To Take Note:

Chapter Twelve: Respiration

Respiration is a series of chemical reactions that releases energy from food.

Breathing is the mechanism for moving air in and out of the lungs; this supports the chemical reactions of respiration.

Gas Exchange Surfaces

Oxygen Goes Out; CO2 Goes IN to Alveolus.

• Large Surface Area — To allow faster diffusion of gases across the surface.
• Thin Walls — Ensure diffusion distances remain short and efficient.
• Good Ventilation with Air — Diffusion gradients can be maintained steep.

Respiratory System

The ribs are bone structures that protect internal organs such as the lungs. Between the ribs are the intercostal muscles, which control the movement of the ribs and play an important role in inhalation and exhalation.

The diaphragm is a sheet of connective tissue and muscle located at the bottom of the thorax; it helps change the volume of the thorax to allow breathing. Air enters through the trachea, or windpipe, which connects the mouth and nose to the lungs.

The larynx, also known as the voice box, allows us to produce sound when air passes through it.

The trachea branches into two large tubes called bronchi (singular: bronchus), with one leading to each lung. Inside the lungs, the bronchi divide into smaller tubes called bronchioles, which lead to tiny air sacs known as alveoli. The alveoli are the sites where gas exchange takes place— oxygen enters the blood, and carbon dioxide is removed.

Intercostal Muscles

• Muscles are only able to pull on bones, they can’t push on them.
• Two sets of intercostal muscles; one to pull the rib cage up and another set to pull it down
  • One set of intercostal muscles is found on the outside of the ribcage (the external int. muscles)
  • The other set is found on the inside of the rib cage (the internal intercostal muscles)

Cartilage in Trachea

• Rings of C-shaped cartilage surround the trachea (and bronchi).
  • The function of the cartilage is to support the airways and keep them open during breathing and respiration.

Inspired & Expired Air

— Inspired Air: Air that is inhaled. (Inspiration = Inhalation) — Expired Air: Air that is exhaled. (Expiration = Exhalation)

They differ in its gas composition; due to process of gas exchange.

• Inhaled air contains around 21 % oxygen & exhaled air contains around 16 % oxygen
• Inhaled air contains around 0.04 % CO2 and exhaled air contains around 4 % CO2

Volume & Pressure Change