Respiration 1

• Ventilation: Exchange of air between atmosphere and alveoli • Exchange of O2 and CO2 between alveolar air and blood in lung capillaries by diffusion • Transport of O2 and CO2 through pulmonary and systemic circulation by bulk flow • Exchange of O2 and CO2 between blood in tissue capillaries and cells in tissues by diffusion • Cellular utilisation of O2 and production of CO2

Upper: nasal cavity, nostril, mouth, pharynx, larynx Lower: Trachea, lungs, bronchi, diaphragm

trachea&bronchi = low resistance pathway for air flow, C-shaped bands of rigid cartilage keep airways open, trachealis muscle spans between ends of cartilage bands (contracts to aid expulsion of blockages - when coughing and sneezing) bronchioles = no cartilage, smooth muscle bundles, these are normally relaxed (allowing air to reach alveoli), contraction prevents irritants and particles from entering alveoli

up to 8 divisions

Region of the lower respiratory tract which carries air to the alveoli. It has too many layers for gas exchange to occur.

No cartilage. Smooth, muscle bundles - normally air to reach alveoli. Contraction prevents irritants and particles from entering alveoli.

Respiratory bronchioles Alveolar ducts Alveoli

Gas Exchange: Respiratory bronchioles: Minimal actual gaseous exchange. They branch into individual alveoli or alveolar ducts. Alveolar duct and sacs: Site of gaseous exchange. Extensive blood supply, surrounded by blood capillaries.

• High surface area - Very thin walls

Both pneumocytes Type 1 flattened epithelium (for gaseous exchange) Type 2 thicker cells (secrete surfactant).

Allow entry of air even if alveolar ducts are blocked.

• Provide oxygen and remove carbon dioxide • Form speech sounds • Protection from microbes and other foreign matter • Regulates blood hydrogen ion concentration

• In normal steady breathing, the volume of air breathed in per breath • Maximum amount that lung volume can be increased above tidal volume • A further maximal exertion of the expiratory muscles after tidal volume • Even after maximal expiratory effort, the volume of air left in the lungs • 500ml • 3000ml • 1200ml • 1200ml

What is left in the lungs after a normal breath - expiratory reserve & residual volume

Sum of two or more volumes Inspiratory capacity = tidal volume + inspiratory reserve Vital capacity = inspiratory reserve volume, tidal volume, expiratory reserve Functional Residual capacity = expiratory reserve + reserve volume Sum of inspiratory reserve, expiratory reserve, tidal volume and residual volume = total lung capacity.

Ventilation is exchange of air between the atmosphere and the alveoli. Minute ventilation - total ventilation per minute This is respiratory rate X tidal volume. Alveolar Volume = volume of fresh air reaching alveoli per minute. This is different because gaseous exchange occurs primarily in alveoli and minimally in respiratory bronchioles, while pharynx and conducting zone do not contribute. Alveolar V will be less as less air is getting to the alveoli than is breathed in.

Anatomical dead space 150ml Conducting zone

500-150=350ml reaching alveoli Tidal volume = alveolar ventilation and alveolar dead space Alveolar vent = minute ventilation - dead space ventilation (500x12) - (150x12) = 4200ml/min

Alveolar dead space = alveoli are poorly perfused with blood, then no gas exchange occurs in those areas. Physiological dead space = anatomical dead space + alveolar dead space Anatomical dead space is fixed (150ml) but physiological dead space is not as alveolar dead spaces changes.

Air moves from a region of high pressure to a region of low pressure. Flow = difference in pressure / resistance The pressures here are atmospheric pressure - alveolar pressure (the difference between pressure inside and outside lung).

Atmospheric pressure is higher than alveolar pressure means airs move in. Vice versa for air to move out. In between breaths.

Pressure in a gas is inversely proportional to volume. Diaphragm goes down in inspiration, increases volume, decreasing pressure so air flows into lungs as pressure is lower in lungs.

at the end of normal breathing out… respiratory muscles are relaxed and inward recoil of lungs is balanced by outward recoil of chest wall

Intrapleural (pressure between two membranes. This is usually slightly negative as lungs recoil inwards and chest wall recoils outwards) Alveolar pressure Difference: alveolar - intrapleural is called trans- pulmonary pressure. Higher after breathing in as intrapleural pressure decreases.