Bio 20IB- Respiratory system

• Air enters the nasal cavity and mouth and the nasal cavities contain hairs and mucus that traps particles and keeps cells moist
• air travels through the pharynx, which separates the trachea and the esophagus
• when eating, an enlarged flap of cartilage called the epiglottis covers the trachea to prevent food from entering the lungs
• food and drink that enter the trachea stimulates the cilia that lines the respiratory tract, producing a cough
• the larynx is composed of thin sheets of elastic ligaments (the vocal cords)
• when you inhale, the pressure inside the lungs is lower than the outside
• when you exhale, the pressure within the lungs is higher than the atmospheric pressure
• the change in lung pressure is created by changing the volume of the lungs due to the movement of the diaphragm
• When you inhale, the intercostal muscles contract, and the rib cage moves up and out. The diaphragm contracts and moves down. pressure in the lungs decreases.
• When you exhale, the intercostal muscles relax and the rib cage moves down and in. The diaphragm relaxes and moves up. The pressure in the lungs increases
• the normal volume of air that is exhaled and inhaled is known as tidal volume
• the total volume of air that our lungs can contain is known as vital capacity
• gases are exchanged between the air in the alveoli and the blood of the capillaries
• oxygen will diffuse out of the alveoli and into the capillary while carbon dioxide moves in the opposite direction
• within tissues, oxygen leaves the blood and diffuses into the tissue, while carbon dioxide diffuses out of the tissue and into the blood
• 99% of the oxygen in the blood is bonded to hemoglobin molecules found in your RBC, allowing the blood to carry more oxygen
• carbon dioxide can be transported by hemoglobin (carbaminohemoglobin), but only 23% is carried this way

  most of the carbon dioxide in the blood is in the form of bicarbonate ions
• most carbon dioxide combines with water to form carbonic acid and the reaction is sped with the enzyme carbonic anhydrase.
• carbonic acid must be buffered: It dissociates into bicarbonate and hydrogen ions. The hydrogen ions dislodge oxygen from hemoglobin, then binds to it so it becomes reduced hemoglobin. The reduced hemoglobin acts as a buffer
• once venous blood reaches the lungs, the oxygen dislodges hydrogen ions from hemoglobin binding sites. the free hydrogen and bicarbonate ions combine to form carbon dioxide and water, and then diffuses from the blood into the alveoli. It is then eliminated during exhalation.
• a buffer is a substance capable of neutralizing acids and bases, thus maintaining the original PH of the solution
• breathing rate is controlled by carbon dioxide receptors in the area of the brain known as the medulla oblongata