The Respiratory System

The Respiratory System

Warning: Terminology!

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“Respiration” is used several different ways:

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Cellular respiration is the aerobic breakdown of glucose in the
mitochondria to make ATP

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Respiratory systems are the organs in animals that exchange
gases with the environment

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“Respiration” is an everyday term that is often used to mean
“breathing”

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The proper term is for the physical act of bringing air in and
out of the lungs is ventilation

Respiratory System Function

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Respiratory systems allow animals to move oxygen
(needed for cellular respiration) into body tissues and
remove carbon dioxide (waste product of cellular
respiration) from cells

The Gas Pathway

Nasal Cavity

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Air enters nostrils, is filtered by hairs, warmed, humidified,
and sampled for odours as it flows through a maze of
spaces

Pharynx

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Connects nasal cavity and mouth to
larynx and esophagus/trachea

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Pharynx (Throat): Intersection where
the pathway for air and food is open,
except when we swallow

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Epiglottis - flexible elastic cartilage
attached to the wall of the pharynx
near the base of the tongue - prevents
food from entering the trachea

Trachea

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Also known as the
“windpipe”

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16 rings of cartilage
hold the trachea open

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The trachea forks into
two bronchi which enter
the lungs

Bronchi

●Bronchi (singular Bronchus):
Each bronchus leads into a lung
and branches into smaller and
smaller bronchioles, resembling
an inverted tree

●Bronchioles: fine tubes that allow
passage of air

●Epithelium of bronchioles is
covered with cilia and mucus

●Mucus traps dust and other
particles

●Cilia beat upwards and remove
trapped particles from the lower
respiratory airways

Lungs

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The main organ of respiration

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There are two: the left lung is
more narrow to allow space for
the heart; the right lung is
shorter to allow space for the
liver

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In the lungs millions of alveoli
and blood Capillaries
exchange oxygen and carbon
dioxide

Alveoli

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Alveoli - small air sacs
where gases are
exchanged

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The capillaries that
surround the alveoli are
the site of gas
exchange

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Carbon dioxide
diffuses through the
capillaries and enters
the alveoli

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Oxygen gas diffuses
from the alveoli into the
capillaries

Gas Exchange

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The respiratory surface is
made up of the alveoli and
capillary walls

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Air entering the lungs
contains more oxygen and
less carbon dioxide than
the blood that flows in the
pulmonary capillaries

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How do these differences in
concentrations assist in gas
exchange?

Oxygen Transport

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Oxygen that diffuses into
the bloodstream from the
alveoli binds to
hemoglobin

●

What are some advantages
to using hemoglobin to
transport oxygen?

Carbon dioxide transport

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Carbon dioxide can dissolve in
blood plasma, and about 70% is
transported this way

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Some carbon dioxide can bind to
hemoglobin at the body tissues
for transport

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The CO2 is released from the
body during expiration

What is diffusion? Write a brief
summary of how oxygen and
carbon dioxide diffuse into and
out of the lungs.