Exchange Surfaces

• Metabolic rate


  The amount of energy expended by that organisms within a given period of time
• BMR


  The metabolic rate of an organism at rest
• Alveoli


  • Tiny air sacs that serve as the primary gaseous exchange surface
  • Consist of a thin epithelial cell layer, collagen and elastic fibres
• Gills


  • The organs of gaseous exchange in fish
  • Contained in a gill cavity
  • Made up of gill lamellae, gill filaments and gill plates
• Inspiration


  1. Diaphragm contracts and flattens

  2. External intercostal muscles contract, moving the ribs up and out

  3. Volume of the thorax increases

  4. Thoracic pressure falls below air pressure

  5. Air moves into the trachea
• Expiration


  1. Diaphragm relaxes and reverts to a dome

  2. External intercostal muscles relax, moving the ribs down and in

  3. Volume of the thorax decreases

  4. Thoracic pressure exceeds air pressure

  5. Air moves out of the trachea
• Internal intercostal muscles


  • Muscles found between the ribs
  • Responsible for forced exhalation
• Mammalian gaseous exchange system

  • A complex system found in mammals
  • Oxygen and carbon dioxide gases are exchanged
• Trachea


  • The primary airway
  • Carries air from the nasal cavity down into the chest
  • A tube supported by incomplete rings of cartilage
• Bronchioles


  • Many small divisions of the bronchi
  • Contain smooth muscle to restrict airflow to the lungs
  • Do not have cartilage
  • Lined with a thin layer of ciliated epithelial cells
• Bronchi


  • Divisions of the trachea that lead into the lungs
  • Small tubes supported by incomplete rings of cartilage
• Elastic fibres


  • Fibres of elastin
  • Allow the alveoli to stretch as air is drawn in and recoil back to normal size, expelling air
  • Also found in the trachea, bronchi and bronchiole
• Goblet cells


  • Specialised cells that secrete mucus onto the trachea lining
  • Mucus traps harmful substances and microorganisms, preventing their entry into the lungs
• Human Thorax


  • A collection of organs and tissue in the chest cavity
• Ciliated epithelial cells


  • Specialised cells with tiny hair-like cilia
  • Found lining the trachea
  • Waft bacteria-containing mucus up to the back of the throat, where it is swallowed
• Mucous glands


  • Work with the goblet cells in the trachea and bronchi to produce mucus
• Cartilage


  • Strong, flexible connective tissue
  • Supports the walls of the trachea and bronchi, preventing collapse
  • Found in an incomplete ring shape
• Smooth muscle


  • An involuntary muscle found in the walls of the trachea and bronchi
  • Constricts the lumen of the bronchi by contracting, reducing airflow to the lungs
• Spirometer


  A device used to examine patterns of breathing and determine different aspects of lung volume
• Tidal Volume (TV)


  The volume of air in each breath (normally 0.4 dm3)
• Vital capacity


  The maximum volume of air that can be breathed in or out
• Breathing rate


  How many breaths are taken per unit time (usually per minute)
• Oxygen uptake


  The rate at which a person uses up oxygen (e.g. The number of dm3 used per minute)
• Tracheae (insects)


  • Large tubes that run from the spiracles, into and along an insect's body
  • Supported by spirals of chitin
  • Divide further into smaller tracheoles
• Tracheoles


  • Divisions of the tracheae that run throughout the tissues of an insect, forming a complex network
  • The main site of gas exchange and are completely permeable to gases
• Spiracles


  • Small, external openings along the thorax and abdomen of most insects
  • Air enters and air and water leave the gaseous exchange system
  • Spiracle sphincters open and close the spiracles to control gas exchange
• Tracheal fluid


  • A fluid found at the ends of the tracheoles
  • The amount of fluid affects the surface area available for gaseous exchange and water loss
• Gill filaments


  • The main site of gaseous exchange in fish, over which water flows
  • Found in large stacks, known as gill plates
  • Have gill lamellae which provide a large surface area for exchange
• Gill lamellae


  • The fine branches of the gill filaments
  • Adapted for gaseous exchange by having a large surface area and good blood supply
• Gill plates


  • Large stacks of gill filaments
• Ventilation


  The movement of fresh air into the lungs and stale air out of the lungs via inspiration and expiration
• Operculum


  • A flap that covers the gills of bony fish
  • Protects the gills and helps to maintain a constant stream of water over them
• Counter current flow


  • An adaptation for gaseous exchange in bony fish
  • Blood in the gill filaments and water moving over the gills flow in opposite directions, maintaining a steep oxygen concentration gradient