Respiratory System

• Respiration is a physical process where living organisms take in oxygen from the surrounding medium and emit carbon dioxide
• Respiration also refers to the liberation of energy within cells from fuel molecules like carbohydrates and fats
• Cells use oxygen for metabolic reactions that release energy from nutrient molecules and produce ATP
• The cardiovascular system and respiratory system supply oxygen and eliminate carbon dioxide in the body
• Failure of either system disrupts homeostasis and can lead to rapid death of cells from oxygen starvation
• Pulmonary ventilation involves the inspiration and expiration of air between the atmosphere and the lungs
• External (pulmonary) respiration is the exchange of gases between the lungs and the blood
• Internal (tissue) respiration is the exchange of gases between blood and cells
• The respiratory system includes the nose, pharynx, larynx, trachea, bronchi, and lungs
• The upper respiratory system consists of the nose, pharynx, and associated structures
• The lower respiratory system consists of the larynx, trachea, bronchi, and lungs
• The conducting portion of the respiratory system conducts air into the lungs
• The respiratory portion of the respiratory system is where the exchange of gases occurs
• The nose warms, moistens, and filters incoming air, receives olfactory stimuli, and provides a resonating chamber for speech sounds
• The pharynx functions as a passageway for air and food and provides a resonating chamber for speech sounds
• The larynx connects the pharynx with the trachea and is composed of nine pieces of cartilage
• The larynx contains false vocal cords and true vocal cords for voice production
• The trachea is a passageway for air lined with mucous membrane and supported by cartilage
• The trachea divides into right and left primary bronchi that further branch into bronchioles
• The lungs are cone-shaped organs separated by the heart and other structures in the mediastinum
• The lungs are enclosed by a double-layered serous membrane called the pleural membrane
• Alveoli are microscopic structures where gas exchange occurs in the lungs
• The alveolar-capillary membrane is where the exchange of respiratory gases between the lungs and blood takes place
• Blood supply to the lungs includes deoxygenated blood from the heart passing through the pulmonary trunk and oxygenated blood returning via the pulmonary veins
• Pulmonary pressures are relative to atmospheric pressure and include alveolar pressure, intrapleural pressure, and transpulmonary pressure
• Transpulmonary pressure is the force that holds the lungs open and opposes lung collapse
• When the chest wall is pierced, atmospheric air rushes through the wound into the intrapleural space, causing a pneumothorax
• The intrapleural pressure goes from -4 mm Hg to 0 mm Hg, leading to the collapse of the lung as the transpulmonary pressure holding it open is eliminated
• During inspiration, the diaphragm and external intercostal muscles contract, causing the thoracic cavity to expand and air to rush into the lungs
• Expiration is a passive process that starts when the inspiratory muscles relax, leading to a decrease in thoracic cavity size and air moving out of the lungs
• Lung compliance is the magnitude of the change in lung volume produced by a given change in transpulmonary pressure
• Factors affecting lung compliance include the stretchability of lung tissues and the presence of surfactant, which reduces cohesive forces and increases lung compliance
• Airway resistance is directly proportional to the frictional interactions between gas molecules, the length of the airway, and inversely proportional to the fourth power of the airway radius
• Respiration involves one inspiration plus one expiration, with the average healthy adult having 12-16 respirations per minute at rest
• Pulmonary volumes include tidal volume, minute volume of respiration, inspiratory reserve volume, expiratory reserve volume, residual volume, and minimal volume
• Pulmonary capacities include inspiratory capacity, functional residual capacity, vital capacity, and total lung capacity
• Gas pressure in a mixture of gases in the atmosphere is the sum of the partial pressures of each gas, determined by multiplying the percentage of the gas by the total pressure
• Gases dissolved in water or body tissues exert pressure proportional to their concentration, determined by the pressure and solubility coefficient
• Net diffusion of gas occurs from areas of high pressure to low pressure, whether in a gaseous mixture, dissolved gases in a solution, or gases diffusing into liquids
• Factors affecting gas diffusion in a liquid include pressure difference, gas solubility, cross-sectional area, diffusion distance, molecular weight, and temperature