The Respiratory System Chapter 23 (6th edition chapter 22)

Functions of the Respiratory System Supply oxygen to the circulatory system for delivery to the tissues Remove CO2 (and some other wastes) from blood.

There are 4 processes that we call “respiration”. Pulmonary ventilation - Movement of air into and out of the lungs (also referred to as “breathing”). 2. External respiration - Gas exchange in the lungs between the blood of the capillaries and the spaces in the air sacs (alveoli) Transport - The movement of gases by the circulatory system Strictly speaking, a function of the blood. Internal respiration - Gas exchange between the blood and the tissues of the body

Overview of respiratory system anatomy

External Structures of the nose

Nasal skeletal structures

Internal anatomy of the upper respiratory tract

The larynx and associated structures

Cross section of the trachea and esophagus

The Lungs

The Lungs

The lower lung

Alveoli and the respiratory membrane

Structure of an alveolar sac

Respiratory Physiology Boyle’s law: P1V1 = P2V2

Pressure relationships The negative intrapleural pressure keeps the lungs inflated

Mechanics of Breathing: Inspiration

Mechanics of Breathing: Expiration

Changes in pressure & volume relationships

Respiratory Physiology Resistance: F = P/R R = resistance P = change in pressure (the pressure gradient)

Respiratory Volumes

Respiratory Physiology: Dalton’s Law of Partial Pressures The total pressure of a mixture of gases is the sum of the partial pressures exerted independently by each gas in the mixture. Location Atmosphere at sea level Alveoli of lungs Gas Approximate % Partial pressure in mmHg N2 78.6 597 74.9 569 O2 20.9 159 13.7 104 CO2 0.04 0.3 5.2 40 H2O 0.46 3.7 6.2 47 Total 100.0 760

Partial pressure relationships: Movement of gases between the lungs and the tissues

Most soluble Least soluble Solubility: Differential solubility of gases contributes to the balance of gas exchange Most soluble Least soluble CO2 >>>>>>>>>>>>>>>>> O2 >>>>>>>>>>>>>>>>>>> N2 CO2 is 20 times more soluble than O2 N2 is about half as soluble as O2

Ventilation-Perfusion Coupling Breathing and blood flow are matched to the partial pressure of alveolar gases

Respiratory Gas Transport Oxygen - about 98.5% is bound to hemoglobin (Hb) and 1.5% in solution. The affinity of O2 for hemoglobin is influenced by partial pressure

Factors influencing Hb saturation: Temperature

Factors influencing Hb saturation: Pco2 and pH

BPG (2,3-bisphosphoglycerate) The Bohr Effect Decreased pH that results from increased Pco2 lowers the binding affinity between O2 and Hb. The result is that, under acidosis, Hb saturates at a lower Po2. This allows more oxygen to be unloaded at the where it is needed. BPG (2,3-bisphosphoglycerate) This compound is produced during glycolysis, anaerobic means of producing energy from glucose. BPG binds to Hb and decreases O2 affinity. This results in a right-shifted O2 - Hb dissociation curve, Like we see in the Bohr effect

CO2 Transport 7 - 10% dissolved in the plasma ~ 20% bound to the amine groups of the Hb molecule as carbaminohemoglobin ~ 70% as bicarbonate ion in the plasma

CO2 Transport & Exchange: at the tissues

CO2 Transport & Exchange: in the lungs

The Haldane Effect

Control of Respiratory Rhythm

Medullary Respiratory centers Neural and chemical influences

Pco2 & pH are the primary regulators of ventilation by means of negative feedback

Pathology and clinical considerations Common homeostatic imbalances: COPD (chronic obstructive pulmonary disease) Asthma Tuberculosis Lung cancer

COPD: Emphysema Results: Loss of lung elasticity, hypoxia, lung fibrosis, cyanosis. Common causes: Industrial exposure, cigarette smoking.

Tuberculosis At the beginning of the 20th century a third of all deaths in people 20 - 45 were from TB. Antibiotic-resistant strains of Mycobaterium tuberculosis are a growing problem at the beginning of the 21st century.

Lung Cancer

90% of lung cancer patients had one thing in common…

…they smoked tobacco

Fin