Respiratory System - ANPH111

• Respiratory system


  • Provides the O2 needed in cellular respiration
  • Gets rid of CO2
  • Regulation of blood pH
  • Voice production
  • Olfaction
  • Innate immunity

  
• Conducting zones or dead space


  • Respiratory passages extending from the nose to the terminal bronchioles
  • Filter, humidify and warm air

  
• Respiratory zones


  • Actual sites of gas exchange, composed of the respiratory bronchioles, alveolar ducts and alveoli

  
• Nose


  • Coarse hairs and mucous trap large dust particles
  • Cilia sweep the debris laden mucus toward the pharynx
  • Air is warmed by the blood vessels underlying the mucous epithelium
  • Air is humidified by moisture in the mucous epithelium
• Paranasal sinuses


  • Air-filled spaces with bone
  • Reduce the weight of the skull
  • Produce mucus and influence the quality of the voice by acting as resonating chambers
• Pharynx

  • Nasopharynx - for passage of air
  • Eustachian tube - communicates with middle ear
  • Pharyngeal tonsils
  • Oropharynx - extends from uvula to epiglottis, palatine and lingual tonsils
  • Laryngopharynx - extends from the tip of the epiglottis to the esophagus

  
• Larynx


  • Maintains an open airway
  • Protects the airway during swallowing
  • Produces the voice
• Larynx cartilages


  • Epiglottis - guardian of the airways
  • Thyroid cartilage - Adam's apple, largest shield like cartilage
  • Cricoid cartilage
  • Arytenoids
  • Corniculate
  • Cuneiform

  
• Larynx structures


  • True vocal cords
  • Vocal folds
  • False vocal cords
  • Ventricular folds
  • Rima glottidis - opening between 2 vocal folds
• Laryngitis


  Inflammation of the mucous epithelium of the vocal folds, causes inhibition of voice production
• Trachea


  • Windpipe, reinforced internally by 16-20 C-shaped rings of hyaline cartilage
  • Posterior wall - bundles of smooth muscle which contract with coughing
  • Allows air to flow into the lungs

  
• Bronchial tree


  • Cartilage + smooth muscle in trachea and bronchi
  • Smooth muscle, no cartilage in bronchioles
  • Alveolar structures - alveolar ducts, alveolar sacs, alveoli

  
• Respiratory membrane


  • Formed by walls of the alveoli and the surrounding capillaries
  • Site of gas exchange between the air and blood
  • Consists of 2 layers of simple squamous epithelium, alveolar fluid and separating spaces

  
• Types of cells in the respiratory membrane

  • Type I pneumocytes - walls of the alveoli
  • Type II pneumocytes - secrete surfactant
  • Alveolar macrophages - dust cells

  
• Pleura


  • Lubricant
  • Helps hold the pleural membranes together
• Processes of respiration


  1. Ventilation

  2. External respiration

  3. Internal respiration

  
• Ventilation


  • Breathing = "pulmonary ventilation"
  • Inspiration (inhalation) - air in
  • Expiration (exhalation) - air out
  • Mechanical forces cause the movement of air
  • Gases always flow from higher pressure to lower

  
• Normal quiet inspiration


  1. Active process, caused by contraction of the diaphragm & external intercostal muscles

  2. Diaphragm is the main muscle of inspiration (75% of inspiratory act)

  3. Increase in the vertical diameter of thoracic cavity

  4. External intercostal muscles contraction - increase in the lateral dimensions of thoracic cavity

  
• Forced inspiration


  Aided by accessory muscles of inspiration - sternocleidomastoid, scalene muscles, pectoralis minor, quadratus lumborum, erector spinae
• Normal quiet expiration


  Passive process, due to relaxation of muscles of inspiration, elastic recoil of the lungs, descent of thoracic cage by gravity, relaxing diaphragm moves superiorly
• Forced expiration


  Active process, caused by contraction of abdominal muscles and internal intercostal muscles
• Factors of normal respiration

  • Elastic recoil of the lungs
  • Lung surfactant
  • Compliance - measure of the ease of inflation of the lungs
  • Airway resistance - friction encountered by air in the airways

  
• External respiration


  • Diffusion of gases between the alveoli and blood in the pulmonary capillaries
  • Influenced by thickness of the membrane, total surface area of the respiratory membrane, partial pressure of gases across the membrane

  
• Healthy lungs have a respiratory membrane thickness of 0.5 to 1 um

  
• In external respiration, alveolar pO2 is greater than pO2 in pulmonary capillaries, and pulmonary capillary pCO2 is greater than alveolar pCO2

  
• Internal respiration


  • Gas exchange that occurs at the tissue level
  • Tissue pO2 is 40 mm Hg, blood pO2 is 100 mm Hg
  • O2 dissociates from hemoglobin and diffuses into tissues
  • Tissue pCO2 is greater than blood pCO2, so CO2 diffuses into the blood

  
• Oxygen transport


  1.5% dissolved in plasma, 98.5% combined with hemoglobin (oxyhemoglobin)
• Carbon dioxide transport


  7% dissolved in plasma, 23% bound to proteins (hemoglobin), 70% exists as bicarbonate
• Pneumonia


  Infection that affects one or both lungs, causes the air sacs (alveoli) to fill with fluid or pus
• Asthma


  • Characterized by chronic airflow obstruction, chronic airway inflammation, airway hyperreactivity
  • Symptoms: tachypnea, wheezing, coughing, shortness of breath
  • Stimuli: allergens, inhaled substances, ingestion of substances, exercise
• Respiratory volumes

  • Tidal volume
  • Inspiratory reserve volume
  • Expiratory reserve volume
  • Residual volume

  
• Respiratory capacities


  • Inspiratory capacity
  • Functional residual capacity
  • Vital capacity
  • Total lung capacity

  
• Pulmonary function tests


  • Forced vital capacity - amount of air expelled when a deep breath is taken then forcefully exhaled maximally
  • Forced expiratory volume - amount of air expelled during specific time intervals of the FVC
  • FEV1 - amount exhaled during first second of FVC (normally 80%)

  
• Bronchial tree refers to the network of airways within the lungs.
• The bronchi are two tubes that branch off from the trachea into the lungs.
• The trachea is the windpipe, which connects to the larynx.
• Bronchi are tubes that branch off from the trachea into the lungs.
• The trachea is the windpipe, which connects to the larynx.
• Alveoli are tiny air sacs where gas exchange occurs between the bloodstream and the atmosphere.
• Lungs are organs responsible for gas exchange between the body's circulatory system and the external environment.