Respiratory System Study Guide (8th ed) PDF

Study Guide for the Respiratory System Mechanistically, respiration can be divided into four basic processes: 1) Ventilation (ie the exchange of gas between the lungs and the environment), 2) Gas exchange between the lungs and the blood, 3) Transport of gases by the blood, and 4) Exchange of gases b...

Study Guide for the Respiratory System Mechanistically, respiration can be divided into four basic processes: 1) Ventilation (ie the exchange of gas between the lungs and the environment), 2) Gas exchange between the lungs and the blood, 3) Transport of gases by the blood, and 4) Exchange of gases between the blood and the tissues. All the topics discussed in lecture relate to these four mechanisms. Anatomically, the respiratory system consists of two parts: 1) The airways, which can be divided into upper and lower tracts. 2) The bones, muscles, and connective tissues of the chest. In addition to serving as a conduction pathway between the atmosphere and the gas exchange surface, the airways also condition the air in three ways: 1) Adding moisture to inhaled air and taking moisture out of the exhaled air. 2) Adding heat to the inhaled air and taking heat out of the exhaled air. 3) Filtering out the pathogens and dust particles. The airways, except for the alveoli, are lined by ciliated epithelium that secretes mucous and saline. The mucous serves to trap particles and microbes that may enter the lungs and the cilia move the mucous up towards the upper airways where the mucous is passed to the throat and either swallowed or spit out. You should know the four gas laws. These laws govern the movement of gases and are fundamental in understanding the movement of gases at all levels of the respiratory system, For example, the second and third gas laws govern the movement of air into and out of the lungs. In order to move air into the lungs the air pressure inside the lungs has to be lower than the air pressure of the atmosphere (760mmHg at sea level). This is achieved by increasing the volume of the lungs, which decreases the pressure in the lungs (3rd gas law) relative to the atmospheric pressure. As a result of the lower pressure in the lungs air is pushed from the atmosphere into the lungs (2nd gas law). In moving air out of the lungs the reverse happens. The volume of the lungs decrease, which increases the pressure inside the lungs (3rd gas law) relative to the atmospheric pressure and as a result air is pushed out of the lungs into the atmosphere. To achieve the change in the lung (and chest volume) during inspiration requires muscular activity. You should know the muscles involved in this process. During normal expiration reduction in lung volume is passive, ie it does not require muscle activity. During forced expiration the extra decrease in lung volume requires that the thoracic cavity be squeezed to a lesser volume than normal. You should know the muscles involved in breathing and their roles. The amount of work required to expand the lungs during inspiration depends on two factors: 1) the ability of the lung tissue to stretch (Compliance) and 2) The resistance of the airways to airflow. Diseases that restrict the stretch decrease compliance of the lung tissues and are called restrictive lung diseases. Don’t worry about knowing the specific names of the diseases but be sure you know the two main causes of restrictive lung disease. You should particularly know the significance of surfactant in increasing the lung compliance in newborns. You should also understand the difference between compliance and elastance. Airflow in the lungs follows the same principles as blood flow in the circulatory system. So if you understood blood flow there are no new principles to learn. The main site of variable resistance to airflow in the lungs is the bronchioles, which have walls consisting of epithelial lining and a layer of smooth muscle, much like arterioles. There are three main influences on the degree of contraction (bronchoconstriction) or relaxation (bronchodilation) of bronchioles: 1) CO2 in the exhaled air, 2) The autonomic nervous system input (parasympathetic and epinephrine from adrenal gland), 3) Histamines. You should know how each of these affects the bronchioles. You should understand how total pulmonary ventilation (TPV) and alveolar ventilation (AV) are calculated and why AV is a more accurate measure of ventilation. You should also understand the relationship between alveolar ventilation and alveolar PO2 and PCO2. All exchange of O2 and CO2 between the blood and air in the alveoli occurs across the capillary-alveolar interface. The main determinant of gas movement (O2 and CO2) across the capillary-alveolar interface is the partial pressure gradients of the individual gases (gas laws). You should be able to summarize in detail the transport of O2 and CO2 from the tissues to the alveoli and vice versa. Most O2 (and 23% of the CO2) that is transported is bound to hemoglobin. You should know the general structure of the hemoglobin molecule as presented in lecture. You should understand the oxy-hemoglobin curve and the factors that affect the O2 affinity of hemoglobin. Relating the factors to their physiological significance can be helpful in remembering them and how they affect the O2 affinity of hemoglobin. You should know how CO2 is transported in the blood, and the significance of the carbonic anhydrase reaction in the transport of CO2. Respiration is a rhythmic process consisting of inhalation and exhalation. The primary control centers for respiration are in the medulla oblongata of the brain. There are two respiratory centers in the medulla: the dorsal (or inspiratory) nucleus, and te ventral (or forced expiratory) nucleus. You should understand the role of each nucleus in respiration and the inputs these nuclei receive (ie, inputs from the cerebral cortex give you voluntary control of your breathing). Finally, you should know what the peripheral and central chemoreceptors sense and the role that the chemoreceptors play in controlling the respiratory cycle during normal breathing. Don’t worry about the Hering-Breur reflex beyond that it is a protective reflex preventing over-inflation of the lungs. End of the Chapter Questions for Chapter 17 8th ed.: 1, 2, 3, 4, 5, 6, 8,12,13,14,15,16,17,19, 22, 23, 24, 25, 26, 29, 30, 31, 32 End of the chapter questions for Chapter 18 8th ed.: 1, 2, 3, 5, 6, 8, 9, 11, 12, 13, 16, 17, 18, 20