Respiratory Physiology Ventilation Gas exchange Oxygen uptake & utilization

From this study you should be able to: Describe the need to breath as a part of a metabolic process Describe the function of the respiratory conducting zone Describe pulmonary ventilation Briefly explain how surface tension arises & is stabilized Define lung volumes & lung capacities Explain gas movement during external & internal respiration Briefly describe neurological control of breathing with description of the stimulation of central chemoreceptors State the role of Hb in gas movement Explain how O2 & CO2 are carried in the blood

The Need to Breath Oxygen helps us to release energy from food we eat Every cell in the body needs energy Glucose + Oxygen = Energy + Carbondioxide + water Waste products of energy production From the atmosphere

Dealing with waste products Carbondioxide + water CO2 plus H2O= COO + HHO H2 CO3 A weak acid substance CARBONIC ACID

Respiration Ventilation: Gas exchange: Oxygen (02 ) utilization: Breathing. Gas exchange: Occurs between air and blood in the lungs. Occurs between blood and tissues. Oxygen (02 ) utilization: Cellular respiration.

Quiet Inspiration - Process Contract your diaphragm, to achieve vertical expansion of your lungs. Contract your Intercostal Muscles, to increase thoracic volume laterally.

Pressure changes on Quiet Inspiration Atmospheric pressure (at sea level) = 760 mmHg The chest expands (actively) Intrapulmonary press 757 mmHg so air moves into the lungs Pulmonary pressure rises by + 3 mm Hg.

Expiration Hold your breath- Are your respiratory muscles getting tired? After stretching the lungs) (by contracting both diaphragm and thoracic muscles) the diaphragm, thoracic muscles relax & the thorax, and lungs recoil The decrease in lung volume raises the pressure inside to above 763mmHg This is greater than atmospheric pressure- so air moves out of the lungs.

Recap

The Pleura 2 layers- Visceral & Parietal. Intrapleural space -a film of fluid-secreted by the pleura & NO AIR The lungs remain in contact with the chest wall –allowing them to move with the thoracic cavity

PRINCIPLE 1 Boyle’s Law Changes in intrapulmonary pressure occur as a result of changes in lung volume. (Pressure of gas is inversely proportional to its volume). Increase in lung volume decreases intrapulmonary (alveolar) pressure. Air goes in. Decrease in lung volume, raises intrapulmonary pressure above atmosphere. Air goes out. animation

Dead Space Air passes thro’ 150 ml of space before reaching the respiratory zone. Air is Warmed and humidified, Filters and cleaned: (Mucous traps particles ) Mucus moved by cilia to be expectorated.

Lung Volumes Volume of gas inspired/expired in an unforced breath Tidal volume Volume of gas inspired/expired in an unforced breath Inspiratory reserve volume The maximum volume of air that can be inspired during forced breathing Expiratory reserve volume The maximum volume of gas that can be expired during forced breathing Residual volume The volume of gas remaining in the lungs after a maximum expiration

Lung Capacities Total lung capacity The total amount of gas in the lungs after a maximum inspiration Vital capacity The maximum amount of gas that can be expired after a maximum inspiration Inspiratory capacity The maximum amount of gas that can be inspired after a normal tidal expiration Functional residual capacity The amount of gas remaining in the lungs after a normal tidal expiration

Respiratory Zone Where gas is exchanged between air and blood. Gas exchange occurs by diffusion.

Alveoli Clustered like a honeycomb. 300 million air sacs. Large surface area (60 – 80 m2). Each alveolus is 1 cell thick. 2 types of cell: Alveolar type I: Structural cells. Alveolar type II: Secrete surfactant.

Surface Tension H20 molecules at the surface are attracted to other H20 molecules by attractive forces. What could happen to alveoli if this was not corrected?

Surfactant- reduces surface tension A Phospholipid produced by alveolar type II cells. Lowers surface tension. Think of a detergent Reduces attractive forces between H20 molecules. As alveoli radius decreases, surfactant’s ability to lower surface tension increases.- so the alveolus does not collapse

Principle 2 Gases move from an area of high concentration to an area of low concentration Gas movement relies on concentration gradients

Principle 3 Gas Exchange: Dalton’s Law Total pressure of a gas mixture is = to the sum of the pressures that each gas in the mixture would exert independently. Think of being in a crowded lift Now think of Partial Pressure

External Respiration

Internal Respiration animation

Recap-Blood P02 & PC02 After gas exchange, Arterial blood P02 is normally about 100 mm Hg & PC02 is 40mm Hg P02 in systemic veins is about 40 mm Hg. PC02 in systemic veins is 46 mm Hg.

Regulation of Breathing Neurons in the medulla oblongata forms the rhythmicity center: Controls automatic breathing. Brain stem respiratory centers: Medulla. Pons.

Chemoreceptor Control C02 + H2O H+ cannot cross the blood brain barrier. C02 can cross the blood brain barrier and will form Carbonic acid & then H+ H2C03 H+ HC03 This is Carbonic acid What is this? Bicarbonate H+ is the trigger for the chemoreceptors

Haemoglobin and 02 Transport Each haemoglobin has 4 protein chains and 4 hemes. Each heme has 1 atom iron that can combine with an 02 molecule.

Clinical relevance point 1 Haemoglobin production controlled by erythropoietin. (Produced re P02 delivery to kidneys). Loading/unloading of gas on Hb depends on: Hb level & capacity in the blood Enzymes: ↑ 2,3 DPG - increases unloading of O2 Temp: ↑Heat increases unloading of O2 Acid/base: ↓pH increases unloading of O2 This enzyme is produced when Hb is low

C02 Transport C02 transported in the blood: HC03- (70%). Dissolved C02 (10%). Carbaminohemoglobin (20%).