Human systems respire and circle

• Respiration


  All processes involving the exchange of oxygen and carbon dioxide between cells and the environment, including breathing, gas exchange, and cellular respiration
• Respiration


  • Intricately connected to circulation
  • Main function is gas exchange between the external environment and the circulatory system of the body
  • Primary goal is to get oxygen from lungs to blood to cells
  • You can only live few minutes without oxygen, brain death starts after about 7 minutes without oxygen
• Stages of Respiration


  1. Breathing - movement of air between external environment and body across respiratory membrane (in alveoli between alveoli and capillaries)

  2. External Respiration - in alveoli of lungs, exchange of O2 and CO2 molecules between air and blood

  3. Internal Respiration - Exchange of O2 and CO2 molecules between blood and body tissues

  4. Cellular Respiration - production of ATP as oxygen as final electron acceptor
• Respiratory Anatomy


  • Mouth and nasal cavity
  • Trachea
  • Bronchi
  • Bronchioles
  • Alveoli
  • Blood
• Respiratory Anatomy


  • Structures manipulate and filter air along the way as it enters the lungs
• Nasal hairs and mucous cells lined with cilia


  • Filter and trap debris, preventing it from entering lungs
  • Cilia get burned when someone smokes and mucous gets dried, thus smokers get chest colds more than non-smokers
• Trachea and esophagus


  • Branch from pharynx (transition between mouth and nasal cavity)
  • Epiglottis covers the opening of the trachea during swallowing
  • Trachea is supported by bands of tough cartilage, which keep it open
• Larynx


  • Voice box, located at the top of the trachea underneath the epiglottis
  • Two sheets of elastic ligaments that form vocal cords
  • Vocal cords vibrate as air passes through them, changing the tension on them creates different pitched sounds
  • Cartilage increases in size and thickness at puberty, more so in males than females, creating a lower pitch
• Lung Branching


  1. Trachea separates into two bronchi, one for each lung

  2. Bronchi branch into smaller twigs called bronchioles, which have no cartilage rings

  3. At the end of bronchioles are alveoli, like the fruits on the end of tree branches
• Alveoli


  • Site of gas exchange in lungs
  • Gases move by diffusion
  • Alveoli are lined with capillaries, oxygen diffuses into capillaries, carbon dioxide diffuses into alveoli and out of respiratory tract
  • 150 million alveoli present, surface area covers half a tennis court, single layer thick, permits rapid gas exchange
• Pleural Membrane


  • Outer surface of lungs and inner wall of chest cavity, cartilaginous, contains fluid between the two layers of the membrane
  • Fluid reduces friction between lungs and chest cavity during inhalation, the adhesion between these two membranes allows lungs to expand and draw in air
  • Fluid buildup due to infection makes expiration easier but inhalation harder