2.1 Structure and Function of the Ventilatory System

• Nose • Mouth • Pharynx • Larynx • Bronchi • Bronchioles • Lungs • Alveoli

• Air enters the nostrils/mouth • Passes through larynx • Into the trachea • Into the right and left lungs - starting at bronchi, which branches into • Bronchioles, each of which terminates in a cluster of • Alveoli

• Low resistance pathway for air flow • Defence against chemicals and other substances that are inhaled • hair in nose • mucus • Warming and moistening the air • nose

Inflow and outflow of air between the atmosphere and lungs (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 breathed in and out in any one breathe

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

Air flows because of the pressure difference between atmosphere and gases in the lungs During inhalation • Intercostal muscles and diaphragm contract to expand the chest cavity • diaphragm - moves downwards • intercostal muscles - move rib cage upwards and out • this increases space for the lungs • Increases in size decreases the internal air pressure • so air from outside (now higher pressure) rushes into the lungs to equalise the pressures During exhalation • Intercostal muscles and diaphragm relax to their resting positions • Reduces the size of the thoracic cavity and increases pressure forcing air out of the lungs

Accessory muscles are also important during strenuous exercise Includes diaphragm and intercostal muscles

• Ventilation increases as a direct result of increases in blood acidity levels (low pH levels) • Acidity due to increased CO2 content of the blood detected by the respiratory centre • Results in increase in rate and depth of ventilation • Neural control of ventilation includes lung stretch receptors, muscle proprioreceptors and chemoreceptors

When lung expands, receptors initiate the reflex in which reduces the respiratory rate

A nerve ending that functions as a sensory receptor - relay information about motion or position and make us aware of our own body position and movement in space

Detect changes in chemical concentrations (e.g. pH levels)

• 98.5% of oxygen in blood is transported by hemoglobin as oxyhemoglobin within RBC • Hemoglobin is the protein that allows oxygen to bind to RBC - can hold up to 4 oxygen atoms per hemoglobin • Oxygen atoms diffuse into tissues once they reach their target • While oxygen is diffusing, they also pick up CO2 and return it back to the lungs so it can be exhaled into the atmosphere

• Gas exchange is carried out by the alveolus attached to the branches of the bronchial passage • Alveolus inflate and deflate with inhalation and exhalation • Gas moves by diffusion from high to low conc. • Alveoli create pressure gradient • Once alveoli fill up w/ air during inhalation, oxygen diffuses from air in alveoli and into blood • CO2 diffuse from arriving blood and into lungs and out of body during exhalation