I. The Respiratory system
· Is responsible for taking oxygen into the body and removing carbon dioxide and water vapor.
II. Traveling through the respiratory system
· Nose and pharynx (throat).
Ø First air is taken into the nose through the nostrils.
v Hairs in the nose help to trap foreign particles and microbes. Once trapped a sneeze helps to remove these invaders.
v Vessels in the lining of the nasal cavity help to warm the air.
v Mucus helps to moisten the air and keep the nasal membranes from drying out.
· From the nose air moves to the pharynx (throat).
Ø The pharynx is shared with the digestive tract.
Ø A structure called the epiglottis prevents food and liquids from entering the lower respiratory tract.
· Larynx. (voice box)
Ø Located on top of the trachea.
v The larynx is made up of cartilage with inner folds of tissue called vocal cords.
v When air passes out through the vocal cords they vibrate creating sound. The tighter the vocal cords the higher the pitch of the sound
· Trachea (wind pipe).
Ø The trachea is made of cartilage rings and smooth muscle.
v This gives the trachea strength and flexibility.
v The trachea is lined with cilia. Tiny hair-like structure that help to trap foreign particles and microbes.
ü Once trapped they sweep the materials up toward the pharynx.
ü Also coughing helps to remove this trapped material.
· Bronchus.
Ø Air passes from the trachea into the bronchus.
Ø The bronchus are tubes. (bronchi is plural)
Ø Right bronchus enters the right lung, and the left bronchus enters the left lung.
v These tubes branch into smaller and smaller tubes called bronchioles.
v The bronchi and all the smaller tubes are called the bronchial tree.
· The lungs
Ø The lungs are the main organ of the respiratory system.
Ø In the lungs the smallest branches of the bronchial tree lead to structures called alveoli.
v Alveoli are tiny grape like clusters of tissue that resemble balloons.
v Each thin walled alveoli is surrounded by a network of capillaries.
v Gas exchange takes place here.
ü Oxygen from the lungs moves into the capillaries from the alveoli using the process of diffusion. From here it goes to the heart.
ü Carbon dioxide from the capillaries moves into the alveoli using the process of diffusion, and is then exhaled.
II. The mechanics of breathing
· When you inhale.
Ø Muscles attached to the ribs contract and move up and outward.
Ø The diaphragm (a muscle located at the bottom of your chest) contracts and moves downward.
v These 2 actions make the chest cavity larger.
v This makes the air pressure inside your lungs less than the air pressure in the environment.
ü As a result air rushes into your lungs.
· When you exhale
Ø Muscles that are attached to the ribs relax
( the chest goes back down).
Ø Your diaphragm relaxes and moves upward.
v These 2 actions make the chest cavity smaller.
v As a result the air pressure inside your lungs is greater than the air pressure in the atmosphere.
ü As a result air rushes out of your lungs.
· Breathing is controlled by signals from your brain.
Ø The brain determine your breathing rate based on CO2 (carbon dioxide) levels in your blood.