Download Gas Exchange and Smoking

Part 1
Gas Exchange
Multicellular
 Plants & Animals respire
 Specialized gas exchange
surface in Humans
 Alveoli in the lungs
Unicellular
 O2 diffuses across cell
membrane from fluid around
cell into cytoplasm
 CO2 diffuses out of
cytoplasm, across cell
membrane, out of organism
Adaptations of Human Respiratory
System
1. Clean, warm air enters during
breathing
2. Increase surface area for
diffusion of O2 and CO2 b/t
blood and atmosphere
3. Minimize distance for this
diffusion
4. Maintains diffusion
gradients
1. Clean, warm air enters during breathing
 Air warmed to body temp
 Moistened by evaporation from
lining
 Protects lung tissue from
desiccation (drying out)
 Hair and mucus provide
protection
 Catch particles larger than 5-10
um
 Goblet cells
 Produce mucus in trachea and
bronchi (more about this in a
bit…)
2. Increase surface area for diffusion of O2 and CO2 b/t blood and atmosphere
 Alveoli tiny but
numerous
 Collectively large
surface area for gas
exchange (70 m2)
 Increases # of O2 and
CO2 molecules that
diffuse across surface
at any moment
 Speed up rate of gas
exchange
3. Minimize distance for this diffusion
 Capillaries surround each
individual alveoli
 Enables RBC carrying CO2
to get very close to gas
exchange surface (alveoli)
 Enables oxygen in alveoli to
diffuse across capillaries to
haemoglobin in RBC
 Diffusion across alveoli wall
and across the capillary
epithelium is NOT the same
as considering diffusion
across membranes of
individual epithelial cells
4. Maintains diffusion gradients by:
 Breathing movements draws air in from outside of the
body into lungs and then push it out again

Maintains a relatively high concentration of O2 and low
concentration of CO2
 Blood flow past alveolus


Deoxy blood brought TO alveoli
Oxy blood carried AWAY from lungs
DIAPHRAGM muscle that
contracts and relaxes during
respiratory cycle
Terms
and
Structures
to
Know
 Cartilage
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Ciliated epithelium
Goblet cells
Smooth muscle cells
Elastic fibers
Ciliated Epithelial cell
Cilia
Goblet cell
Basement membrane
Mucus
Lungs
Trachea
Cartilage
Bronchus
Rib
External intercostal muscle
Internal intercostal muscle
Bronchiole
Alveolus
Epithelium
 relatively avascular
and almost wholly
cellular (i.e., having
little or no
connective tissue
associated with it)
aggregation of cells
which are in
apposition over a
large part of their
surfaces, and which
are specialized for
absorptive, secretory,
protective, or
sensory activities.
PCCE =
pseudostratified ciliated columnar epithelium
Lungs
 Thoracic cavity
 Surrounded by pleural
membranes (air tight)
 small amount of fluid
 Prevents friction
between lungs, ribs, and
diaphragm
 Air enters lungs through
airways
Airways (from largest to smallest)
 Trachea
 Regular C-shaped rings of
cartilage
 2 Bronchi (bronchus)
 Irregular blocks of cartilage
 Bronchioles (many small
branches)
 Smooth muscle
contract/relax to adjust
diameter of airways
 No cartilage = allow
muscles to relax during
exercise to allow more O2 in
 Terminal bronchioles
 Respiratory bronchioles
(smaller branches of
terminals, hold bunches of
grapes/alveoli
 Alveoli
Overview
 Cartilage
 Trachea and Bronchi
 support
 Ciliated epithelium
 Trachea, bronchi, some bronchioles
 Move mucus
 Goblet cells
 In ciliated epithelium
 Produce mucus
 Smooth muscle cells
 Trachea, bronchi, bronchioles
 Widen or narrow tubes
 Elastic Fibres
 Trachea, bronchi, bronchioles, alveoli
 Elasticity
Cartilage
 Found in trachea and bronchi
 Provide support
 Prevents collapse of airway tubes when air pressure is
low
 C-shaped in trachea
 Irregular in bronchi
Smooth Muscle Cells
 Found in walls of
 Trachea
 Bronchi
 Bronchioles
 Contracts slowly, over long
periods of time, does NOT tire
 Contraction reduces diameter
of tubes
 During exercise, it relaxes,
widening tubes, move Oxygen
into lungs
Elastic Fibers
 Found in walls of ALL tubes AND between alveoli
 Breathing in  fibers stretch to allow alveoli and
airways to expand
 Breathing out  fibers recoil to help reduce volume of
alveoli and expand air out of lungs
Goblet cells
 On ciliated epithelium of trachea and
bronchi
 Very FEW goblet cells in bronchioles.
Why?
 Mucus would hinder gas exchange in the
alveoli
 Upper portion of cell swollen with
MUCIN droplets
 Mucin (glycoproteins) makes up mucus
 Slimy solution (water, proteins, lipids)
 Traps inhaled particles
 Made also made by mucus glands
beneath epithelium
Ciliated epithelium
 Structure
 Single layer of cells
 Outer surface covered with many thin
extensions (cilia) that move
 Function
 Move mucus upwards towards mouth
to prevent dust and particles from
reaching lungs
 Carry mucus upward toward larynx
and pharynx (1 cm/min)
 Nasal cavity

Move mucus in down respiratory tract,
into throat so it can be broken down by
enzymes in the stomach and pathogens
destroyed by acid in stomach
 Trachea and Bronchi
 Move mucus up to pharynx to be
swallowed
 Sneezing and coughing
 When large particles are caught in
mucus OR build up of mucus in
bronchi and trachea
Trachea
 Lining made of ciliated epithelium
resting on basement membrane (basal
cells) of protein fibers
 Goblet cells in between ciliated cells
 Loose tissue and glands beneath
epithelium
Bronchus
 Fewer Goblet cells per
cm2 than trachea
 Epithelial cells not as tall
as epithelial cells in
trachea
 Elastic fibers beneath
epithelium
 Irregular blocks of
cartilage
Bronchiole
 No cartilage
 Terminal bronchiole
 Respiratory
bronchiole
 No Smooth muscle
surrounding
epithelium of
 Connect to alveoli
Alveoli
 Thin epithelial lining
 squamous epithelial
cells
 0.5 um thick
 Surrounded by many
blood capillaries
carrying deoxy. Blood
 Oxygen& Carbon
dioxide diffuse down
their concentration
gradients
 Walls contain elastic
fibers
Gas Exchange at Alveolar Surface
 Air in alveoli = high Oxygen
concentration, low
concentration of Carbon
Dioxide
 High partial pressure of
oxygen
 Low partial pressure of
carbon dioxide
 Blood brought to lungs by
pulmonary artery = low
concentration of oxygen,
high concentration of
carbon dioxide
 Oxygen diffuses through
the thin walls of the alveoli
and into the capillary
 Carbon dioxide diffuses
from capillary into alveoli
and is breathed out of body
Volume of Lungs
 Tidal Volume
(normal)
 Volume of air moved
into and out of lungs
in one breath
 About 0.5 dm3
 Vital Capacity (max)
 Maximum amount
of air that can move
in/out of lungs
during deepest
breath
 3-5 dm3
Inhale/Exhale
 Inhalation
 Contraction of external
intercostals and diaphragm
 Increases volume of thoracic
cavity
 Draw in air through trachea
through bronchi into
bronchioles
 Exhalation
 Relaxation of external
intercostals and diaphragm
 Air flows out, down pressure
gradient