Gaswisseling (BOOK)
43.5
Partial pressure is the pressure exerted by a particular gas in a mixture of gases. A gas
always undergoes net diffusion from a region of higher partial pressure to a region of lower
partial pressure.
Gills are outfoldings of the body surface that are suspended in the water. In fishes, the
efficiency of gas exchange is maximized by countercurrent exchange, the blood flows in a
direction opposite to that of water passing over the gills. As the blood continues it passage
its Po2 steadily increases, but so does that of the water (countercurrent exchange). This
results in a partial pressure gradient that favors the diffusion of O2 from water to blood
along the entire length of the capillary.
A tracheal system (insects) is a network of air tubes that branch throughout the body. The
biggest parts are the trachea which are exposed to air.
In addition to tracheal systems, lungs are localized respiratory organs. In humans air passes
the trachea from the larynx. The trachea branches into two bronchi, which branch into finer
tubes called bronchioles. Alveoli are air sacs clustered at the tips of the tiniest bronchioles.
Alveoli produce a mixture of phospholipids and proteins called surfactant, which coats the
alveoli and reduces surface tension, which prevents the alveoli form collapsing due to the
high pressure.
43.6
Amphibian
Positive pressure breathing is inflating the lungs with forced airflow.
Birds
Passage of air through the entire system requires two cycles of inhalation and exhalation;
43.7
Mammals
, Negative pressure breathing is pulling air into the lungs.
The lungs are surrounded by two membranes, the inner one adheres to the outside of the
lungs and the outer one two the wall of the thoracic cavity. The two layers are separated by
a piece of fluid which makes it impossible to separate them (like two plates with water
between it).
The tidal volume is the volume of air inhaled and exhaled with one breath (about 500mL in
rest). The vital capacity is the vital volume during maximum inhalation and exhalation (about
3.4 (v) and 4.8 (m) L). The air that remains after forced exhalation is called the residual
volume.
The most neurons which are responsible for regulating breathing are located in the medulla
oblongata, near the base of the brain. The medulla uses pH as an indicator of CO2
concentration. CO2 can react with H2O and form H2CO3 which can react to HCO3- and H+,
which lowers the pH. So when CO2 rises the pH rises. O2 has almost no effect on regulating
the breathing system, but when O2 levels drop very low, O2 sensors in the aorta and the
carotid arteries in the neck send signals to the breathing control centers.
43.5
Partial pressure is the pressure exerted by a particular gas in a mixture of gases. A gas
always undergoes net diffusion from a region of higher partial pressure to a region of lower
partial pressure.
Gills are outfoldings of the body surface that are suspended in the water. In fishes, the
efficiency of gas exchange is maximized by countercurrent exchange, the blood flows in a
direction opposite to that of water passing over the gills. As the blood continues it passage
its Po2 steadily increases, but so does that of the water (countercurrent exchange). This
results in a partial pressure gradient that favors the diffusion of O2 from water to blood
along the entire length of the capillary.
A tracheal system (insects) is a network of air tubes that branch throughout the body. The
biggest parts are the trachea which are exposed to air.
In addition to tracheal systems, lungs are localized respiratory organs. In humans air passes
the trachea from the larynx. The trachea branches into two bronchi, which branch into finer
tubes called bronchioles. Alveoli are air sacs clustered at the tips of the tiniest bronchioles.
Alveoli produce a mixture of phospholipids and proteins called surfactant, which coats the
alveoli and reduces surface tension, which prevents the alveoli form collapsing due to the
high pressure.
43.6
Amphibian
Positive pressure breathing is inflating the lungs with forced airflow.
Birds
Passage of air through the entire system requires two cycles of inhalation and exhalation;
43.7
Mammals
, Negative pressure breathing is pulling air into the lungs.
The lungs are surrounded by two membranes, the inner one adheres to the outside of the
lungs and the outer one two the wall of the thoracic cavity. The two layers are separated by
a piece of fluid which makes it impossible to separate them (like two plates with water
between it).
The tidal volume is the volume of air inhaled and exhaled with one breath (about 500mL in
rest). The vital capacity is the vital volume during maximum inhalation and exhalation (about
3.4 (v) and 4.8 (m) L). The air that remains after forced exhalation is called the residual
volume.
The most neurons which are responsible for regulating breathing are located in the medulla
oblongata, near the base of the brain. The medulla uses pH as an indicator of CO2
concentration. CO2 can react with H2O and form H2CO3 which can react to HCO3- and H+,
which lowers the pH. So when CO2 rises the pH rises. O2 has almost no effect on regulating
the breathing system, but when O2 levels drop very low, O2 sensors in the aorta and the
carotid arteries in the neck send signals to the breathing control centers.
