Respiratory system IB SEHS 2.1

Parts of the Respiratory System 2.1.1 Nose and Mouth Adjusts ambient air to body temperature Filters the ambient air Humidifies air Larynx Trachea Continues nose and mouth processes Bronchi

Lungs Bronchioles Alveoli Provide gas exchange surface that separates blood from the surrounding alveolar gas environment Oxygen transfers from alveolar air into alveolar blood, simultaneously, the blood’s carbon dioxide moves into the alveolar chambers where it subsequently flows into ambient air Bronchioles Smaller passages leading to alveoli Alveoli 300 million

Respiratory System

Purpose of Conducting Airway 2.1.2 Nasal passages are a low resistance pathway for air flow Nasal hair and mucous defend against chemicals and other harmful substances that are inhaled Breathing through the nose helps to warm and moisten the air before reaching the lungs

Respiratory Terms 2.1.3 Pulmonary Respiration - process of moving and exchanging ambient air with air in the lungs (breathing) Vital Capacity (VC) - total volume of air voluntarily moved in one breath Tidal Volume - volume of air inhaled or exhaled in a single breath Residual Volume (RV) - volume of air in the lungs following a maximal inspiration Forced Vital Capacity (FVC) - total volume of air voluntarily moved in one breath from full inspiration to maximum expiration

Inspiratory Reserve - volume of gas that can be inspired at the end of a tidal inspiration Expiratory Reserve - volume of gas that can be expired at the end of a tidal expiration

Mechanics of Breathing Inspiration 2.1.4 A substance (air) will flow from an area of higher pressure to an area of lower pressure For inspiration to occur the air pressure in the lungs needs to be lower than in the atmosphere At rest the diaphragm (at the base of the chest cavity) pulls downwards thus increasing the volume of the of the lungs The increase in lung volume reduces the pressure in the lungs causing air to flow from the atmosphere into the lungs to balance the pressure gradient

During exercise, when more oxygen is needed by the active muscles and more carbon dioxide is being produced by the muscles, more air needs to be inhaled and exhaled at a faster rate Additional muscles become active: external intercostals, abdomen and shoulders which assist with increasing the lung volume

Expiration At rest, exhalation is passive (no energy required) as the diaphragm relaxes and therefore recoils back to its original position without any conscious muscular work This reduces the volume of the lungs increasing the pressure to greater than that of the atmosphere causing air to flow back out again

During exercise expiration is an active process, requiring energy to fuel the muscles of the chest and abdomen The external intercostals and abdominal muscles compress the lungs faster and more forcefully than the natural recoil

Nervous and Chemical Control of Ventilation during Exercise 2.1.5 Ventilation increases as a direct result of increases in blood acidity levels (low pH) due to increased carbon dioxide content of the blood detected by the respiratory center This results in an increase in the rate and depth of ventilation Neural control of ventilation includes lung stretch receptors, muscle proprioceptors (receptors that provide information about the position and movement of the body) and chemoreceptors (a neuroreceptor that is stimulated by the presence of chemical molecules

Hemoglobins Role in Oxygen Transport 2.1.6 99% of the O2 transported in the blood is chemically bound to hemoglobin (a protein contained in red blood cells or erythrocytes)

Diffusion of Gases 2.1.7 Gas exchange in the lungs occurs across about 300 million tiny alveoli. The enormous number of these structures provides the lung with a large surface for diffusion. It is estimated that the total surface area available for diffusion in the human lung is 60 to 80 square meters or the about the size of a tennis court. The rate of diffusion is further assisted by the fact that each alveolus is only one cell layer thick, so that the total blood-gas-barrier is only two cell layers thick.