Download RESPIRATORY SYSTEM READING

RESPIRATORY SYSTEM READING
1. Get familiar with the respiratory system by first coloring the human respiratory system diagram.
2. Follow the directions below for dissection of the rat respiratory system.
Air enters the nasal passages through the nares which are separated by a nasal septum. The
olfactory receptors are very concentrated in the nasal cavity and send senses of smell to the brain.
Open the mouth as far as possible. The mouth may be closed quite tightly however. You
may need to use scissors to cut the jaw bones and view the inside of the mouth. At the posterior end of
the mouth is located the pharynx (throat) which serves both the digestive and respiratory system.
Look carefully at the back of the tongue for the glottis or opening to the larynx. When the rat swallows,
the epiglottis closes the glottis to prevent food from getting into the trachea by directing it into the
esophagus. You will need to look underneath the sternohyoid muscle to see the trachea. Carefully snip
ONE END of the sternohyoid and lift up on the muscle to reveal the trachea. You will recognize the
trachea because it is supported by rings of cartilage.
Follow the trachea down to the lungs, looking carefully for the point where the trachea divides into an
inverted “Y.” You may have to look particularly carefully because the “Y” is located underneath the
heart. The trachea branches into right and left divisions called bronchi. Each bronchus (singular for
bronchi) continues to a lung where is further subdivides into bronchioles.
The left lung has only one lobe but the right lung has four distinct lobes. Look carefully for these
lobes. Remove a small, flat piece of lung tissue. Place the tissue on a Petri dish and examine under the
stereomicroscope. Note the large amount of vascularization or blood vessels. Use color pencils to make
a diagram of the lung tissue.
Below the lungs is the diaphragm, a muscular wall separating the thoracic from the abdominal cavity.
It is the most important muscle for breathing, permitting inhaling and exhaling. Three major vessels
pass through the diaphragm: the aorta, inferior vena cava, and the esophagus. The aorta is a large
artery (now filled with red latex) that sends oxygenated blood out to all parts of the body. The inferior
vena cava is a large vein (now filled with blue latex) that returns deoxygenated blood to the heart from
the lower body. The esophagus is a digestive system tube that moves food to the stomach.
3. Draw your own diagram of the rat respiratory system.
a. Draw an outline of the system in pencil.
b. Color your line drawing with the same color key as the human diagram.
c. Remember that the right and left lungs differ in the number of lobes.
4. Complete the Checking for Understanding questions.