Unit 7: Respiratory System

Overview

• Previously covered digestive and circulatory systems.
• Now focusing on the respiratory system.

Functions of the Respiratory System

• Allows gas exchange: Oxygen into blood, Carbon Dioxide out to air.
• Works with circulatory system for:
  • External respiration (air and blood exchange).
  • Transportation of gases.
  • Internal respiration (blood and tissue fluid exchange).

Respiratory System Structures

• Nasal Cavities:
  • Filter air (hair and mucus).
  • Moisten air (mucus).
  • Warm air (blood vessels).
• Pharynx:
  • Connects nasal cavities to larynx.
  • Involved in swallowing reflex.
• Larynx (Voice Box):
  • Contains vocal cords for sound production.
  • Epiglottis prevents food from entering the trachea.
• Trachea (Windpipe):
  • Supported by cartilaginous rings.
  • Lined with cilia and mucus.
• Bronchi and Bronchioles:
  • Two bronchi enter the lungs.
  • Bronchioles are smaller branches.
• Alveoli:
  • Air sacs for gas exchange.
  • Surrounded by capillaries.
  • Contain macrophages and lipoprotein film to prevent sticking.

Lung Anatomy

• Lobes:
  • Right lung: 3 lobes.
  • Left lung: 2 lobes (space for heart).
• Pleural Membrane:
  • Double membrane sac around lungs.
  • Contains pleural fluid to reduce friction.

Ventilation (Breathing)

• Inspiration (Inhalation):
  • Active process; requires ATP.
  • Rib cage moves up and out.
  • Diaphragm contracts and moves down.
• Expiration (Exhalation):
  • Passive process; no ATP required.
  • Rib cage moves down and in.
  • Diaphragm relaxes.
• Controlled by the autonomic nervous system.

Gas Exchange

• External Respiration:
  • Occurs in lungs.
  • Oxygen diffuses into pulmonary capillaries.
  • Carbon dioxide diffuses into alveoli.
• Internal Respiration:
  • Occurs in body tissues.
  • Oxygen is released from oxyhemoglobin to tissues.
  • Carbon dioxide transported mainly as bicarbonate ions.

Carbon Dioxide Transport

• Transported via:
  • Bicarbonate ions (most common).
  • Carboaminohemoglobin.
  • Dissolved CO2 in plasma.

Respiratory Volumes

• Tidal Volume: Normal breath (500 mL).
• Vital Capacity: Max air in forced breathing (~6 L).
• Residual Volume: Air left after exhaling completely (~1 L).

Control of Breathing

• Controlled by medulla oblongata.
• Influenced by:
  • CO2 and H+ concentration increases cause faster breathing.
  • Oxygen concentration monitored by chemoreceptors.

Carbon Monoxide vs. Carbon Dioxide

• Carbon Monoxide (CO):
  • Dangerous; binds to hemoglobin more effectively than oxygen.
  • Sources: gas appliances, car fumes.
  • Effects: can be fatal at high levels.

Conclusion

• Next unit: Nervous System