B3.1 Gas exchange animals

Alveolus (plural alveoli)

air sac that constitutes the gas exchange surface of the lungs.

Bronchi

the two main branches of the trachea that go into the lungs; this then further divides into the bronchioles and alveoli.

Bronchioles

any of the fine, thin-walled, tubular extensions of a bronchus.

Concentration gradient

the gradient resulting from an unequal distribution of ions across the cell membrane.

Diaphragm

a dome-shaped muscular partition separating the thorax from the abdomen. It plays a major role in breathing as its contraction increases the volume of the thorax and so inflates the lungs.

Emphysema

a chronic respiratory disease where there is over-inflation of the air sacs (alveoli) in the lungs causing a decrease in lung function and often breathlessness.

Expiration / Exhalation

when the muscles of the thorax contract to cause the volume to decrease, this increases the pressure in the lungs and air moves from the higher pressure inside the lungs to the lower pressure outside the body.

Inspiration / Inhalation

when the air moves from a higher pressure (outside the body) to the lower pressure (inside the lungs).

Intercostal muscles

muscles found between the ribs.

Pneumocyte

one of the cells lining the alveoli (the air sacs) in the lung that assists in gas exchange and in the secretion of pulmonary surfactant.

Spirometer

an instrument for measuring the volume of air entering and leaving the lungs.

Surface tension

the force that causes the molecules on the surface of a liquid to be pushed together and form a layer.

Surfactant

a substance composed of lipoprotein that is secreted by the alveolar cells of the lung and serves to maintain the stability of pulmonary tissue by reducing the surface tension of fluids that coat the lung.

Trachea

thin-walled, cartilaginous tube descending from the larynx to the bronchi and carrying air to the lungs.

Ventilation rate

the volume of air passing into and out of the lungs per minute.

gas exchange

the uptake of molecular O2 from the environment and the discharge of CO2 to the environment

properties of gas exchange surfaces

1.Permeable

2.Large

3.Moist

4.Thin

Mucles that contract in Inhalation/Inspiration

Diapgram

External intercostal muscal

Mucles that contract in Exhalation/Expiration

Abdomen wall muscles

internal intercostal muscal

Total capacity

absolute lung volume. About 6 litres

Vital capacity

volume at maximum inhalation and exhalation. About 4.5 litres

Residual volume

The amount of non-exhalable air that remains in the lungs. About 1.5l

Tidal volume

normal breathing at rest. About 0.5 litres

Location of the breathing control center

medulla oblongata

blood pH

Measured to control the breathing rate /ventilation