Transcript Gas Exchange in Humans

Gas Exchange in Humans
Ch. 9 pp. 116-119
9.5 Gas exchange occurs at
special surfaces
• Animals and plants get their oxygen directly from
their surroundings
• During aerobic respiration, carbon dioxide, a
waste product, is produced and has to be
removed.
• Organisms have special areas where the oxygen
enters and the carbon dioxide leaves gas
exchange
– Surfaces have to be permeable along with the other
characteristics to follow:
9.8 Alveolar walls are the surface
for gas exchange
• Alveoli= tiny air
sacs at the end of
each bronchiole;
where gas
exchange takes
place
• Oxygen diffuses
into the blood in
the alveoli
• Because they are
Alveoli
Characteristics of alveolar walls for
gas exchange:
• 1. They are thin
– Only one cell thick
– Allows quick and efficient diffusion of gases
– Capillary walls are also only one cell thick…
oxygen has to diffuse across the small
thickness of the capillary and alveoli to get
into the blood.
Characteristics of alveolar walls for
gas exchange:
• 2. they are close to an efficient transport
system
– Blood is constantly being pumped to the lungs
via the pulmonary artery that branches into
thousands of capillaries which take blood to
all parts of the lungs
– Allows CO2 in the blood to diffuse out into the
lungs and oxygen to diffuse into the blood to
be pumped to the rest of the body
Characteristics of alveolar walls for
gas exchange:
• 3. They are kept moist
– Special cells in the alveoli secrete a watery
liquid
– Liquid covers the surface of the cell sin the
alveoli and prevents them from drying out
Characteristics of alveolar walls for
gas exchange:
• 4. They have a large surface area
– Allows for more gas exchange to occur
– The total surface area of all the alveoli in your
lungs is over 100 m2
• 5. They have a good supply of oxygen
– Your breathing movements keep your lungs
well supplied with oxygen
9.6 The Structure of the Breathing
System
• 1. Nose & Mouth
– Air can enter the
body through either
– Nose contains
goblet cells that
make a liquid
containing water
and mucus which
helps to keep the
noise moist
– Other cells contain
• 2. Trachea
– Windpipe; carries
air from
nose/mouth to
bronchi
– Has rings of
cartilage around it
that keeps it open
• 3. Larynx
– Voice box; contains
the vocal cords that
• 4. Bronchi
– Trachea divides
into two bronchi
– One bronchus
goes to each lung
and then branches
out into smaller
tubes
• 5. Bronchioles
– Smaller tubes
branching from
bronchus