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Unit 2A
Human Form & Function
Body systems
The respiratory system
Further information
• Further information about
this topic can be found in
Our Human Species
(3rd edtn)
Chapter 11, sections 1-2,
4-6
Background reading
• Our Human Species (3rd edtn.)
Chapter 11, Gas Exchange
Sections 1, 2, 4, 5, 6, 7
Student work book
Topic 9, Respiratory system
The respiratory system
Structure
Organs of the respiratory system
Larynx
Trachea
Rib cage
Bronchus
Mediastinum
Lung
Diaphragm
Section through the head
Nasal cavity
Palate
Teeth
Tongue
Pharynx
Epiglottis
Hyoid bone
Vocal cords
Larynx
Esophagus
The Miles Kelly Art library, Wellcome Images
The mucous lining
• The nasal cavity and upper airways
have a mucous lining.
• The epithelial lining contains goblet
cells which secrete a clear, sticky
mucus.
• The function of mucus is to trap dirt
particles and microbes before they
enter the lungs.
The nose (nasal cavity)
• Air enters and leaves the body
through the nose.
• Here it is cleaned, warmed and
moistened before entering the
body.
• The nasal secretions contain an
anti-bacterial enzyme – lysozyme.
A section through the nasal cavity
Sinus
Hard palate
NASAL
CAVITY
Soft palate
Nostril
The Miles Kelly Art library, Wellcome Images
The larynx (Adam’s apple or voice box)
• The larynx is a box-like
structure constructed
from nine cartilages
and is the entrance to
the trachea and lungs.
• The larynx houses the
vocal folds or vocal
cords.
• The entrance to the
larynx is protected by
the epiglottis.
Gray’s Anatomy
The bronchial tree
Larynx
Trachea
Bronchus
Bronchiole
The Sourcebook of Medical Illustration (The Parthenon Publishing Group, P. Cull, ed., 1989)
Trachea & bronchi
• The trachea & bronchi are
reinforced with C-shaped rings of
cartilage (these prevent the tubes
collapsing during inhalation).
The bronchi
Cartilage
rings
Muscular
wall
Mucous
lining
The Miles Kelly Art library, Wellcome Images
• The upper airways are lined
with a ciliated mucous
membrane
–The sticky mucus traps dirt &
microbes
–The cilia sweep the dirty mucus
up the trachea and into the
throat.
The ciliated lining tissue
Mucussecreting
goblet cells
Cilia
G. Meyer, ANHB-UWA,
EM of ciliated epithelium & goblet cells
D Gregory & D Marshall, Wellcome Images
Alveoli
Alveoli
G. Meyer, ANHB-UWA
• The brochioles terminate in microscopic
clusters of air sacs – the alveoli.
• Gas exchange takes place in the alveoli.
The alveoli (air sacs)
The Miles Kelly Art library, Wellcome Images
Section through a lung showing alveoli
and blood supply
M I Walker, Wellcome Images
The respiratory system
Gas exchange
Exchange surfaces
• Like all exchange surfaces, the
alveoli:
–are very thin
–have a large surface area
–are moist
–have a rich blood supply
Breathing
• Breathing (sometimes referred to
as ventilation) is the process of
moving air into and out of the
lungs.
• The purpose of breathing is to
exchange oxygen and carbon
dioxide between the lungs and
the air .
Boyle's law
• Boyle's law states that: for a fixed amount
of gas kept at a fixed temperature,
pressure (P) and volume (V) are inversely
proportional (while one increases, the
other decreases).
• This can be stated mathematically as:
PV = k
• where: P is the pressure, V is the volume
& k is a constant value representative of
the pressure and volume of the system.
Respiration
• Respiration is the transport of
oxygen from the air to the
tissues and the transport of
carbon dioxide in the opposite
direction.
[not to be confused with the process of
cellular respiration discussed earlier]
External respiration and
Internal respiration
• External respiration is the
movement of O2 and CO2 between
the lungs and the bloodstream.
• Internal respiration is the
exchange of O2 and CO2 between
the blood and the tissues.
External respiration
Partial pressure (mmHg)
Alveolar air
Deoxygenated
blood
Oxygenated
blood
Oxygen
100
40
100
Carbon
Dioxide
40
44
40
Breathing maintains the correct
concentration of gases in the lungs
Concentration
gradient
Breathing – inhaling
(remember P1V1 = P2V2)
Anatomical
changes
• Rib cage
raised
• Diaphragm
flattens
V
P1
Increases
Decreases
V = volume of thoracic cavity
P1 = pressure in thoracic cavity
P2 = air pressure
P1:P2
P1<P2
Result
Air
drawn
into
lungs
Thoracic volume
Rib cage relaxes
Diaphragm domed
Rib cage raised
Diaphragm flattens
A bicycle pump works
in much the same way
as the lungs
P1V1 = P2V2
The lungs work in much the same
way as a bicycle pump
If you increase the volume of the
chamber air is sucked in
If you decrease the volume of the
chamber air is forced out
Breathing – exhaling
(remember P1V1 = P2V2)
Anatomical
changes
• Rib cage
relaxes
• Diaphragm
domed
V
P1
Decreases Increases
V = volume of thoracic cavity
P1 = pressure in thoracic cavity
P2 = air pressure
P1:P2
P1>P2
Result
Air forced
out of
lungs
INHALE
Thoracic volume
increased
Thoracic pressure
< air pressure
Ribcage
raised
Diaphragm
flattened
EXHALE
Thoracic volume
decreased
Thoracic pressure
> air pressure
Ribcage
lowered
Diaphragm
domed
The Miles Kelly Art library, Wellcome Images
Why breathe?
Fresh air passing
through the lungs
delivers oxygen to the
red blood cells. At the
same time, waste
carbon dioxide is
removed from the
blood.
This can only occur if
fresh air is constantly
circulating through the
lungs.
Carbon
dioxide
Oxygen
Wellcome Photo Library
Oxygen transport
• Oxygen combines with haemoglobin in
RBCs to form oxyhaemoglobin.
Carbon dioxide transport
-
• Most CO2 is transported in the plasma
as dissolved bicarbonate ions.
Oxygen saturation
Diseased lung tissue
B
A
CDC
C
Photo by Pöllö
A. healthy lung tissue
B. Smoker’s lung
C. Emphysema
Study Guide
Read:
• Our Human Species
Chapter 11, sections 1-2, 4-6
Complete:
• Workbook
Topic 9, Respiratory system