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Unit 5
THE BREATH OF LIFE
TRANSPORT AND CIRCULATION
NUTRIENTS AND DIGESTION
TODAY
THE BREATH OF LIFE!
Cellular Respiration
The opposite of photosynthesis.
8.1 – The Task of Respiration
• Aerobic organisms require Oxygen (O2)
• O2 is necessary for cellular respiration
 releases energy to drive all cellular functions
• CO2 is the waste product of cellular respiration
that must exit the cell.
• Gas Exchange:
the process that ensures O2 enters each cell of
an organism and CO2 can leave each cell.
• Gas exchange systems/Respiratory systems vary for
different organisms
• but all must have TWO requirements:
• Surface Area:
– Must be large enough for enough O2 to enter and CO2 to leave
in order to meet the metabolic needs of the organism.
•
• Moist Environment:
• Allows for gas exchange to take place
•  since O2 and CO2 must be dissolved in order to be
transported
• SIMPLE GAS EXCHANGE (Respiratory)
SYSTEM:
• Unicellular organisms – eg. amoeba, algae
• Exchange gas through membrane by diffusion
• Membrane must be moist (live in moist
environment)
Hydra, planarian, and ameoba.
• PROBLEMS with being multicellular:
• Diffusion is only effective over a distance of a
few cells.
• As the body surface becomes more
specialized, the surface area available for gas
exchange is reduced.
SOLUTIONS:  Specialized Respiratory
Systems
• Skin Respiration
• eg. earthworms, leeches (see textbook p.
252)
• Skin must remain moist
• Skin lined with tiny capillary vessels
• O2 carried through circulatory vessels to other
cells of the organism
• Gills
• eg. fish, crayfish (see textbook p. 253)
• Structural changes increase the surface area
of the body parts involved in gas exchange
• Mechanism has evolved which enables the
organism to ventilate this surface
•  oxygen-containing aquatic medium
moves over respiratory surface
• Example: fish gills
• feathery tissue structures consisting of
numerous delicate branches
•  ensures a large surface area in a limited
space
• connected to vascular system to transport O2
and CO2 to and from cells
• What about Terrestrial Organisms?
• they have an internal gas exchange system
• BREATHING:
• is an important process as it forces O2 across
the gas exchange surface.
• It relies on a basic law of physics
•  air moves from a region of high pressure to
a region of low pressure until equilibrium is
reached. (see textbook p. 254)
• Tracheal Respiratory System
• eg. insects like grasshoppers
• An internal system allows to maintain a moist
environment
• Consists of external pores called “spiracles” 
controlled by valves
• Connected to internal network of tubes called
“tracheae”
• Air is ventilated via contraction and relaxation of the
abdomen
• (Breathing)
• Note:
• The circulatory system is separate from the
respiratory system
•  branches of tracheal tubes ensure contact
with the cells
MAMMALIAN GAS EXCHANGE
Be able to distinguish between the following
terms:
• Breathing
• Gas Exchange
– External – from air in lungs to capillaries
(circulatory system)
– Internal – from circulatory system to body cells.
• Cellular Respiration
• The Gas Exchange System:
What is its overall function?
• To supply cells with O2 and to remove CO2
• Note: there is a need for a circulatory system
to transport the gases to and from the cells
• Why is our system highly specialized?
• Since we are warm blooded  must maintain
constant internal temp.
• To maintain the temp  requires lots of
energy
•  lots of O2 is needed for cellular respiration
• Our Gas Exchange System must have:
• Large surface area  to maximize O2
exchange
• Moist surface area  for diffusion
• Ventilation Mechanism  force O2 across lung
surface
• Therefore: Breathing  Gas Exchange 
Cellular Respiration
• What is inhalation? Inspiration?  breathing
in
• What is exhalation? Expiration?  breathing
out
Major parts of the respiratory
System
Upper Respiratory Tract & Lower Respiratory
Tract.
Upper Respiratory Tract
Upper Respiratory Tract
• Why does it usually take place through the
nose?
• Nose hair  filters dust from air
• Capillaries close to surface  warm the air
• Mucus  moistens the air
• Where does air go after the
nose?
• Pharynx  opening to
digestive system (esophagus)
 opening (glottis) to gas
exchange system (trachea)
• Note: Why don’t we choke
when we eat?
•
 epiglottis closes over
trachea when swallowing
• What adaptations does the trachea have?
Why?
• Larynx  voice box
• Mucus/Cilia  move dust and foreign
particles out of lungs
• Cartilage Rings  to maintain an open airway
Lower Respiratory Tract
Lower Respiratory Tract
• After the trachea, where does the air go?
• Bronchi (two branches of the trachea) 
branches further to “Bronchioles”
• What is the actual site of Gas Exchange:
ALVEOLI
•  grape-like cluster of tiny sacs at the end of
each bronchiole
•  kept moist for gas exchange
•  sac wall is a thin membrane (1 cell thick)
•  capillary bed (containing blood) surrounds
air sac
• Structure of Lungs:
Where are the lungs located? Why?
• in the pleural or chest cavity  protected by ribs
•
•
•
•
What stops the lungs from collapsing?
Pleural membrane surrounds lungs
 two layers with lubricating fluid between them
Elastic connective tissue fills the spaces in between the
structure
• Alveoli lined with a lubricating film
• How many lobes does each lung have?
• Right lung  3 lobes
• Left lung  2 lobes
• How does enough air get down to the
alveoli?
• By “Breathing Movements” (see text p. 260)
• GAS EXCHANGE – Some More Details
• O2 and CO2 are exchanged across the cell membrane.
• Alveoli and adjacent capillaries are only one cell thick.
•
•
•
•
•
Inhaled Air contains:
 ~ 20.94 % O2
 ~ 0.04 % CO2
Oxygen diffuses into blood from the alveoli (by simple and facilitated
diffusion)
• Exhaled Air contains:
•  ~ 16.49 % O2
•  ~ 4.49 % CO2 (CO2 diffuses out of the blood into the alveoli)
REVIEW QUESTIONS
Respiratory System Handouts
Page 255, #1, 2, 3, 4, 5, 6.
Page 259, # 1, 2, 3, 4.
Read Page 262-263, copy figure 8.20, and briefly
define each term in the figure.