The Respiratory System

• The respiratory system supports respiration

Respiration

• The release of energy from glucose, in the form of ATP, which cells use for energy requiring processes
• Occurs in all living cells
• Usually aerobic, but can switch to anaerobic respiration in muscles during vigorous exercise
• Produces carbon dioxide and water as wastes

Gas Exchange

• The respiratory system absorbs oxygen into the blood
• The respiratory system removes carbon dioxide from the blood in the lungs

Respiratory System Mechanics

• Movement of oxygen and carbon dioxide between air and blood occurs by diffusion
• Diffusion depends on concentration gradients
• Concentration gradients are maintained by breathing, which ventilates the lungs, and blood flow through the pulmonary capillaries
• Breathing movements are brought about by the diaphragm and intercostal muscles between the ribs
• Blood flow is maintained by the concentration of the right ventricle

Breathing Movements

• Inhalation involves:
  • Intercostal muscles contracting, moving the ribs up and out
  • The diaphragm contracting and lowering
  • Volume of the chest increasing, which lowers pressure
  • Chest pressure being below atmospheric pressure
  • Air flowing into the lungs
• Exhalation involves:
  • Intercostal muscles relaxing, moving the ribs down and inwards
  • The diaphragm relaxing and raising
  • Volume of the chest contracting, which raising pressure
  • The chest pressure being above atmospheric pressure
  • Air flowing out of the lungs

Alveoli and Gas Exchange

• Oxygen diffuses from the air in the alveolus to the red blood cells in the capillary
• Carbon dioxide diffuses from the blood to the are in the alveolus
• Blood flow in the capillary and airflow from breathing maintain concentrate gradients simultaneously

How Alveoli Facilitate Gas Exchange

• There are millions, providing a large surface area for diffusion
• Walls are one cell thick, so there is small distance for efficient diffusion
• Each alveolus has a good capillary network
• A film of moisture allows oxygen to dissolve prior to diffusing across

Cleaning

• The walls of the airways have cells that produce sticky mucus
• The mucus traps dust and bacteria
• Other cells have cilia, tiny hairs that move the mucus to the top of the airway
• Dust and bacteria are removed from the airway to prevent inflammation and infection

Smoking

• Cigarette smoke contains hundreds of chemicals
• Nicotine is highly addictive and causes CHD
• Other chemicals inactivate the cilia leading to accumulation of mucus and bronchitis
• Alveolar walls may become inflamed and break down causing emphysema
• Emphysema causes shortness of breath and difficulty absorbing sufficient oxygen
• Chemicals in tar can cause normal cells to become cancerous, leading to cancers of the lung, larynx and bladder

Exercise Effects

• Heavy exercise immediately increases heart and breathing rates, but differently for fit and unfit people
• Stroke volume (blood pumped per beat) and tidal volume (air breathed per breath) also increase
• Changes increase ventilation and blood flow, providing steeper concentration gradients for gas exchange
• Breathing and heart rates fall after exercise but not immediately

The respiratory system facilitates gas exchange, absorbing oxygen and removing carbon dioxide from the blood. Breathing mechanics, including inhalation and exhalation, are driven by the diaphragm and intercostal muscles. This process supports respiration, where energy in the form of ATP is released from glucose.