Module 3 - Exchange and Transport

• Alveoli:

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

  • The number of breaths per minute
• Bronchi:

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

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

  • Strong, flexible connective tissue that supports the walls of the trachea and bronchi, preventing collapse
  • Found in an incomplete ring shape
• 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
• Countercurrent 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
• Elastic fibres:

  • Fibres of elastin that allow the alveoli to stretch as air is drawn in and recoil back to normal size
  • Found in the trachea, bronchi and bronchioles
• Exchange surface:

  • A surface over which materials are exchanged from one region to another
  • An effective exchange surface has a large surface area, thin layers, a good blood supply, and ventilation to maintain a steep diffusion gradient
• Expiration:

  • During expiration (exhalation), the diaphragm relaxes and reverts to a dome
  • The external intercostal muscles relax, moving the ribs down and in
  • Air moves out of the trachea
• Gill filaments:

  • The main site of gaseous exchange in fish, over which water flows
  • Found in large stacks, known as gill plates, and 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
• Gills:

  • The organs of gaseous exchange in fish
  • Contained in a gill cavity and made up of gill lamellae, gill filaments and gill plates
• Goblet cells:

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

  • During inspiration (inhalation), the diaphragm contracts and flattens
  • The external intercostal muscles contract, moving the ribs up and out
  • Air moves into the trachea
• Internal intercostal muscles:

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

  • A complex system found in mammals for the exchange of oxygen and carbon dioxide gases
• Operculum:

  • A flap that covers the gills of bony fish
  • Protects the gills and helps maintain a constant stream of water over them
• Smooth muscle:

  • Involuntary muscle found in the walls of the trachea and bronchi
  • Constricts the lumen of the bronchi by contracting, reducing airflow to the lungs
• Spiracles:

  • Small, external openings along the thorax and abdomen of most insects
  • Air enters and leaves the gaseous exchange system through spiracles
  • Spiracle sphincters open and close to control gas exchange
• Spirometer:

  • A device used to examine breathing patterns and determine lung volume aspects
• Surface area to volume ratio:

  • The surface area of an object divided by its volume
  • The larger the surface area to volume ratio, the smaller the object
• Tidal volume:

  • The volume of air that moves into and out of the lungs during a normal breath
• Trachea (mammals):

  • The primary airway carrying air from the nasal cavity down into the chest
  • A tube supported by incomplete rings of cartilage
• Tracheae (insects):

  • Large tubes running from the spiracles into and along an insect’s body
  • Supported by spirals of chitin and divide further into smaller tracheoles
• Tracheal fluid:

  • Found at the ends of the tracheoles
  • Amount of fluid affects the surface area available for gaseous exchange and water loss
• Tracheoles:

  • Divisions of the tracheae running throughout the tissues of an insect
  • Main site of gas exchange and completely permeable to gases
• Ventilation:

  • Movement of fresh air into the lungs and stale air out via inspiration and expiration
• Affinity:

  • The tendency of one substance to bind with another substance
• Vital capacity:

  • The largest volume of air that can be breathed in following the strongest possible exhalation
• Aorta:

  • The artery carrying oxygenated blood away from the heart to the body
• Arteriole:

  • Blood vessel connecting arteries and capillaries
  • Walls contain large amounts of smooth muscle, some elastic fibres, and some collagen
• Artery:

  • Blood vessel carrying blood away from the heart to the tissues under high pressure
  • Walls contain collagen, smooth muscle, and elastic fibres
• Atrial fibrillation:

  • An arrhythmia involving rapid contraction of the atria, preventing complete ventricular filling
• Atrial systole:

  • The stage of the cardiac cycle where the atria contract, pushing blood into the ventricles
  • AV valves are pushed open fully and the atria are emptied of blood
• Atrioventricular node (AVN):

  • Group of cells located between the atria that slow down the wave of excitation and pass it between the ventricles, along the bundle of His
• Atrioventricular (AV) valves:

  • Valves found between the atria and ventricles
  • Prevent the backflow of blood from the ventricles into the atria
  • Two types: bicuspid and tricuspid
• Bicuspid valves:

  • Atrioventricular valves found between the left atrium and left ventricle
• Blood:

  • Transport medium in the mammalian circulatory system
  • Consists of plasma, red blood cells, white blood cells, and platelets