While making rounds, a doctor points out an
X-ray to a group of medical students.
"As you can see," she says, "the patient
limps because his left fibula and tibia are
radically arched. Morris, what would you do
in a case like this?"
"Well," ponders the student, "I suppose I’d
limp too.
A mother complained to her doctor
about her daughter's strange eating
habits. 'All day long she lies in bed
and eats yeast and car wax. What will
happen to her?‘
'Eventually,' said the Doctor, 'she
will rise and shine.'
The
Respiratory
System
SONG
Try to label the diagram
Respiration
“Respiration:” All the processes involved in the
exchange of gases between cells and the
environment
1. External respiration:
-breathing and gas
exchange
2. Internal respiration
-cellular respiration
DRY AIR: 78% Nitrogen 0.03% Carbon
21% Oxygen
Dioxide
0.97% other gases
Functions of Respiratory System
1. Gas Exchange
 Oxygen is brought into the body for cellular
respiration in the cells
 Carbon Dioxide is released from the body
2. Protection
 The lining of the respiratory tract filters or traps
harmful substances
•
Example: bacteria, dust, pollen etc.
3. Communication
 Air moving across the vocal cords creates vibrations
The Pathway of Air
1. Nasal Cavities
 Tiny hairs line the passageway act as filtering system
 Mucus traps particles
 Warms and moistens air
2. Pharynx
 Air-filled channel in the back of mouth
 Divides into two openings:
•
•
Trachea “windpipe” [respiratory system]
Esophagus [digestive system]
 The epiglottis is the flap-like structure that closes over
the glottis (opening to the trachea) during swallowing
The Pathway of Air
2. Pharynx
 If food bypasses the epiglottis, cells lining the
trachea have cilia that sweep foreign debris back up
out of the trachea
3. Trachea
 Wall of trachea supported by
cartilage rings to keep it open
 Contains the larynx “voicebox”
containing the vocal cords
 Divides into 2 bronchi
(one per lung)
The Pathway of Air
4. Bronchi (singular: Bronchus)
 Passage from the trachea to the
left or right lung
 Contain cartilage rings
 Divides into many bronchioles
5. Bronchioles (sg. Bronchiole)
 Smallest passageways of the
respiratory tract
 Do NOT contain cartilage
 End at alveoli
The Pathway of Air
6. Alveoli (singular: Alveolus)
 Sacs of the lung in which gases are surrounded by a
network of capillaries
 Where GAS EXCHANGE occurs!!
 Each lung contains about
150 million alveoli
The Pathway of Air
Pleural Membrane
 A thin, fluid-filled membrane that surrounds the outer
surface of the lungs and lines the inner wall of the
chest cavity
 Space between the pleural membranes is filled with
fluid which reduces friction between the lungs and
chest cavity during inhalation
 Pleurisy (Pleuritis)
• Inflammation of pleural
cavity, causing pain
when breathing IN
Gas Exchange
Blood entering the capillary network (from the
body organs/cells):
 Low in oxygen concentration
 High in carbon dioxide concentration
 Carbon dioxide diffuses out
of the blood (high) and into
the alveoli (low)
 Oxygen gas diffuses out of the
alveoli (high) and into the
capillaries (low)
Gas Exchange
Blood leaving the capillary
network (to the body organs/cells):
 Low in carbon dioxide
 High in oxygen
 Diffusion is driven by the concentration gradient
(high to low concentration) of oxygen between
the interior of the organism and the external
environment
 Gases are then distributed throughout the body
by the circulatory system
 VIDEO (Gas Exchange)
Alveoli Picture
Capillary
Wall of
the air
sac
Carbon
Dioxide is
dropped off
Oxygen is
picked up
Red Blood
Cell
The Breathing Process
Inhalation
 Rib intercostal muscles contract, expanding ribcage
 Diaphragm muscle contracts and lowers; increasing the
volume of the chest (thoracic) cavity
  volume of thoracic cavity =  in pressure
= air flows IN
Exhalation
 Diaphragm and intercostal muscles relax, ribcage
contracts
  volume of thoracic cavity =  in pressure
= air flows OUT
Regulation of Breathing
 Breathing is an automatic process controlled
by a part of the brain (brain stem)
 Nerve signals are sent to the diaphragm and
intercostal muscles, this triggers inhalation
 When the signals stop, exhalation begins
 The automatic control can be voluntarily
overridden by holding your breath!
Regulation of Breathing
 When breathing stops, concentration of CO2
increases and is detected by special
receptor cells in the aorta and carotid artery
These receptor cells send impulses to the
“breathing control centre” to resume
breathing
 Example: Hyperventilation – so much CO2 is removed
from the blood that the breathing control center sends
a “stop breathing” message
VIDEO - Overview
Measuring Air Volume
 Tidal Volume (TV)
 volume of air inhaled and exhaled in a single breath
 Avg=~500mL of air (with exercise ~3000mL!!)
 Inspiratory Reserve Volume (IRV)
 Additional air available when breathing in maximally
 Expiratory Reserve Volume (ERV)
 Additional air expelled by breathing out maximally
 Vital Capacity (VC)
 total useable lung capacity achieved by forceful,
maximum inhalation and exhalation