Download 37.1: The Respiratory System

20.2: The Respiratory System: the exchange
of gases
• Section Objectives:
• Identify the structures involved in external respiration.
• Contrast external and cellular respiration
• Explain the mechanics of breathing.
Why do we need a respiratory system?
• Need O2 in
– for cellular respiration
– make ATP
• Need CO2 out
food
– waste product
O2
ATP
CO2
Passageways and Lungs
• respiratory system consists of a pair of lungs & a system of tubes
that carry air to them
• Breathing is just one of the functions that the respiratory system
carries out.
The path air takes
• air enters through
the nasal cavity
– It passes through
the pharynx and
larynx into the
trachea
– The trachea forks to
form two bronchi
– Each bronchus
branches into
numerous
bronchioles
• The bronchioles end
in clusters of tiny
sacs called alveoli
Lungs
• Structure
spongy texture
• high surface area
• more absorption of O2
– alveoli
• small air sacs
– moist lining
• mucus traps dust,
pollen, particles
– covered by cilia
• hair-like extensions of cells
• move mucus upward to
clear out lungs
Moving gases into bloodstream
• Inhale
– O2 passes from alveoli
to blood
– by diffusion
• Exhale
– CO2 passes from blood
to alveoli
– by diffusion
capillaries
(circulatory system)
Gas exchange: Diffusion of gases
• Gases move by diffusion from high to low
concentration
– capillaries are thin-walled tubes of circulatory
system
– alveoli are thin-walled sacs of respiratory system
capillaries in lungs
capillaries in muscle
O2
O2
O2
O2
CO2
CO2
CO2
CO2
External respiration: exchange of
gases between alveoli and blood
blood
lungs
Internal respiration: exchange of
gases between blood and ce4lls
blood
body
The Mechanics of Breathing
• Breathing ventilates the lungs
• The action of your diaphragm and the muscles between your
ribs enable you to breathe in and breathe out.
• Breathing is the alternation of inhalation (active) and
exhalation (passive)
Control of Respiration
• Breathing is usually an involuntary
process.
• partially controlled by an internal
feedback mechanism that involves
signals being sent to the medulla
oblongata about the chemistry of
your blood.
– measure blood pH
• CO2 = pH (acid)
– coordinate
breathing,
heart rate &
body’s need
for energy
• will send nerve signals to the rib
muscles and diaphragm.
• nerve signals cause these muscles
to contract, and you inhale.
Breathing and Homeostasis
• Homeostasis
ATP
– keeping the internal environment of the
body balanced
– need to balance O2 in and CO2 out
– need to balance energy (ATP) production
• Exercise
– breathe faster
O2
• need more ATP
• bring in more O2 & remove more CO2
• Disease
– poor lung or heart function = breathe faster
• need to work harder to bring in O2 & remove CO2
CO
Cleaning dirty air
• To prevent foreign material
from reaching the respiratory
system is lined with ciliated
cells that secrete mucus.
• The cilia constantly beat
upward in the direction of
your throat, where foreign
material can be swallowed or
expelled by coughing or
sneezing