Life Science Notes - March 5th 2026

Overview of the Respiratory System

  • Breathing facilitates cellular respiration by supplying oxygen and removing carbon dioxide (CO2).

Cellular Respiration Formula

  • Glucose + Oxygen → CO2 + Water + ATP (Adenosine triphosphate).

Parts of the Respiratory System

  • Nose/Mouth: Entry points for air.

  • Pharynx: Upper part of the throat connecting to the larynx.

  • Epiglottis: Flap preventing food from entering the windpipe.

  • Larynx: Voice box, at the top of the trachea.

  • Trachea: Windpipe supported by cartilage rings.

  • Bronchi/Bronchioles: Branching tubes leading to each lung, resembling an inverted tree.

  • Alveoli: Tiny air sacs where gas exchange occurs, surrounded by capillaries.

  • Diaphragm: Main muscle for inhalation and exhalation, regulated by pressure changes (Boyle's law).

Breathing Mechanics

  • Inhalation: Diaphragm contracts and moves down, increasing lung volume and decreasing pressure, allowing air to flow in.

  • Exhalation: Diaphragm relaxes, decreasing lung volume and increasing pressure, pushing air out.

Boyle's Law

  • At constant temperature: Pressure × Volume = Constant.

  • With increasing volume, pressure decreases and vice versa.

Gas Exchange Processes

  • External Respiration: Gas exchange between lungs and blood.

  • Internal Respiration: Gas exchange between blood and tissue cells.

  • Oxygen delivered from lungs to tissue; CO2 transported back to lungs.

Air Pathway and Filtration

  • Air is filtered, warmed, and moistened in the nasal passages; mucus and cilia trap debris.

  • Advantages of nasal breathing: better oxygen absorption and filtration.

Alveoli Characteristics

  • Alveoli increase surface area for gas exchange; flatten out equaling the size of a tennis court.