Respi

• Respiration


  Process of taking up oxygen and removing carbon dioxide from cells of the body

  
• External respiration


  Gas exchange between atmosphere and lungs, and between lungs and blood

  
• Internal respiration


  Transport of gases in the blood, and gas exchange between blood and tissue cells

  
• Respiratory system functions


  • Gas exchange: oxygen enters blood and carbon dioxide leaves
  • Regulation of blood pH: altered by changing blood carbon dioxide levels
  • Sound production: movement of air past vocal folds makes sound (phonation) and speech
  • Olfaction: smell occurs when airborne molecules are drawn into the nasal cavity
  • Thermoregulation: heating & cooling of the body
  • Protection: against microorganisms by preventing entry and removing them

  
• Metabolic role of respiratory system

  Synthesizes & metabolizes numerous compounds
• Thorax & thoracic cavity

  • 1 kilogram
  • 60% - lung tissue (Alveolar space, interstitium)
  • 40% - blood
• Lungs


  • Right lung: 3 lobes (Upper, Middle, Lower)
  • Left lung: 2 lobes (Upper, Lower)
  • 2 interlobar fissures: Oblique, Horizontal (right lung only)
  • Only contains Oblique Fissure (left lung)

  
• Pleura


  • Visceral pleura: adherent to the lungs
  • Parietal pleura: adherent to the chest wall
  • Pleural fluid produced by pleural membranes acts as a lubricant and helps hold the parietal and visceral pleural membrane together

  
• Anatomical division of respiratory system

  • Upper airway: Nose, Sinuses, Pharynx, Vocal Cords and Larynx
  • Lower airway: (tracheobronchial tree) begins with the trachea and ends in most distal alveoli

  
• Upper airway


  • Major function is to condition the inspired air (body & temperature and fully humidified)
• Nose


  • Ciliated columnar epithelium/ goblet cells
  • Olfactory function
  • Volume = 20ml (surface area increased by Nasal Turbinates)
  • The volume of air entering the nose/day – 10,000 – 15,000L
  • Airflow resistance – 50% (8cmH2O/L/sec)
  • Nasal hairs serve as a filter, mucosal lining traps particles and bacteria
• Paranasal sinuses


  Functions: Lighten the skull, Offer resonance to the voice
• Pharynx


  • Nasopharynx, oropharynx, laryngopharynx
  • Common opening for digestive and respiratory systems
  • Abductor muscles in the larynx contract during inspiration
  • Adductor muscles contract during swallowing

  
• Larynx


  • Epiglottis, arytenoids, and vocal cords
  • Epiglottis & arytenoids hood/ cover the vocal cord during swallowing
  • Function: prevent aspiration of food and liquid into lower respiratory tract
• Trachea


  • Divides to form right and left main bronchi
  • 16 – 20 C-shaped rings of hyaline cartilage joined by fibroelastic connective tissue
  • Carina – mucosa highly sensitive to irritants: cough reflex

  
• Tracheobronchial tree


  • Elastic tissue: responsible for recoil of bronchial tree during expiration
  • Cartilaginous rings ensure patency of the tubes
• Physiological division of respiratory system

  • Conducting zone (anatomic dead space): from the trachea up to the terminal bronchiole, does not participate in gaseous exchange, approx. 150ml vol.
  • Respiratory zone/ unit: 17 – 23 generations (vol: 2500 ml, surface area: 70 m2), participates in gaseous exchange

  
• Alveoli


  • Honeycomb-like cluster
  • 250 um diameter
  • 300 million
  • Large surface area (60-80 m2)
  • Each alveolus: only 1 thin cell layer
• Respiratory membrane


  The area where gas exchange between air and blood occurs, fused alveolar and capillary walls (3 layers: alveolar epithelium, fused basal laminae, capillary endothelium)

  
• Cells of the airway

  • Ciliated cells
  • Surface secretory cells (goblet cells)
  • Submucosal tracheobronchial glands
  • Clara cells
  • Kultschitzky cells

  
• Cells of the alveoli

  • Dust cells (alveolar macrophages)
  • Alveolar cells type I
  • Alveolar cells type II
• Surfactant


  • Thin film lining the alveolar surface, phospholipid produced by alveolar type II cells, main component: Dipalmitoyl phosphatidyl Choline (DPPC)
  • Functions: lowers surface tension, promotes stability among alveoli, reduces capillary filtration forces
• Blood supply to the lungs

  • Pulmonary circulation: brings deoxygenated blood from the right ventricle to the gas exchanging units
  • Bronchial circulation: blood supply to the conducting airways (which do not participate in gas exchange)

  
• Pulmonary circulation


  • Ejected from the right ventricle and is delivered to the lungs via the pulmonary artery
  • Pulmonary arteries branch into increasingly smaller arteries and travel with the bronchi toward the respiratory zones
  • Pulmonary veins return blood to the left atrium

  
• Pulmonary circulation vs systemic circulation

  Thinned walled arteries and its branches, contain less elastin and smooth muscle, high flow, high compliance, low resistance, and a low-pressure system

  
• Bronchial circulation


  Receives 1 -2% of cardiac output, bronchial arteries supply oxygenated, systemic blood to the conducting airways, bronchial veins drain blood to right and left atrium

  
• Pulmonary lymphatics


  Supplied by the superficial and deep lymphatic vessels which exists from the hilus, remove plasma filtrate, particular matter absorbed from alveoli, and escaped protein from the vascular system, help maintain negative interstitial pressure

  
• Autonomic nervous control of the lungs


  • Sympathetic control: bronchodilation, blood vessel constriction, inhibit gland secretion
  • Parasympathetic control: bronchoconstriction, blood vessel dilation, glandular secretion

  
• Local control of the lungs

  Exerted by substances released in the lungs by mast cells: histamine, SRS-A, prostaglandin E, prostaglandin F

  
• Inspiration vs expiration


  Inspiration is normally active, expiration is normally passive
• Muscles of respiration


  • Inspiratory muscles: diaphragm, external intercostals, accessory muscles
  • Expiratory muscles: abdominal muscles, internal intercostals

  
• Diaphragm


  • Movement accounts for 75% of the change in intrathoracic volume during quiet inspiration
  • Innervated by phrenic nerve (C3, C4, C5)
  • During inspiration: contraction pulls the lower surfaces of the lungs downward
  • During expiration: relaxation and elastic recoil compresses the lungs

  
• External intercostal muscles


  • Lift 2nd – 6th ribs, ribs move like a bucket handle, sternum moves like a water pump
• Expiratory muscles


  • In quiet respiration, expiration is purely passive when muscles of inspiration relax and by lung recoil
  • In forced expiration, abdominal muscles compress the abdominal cavity and push air out, internal intercostals pull the ribs downward and inward

  
• Protective mechanisms of the respiratory system

  • Mucociliary clearance system
  • Sneeze reflex
  • Cough reflex

  
• Mucociliary clearance system


  Also known as mucociliary elevator, mucus continually secreted by goblet cells traps particles and debris, IgA protects against bacteria and viruses, impaired by toxins from cigarette smoking
• Respiration


  • Major organ: lungs
  • Main function: to provide oxygen to the tissues and remove carbon dioxide
• Major components of respiration

  • Pulmonary ventilation
  • External respiration
  • Internal respiration (cellular)
  • Regulation of ventilation and other facets of respiration
• Functions of respiration


  • Gas exchange
  • Regulation of blood pH
  • Sound production
  • Olfaction
  • Thermoregulation
  • Protection
• Metabolic role of lungs

  • Manufacture surfactant for local use
  • Contain a fibrinolytic system that lyses clots in the pulmonary vessels
  • Release a variety of substances that enter the systemic arterial blood
  • Remove other substances from the systemic venous blood that reach them via the pulmonary artery