2.1 Structure and function of the ventilatory system

• Low resistance pathway for airflow • Defence against chemicals and other harmful substances that are inhaled • Warming and moistening the air

Nasal passages are a low resistance pathway for airflow. Allows ventilation to occur easily. Important for supplying the body with oxygen.

The nose and throat contain tiny hairs, called cilia. They filter the air and trap particles that are present. This stops them from entering the lungs and causing infections.

Air needs to be warmed to aid with thermoregulation of the body - cold air in the lungs could cause capillaries to vasoconstrict (get smaller). Environment of the lungs needs to remain moist to allow for gas exchange to take place. The nose and trachea moisten the air that is inspired.

Inflow and outflow of air between the atmosphere and the lungs (also called breathing)

Volume of air in the lungs after a maximum inhalation

Maximum volume of air that can be exhaled after a maximum inhalation

Volume of air breathing in and out in any one breath during normal breathing

Volume of air in excess of tidal volume that can be exhaled forcibly

Additional inspired air over and above tidal volume

Volume of air still contained in the lungs after a maximal exhalation

External intercostal muscles contract which makes the ribs move up and out. This lowers the pressure relative to the outside pressure. The volume increases. This all makes air move into the lungs. Air moves from high to low pressure. Diaphragm contracts which increases volume.

Internal intercostal muscles relax which makes the ribs fall. This decreases the volume in the lungs which increases the air pressure relative to the air outside. This all makes air move out of the lungs. Air moves high to low pressure. Diaphragm relaxes which decreases the volume.

Main protein in the red blood cells that transports oxygen around the body

Erythrocytes (red blood cells) are found i the red bon marrow (spongey bone) of long bones

Erythropoetin (EPO)

Oxyhaemoglobin - the bond is unstable and reversible

The air that is breathed in fills the sack. The alveoli has a large surface area which allows for a faster diffusion of gases. Balloon-like structure.

diagram of ventilatory system diagram of breathing patterns how air comes in and out of the lungs diagrams of alveolus and capillary

Alveolus packed with oxygen and capillaries packed with CO2. Diffusion makes O2 and CO2 want to move to a lower concentration. CO2 is unloaded into the lungs while haemoglobin takes on the O2.

‘The rate of diffusion is proportional to both the surface area and concentration difference and is inversely proportional to the thickness of the membrane’ —> rate of diffusion (weird x - is proportional to) (surface area x concentration difference)/thickness of membrane

• Surface area or concentration difference is doubled • Thickness of the exchange membrane is halved • Exchange surfaces consist of cell membranes which are thin and this allows fast diffusion (high concentration to low concentration) across membranes

Dalton’s law states that in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases Dissolved gases always diffuse down their partial pressure gradients (high pressure to low pressure)