Respiratory System

Respiratory System Major function is to supply the body with oxygen and dispose of carbon dioxide Most of the carbon dioxide waste is used as blood’s buffer system

4 Processes of Respiration Pulmonary ventilation: movement of air into and out of the lungs so that gases are continuously refreshed. External respiration: movement of oxygen from the lungs to the blood and of carbon dioxide from the blood to the lungs

4 Processes cont. Transportation: movement of oxygen to the tissues and carbon dioxide from the tissues to the lungs. Internal respiration: movement of oxygen from blood to the tissue cells and of carbon dioxide from the cells to blood.

Atmospheric Gas: mixture Nitrogen: 78% Must be eaten to obtain for body Nitrogen is fixed by bacteria for plants to absorb Nitrogen is introduced to the soil also through lightning Oxygen: 20.9% Combustible at 22% Released by organisms that perform photosynthesis Used by organisms for cellular respiration

Atmospheric Gases, cont. Carbon dioxide: 0.04% Waste product of cellular respiration Carbon dioxide comes from pollution Green organisms use CO2 for photosynthesis Water Vapor: 0.46% Percentage of water vapor in air is called dewpoint Higher the dewpoint = higher the humidity

Respiratory System Parts 1. nose: external portion supported by bone and cartilage Internal nasal cavity is divided by the septum and lined with mucosa. Roof is lined with olfactory epithelium Terbinate bone line the nasal cavity Produce mucus, filter, warm, and humidify the incoming air, resonance chamber for speech.

Parts, cont. 2. paranasal sinuses: mucosa lined air-filled cavities Decreases the weight of the skull, and performs the same functions as the nose

Parts, cont. 3. Pharnyx: back of the throat. 3 divisions: nasopharynx. Oropharnyx, and laryngopharynx Houses the tonsils- lymphoid tissue Passageway for both food and air

Parts, cont. 4. Larynx: connects the throat to the trachea Contains a cartilage framework that includes the epiglottis Epiglottis closes over the trachea when swallowing Houses vocal cords Air passageway into the lower respiratory tract

Parts, cont. Trachea: flexible tube connecting the larynx and the bronchi Walls contain C-shaped cartilage rings that are incomplete posteriorly (keep the airway open) **air passageway, cleans, warms, and moistens the incoming air

Parts, cont. Bronchial tree: right and left bronchi that subdivides into the bronchioles Has the same function as the trachea, can become inflamed and can restrict air flow- asthma

Parts, cont. Alveoli: microscopic chambers at terminal bronchioles Walls are simple squamous epithelium Site of gas exchange

Parts, cont. Pleurae membranes Produces surfactant; lubricating solution that decreases friction

Mechanics of Breathing Remember Boyle’s Law??? If the volume increases, then the pressure must decrease (or vice versa) P1V1 = P2V2

Breathing occurs when the contraction or relaxation of muscles around the lungs changes the total volume of air within the air passages (bronchi, bronchioles) inside the lungs. When the volume of the lungs changes, the pressure of the air in the lungs changes in accordance with Boyle’s Law.

If the pressure is greater in the lungs than outside the lungs, then air rushes out. If the opposite occurs, then air rushes in.

Mechanics of Breathing: Inspiration Diaphragm contracts and lowers, thus increasing the size of the thoracic cavity. External intercostal muscles contract elevating the ribs and sternum. Total volume of internal air passages increases, air pressure inside the lungs decreases below that of air outside the body. Because gases move from regions of high pressure to low pressure, air rushes into the lungs.

Mechanics of Breathing: Expiration Diaphragm relaxes and raises, thus decreasing the size of the thoracic cavity. External intercostal muscles relax lowering the ribs and sternum. Elastic fibers cause the lungs to recoil to original volume Total volume of internal air passages decrease, air pressure inside the lungs increases below that of air outside the body, air rushes out.

https://www.youtube.com/watch?v=F0OB kR00OZE

Control of Breathing The autonomic nervous system controls breathing. The respiratory center that controls the rate of breathing is in the medulla.

Factors that influence the Medulla Oxygen: Peripheral chemoreceptors located in the carotid and aorta detect the amount of oxygen in the blood. If the oxygen concentration is low, they tell the medulla to increase breathing. Carbon dioxide: These receptors also monitor carbon dioxide levels in the CSF. If too high, then signals are sent to respiratory centers to increase the rate and depth of breathing.

Other Factors that influence the Medulla pH: If the blood becomes too acidic, then signals are sent to the centers to speed up Stretch: If the lungs are overinflated, respiratory centers are signaled to exhale Signals from brain centers: Nerve cells in the hypothalamus and cortex During pain or strong emotions, hypothalamus tells the centers to speed up, slow down, or stop