Respiration in Animals
How Animals Live
Why Do Animals Need to Breathe?
• Every cell in an animal requires oxygen to perform cellular respiration
which gives off carbon dioxide and water as waste products.
• Respiration is the process by which animals exchange these gases with their
environment.
• Animals have specialized systems of structures that help them to do this
successfully and efficiently.
• Even a fish will drown if it cannot successfully breathe underwater!
How Mammals Breathe
• The chief organ in mammalian respiration is the lungs.
• The lungs are actively ventilated via a suction-pump mechanism of
inhalation (breathing in) and exhalation (breathing out).
• Breathing depends on the rib muscles and the diaphragm, which is a
structure located just beneath the lungs like a dome-shaped floor
Inhale
• Inhalation happens when the rib cage opens
up and the diaphragm flattens and moves
downward.
• The lungs can then expand into the larger
space that causes the air pressure inside them
to decrease, and the drop in air pressure inside
the lung makes the outside air rush inside.
Exhale
• Exhalation is the opposite process.
• The diaphragm and the rib muscles
relax to their neutral state that causes
the lungs to contract.
• The squashing of the lungs increases
their air pressure and forces the air to
flow out.
It Starts with the Nose
• In most mammals, the first place
that air enters upon inhalation is the
nose.
• It gets warmed, moistened, and
filtered by cilia and mucus
membranes which can trap dust and
pathogens.
The epi-what?
• Air then reaches the epiglottis, which
is the tiny leaf shaped flap at the back
of the throat.
• The epiglottis regulates air going into
the windpipe and closes upon
swallowing to prevent food from being
inhaled
Down to the Trachea
• Next, the air travels through a tube
called a trachea.
• The trachea is a long structure of
soft tissue surrounded by c-shaped
rings of cartilage.
• In humans the trachea splits into two
bronchi branches that lead to each
lung.
Bronchi and Alveolus
• Each bronchi divides into increasingly smaller
branches, until they form a big tree of tubes.
• The smallest branches are called
the bronchioles
• Each bronchiole ends with a tiny air sac (no
larger than a grain of sand) called an alveolus.
• The tiny alveoli are important because they
increase the surface area that can be used for
gas exchange.
The In’s and Out’s of Breathing
• Capillaries are small blood
vessels that take oxygen into the
bloodstream.
• Oxygen is taken into the
bloodstream for cells.
• Carbon dioxide is taken out of
the bloodstream and sent
outside the body.
It’s in Your Blood
• The blood is able to carry the fresh oxygen in red blood
cells because of the hemoglobin protein, which can
attach oxygen molecules.
• Think of hemoglobin like a bus that carries oxygen
passengers.
• Each hemoglobin protein can carry four passengers of
oxygen at one time.
• When red blood cells are oxygen rich they are bright red,
and when they are deoxygenated they are a deep purple.
The Heart of the Matter
The heart
pumps blood
low in oxygen
to the lungs
In the lungs, the blood
takes in oxygen then is
pumped back into the
heart to be sent out all
over the body
How Reptiles and Amphibians Breathe
• Reptiles and amphibians both have lungs and exchange gases in the
capillaries like mammals.
• Reptiles do not typically breathe the same way as mammals since many
reptiles lack a diaphragm.
• Then how do they breathe?!
Pump it Up!
• Amphibians are capable of buccal pumping to push
air into the lungs.
• This begins by muscles pulling air through the mouth
or nose into a buccal cavity.
• Throat muscles then pump and move the floor of the
mouth up in a way that is visible from the outside.
• This forces air out of the mouth and into the lungs.
Look at this frog's throat constantly moving.
Breathing for the Birds
• Birds have air sacs that collect air.
• They then force the air through their lungs like bellows stoking a fire.
• When a bird inhales, air is brought into the posterior air sacs, which
expand.
• Upon exhalation, the air is forced from the posterior air sacs into the
lungs. This is where gas exchange takes place.
• A second inhalation will move the air from the lungs to the anterior
air sac.
• A second exhalation will push the air out of the body.
A fishy way to breathe
• In fish, respiration takes place in their gills.
• Gills can collect dissolved oxygen from the water and release carbon dioxide.
• Gills are much more complex than just a slit in the cheek of a fish.
Gills
• Gills are comprised of gill arches with
hundreds of gill filaments extending from
them.
• Each filament is lined with rows of lamellae,
and the gas exchange takes place as water
flows through them.
• The frills and flaps increase the surface area to
allow more gas exchange to take place, just as
the alveoli do in the lungs.
How Insects Breath
• The respiratory apparatus in insects consists of a system of tubes, called
tracheae, which directly ventilate the tissues.
• When an animal actively moves air to the site of gas exchange, it is
called ventilation.
• The tubes divide and branch out into smaller and smaller tubes extending
into all parts of the insect like plumbing pipes.