Download Gas Exchange and Smoking

GAS EXCHANGE AND SMOKING
Chapter. 9
GAS EXCHANGE VIDEO
https://www.youtube.com/watch?v=AJpur6XUiq4
GROSS STRUCTURE OF HUMAN GAS EXCHANGE
SYSTEM
• All organisms take in gases from their environment and release gases
to the environment. Animals take in O2 for aerobic respiration and
release CO2. Plants also respire, but during daylight hours they
photosynthesise at a greater rate than they respire, and so take in
CO2 and release O2.
• The body surface across which these gases diffuse into and out of the
body is called the gas exchange surface. In mammals, including
humans, the gas exchange surface is the surface of the alveoli in the
lungs.
• The gas exchange surface in the lungs is extensive, very thin, well
supplied with blood and well ventilated. The trachea and bronchi
provide little resistance to the movement of air to and from the alveoli.
GROSS STRUCTURE OF HUMAN GAS EXCHANGE
SYSTEM
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PLAN DIAGRAMS OF THE STRUCTURE OF THE
WALLS OF THE TRACHEA,
BRONCHI, BRONCHIOLES
PLAN DIAGRAMS OF AVEOLI AND
DISTRIBUTION OF CARTILAGE,
CILIATED EPITHELIUM, GOBLET
CELLS, SMOOTH MUSCLE,
SQUAMOUS EPITHELIUM AND BLOOD
VESSELS
FUNCTIONS AND WHAT IS…
•
Cartilage in the walls of the trachea and bronchi provides support and prevents the tubes
collapsing when the air pressure inside them is low.
•
Cillated epithelium is found lining the trachea, bronchi and some bronchioles. It is a single
layer of cells whose outer surfaces are covered with many thin extensions (cilia) which are able
to move. They sweep mucus upwards towards the mouth, helping to prevent dust particles and
bacteria reaching the lungs.
•
Goblet cells are also found in the ciliated epithelium. They secrete mucus, which traps dust
particles and bacteria.
•
Mucus glands are beneath the epithelium and also makes mucus.
•
Smooth muscle cells are found in the walls of the trachea, bronchi and bronchioles. This type
of muscle can contract slowly but for long periods without tiring. When it contracts, it reduces
the diameter of the tubes. During exercise it relaxes, widening the tubes so more air can reach
the lungs.
•
Elastic fibres are found in the walls of all tubes and between the alveoli. When breathing in,
these fibres stretch to allow the alveoli and airways to expand. When breathing out, they recoil,
helping to reduce the volume of alveoli and expel air out of the lungs.
PROCESS OF GAS EXCHANGE BETWEEN AIR IN
THE AVIOLI AND THE BLOOD
•
The air inside an alveolus contains a higher
concentration of O2, and a lower concentration of
CO2, than the blood in the capillaries. This blood has
been brought to the lungs in the pulmonary artery,
which carries deoxygenated blood from the heart. O 2
therefore diffuses from the alveolus into the blood
capillary, through the thin walls of the alveolus and
the capillary. CO 2 diffuses from the capillary into the
blood.
•
The diffusion gradients for these gases are
maintained by:
•
•Breathing movements, which draw air from outside
the body into the lungs, and then push it out again;
this maintains a relatively high concentration of
O2 and low concentration of CO 2 in the alveoli;
•
Blood flow past the alveolus, which brings
deoxygenated blood and carries away oxygenated
blood.
https://www.youtube.com/watch?v=XTMYSGXhJ4
E
SMOKING
•
Smoking is one of the major avoidable risk factors of chronic, life-threatening diseases
of the gas exchange and circulatory systems
•
The smoke from cigarettes contains several substances that affect the gas exchange
system and the cardiovascular system. These include:
•
tar, a mixture of substances including various chemicals that act as carcinogens.
•
nicotine, an addictive substance that affects the nervous system by binding to receptors
on neurons (nerve cells) in the brain and other parts of the body. It increases the release
of a neurotransmitter called dopamine in the brain, which gives feelings of pleasure. It
increases the release of adrenaline into the blood, which in turn increases breathing rate
and heart rate. There is also some evidence that nicotine increases the likelihood of blood
clots forming.
•
CO, which combines irreversibly with Hb, forming carboxyhaemoglobin. This reduces the
amount of Hb available to combine with O2, and so reduces the amount of O2 that is
transported to body tissues.
LUNG CANCER
•
Various components of tar can cause
changes in the DNA in body cells,
including the genes that control cell
division, which can cause cancer.
These substances are therefore
carcinogens. Cancers caused by
cigarette smoke are most likely to
form in the lungs but may form
anywhere in the gas exchange
system, and also in other parts of the
body. Smoking increases the risk of
developing all types of cancer.
•
Symptoms of lung cancer include
shortness of breath, a chronic cough
- which may bring up blood - chest
pain, fatigue and weight loss.
CHRONIC OBSTRUCTIVE PULMONARY DISEASE
(COPD)
•
This is a condition in which a person has chronic bronchitis and emphysema. It can be
extremely disabling.
CHRONIC BRONCHITIS
•
Various components of cigarette smoke,
including tar, cause goblet cells to
increase mucus production and cilia to
beat less strongly. This causes mucus to
build up, which may partially block
alveoli. This makes gas exchange more
difficult, as the diffusion distance between
the air in the alveoli and the blood in the
capillaries is greater. The mucus may
become infected with bacteria, causing
bronchitis.
EMPHYSEMA
•
Smoking causes inflammation in the
lungs. This involves the presence of
increased numbers of white blood cells,
some of which secrete chemicals that
damage elastic fibres. This makes the
alveoli less elastic. They may burst,
resulting in larger air spaces. This
reduces the surface area available for gas
exchange. This is called emphysema. A
person with emphysema has shortness of
breath, meaning they struggle to breathe
as deeply as they need to, especially
when exercising.
SHORT-TERM EFFECTS OF NICOTINE AND
CARBON MONOXIDE ON THE CARDIOVASCULAR
SYSTEM
•
The nicotine and CO in tobacco
smoke increase the risk of
developing atherosclerosis.
Atherosclerosis is a thickening
and loss of elasticity in the
walls of arteries. It is caused by
build-up of plaques in the blood
vessel wall. The plaques
contain cholesterol and fibres.
They produce a rough surface
lining the artery, which
stimulates the formation of
blood clots.
•
A blood clot may break away from the artery wall and get stuck in a narrow vessel elsewhere in
the blood system, for example in the lungs or in the brain. This prevents blood passing through so
cells are not supplied with O2 and die. If this happens in the brain it is called a stroke.
•
The loss of elasticity In an artery or arteriole also makes it more likely that the vessel will burst
when high-pressure blood pulses through. This is another cause of stroke.
•
If atherosclerosis happens in the coronary arteries that supply the heart muscle with oxygenated
blood, the person has coronary heart disease (CHD). Parts of the muscle may be unable to
function properly as they do not have enough O 2 for aerobic respiration. The muscle may die.
Eventually, this part of the heart may stop beating, causing a heart attack.
SMOKING EFFECTS
https://www.youtube.com/watch?v=gwuwrRKI2Y&index=4&list=PLXgIlX9mrPCoCZmX4Gx9AL
HEYmYW7INGg
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2:12-3:23
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3:47-4:30
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5:30-7:15