Transcript Gas Exchange - IB

Gas Exchange
6.4.1 Distinguish between
ventilation, gas exchange
and cell respiration
• Ventilation maintains concentration
gradients of oxygen and carbon
dioxide between air in alveoli and
blood flowing in adjacent capillaries
• The
exchange
(diffusion) of
oxygen and
carbon
dioxide to
and from the
blood at the
alveoli and
the respiring
tissues
Cell Respiration
• Movement
of air into
and out of
the lungs in
two stages:
inspiration &
expiration.
Controlled by
diaphragm &
ribcage.
Gas Exchange
Ventilation
Breathing is NOT respiration!
• This is
production
of ATP at the
cellular level
(mitochondri
a). Aerobic
respiration
uses oxygen,
whereas
anaerobic
does not.
Ventilation
• Movement of
gases
– 1st , in the lungs
where oxygen
moves from the
air into the
bloodstream
– 2nd, in a capillary
bed elsewhere in
the body where
the opposite gas
exchange occurs,
(O2 & CO2)
6.4.2 Explain the need for a
ventilation system
Why do we need a
ventilation system?
• We are large
organisms. Oxygen
cannot diffuse into
all our cells directly
from the air, nor
can waste products
be directly ejected
from the body. The
ventilation system
ensures the blood
can be the medium
for this.
Why a ventilation system?
• We are land-borne.
• Gases need moist
surfaces in order to
diffuse
• Lungs are moist
membranes
• Vent. System
maintains a large
concentration
gradients
• The constant flow
of blood past the
alveoli brings
blood with a high
CO2 concentration
and low O2
concentration
• Exhaling keeps the
CO2 concentration
in the alveoli low,
so it diffuses out.
Ventilation System
• High concentration
gradients must be
maintained in the
alveoli.
• Breathing in
increases the
concentration
gradient of oxygen
between the
alveoli & blood
(diffuse in)
• Breathing out
removes (CO2)
increasing the
concentration
gradient of CO2
between blood
and alveolus – CO2
diffuses out
Gas Exchange
• If the alveoli were not ventilated,
equilibrium would be reached and
no gas could be exchanged.
Respiratory Basics
6.4.3 Describe the features
of alveoli that adapt them to
gas exchange
Alveoli are well adapted to
gas exchange
Surfaces
are wet
• Alveoli increase the
surface area for gas
exchange.
• Millions in number
(300), each with their
own network of
capillaries
• Rich blood supply
maintains a high
concentration
gradient of O2 and CO2
Alveoli
• Membranes are
very thin
– Both of the alveoli
and the capillaries
• Diffusion path is
short
• Composed of
single layer of cell
(2 different types
of cells)
2 Types of Pneumocytes
Type 1 pneumocytes
• Very thin
• Large membrane
surface area
• Great for diffusion
• If damaged – no
mitosis
Type 2 pneumocytes
• Cuboidal in shape
• Little membrane surface
area
• Produce & secrete a
solution that acts as a
surfactant
• Prevents the sides of the
alveoli from sticking to
each other
• Damaged – stil mitosis
Which process(es) of
membrane transport are being
used in gas exchange at the
membranes of the alveoli?
How many membranes must an oxygen molecule
pass through in order to enter an erythrocyte?
•
6.4.4 Draw and label a
diagram of the ventilation
system, including trachea,
lungs, bronchi, bronchioles
and alveoli.
6.4.5 Explain the
mechanism of ventilation of
the lungs in terms of volume
and pressure changes
caused by the internal and
external intercostal muscles,
the diaphragm and
abdominal muscles.
Gas Exchange
Gas exchange
Mechanisms of inspiration
1. The diaphragm contracts & at the
same time the abdominal muscles
and intercostal muscles help to raise
the rib cage. All of these help
increase the volume of the thoracic
cavity.
2. Because of the increase in volume,
the pressure inside the cavity
decreases. Leads to less pressure
“pushing on” the passive lung tissue
Mechanism of inspiration
3) The lung tissue increases its volume
because there is less pressure
exerted on it.
4) This leads to a decrease in pressure
inside of the lungs, also known as a
partial vacuum
5) Air comes in through your open
mouth or nasal passages to counter
the partial vacuum within the lungs
Mechanism of Expiration
• Previous steps reversed.
Emphysema
• Alveoli are progressively destroyed
• Main cause smoking
• COPD(chronic obstructive pulmonary
disease)
• Turns healthy alveoli into large,
irregularly shaped structures with
gaping holes
Lung Cancer
• Cancerous growth
beginning in lungs
• Prone to spreading
(metastisizing)
• Lung becomes
dysfunctional
• May cause internal
bleeding in the
lungs
• Caused by
carcinogens