ANSC Final Respiratory I: Structure and Function

Function of the Respiratory System Respiratory Function – gas transport for metabolism  Move oxygen from the air – pulmonary blood  Clearance of carbon dioxide Non-respiratory Function:  Lunges receive 95% of cardiac output (right heart)  Filter blood, chemical processing, maintenance and defenses (part of the first line of defense)  Facilitate venous return (respiratory pump) Respiration – interchanging of gases between atmosphere and the cells of the body Ventilation (Breathing) – transport of air to and from the lungs Gas Exchange – O2/CO2 exchange between the air in the lunges and cells in the body Cellular Respiration – oxidation of cellular molecules that produces CO2, water and ATP Overall Gas Transport 1. Ventilation – movement of bulk airflow, delivering air to the respiratory zone where gas exchange occurs (Alveoli) Air transported through the airways from the atmosphere to the respiratory zone of the lungs Airways = system of tubular structures  Nasal and oral cavities  Pharynx and larynx  Trachea  Bronchi  Bronchioles *Bronchioles connect to alveoli where gas exchange occurs 2. Lung Diffusion – gas exchange between respiratory zone and blood; O2 moves across alveolar membrane – red blood cells; reverse process for CO2 3. Circulation (Blood - Tissues) – Requires adequate function of the pulmonary and systemic circulations 4. Tissue Diffusion – erythrocyte/plasma - tissue cells = passive diffusion 5. Internal Respiration – Metabolism using O2 and producing CO2 Main Function of Airways: Delivering gas to the respiratory zone (alveoli) Conditioning of the inhaled air  Air warmed to core body temperature (prevents temperature choc in the alveoli)  Gas humidification – saturation with vapour to prevent dehydration of the respiratory epithelium in alveoli  Filtration cleansing – prevents foreign objects and microorganisms to enter the lunges (reduces risks of injury and infection) o Done by: o Cilia (tiny hair-like projections on cells that sweep foreign bodies out of the airways) o Mucus Layer (Goblet Cells; trap pathogens and other particles from entering the lungs) o Alveolar Macrophages (type of white blood cell on the surface of alveoli that protect the alveoli when cilia and mucus layers cannot) Structure: Nasal/Oral Cavities  Inner surface = mucous membrane that warms and humidifies air  Hair in nostrils act as first filter  Epithelium contains ciliated cells and mucus cells (goblet) – trap foreign objects and move mucus towards the pharynx Pharynx  Connection between nasal/oral cavity and the larynx Larynx  Connects pharynx and the trachea – glottis and epiglottis = cartilage that prevents food to enter the trachea  Contains the vocal cords Trachea  Flexible tube kept open by cartilage rings o C-shaped cartilage rings  Inner surface lined with ciliated and mucus cells Bronchi  Possess cartilage plates to maintain the shape  Starts with 1 tube per lung = primary bronchi  Branches off to narrower tubes with less cartilage Bronchioles  Lack cartilage – depend upon lung recoil to maintain potency o Possess smooth muscle **Bronchi and bronchiole also possess ciliated and mucus producing epithelial cells In general 20-24 branching from trachea and the terminal alveoli Airway Cross-Sectional Area: Increases DRAMATICALLY movie from trachea to respiratory zone  Geometric increase in number of small airways  Reduction in velocity of airflow to ZERO  Movement of gas in respiratory zone by DIFFUSION only  Velocity (cm/sec) = flow (cm3 /sec)/cross-section area (cm2 ) Airway Clearance: Cilia and goblet cells work to move thin sheet of mucus from lower parts of the lungs to the throat region Defensins – airway “Lysol”; destroy bacteria, first line of defense (2nd line is immune system proper) **Accumulation of mucus and pus in the trachea associated with inflammation of the lower