Transcript File

Lungs
By the end of the chapter you should be able
to:
 Label the internal structures of the lungs
 State the features of the alveoli which
allow efficient gas exchange
 Explain the role of diffusion in gas
exchange
 State the features of the capillary network
that allow efficient gas exchange
Gaseous exchange
 How are the structure and functions of
the cardiovascular system and gaseous
exchange linked?
 How are they affected by physical
activity and our overall level of health?
gaseous exchange system
 - links the circulatory system with the
atmosphere
 clean warmed air enters during breathing
 surface area is maximized for the
diffusion of O2 and CO2 between the
blood and the atmosphere
gaseous exchange system
 minimize the distance for diffusion
 maintain adequate gradients for this
diffusion
Breathing
footprints breathing
The lungs
 organs that allow gas
exchange
 oxygen in / CO2 out
trachea
- has rings of cartilage
bronchi (bronchus)
bronchioles
alveoli (alveolus)
computer animation
Lungs
 - site of gaseous exchange between air
and blood
 huge surface area in/out
 in the thoracic (chest) cavity
 surrounded by an airtight space
between the pleural membranes
Lungs
 small quantity of liquid in this area allows
friction-free movement
 pleurisy – inflammation of the pleural
membranes
 ventilated by the movement of the
diaphragm and ribs
Trachea, bronchi, bronchioles
 lungs ventilated when air passes through
a branching system of airways
 trachea – leads from the throat to the
lungs
 bronchi (two) – at base of the trachea
Trachea, bronchi, bronchioles
 bronchus – subdivide and branch
extensively forming bronchial tree
 cartilage – in the trachea and bronchi
keep the airways open, air resistance
low, and keeps them from collapsing or
bursting as the air pressure changes
during breathing
Trachea, bronchi, bronchioles
 trachea - C-shaped rings of cartilage
 bronchi – irregular blocks of cartilage
 small bronchioles lack cartilage –
surrounded by smooth muscle which can
contract or relax to adjust the diameter
of the bronchioles allowing greater air
flow to the alveoli during exercise
Warming and cleaning the air
 air warmed (to body temperature)
and moistened (from evaporation
from the lining) as it travels through
the nose and trachea
 warming and moistening the air
protects the inside of the lungs from
desiccation (drying out)
Warming and cleaning the air
 hairs and mucus lining the nasal
passages – remove particles larger
than 5-10 μm (dust, pollen, bacteria,
fungal spores, sand, and viruses)
 goblet cells – cells of the ciliated
epithelium that produce mucus
Warming and cleaning the air
 upper part of each goblet cell is
swollen with mucin droplets
 mucin – slimy solution of
glycoproteins with many
carbohydrates chains (makes it sticky
and able to trap inhaled particles)
 rest of cell contains the nucleus and
is quite slender like the stem of a
goblet
Warming and cleaning the air
 mucus – also made by glands
beneath the epithelium
 some pollutants – sulphur dioxide and
nitrogen dioxide can dissolve in
mucus to form acid and irritate the
lining of the airways
 ciliated cells – between goblet cells
Warming and cleaning the air
 continual beating carries the carpet of
mucus upwards towards the larynx at
a speed of 1 cm/min
 mucus usually then swallowed and
the pathogens are destroyed by
stomach acids
Warming and cleaning the air
 macrophages – phagocytic white
blood cells patrol the surfaces of the
airways scavenging small particles
such as bacteria and fine dust
particles
 during infections - macrophages
are joined by other phagocytic cells
which leave the capillaries
Alveoli
 alveoli – at the end of the pathway
bewteen the atmosphere and
bloodstream
 very thin epithelial lining surrounded
by many blood capillaries carrying
deoxygenated blood
 short distance – allows efficient
diffusion
Alveoli
 elastic fibers - in alveolar walls
stretch during breathing and recoil
during expiration to help force air out
 fully expanded during exercise –
surface area for diffusion increases
Alveoli (air sacs)
 provide large surface
area for gas exchange
 one lung equivalent to a
tennis court of surface
area using alveoli
footprints alveoli
oxygenated blood
air in
air out
air sac in
lungs
skool gas exchange
deoxygenated blood
body
cells
ciliated
epithelium,
goblet cells
hyaline cartilage,
mucous
glands
ciliated, stratified appearance.
cartilage ring-like
•in appearance.
more smooth muscles
as progress into
bronchiole.
-less mucus glands & cartilage
terminal respiratory bronchioles
alveoli
macrophage in
alveoli
monkey lung
Features of Alveoli for efficient
gas exchange - summary
 large surface area to absorb oxygen.
 moist surface to allow oxygen to
dissolve.
 Surfactant – reduces surface tension,
keeps alveoli from recoiling and sticking
together
 thin lining to allow easy diffusion of
gases..
skool adaptation of alveoli
Features of capillaries for
efficient gas exchange
 dense network to carry CO2 and O2
 Large surface area to transport gases
 Lining is one cell thick so gases can
pass through quickly and easily.
Airway
Number
Approx.
diameter
Cartilage
Goblet
cells
Smooth
muscle
Cilia
Site of
gas
exchange
trachea
1
1.8 cm
yes
yes
yes
yes
no
bronchus
2
1.2 cm
yes
yes
yes
yes
no
terminal bronchiole
48 000
1.0 mm
no
no
yes
yes
no
respiratory bronchiole
300 000
0.5 mm
no
no
no
yes
no
alveolar duct
9X106
400 μm
no
no
no
no
yes
alveoli
3X109
250 μm
no
no
no
no
yes
Breathing rate and heart rate
 as body activity varies the rate cells
need oxygen also varies
 rate of supply of oxygen to the cells is
determined by the rate and depth of
 1) breathing and
 2) rate at which the heart pumps blood
around the body
 breathing refreshes the air in the
alveoli
Breathing rate and depth
 changing the depth and rate of
breathing - maintains a constant
concentration of O2 and CO2 no
matter the level of activity
 at rest – ventilate about 6.0 dm3 of
air per minute
Breathing rate and depth
 about 0.35 dm3 of new air enters the
alveoli with each breath, only 1/7th of
the total volume of air in the alveoli
 means large changes in the
composition of alveolar air never
occur
 impossible to empty the lungs
completely even during forced
exhalation
Breathing rate and depth
 residual volume - about 1.0 dm3 of
air remains in the alveoli and airways
 about 2.5 dm3 of air remains in the
lungs after breathing out normally
 breathing deeply – lungs can increase
volume by as much as 3 dm3
 exercise increases the depth of
breathing and breathing rate
Breathing rate and depth
 Tidal volume – volume in a single
normal breath
 Vital capacity - volume breathed in
after maximum expiration
 ventilation rate – total volume of air
moved into lungs in one minute
 ventilation rate = tidal volume x
breathing rate
 expressed as dm3min-1
Breathing rate and depth
 well trained athlete – achieve
adequate ventilation by increasing
the tidal volume with only a small
increase in the breathing rate,
training improves efficiency of the
muscles involved with breathing
Pulse rate
 ventricles contract – a surge of
blood flows into the aorta and the
pulmonary arteries under pressure
 stroke volume – volume of blood
pumped out from each ventricle
 cardiac output – total volume
pumped out per minute
Pulse rate
 pulse – a blood surge distends the arteries
(which contain elastic tissue) which stretch
and subsequently recoil of aorta and
arteries travels as a wave along all the
arteries
 pulse rate – identical to the heart rate
 pulse measured – at wrist where the
radial artery passes over bone or at the
carotid artery in the neck
 resting pulse – an indication of fitness
Pulse rate
 at rest – cardiac output is about 5
dm3 of blood every minute
 cardiac output – achieved by large
stroke volume with a low pulse rate
or small stroke volume with a high
pulse
 more efficient – to pump slowly as
the heart uses less energy than when
pumping at a high rate
Pulse rate
 physically fit – resting pulse low,
stroke volume high, only a small
increase in pulse is necessary to
achieve the required blood supply –
pulse rates return to resting level
quickly after exercise
Pulse rate
 normal range – adult resting pulse
rates 60-100 bpm
 average fit young adult – 70 bpm,
falls with age
 pulse rate higher during/after
exercise, after easting or smoking
 pulse rate lowest when sleeping
Blood pressure
 systole – both ventricles contract
 left ventricle force oxygenated blood
out of the heart to supply the body
 maximum arterial pressure –
systolic pressure during active stroke,
when blood leaves the heart through
the aorta
Blood pressure
 heart relaxes – left ventricular
pressure falls, high pressure in the
aorta closes the semilunar valve
 head of pressure – elastic recoil of
the aorta and the main arteries
provides a steady flow of blood in the
arteries towards the capillaries
 diastolic pressure – minimum
pressure in the arteries
Blood pressure
 reflect resistance – of the small
arteries and capillaries to blood flow
and therefore the load against which
the heart must work
 resistance high, so is the diastolic
pressure – results from arteries not
stretching well because they may
have hardened
Blood pressure
 sphygmomanometer – measures
blood pressure
 systolic – 120 mm Hg (15 kPa)
 diastolic – 80 mm Hg (10.5 kPa)
 120/80 – typical blood pressure
Blood pressure




BP – rise and fall during the day
young adult – 110/75
60 years – 130/90
exercise – systolic 200 mm Hg,
while diastolic rarely changes
Hypertension
 hypertension - high systolic and
diastolic blood pressures at rest
 no sharp distinction between ‘normal’
and ‘high’ blood pressure
 risk of stroke and coronary heart
disease increases considerably with
blood pressures in excess of 140/90
(hypertensive)
Hypertension
 causes generally unknown
 short term hypertension - because
of the contraction of smooth muscle
in the walls of small arteries and
arterioles
 may be as a result of increase in the
concentration of the hormone
noradrenaline which stimulates the
arterioles to contract
Hypertension
 contraction increases the resistance
of the blood vessels and the heart
works harder to force blood through
the circulatory system
 long term hypertension – imposes
a strain on the cardiovascular system
 can lead to heart failure when heart
muscles weaken and are unable to
pump properly
Category
Blood pressure (mmHg)
systolic
diastolic
optimal
< 120
< 80
normal
< 130
< 85
high normal
130-140
85-90
hypertension
> 140
> 90
Hypertension
 ‘silent killer’ – no prior symptoms to
give a warning of impending heart
failure
 90% of cases the exact cause of
hypertension is unknown but linked
to: excessive alcohol intake, smoking,
obesity, too much salt in the diet, and
genetic factors
Lungs
Can you?
 Label the internal structures of the lungs
 State the features of the alveoli which
allow efficient gas exchange
 Explain the role of diffusion in gas
exchange
 State the features of the capillary network
that allow efficient gas exchange
 [PA] Using Figure 9.3 as your
microscope view, make a labeled
drawing of each slide; a, b, & c and
provide a description of the structure
of the walls of the trachea,
bronchioles, and alveoli with their
associated blood vessels. Why is
there a folded membrane in c? [9]