
Water
Vein
Water
Gill filaments
Direction of blood flow
Direction of water flow
RESPIRATION IN AQUATIC
VERTEBRATES
Countercurrent exchange
• Moving the water past
the gills in the same
direction permits
countercurrent flow.
Blood (85%
O2 saturation)
85%
80%
• This process is an
70%
extremely efficient way of
extracting oxygen.
60%
• Blood flows through a gill
50%
filament in an opposite
40%
direction to the
movement of water.
30%
• The blood in the blood
20%
vessels always encounters
10%
water with a higher
oxygen concentration,
Blood (0%
resulting in the diffusion of
oxygen into the blood O2 saturation)
vessels.
(a)
Water (100%
O2saturation)
Concurrent exchange
Blood (50%
O2 saturation)
Water (50%
O2 saturation)
100%
90%
80%
No further
net diffusion
70%
60%
50%
50%
50%
40%
60%
40%
30%
70%
30%
20%
80%
15%
10%
90%
Blood (0%
O2 saturation)
Water(15%
O2 saturation)
Water(100%
O2saturation)
(b)
RESPIRATION IN TERRESTRIAL
VERTEBRATES
• Lungs are less efficient than gills because
new air that is inhaled mixes with old air
already in the lung.
• But there is so much more oxygen in air than in
water.
RESPIRATION IN TERRESTRIAL
VERTEBRATES
• The lungs of mammals possess on their inner
surface many small chambers called alveoli,
which greatly increases surface area for the
diffusion of oxygen.
Bronchiole
Bronchiole
Alveoli
Alveoli
(a) Amphibian
(b )Reptile
(c) Mammal
RESPIRATION IN TERRESTRIAL
VERTEBRATES
• Flying creates a respiratory demand for oxygen
that exceeds the capacity of the saclike lungs
of even the most active mammal.
• Birds have evolved the most efficient lung.
• An avian lung is connected to a series of air sacs
outside of the lung.
Trachea
Lung
Anterior
air sacs
Parabronchi of lung
Anterior
air sacs
Posterior
air sacs
Trachea Inspiration
Cycle 1
Expiration
Inspiration
Cycle 2
Expiration
Posterior
air sacs
(a)
http://youtu.be/kWMmyVu1ueY
(b)
RESPIRATION IN TERRESTRIAL
VERTEBRATES
• This creates a unidirectional flow of air through
the lungs.
• Blood flow and airflow are not opposite but flow
at perpendicular angles in crosscurrent flow.
Mammalian lungs
Fish gills
(c)
Blood
Avian lungs
Counter current
Uniform pool
Cross current
THE MAMMALIAN RESPIRATORY
SYSTEM
• In the mammalian
respiratory system, air
passes in and out of the
lungs, which are housed in
the thoracic cavity.
• Air is warmed and
filtered as it flows through
the nasal cavity.
• It passes next through
the pharynx, then the
larynx (or voice box),
then to the trachea, or
windpipe.
Nasal cavity
Nostril
Pharynx
Epiglottis
Glottis
Larynx
Trachea
Left lung
Right lung
Left
bronchus
THE MAMMALIAN RESPIRATORY
SYSTEM
• From there, air passes
through several
branchings of bronchi
in the lungs and then
to the bronchioles.
• The tissue of the
lungs is divided into
tiny air sacs called
alveoli; through
these thin-walled
cells, gas exchange
with the blood
occurs.
Blood flow
Smooth muscle
Bronchiole
Pulmonary arteriole
Pulmonary venule
Alveolar
sac
Capillary network
on surface
of alveolus
Alveoli
THE MAMMALIAN RESPIRATORY
SYSTEM
• The mammal respiratory apparatus is simple
in structure and functions as a one-cycle
pump.
• A diaphragm muscle separates the thoracic
cavity from the abdominal cavity.
• Each lung is covered by a thin, smooth
membrane called the pleural membrane.
• This membrane adheres to another pleural
membrane lining the walls of the thoracic cavity,
basically coupling the lungs to the thoracic
cavity.
THE MAMMALIAN RESPIRATORY
SYSTEM
• Air is drawn into the lungs by the creation of
negative pressure.
• The active pumping of air in and out is
called breathing.
• During inhalation, muscular contraction causes
the chest cavity to expand.
• During exhalation, the ribs and diaphragm return
to their original position.
KEY BIOLOGICAL PROCESS:
BREATHING
1
2
3
Pair
Plung
Diaphragm
relaxed
Plung
Plung = Pair
Before inhalation, the air pressure in the
lungs (Plung) is equal to the atmospheric
pressure (Pair).
Pair
Pair
Inhalation
Exhalation
Chest
cavity
expands
Diaphragm P
lung < Pair
contracts
During inhalation, the diaphragm
contracts, and the chest cavity expands
downward and outward. This increases
the volume of the chest cavity and lungs,
which reduces the air pressure inside the
lungs, and the air from outside the body
flows into the lungs.
Plung
Diaphragm
Plung > Pair
relaxed
During exhalation, the diaphragm relaxes,
decreasing the volume of the chest
cavity. The pressure increases in the
lungs, forcing air out of the lungs.
14
HOW RESPIRATION WORKS:
GAS EXCHANGE
• Oxygen moves through the circulatory
system carried by the protein hemoglobin.
• Hemoglobin molecules contain iron, which binds
oxygen in a reversible way.
Heme group
Beta (β) chains
Oxygen (O2)
Iron (Fe++)
Alpha () chains
HOW RESPIRATION WORKS:
GAS EXCHANGE
• Hemoglobin molecules act like little sponges
for oxygen.
• At the high O2 levels that occur in the blood
supply at the lung, most hemoglobin molecules
carry a full load of O2.
• In the tissues, the O2 levels are much lower, so
hemoglobin gives up its bound oxygen.
• In the presence of CO2, the hemoglobin assumes
a different shape that gives up its oxygen more
readily.
HOW RESPIRATION WORKS:
GAS EXCHANGE
• CO2 must also be transported by the blood.
• About 8% simply dissolves in the plasma.
• 20% is bound to hemoglobin but at a different site
than where O2 binds.
• The remaining 72% diffuses into the red blood
cells.
• In order to maintain the gradient for CO2 to
leave the tissues and enter the plasma, the
CO2 levels in the plasma must be kept low.
HOW RESPIRATION WORKS:
GAS EXCHANGE
• The enzyme carbonic anhydrase combines
CO2 with water to form carbonic acid
(H2CO3).
• This acid dissociates into bicarbonate (HCO3–)
and H+.
• Bicarbonate also acts as buffer in the blood plasma.
• In the lungs, the reverse reaction takes place, and
CO2 is released.
THE NATURE OF LUNG CANCER
• Lung cancer is one of the leading causes of
death among adults.
• Mutations to two tumor-suppressing genes are
implicated in the development of cancer.
• Rb codes for Rb protein, which acts as a brake
on cell division.
• p53 codes for p53 protein, which detects
damaged or foreign DNA and prevents its
replication.
THE NATURE OF LUNG CANCER
• Smoking causes lung
cancer.
• The annual incidence of
lung cancer is much
higher for smokers than
for nonsmokers.
• Changes in the incidence
of lung cancer have
mirrored changes in
smoking habits.
• Many types of mutagens are found in cigarette
smoke that can damage genes.
• The p53 gene is damaged in 70% of lung
cancers.
• Smoking also leads to nicotine addiction.
3000
10
Males
80
2000
Cigarette
consumption
60
1500
30years
Lung
cancer
deaths
50
40
1000
30
20
500
10
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010
Time
3000
100
Females
2500
80
70
2000
60
1500
Cigarette
consumption
50
40
1000
30
30years
500
Lung
cancer
deaths
20
10
1900 1910 1920 1930 1940 1950 1 960 1970 1980 1990 2000 2010
Time
Lung cancer death rates per 100,000
90
Per capita cigarette consumption
INCIDENCE
OF LUNG
CANCER IN
MEN AND
WOMEN
70
Lung cancer death rates per 100,000
Per capita cigarette consumption
90
2500