breathing and smoking

Question 1

Human Respiratory System –> Structure and Function

Answer 1

Air moves sequentially from the nose and mouth to
the
◼ pharynx, where digestive and respiratory systems meet,
◼ larynx (voice box), down the trachea (windpipe),
◼ Into the bronchi (one bronchus to each lung),
◼ bronchioles, (smallest branches of tubes within lungs), and
◼ Into the alveoli (air sacs where gas exchange primarily
occurs)

Question 2

Ventilation of the Lungs

Answer 2

Breathing: alternating process of inhalation & exhalation

Thorax is an air-tight chamber
◼ a change in thorax volume will cause a change in
lung pressure
◼ Air is drawn into the alveoli when the air pressure in
the lungs is lower than atmospheric pressure, and
◼ Air is forced out when the pressure is higher than
atmospheric pressure.

inhalation: inspiration
- intercostal muscles contract
- ribs move upwards and outwards
- diaphragm moves down
- diaphragm muscles contract
- volume of thorax and lungs increase
- pressure is reduced below atmospheric pressure and air flows in

exhalation: expiration
- intercostal muscles expand
- ribs move downwards and inwards
- diaphragm moves up
- diaphragm muscles expand
- volume of thorax and lungs decrease
- pressure is increased above atmospheric pressure and air flows out

Question 3

Trachea, Bronchi and Bronchioles

Answer 3

To protect delicate lining of alveoli, air reaching the alveoli must be
warmed, moist and free of dust particles and other foreign bodies:
◼ In the nasal cavity,
◼ Hairs in nostrils trap and filter out large dust particles from incoming air stream
◼ Superficial blood vessels start to warm the incoming air
◼ In the trachea and bronchi:
◼ numerous goblet cells secrete sticky mucus to moisten incoming air and trap finer dust particles, while
◼ ciliated epithelium sweeps the mucus upstream to the buccal
cavity (where it is swallowed)

Question 4

Alveolar Structure and Gaseous Exchange

Answer 4

Alveoli and terminal bronchioles have elastic connective
tissue that allows it to expand during inhalation and recoil
during expiration

Capillary systems wrap around the clusters of alveoli
◼ Each capillary is connected to a branch of the pulmonary artery, and is
◼ drained by a branch of pulmonary vein

◼ The wall of an alveolus is one cell thick.

◼ The wall of blood capillary is one cell thick.

◼ Capillaries are extremely narrow, just wide enough for
RBCs to squeeze through

The oxygen and carbon dioxide concentration gradients
between alveolar air and blood are maintained by:
▪ A continuous flow of blood through blood capillaries; and
▪ Movement of air in and out of alveoli, when breathing

Question 5

Characteristics of alveoli allowing for \ efficient gas exchange

Answer 5

One-cell thick alveolar & blood capillary wall – short diffusion distance for gases, higher rate of exchange
◼ Extremely narrow capillaries – allows for single file of rbc to pass through, increase surface area for exchange
◼ Rich supply of capillaries closely associated around alveolus – helps maintain concentration gradient of gases for higher rate
of exchange (next slide)
◼ Thin film of moisture (i.e. surfactant) covers inner surface of alveolus – keeps alveolar wall flexible & allows for oxygen to
dissolve in it

Question 6

Uptake of oxygen gas molecules

Answer 6

Blood arriving in the lungs is low in O2 but high in CO2
◼ As blood passes the alveoli, gaseous exchange occurs
by diffusion
◼ Oxygen dissolved in the surface film of water, diffuses
across the alveolar walls and capillary epithelium into
the blood plasma and red blood cells where it combines
with haemoglobin to form oxyhaemoglobin.
◼ At the same time, CO2 diffuses from the blood into the
alveolus.

One cell thick alveolar wall that separates blood capillaries from alveolar air is permeable to oxygen and carbon dioxide

Since alveolar air contains a higher concentration of oxygen than blood,
oxygen dissolves in the thin film of moisture lining the alveolar walls and
diffuses into the blood capillaries

Oxygen combines with haemoglobin in RBCs to form oxyhaemoglobin -
reversible reaction, depending on the amount of oxygen in surroundings

In the lungs where the oxygen concentration is high, oxygen combines with
haemoglobin to form oxyhaemoglobin.

When blood passes through oxygen-poor tissues, oxyhaemoglobin releases
oxygen, which diffuses across walls of blood capillaries into cells of tissues.

Question 7

How is CO2 Removed from Your Lungs?

Answer 7

Tissue cells produce a large amount of CO2 as a result of aerobic respiration.

As blood passes through these tissues (via blood capillaries), CO2 diffuses into the blood and enters the RBCs.

CO2 reacts with water in RBCs to form carbonic acid
- catalysed by carbonic anhydrase in RBCs

Carbonic acid is converted to bicarbonate ions which diffuse out of RBCs.
Most CO2 is carried as bicarbonate ions in blood plasma
with a small amount of dissolved CO2 carried in the RBCs

In the lungs, bicarbonate ions diffuse back into RBCs where they are
reconverted to carbonic acid, and then into water and CO2

CO2 then diffuses out of blood capillaries into alveoli,
where it is expelled during exhalation.

Question 8

Composition of Cigarette Smoke

Answer 8

Properties of Chemical Effects on Body

Tar
Carcinogenic; damages DNA leading to uncontrolled cell division
Cancer-causing; increases risk of lung, nose and throat cancer

Nicotine
Stimulating and relaxing drug; release dopamine for experiencing pleasure
Increases heart rate and blood pressure
Causes addiction
increases risk of blood
clots in arteries

Carbon Monoxide
Combines irreversibly with haemoglobin
to form carboxyhaemoglobin
Less haemoglobin available for transport of oxygen

Irritants (including tar)
Paralyses cilia lining airways
Dust particles trapped in mucus in air passages cannot be removed