Respiratory System
1
Outline
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Respiratory structures
– Gills
– Air-Breathing Animals
– Amphibians and Reptiles
– Mammals
– Birds
Structures and Mechanisms of Breathing
2
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Fig. 44.19(TE Art)
CO2
Epidermis
CO2 O2
O2
Epidermis
O2
Papula
CO2
Blood vessel
Spiracle
O2
Trachea
CO2
CO2
O2
CO2
O2
CO2
O2
Blood
vessel
Alveoli
3
Gases
•
•
Air is
– 21% oxygen
– 78% nitrogen
– Less than 1% carbon dioxide and other
gases
Nitrogen gas usually ignored because it is
not part of the respiratory process
4
The Gill as a Respiratory Structure
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•
External gills provide a greatly increased
surface area for gas exchange.
– disadvantages are that they must be
moved constantly and are easily damaged
Gills of bony fish
– located between buccal cavity and
opercular cavity
5
Bony Fish Respiration
6
7
The Gill as a Respiratory Structure
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Buccal cavity can be opened and closed by
opening and closing the mouth.
Opercular cavity can be opened and closed
by movements of the operculum.
– ram ventilation
blood flows in an opposite direction to
the flow of water, thus maximizing
oxygenation of blood
gill arches
countercurrent flow
8
Structure of a Fish Gill
9
Respiration in Air-Breathing Animals
•
•
Gills replaced in terrestrial animals because:
– air is less buoyant than water
– water vapor diffuses into the air through
evaporation
Two main terrestrial respiratory organs:
– tracheae
– lung
Lungs use a uniform pool of air in
constant contact with gas exchange
surface.
10
Respiration in Amphibians and Reptiles
•
Lungs of amphibians are formed as saclike
outpouching of the gut.
– Amphibians force air into their lungs
creating positive pressure.
fill buccal cavity with air, and then close
mouth and nostrils and elevate floor of
oral cavity
– Reptiles expand their rib cages by
muscular contraction and take air into
lungs via negative pressure breathing.
11
Amphibian Lungs
12
Respiration in Mammals
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Lungs of mammals packed with alveoli.
– Air brought to alveoli through system of air
passages.
Inhaled air taken to the larynx, passes
through glottis into the trachea.
Bifurcates into right and left bronchi
which enter each lung and further
subdivide into bronchioles that deliver
air into alveoli.
13
Human Respiratory System
14
Mammalian respiratory systems
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•
•
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Nose and mouth – air is warmed and
humidified
Mucus in the nose cleans the air of dust
Pharynx
Larynx – vocal cords
Trachea – glottis (opening to trachea)
protected by epiglottis, rings of cartilage, cilia
and mucus trap particles
Lungs
15
•
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Trachea branches into 2 bronchi
Bronchioles – surrounded by circular muscle
to dilate or constrict passage
Alveoli – site of gas exchange
– One cell thick
– Coated with extracellular fluid for gases to
dissolve
– Surfactant prevents alveoli from collapsing
16
Respiration in Birds
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Bird lung channels air through tiny air
vessels called parabronchi, where gas
exchange occurs.
– unidirectional flow
When air sacs are expanded during
inspiration, they take in air.
When they are compressed during
expiration, they push air into and through the
lungs.
17
Respiration in Birds
•
Avian respiration occurs in two cycles.
– Each cycle has an inspiration and an
expiration phase.
Cross-current flow has the capacity to
extract more oxygen from the air than a
mammalian lung.
18
How A Bird Breathes
19
Structures and Mechanisms of Breathing
•
The outside of each lung is covered by a
visceral pleural membrane.
– Second parietal pleural membrane lines
inner wall of thoracic cavity.
pleural cavity between the two
membranes
20
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 44.28(TE Art)
Sternocleidomastoid
muscles
contract
(for forced
inspiration)
Inspiration
Expiration
Abdominal
muscles
contract
Muscles
Muscles
(for forced
relax
contract
expiration)
Diaphragm
Diaphragm
relaxes
contracts
(a)
(b)
21
Hemoglobin and Oxygen Transport
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Hemoglobin is a protein composed of four
polypeptide chains and four organic heme
groups.
– iron atom at center of each heme group
Hemoglobin loads up with oxygen in the
lungs, forming oxyhemoglobin.
– As blood passes through the capillaries,
some of the oxyhemoglobin releases
oxygen and become deoxyhemoglobin.
22
Carbon Dioxide Transport by the Blood
23