Respiratory System Overview

Outcome D1b: Respiratory System

• This outcome explains how the human respiratory system exchanges energy and matter with the environment.

Air Composition

• Air is made up of:
  • Nitrogen (78%)
  • Oxygen (21%)
  • Argon (0.9%)
  • Carbon Dioxide (0.04%)
  • Trace gases (0.06%)
• Oxygen is obtained through breathing into the lungs.
• Lack of oxygen for more than a few minutes can lead to death.

Why Breathe?

• Cells need oxygen for cellular respiration.
• Cellular respiration produces carbon dioxide as waste.
• High carbon dioxide levels are harmful to the body.
• The respiratory system's main function is to take in oxygen and release carbon dioxide.

Respiration Requirements

• Respiration needs a large surface area for efficient gas exchange.
• A moist environment is needed for oxygen and carbon dioxide to dissolve and diffuse across the membrane.

Respiratory Tract: Upper

• The lungs are the primary organs of respiration, located in the thoracic cavity (chest cavity).
• The airway is called the respiratory tract, divided into upper and lower sections.
• The nasal passages warm, moisten, and clean incoming air. Ciliated cells within move foreign particles out of the respiratory tract.
• Turbinate bones increase the surface area of the nasal cavity, aiding in warming and moistening the air, as well as trapping dust particles. Heat from blood vessels in the nasal passages further warms the air.
• The pharynx is the common passageway for air and food.
• The epiglottis is a flap of tissue that covers the trachea (windpipe) to prevent food from entering the airways when swallowing.
• The glottis is the opening to the trachea.
• The larynx, or voice box, contains vocal cords that vibrate to produce sound. The pitch of the voice depends on the length of the vocal cords (longer cords = lower pitch, shorter cords = higher pitch).
• The trachea, or windpipe, carries air to the lungs. It's supported by C-shaped cartilaginous rings to prevent it from collapsing.

Respiratory Tract: Lower

• The bronchi (singular: bronchus) are two branches that extend from the trachea into each lung. They are supported by C-shaped cartilaginous rings for support. The bronchi are lined with cilia and mucous-producing cells.
• Bronchioles are subdivisions of the bronchi inside each lung, and do not contain cartilage. The lining is also lined with cilia and mucous-producing cells.
• Alveoli (singular: alveolus) are clusters of tiny air sacs at the ends of terminal bronchioles. They are the site of gas exchange. Each alveolus wall is extremely thin and is surrounded by a network of capillaries.
• The alveoli have a moist membrane, a large surface area, and thin walls to optimise gas exchange. They are covered in surfactant to prevent the alveoli from collapsing.
• Lungs are divided into lobes (the right lung has three, and the left lung has two).
• The pleural membrane is a double membrane that surrounds the lungs, allowing them to expand and contract with the movement of the chest.
• The diaphragm is a dome-shaped muscle below the lungs that aids in breathing. It works in conjunction with rib muscles to move air in and out of the lungs.

This quiz explores the structure and function of the human respiratory system. It covers air composition, the role of oxygen in cellular respiration, and the requirements for efficient gas exchange. Test your understanding of how the body interacts with its environment through respiration.