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Respiratory System
Humans & Environment

All animals exchange gases with
their environment

Animals take in oxygen (O2),
release carbon dioxide (CO2)
 Process is called respiration
Gases

Oxygen


Reacts with nutrients in mitochondria
to release energy
Carbon Dioxide


Waste product as a result of these
reactions
Gases cannot be stored like nutrients
can, so gases must be exchanged
Endotherms


Humans are large warm-blooded
animals, with very high oxygen
demand
Define endotherm (page 219)
Inhale

Air is warmed, cleaned and
moistened as it enters via mouth or
nasal cavity


Achieved by mucus and tiny hair
Epiglottis (flap-like structures)
covers the trachea when
swallowing, opens when breathing
Pathway


Flowing down windpipe (trachea), air enters
bronchi
Bronchi divide into bronchioles (network of
smaller tubes)

Trachea, bronchi are supported by cartilage
rings holding them open
Goblet Cells

Inner lining of trachea, bronchi and
bronchioles lined with cilia and mucusproducing goblet cells

Mucus traps tiny particles (bacteria, dust, pollen)
carried out of lungs by sweeping action of cilia
‘Bronchiole
Escalator’
Alveoli

Bronchioles branch further into tiny
air sacs called alveoli


This is where gas exchange occurs
Each lung has 150
million alveoli!

Total surface area
times your skin
40
Alveoli cont’d…

Surrounding each air sac, is a
capillary network….


Blood from the heart is pumped here to
obtain oxygen
O2 passes into capillaries via diffusion

At the same time, CO2 diffuses out of the
blood and into the lungs
Oxygenated Blood

How could you describe the
blood leaving the lungs going
back to the heart?
How we breathe…