The Respiratory System

• The respiratory system provides oxygen to cells and removes carbon dioxide.
• Respiration is necessary for cellular survival because cells need oxygen for cellular respiration to produce ATP.
• Respiration is the process of gas exchange.
• Internal respiration involves gas exchange between blood and body cells.
• External respiration involves gas exchange between the lungs and the body.
• Cellular respiration is the process by which cells use oxygen to produce ATP, releasing carbon dioxide.

Organs of the Respiratory System

• Nose: Provides an opening for air.
• Nasal Cavity: Cleans, warms, and moistens incoming air.
• Sinuses: Reduce skull weight and have a mucus lining.
• Pharynx: Passageway for both air and food.
• Larynx: Contains vocal cords and produces sound.
• Trachea: Conducts air to the bronchi.
• Lungs: Site of gas exchange.

Upper Respiratory Tract

• Consists of the nose, nasal cavity, sinuses, pharynx, and larynx.

Lower Respiratory Tract

• Consists of the trachea, bronchi, and lungs.
• Vocal cords vibrate as air passes through, producing sound.
• Pitch is adjusted by changing tension in the vocal cords.
• Intensity is adjusted by changing the force of air passing through the vocal cords.
• Mucus traps dust and pathogens in the respiratory tract.
• Cilia moves mucus upward to be swallowed or coughed out.

Breathing Mechanism

• Inspiration: Diaphragm contracts and moves downwards; intercostal muscles contract to elevate ribs, decreasing intrapulmonary pressure and allowing air flow into the lungs.
• Expiration: Occurs from the elastic recoil of tissue and surface tension in the alveoli, increasing intrapulmonary pressure and pushing air out of the lungs.
• Tidal volume (TV): Amount of air that moves into the lungs during a respiratory cycle.
• Inspiratory Reserve volume (IRV): Additional air that can be inhaled after a normal inhalation.
• Expiratory Reserve volume (ERV): Additional air that can be exhaled.
• Residual volume (RV): Remaining volume in the lungs after forceful exhalation.
• Vital Capacity (VC): Maximum amount of air that can be exhaled after taking a maximal inhalation (VC= TV + IRV + ERV).
• Inspiration Capacity (IC): Maximum amount of air that can be inhaled following exhalation of the tidal volume.
• Total Lung Capacity (TLC): Total volume of the lungs (TLC = VC + RV).
• AVR = (Tidal Volume - Dead Space) x Breathing rate
• Coughing: Clears the lower respiratory passages via deep breath and forceful exhalation against the glottis.
• Sneezing: Clears the upper respiratory passages (same mechanism as coughing).
• Laughing: Expresses happiness via taking breaths and releasing it in short bursts.
• Crying: Expresses sadness via taking breaths and releasing it in short bursts.
• Hiccup: Diaphragm contracts spasmodically while the glottis is closed.
• Yawning: Deep inhalation with mouth wide open.
• Atmospheric pressure: Must be greater than intrapulmonary pressure for inhalation.
• Boyle’s Law: Pressure and Volume are Inversely related (if one increases the other decreases, vice versa) P1V1 = P2V2.
• Intrapulmonary pressure: Pressure inside the lungs in the alveoli.
• Phrenic nerves: Nerves that control the diaphragm.
• Surface tension: Attraction between water molecules in alveoli that can cause collapse; reduced by surfactant.
• Surfactant: Reduces surface tension in the alveoli.
• Compliance: How easily lungs expand.
• Elastic Recoil: Helps lungs return to their resting size after inspiration.
• Spirometry: Measures respiratory volumes.

Control of Breathing

• Medulla Oblongata: Contains the ventral and dorsal respiratory groups.
  • Ventral respiratory group: Provides the basic rhythm of breathing.
  • Dorsal Respiratory Group: Stimulates inspiration by stimulating the diaphragm.
• Pons: Contains the pontine respiratory group.
  • Pontine Respiratory Group: Modulates the rhythm of breathing by influencing the medullary respiratory centers.
• Central Chemoreceptors: Located in the medulla, respond to Hydrogen ions and changes in the pH of cerebrospinal fluid, reflecting CO2 levels.
• Peripheral Chemoreceptors: Located in the carotid bodies and aortic bodies, respond to Oxygen levels and Hydrogen ions, sensing changes in the carotid and aortic bodies.
• Factors of breathing that affect blood pH
• Chemoreceptors: Sensory receptors that respond to changes in Co2, O2, and pH in the blood
• Temperature
• Physical Activity
• Hyperventilation: rapid breasting that lowers CO2 levels and raises blood pH
• Carbon Dioxide levels
• Peripheral Receptors: found in the carotid and aortic bodies, respond to low O2

Alveolar Gas Exchange

• Structure: alveolar wall + capillary wall + joint basement membrane
• Function: Where external gas exchange occurs, via diffusion
• Gases move from areas of high pressure to areas of low pressure
• O2 diffuses from alveoli to blood
• CO2 diffuses from blood to alveoli

Gas Transport

• Oxygen: Carried by hemoglobin molecules, some dissolved in plasma.
• Carbon dioxide: Can be carried as dissolved CO2, CO2 bound to hemoglobin, or as a bicarbonate ion.
• Oxygen: Transported mainly by hemoglobin, needed for cellular respiration.
• Carbon dioxide: Waste product of cellular respiration, either dissolves, binds to hemoglobin, or as a bicarbonate.
• Hemoglobin: Protein in red blood cells that binds to oxygen and some CO2.
• Carbonic anhydrase: Enzyme that helps form bicarbonate in RBCs.
• Albumin: Plasma protein, helps maintain osmotic pressure.
• Chloride shift: Maintains electrical balance between bicarbonate leaves RBCs.
• Carbon monoxide: Binds strongly to hemoglobin, blocking O2.

Life-Span Changes

• Aging increases the risk of developing respiratory diseases.
• Loss of cilia, thickening of mucus, and impaired macrophages raise the risk of infection.
• Dead space increases.
• Alveoli decreases, which decreases the surface area available for gas exchange.