The Respiratory System
What is Respiration?
• Cellular level
• Cellular respiration is when the mitochondria breaks down food using
oxygen to release energy (ATP)
• Organism level
• Respiration refers to gas exchange, the releasing of carbon dioxide
and up taking oxygen between the lungs and the environment.
The Human Respiratory System
• Function: To exchange oxygen and carbon dioxide between the
blood, air and tissues
• Air enters through the nose to a tube at the back of the mouth called
the pharynx, which is the passage way for both food and air.
• Air then moves to the trachea (windpipe), which leads into the lungs
Cilia and Mucus
• Hairs in your nose trap large particles so they do not get into your
lungs
• Mucus moistens the air and traps inhaled particles of dust or smoke
• Cilia sweep the tapped particles and mucus away form the lungs
toward the pharynx
• Then the trapped particles get either swallowed or spit out.
The Larynx
• Is located at the top of the trachea
• It contains two elastic folds of tissue known as the vocal cords.
• Muscles can pull the vocal cords together, and when air passes over
them they create sound
• This is how we can speak, shout, and sing.
The Bronchi
• The trachea leads to two passage ways that bring air into each lung,
the bronchi
• Each bronchus leads into one of the lungs, and then these divide into
smaller passage ways called bronchioles
• At the end of the bronchioles there are millions of tiny air sacs called
alveoli
Gas Exchange
• Gas exchange happens by diffusion across the membrane of an
alveolus and a capillary
• Oxygen dissolves in the moisture on the inner surface of the alveoli an
then diffuses across the thin-walled capillaries into the blood
• Carbon dioxide diffusion in the opposite directions
• Inhaled air is ~ 21% oxygen and ~ 0.04% carbon dioxide, Exhaled air
contains less than 15% oxygen and 4% carbon dioxide.
Breathing
• Breathing is the movement of air into and out of the lungs
• There are no muscles connected to the lungs, the muscle that drives
this is the diaphragm
• The diaphragm is the large flat muscle at the bottom of the chest
cavity that can pull air into your lungs by contracting and allows air to
leave the lungs when it relaxes.
How Breathing is Controlled
• The medulla oblongata is responsible for controlling your breathing,
this is part of your autonomic nervous system, meaning it is
controlled involuntary
• You can control your breathing voluntarily, however your somatic
nervous system will force you to breathe when to much carbon
dioxide is detected in your blood