The Respiratory System


General Functions:
1) Inputs Oxygen to the blood, Outputs Carbon Dioxide from the blood.
2) Allows vocal communication
3) Helps control pH of the body.

Anatomy:
http://www.byronsmith.com/everest2000/gfx/ehb_respiratorysystem.gif
http://www.byronsmith.com/everest2000/gfx/ehb_respiratorysystem.gif

Nose: passageway for air. Warms, filters, moisturizes air as it is breathed in.

Mouth: an alternative passageway for the movement of air.

Pharynx: the connecting area between the Nose, Mouth, Esophagus and Trachea.

Larynx: Area that contains the vocal cords which help allow vocal communication.

Trachea: Passageway to the bronchi that air moves through. Contains cells with upward beating cilia that move mucus out of the lungs.

Bronchi: Passages that get more and more numerous and narrower. Passageways for the movement of air.

Alveoli: Microscopic sacs that are the terminating point of bronchi. This is where Oxygen and Carbon Dioxide exchange between the air and the blood.

Lungs: Organs that hold all the alveoli. Can change in volume to allow air to move in and out.

Diaphragm: Muscular band under the lungs that moves up and down during inspiration/expiration.
http://images.tutorvista.com/content/feed/tvcs/alveoli.JPG
http://images.tutorvista.com/content/feed/tvcs/alveoli.JPG
















Control of Breathing

Inspiration occurs when the ribs move out and the diaphragm moves down. This increases the volume of the lungs, thereby decreasing the pressure in the lungs. The atmospheric pressure around the nose and mouth is now higher than in the lungs. Air moves from the atmosphere (higher pressure) to the lungs (lower pressure).

Expiration occurs when the ribs move in and the diaphragm moves up. This decreases the volume of the lungs, thereby increasing the pressure in the lungs. The atmospheric pressure around the nose and mouth is now lower than in the lungs. Air moves from the lungs (higher pressure) to the atmosphere (lower pressure).

Regulation of respiratory rate is controlled by the brain stem. Under quiet respiration the inspiratory center stimulates inspiratory muscle activity for 2 seconds and then is silent for 3 seconds. During this silent period the ribs and diaphragm passively 'rebound' back to their original positions causing expiration.

During forced respiration the inflation reflex prevents the lungs from over inflating. As the volume in the lungs increases the inflation reflex stimulates the expiratory centers in the brain and inhibits the inspiratory centers in the brain. Conversely, the deflation reflex stimulates the inspiratory centers in the brain and inhibits the expiratory centers in the brain. (If try to continuously inhale, you will feel an increasing urge to exhale and vice versa)

Breathing can also be controlled by chemoreceptors in the carotid arteries and aorta. These sensors are most sensitive to the partial pressure of carbon dioxide. They rely on the fact that normally increasing partial pressure of carbon dioxide means decreasing partial pressure of oxygen and vice versa. Once partial pressure carbon dioxide levels rise to critical levels you will involuntarily take a deep breath!

Gas Exchange at the Respiratory Membrane


http://www.emc.maricopa.edu/faculty/farabee/biobk/humrespsys4.gif
http://www.emc.maricopa.edu/faculty/farabee/biobk/humrespsys4.gif


Partial Pressure is calculated as the percent of the gas in the mixture multiplied by the total pressure. For example, average atmospheric pressure at sea level is 760 mmHg. Air is about 20% oxygen. The partial pressure of Oxygen at sea level is: PO2 = 760 mmHg X .2 = 152 mmHg.

Remember that gasses (like oxygen and carbon dioxide) will diffuse (move from a high concentration to a low concentration) from a higher partial pressure to a lower partial pressure.

Now, open your books (or pamphlets) to page 452. Look at Figure 16-11. Each person/student/pupil is to write a paragraph explaining how/why the partial pressure in blood changes as it moves from the pulmonary to the systemic circuit.

Practice these flashcards until you are great at them!