Cellular Respiration and the Mechanics of Human Breathing

Cellular Respiration: Definition and Function

Respiration is the fundamental process in which glucose, oxygen, and fatty acids are transformed inside the cell into water, carbon dioxide, and energy (ATP). The primary goal is to convert glucose and oxygen into usable energy.

• It happens inside the cells, specifically within the mitochondria.
• Mitochondria are often described as the site of the "burning of food."
• Oxygen is essential to combine with glucose to facilitate this energy transformation.

Understanding Metabolic Rate (MR)

The Metabolic Rate (MR) is an average measure of the amount of energy that a person needs daily. The MR is typically higher in an active person compared to a sedentary individual.

Energy is required constantly, even while sleeping, for vital processes such as:

• Building macromolecules.
• Membrane transport (essential for the nervous system and kidney function).

The Human Breathing System

Function of the Respiratory System

The main function of the breathing system is to facilitate gas exchange: taking in oxygen and expelling carbon dioxide.

Anatomy of the Breathing System

Key components and their functions:

• Nose: Warms up and adds moisture to the inhaled air, and cleans the air from particles using hairs (cilia).
• Trachea: A tube connecting the lungs to the mouth/pharynx. It has rings of cartilage to hold it open, and it aids in cleaning the air.
• Bronchi: Tubes connected to the lungs which also have rings of cartilage to keep the airways open. They participate in cleaning the air.
• Alveoli: Microscopic air sacs where gas exchange and oxygen absorption occur.
• Diaphragm: A sheet of muscle, dome-shaped when relaxed, crucial for breathing movements.
• Intercostal Muscles: Muscles located between the ribs that assist in normal breathing movement and forced breathing.
• Rib Cage: Protects the lungs and heart; the intercostal muscles are attached here.

General Function of Cilia and Mucus

Cilia and mucus work together to clean the air and get rid of impurities before the air reaches the lungs.

Mechanics of Inhalation and Exhalation

The diaphragm is located between the thorax (chest cavity) and the abdomen, situated directly under the lungs.

Inhalation (Breathing In)

During inhalation, the diaphragm contracts and moves downward, becoming flatter. This action increases the volume of the thoracic cavity. As volume increases, pressure decreases, causing air to be pushed into the lungs.

Exhalation (Breathing Out)

During exhalation, the diaphragm relaxes and returns to its original dome shape. This decreases the volume of the thoracic cavity. As volume decreases, pressure increases, forcing the air out of the lungs.

Pathway of Air to the Alveoli

The air follows a specific path from the atmosphere until it reaches the alveoli:

1. Air enters through the mouth or nose.
2. It passes down the trachea.
3. It continues through the bronchi and bronchioles.
4. When the diaphragm contracts, the air reaches the alveoli for gas exchange.