Summary of the IB SEHS Unit 2.1 (structure and function of the ventilatory system). You will find detailed yet summarized information on the topic, organized according to the IB syllabus (contains all necessary information to achieve a 7).
Unit 2.1: Structure and function of the
ventilatory system.
Homeostasis: maintenance of internal environment between a specific (constant) range.
The pulmonary and cardiovascular systems work together to maintain oxygen content in blood, acid-base
status and core body temperature (especially during exercise)
Pulmonary ventilation: Inflow and outflow of air between the atmosphere and the lungs
Principal structures of the ventilatory
system
Conducting airways
Nose
Mouth
Pharynx
Larynx
Trachea
Bronchi
Bronchioles
Gas exchange
Lungs
Alveoli
Functions of conducting airways:
Low resistance pathway for airflow: nasal passages are a low resistance pathway for airflow.
Defense against chemicals and other harmful substances: mainly in the nose and throat where
tiny hairs (cilia) filter the air and trap particles (stops them from entering the lungs and causing
infection). The cells lining the conducting airways have special macrophage cells (defence
against foreign bodies). Mucus exrected by the conducting airways traps particles and pathogens
but also improves gas exchange.
Air is warmed and moistened: inhaled air passes through the conducting airways (nasal and oral
passages, trachea and bronchi). Although no gas exchange takes place here, the air is
warmed, moistened, and filtered by the lining of the airways.
Unit 2.1: Structure and function of the ventilatory system. 1
, Definitions associated with the ventilatory system
Pulmonary ventilation (PV): inflow and outflow of
air between the atmosphere and the lungs (also
called breathing)
Total lung capacity (TLC): volume of air in the
lungs after a maximum inhalation.
-6L for adult males and 4.2 for adult females.
VC + RV = TLC
Vital capacity (VC): maximum volume of air that can be exhaled after a maximum inhalation.
Residual volume (RV): volume of air still contained in the lungs after a maximal exhalation (because if
there were no air in the lungs, the walls would stick). Makes up 20% of TLC
Tidal volume (TV): volume of air breathed in and out in any one breath during normal breathing. Normal
range is 500mL (7-8% of TLC)
Expiratory reserve volume (ERV): volume of air in excess of tidal volume that can be exhaled forcibly.
Inspiratory reserve volume (IRV): additional inspired air over and above tidal volume. (60% off TLC)
Rate of breathing can be measured by counting the number of breaths per
minute.
The ventilatory system can be monitored with a spirometer
Unit 2.1: Structure and function of the ventilatory system. 2
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