Respiratory Physiology: Practice Test! Trivia Quiz

The distribution of ventilation within the lung is influenced by regional variations in lung inflation, regional variations in airway resistance, regional variations in lung compliance, and collateral ventilation. Regional variations in lung inflation refer to the fact that different parts of the lung may inflate to different extents during breathing. Regional variations in airway resistance suggest that different airways within the lung may have different levels of resistance to airflow. Regional variations in lung compliance indicate that different parts of the lung may have different levels of elasticity. Collateral ventilation refers to the flow of air between adjacent areas of the lung, which can affect the distribution of ventilation. Therefore, all of these factors play a role in determining the distribution of ventilation within the lung.

The structures listed in the answer (pharynx, nasal cavity, trachea, bronchi) are all part of the conducting zone of the respiratory system, which is considered to be the anatomic dead-space. The anatomic dead-space refers to the areas within the respiratory system where gas exchange does not occur, and instead, only air is conducted. These structures help in the process of warming, humidifying, and filtering the air before it reaches the respiratory zone where gas exchange takes place in the alveoli.

Pulmonary surfactant can be deficient in premature newborns, as their lungs may not have fully developed the ability to produce enough surfactant. It is produced in type II alveolar cells, which are specialized cells in the lungs. One of the main components of surfactant is dipalmitoyl phosphatidylcholine, a type of phospholipid. The main function of surfactant is to decrease the surface tension of the fluid lining the alveoli, which helps to prevent the collapse of the alveoli during expiration and promotes efficient gas exchange. Therefore, all of the statements are correct.

An increase in pH causes a shift of the oxyhemoglobin dissociation curve to the left, not to the right. This is because an increase in pH indicates a decrease in acidity, which promotes the binding of oxygen to hemoglobin, resulting in a stronger affinity between the two. As a result, oxygen is less likely to be released to the tissues, leading to a leftward shift of the curve.

During inhalation, the diaphragm and external intercostal muscles contract. This contraction of the diaphragm causes it to flatten and move downward, increasing the volume of the thoracic cavity. The contraction of the external intercostal muscles raises the ribs, further expanding the thoracic cavity. As a result, the pleural pressure decreases, creating a pressure gradient that allows air to flow into the lungs. Additionally, the contraction of the diaphragm and external intercostals also causes the alveolar pressure to decrease, facilitating the entry of air into the alveoli.

The tidal volume of 5 L and respiratory rate of 12 breaths/min can be used to calculate the minute ventilation (VE) by multiplying the tidal volume by the respiratory rate. In this case, 5 L x 12 breaths/min = 60 L/min.

The VD/VT ratio of 0.5 can be used to calculate the alveolar ventilation (VA) by subtracting the dead space volume (VD) from the tidal volume (VT) and then multiplying it by the respiratory rate. In this case, (5 L - (0.5 x 5 L)) x 12 breaths/min = 30 L/min.

Therefore, the correct answer is VE=60 L/min and VA=30 L/min.

During exercise, multiple factors contribute to the increase in cardiac output and the relatively smaller increase in pulmonary arterial pressure. First, pulmonary vascular resistance decreases during exercise, allowing for easier blood flow through the pulmonary arteries. Additionally, unperfused capillaries are recruited, increasing the overall surface area available for gas exchange. Previously perfused vessels are also distended, further facilitating blood flow. Finally, factors released by the endothelium during exercise dilate the pulmonary arteries, promoting increased blood flow. Therefore, all of the above factors contribute to the observed phenomenon.

Elevated PaCO2, low pH, and no base excess or deficit are characteristic of acute respiratory acidosis. This occurs when there is a build-up of carbon dioxide in the body due to impaired ventilation, leading to an increase in PaCO2 levels. The low pH indicates acidosis, and the absence of base excess or deficit suggests that the cause is not metabolic in nature. Acute respiratory alkalosis would present with decreased PaCO2 levels and metabolic acidosis or alkalosis would have abnormal base excess or deficit values.

Low PaCO2, acid pH, and base deficit are characteristic of metabolic acidosis. In metabolic acidosis, there is an excess of acid or a loss of bicarbonate in the body, leading to a decrease in pH and an increase in base deficit. This can occur due to various reasons such as diabetic ketoacidosis, lactic acidosis, or renal failure. Chronic respiratory acidosis is characterized by high PaCO2 levels, acute respiratory alkalosis is characterized by low PaCO2 levels, and metabolic alkalosis is characterized by high pH levels. None of these conditions match the given characteristics. Therefore, the correct answer is metabolic acidosis.

The glossopharyngeal nerve carries afferent nerve fibers from the carotid bodies. The carotid bodies are chemoreceptors located in the carotid arteries that sense changes in oxygen and carbon dioxide levels in the blood. These receptors are important in regulating respiratory and cardiovascular function.

An increase in alveolar ventilation refers to an increase in the amount of air reaching the alveoli in the lungs. This leads to more efficient removal of carbon dioxide from the body. As a result, the partial pressure of carbon dioxide in arterial blood (PaCO2) decreases. Therefore, an increase in alveolar ventilation will cause a decrease in PaCO2.

Destruction of alveolar septa and pulmonary capillaries by a disease known as alveolar emphysema will decrease the rate of oxygen transfer between the alveolar air and the pulmonary capillary blood. Alveolar emphysema is a condition characterized by the destruction of the walls of the alveoli and the pulmonary capillaries, leading to a decrease in the surface area available for gas exchange. This reduces the efficiency of oxygen transfer from the alveoli to the capillary blood, resulting in decreased oxygenation of the blood.

The ductus arteriosus is a vascular channel that connects the pulmonary artery to the aorta in a developing fetus. This allows oxygenated blood from the placenta to bypass the non-functioning lungs and be distributed to the rest of the body. After birth, the ductus arteriosus normally closes and becomes a ligament called the ligamentum arteriosum.

Enzymes localized on the pulmonary endothelium are responsible for the conversion of angiotensin I to angiotensin II. Angiotensin I is an inactive precursor molecule that is converted to angiotensin II, which is a potent vasoconstrictor. This conversion is important in regulating blood pressure and fluid balance in the body. Angiotensin II also stimulates the release of aldosterone, a hormone that promotes sodium and water retention, further contributing to blood pressure regulation.

Anemia is the correct answer because it decreases the oxygen content in the blood by reducing the number of red blood cells or the amount of hemoglobin available to carry oxygen. However, it does not alter PaO2 or percentage saturation of hemoglobin because the remaining red blood cells can still be fully saturated with the available oxygen.

HCO3- produced in erythrocyte is the most important form of carbon dioxide transport quantitatively because it accounts for the majority of carbon dioxide carried in the blood. Erythrocytes, or red blood cells, contain an enzyme called carbonic anhydrase, which catalyzes the conversion of CO2 and water into carbonic acid. This carbonic acid then dissociates into bicarbonate ions (HCO3-) and hydrogen ions (H+). The HCO3- ions are then transported out of the erythrocytes into the plasma, where they are carried to the lungs for elimination. This mechanism allows for efficient transport and removal of carbon dioxide from the body.

A decrease in lung volume from FRC to residual volume increases the frictional resistance to breathing because as the lung volume decreases, the airways become narrower. This narrowing of the airways increases the resistance to airflow, making it more difficult for air to move in and out of the lungs. This increased resistance can lead to a sensation of difficulty in breathing and can be seen in conditions such as asthma or chronic obstructive pulmonary disease (COPD).

Fetal hemoglobin having a lower P50 than adult hemoglobin means that fetal hemoglobin has a higher affinity for oxygen compared to adult hemoglobin. This allows the fetus to efficiently extract oxygen from the maternal blood in the placenta, where the oxygen pressure is lower. The lower P50 of fetal hemoglobin ensures that oxygen is readily bound to hemoglobin in the placenta and released to the fetal tissues. This adaptation is crucial for fetal oxygen transport since the fetus relies on maternal oxygen supply for its oxygen needs.

An increase in the alveolar dead-space can result from an increase in the number of high V/Q units in the lung. This statement is correct because high V/Q units refer to areas of the lung where ventilation is greater than perfusion. In these areas, there is inadequate blood flow to match the amount of air being ventilated, leading to wasted ventilation and increased dead space. As a result, an increase in the number of high V/Q units in the lung can lead to an increase in alveolar dead space, which is the volume of air that is ventilated but does not participate in gas exchange.

Carboxyhemoglobin refers to the binding of carbon monoxide (CO) to hemoglobin, not carbon dioxide (CO2). Carbon dioxide is primarily carried in the blood through three mechanisms: conversion to bicarbonate, binding to hemoglobin to form carbamino hemoglobin, and dissolved in the plasma. Therefore, the option "As carboxyhemoglobin" is not utilized for the carriage of carbon dioxide in the blood.

Lung compliance refers to the ability of the lungs to stretch and expand. The given answer states that lung compliance is greater at functional residual capacity (FRC) than at total lung capacity (TLC). This is because at FRC, the lungs are partially inflated and are in a more relaxed state, making them more compliant. At TLC, the lungs are fully inflated and are under more tension, resulting in decreased compliance. Therefore, lung compliance is higher at FRC compared to TLC.

The alveolar oxygen tension (PAO2) can be calculated using the alveolar gas equation: PAO2 = (PB - PH2O) x FiO2 - (PaCO2 / R), where PB is the barometric pressure, PH2O is the partial pressure of water vapor, FiO2 is the fraction of inspired oxygen, PaCO2 is the arterial carbon dioxide tension, and R is the respiratory exchange ratio. Plugging in the given values, we get PAO2 = (750 - 50) x 0.5 - (80 / 1) = 270 mmHg.

Exposure of a cow to the hypoxia of high altitude will cause the greatest increase in pulmonary arterial pressure. At high altitudes, the partial pressure of oxygen in the air decreases, leading to hypoxia. In response, the cow's body will try to compensate by increasing the pulmonary arterial pressure in order to deliver more oxygen to the tissues. This increase in pulmonary arterial pressure helps to maintain adequate oxygenation and perfusion of the organs despite the reduced oxygen availability at high altitudes.

Atelectasis refers to the collapse or incomplete expansion of a lung or a portion of a lung. When one lobe of a dog's lung undergoes atelectasis, it can lead to more low V/Q (ventilation/perfusion) regions within the lung. This is because the collapsed lobe will have reduced ventilation, resulting in a decreased V/Q ratio. As a result, blood flow to this area may be relatively higher compared to ventilation, leading to low V/Q regions. This can impair gas exchange and potentially cause hypoxemia.

The ventilatory response to a change in PaCO2 is mediated through a change in pH of interstitial fluid bathing the central chemosensitive neurons. This response is accentuated in metabolic acidosis because there is less buffering of the interstitial fluid around the central chemoreceptor. The ventilatory response is also modified during exercise, so PaCO2 remains constant despite a large increase in CO2 production. Additionally, this response can occur in the absence of the peripheral chemoreceptors. Therefore, all of the above statements are correct.

An increase in capillary hydrostatic pressure can accentuate the movement of fluid between the pulmonary capillaries and lung lymphatic vessels. This means that when the pressure in the capillaries is higher, it can push fluid out into the lymphatic vessels more easily. This movement of fluid does not occur in a normal animal, but when there is an increase in capillary hydrostatic pressure, it becomes more pronounced. The option "Both b and d" refers to the fact that both an increase in capillary hydrostatic pressure and movement through the alveolar surface can contribute to the movement of fluid between the pulmonary capillaries and lung lymphatic vessels.

The carotid bodies are located near the bifurcation of the internal and external carotid arteries. This means that they are positioned in a strategic location to detect changes in blood oxygen levels and carbon dioxide levels. When the carotid bodies sense low oxygen levels (low PaO2), they can increase ventilation to help increase oxygen levels in the blood. However, they are not involved in responding to an increase in carbon dioxide levels (increase in PaCO2). The other statements in the question are not correct explanations of the carotid bodies.

Metabolic alkalosis is characterized by elevated PaCO2, alkaline pH, and base excess. This condition occurs when there is an excess of bicarbonate in the blood, leading to an increase in pH. It can be caused by conditions such as vomiting, excessive use of diuretics, or excessive intake of alkaline substances. It is important to note that chronic respiratory acidosis, chronic respiratory alkalosis, and metabolic acidosis have different characteristics and are not associated with elevated PaCO2, alkaline pH, and base excess. Therefore, the correct answer is metabolic alkalosis.

Rapidly adapting stretch receptors are thought to initiate a cough in response to a mechanical deformation of the airway. These receptors are located in the airway smooth muscles and respond to changes in lung volume and airway stretch. When the airway is mechanically deformed, such as by the presence of irritants or foreign particles, these receptors send signals to the brain, triggering a cough reflex to clear the airway. Juxtacapillary receptors, slowly adapting stretch receptors, and intercostal tendon organs do not have a direct role in initiating a cough reflex.

The correct answer is "All the above." This means that all of the statements about fetal circulation are true. The right atrial pressure is higher than the left atrial pressure, pulmonary vascular resistance is high, the placenta receives about 45% of the combined output of both ventricles, and the output of the right ventricle is greater than the left ventricle.

The given arterial blood gas tensions indicate that the horse has low oxygen levels (PaO2=55 mmHg) and high carbon dioxide levels (PaCO2=70 mmHg) at rest. When the horse is given oxygen to breathe, the PaO2 increases significantly (to 550 mmHg), but the PaCO2 remains the same. This suggests that the horse is not effectively getting rid of carbon dioxide, indicating alveolar hypoventilation. Alveolar hypoventilation refers to inadequate ventilation of the alveoli, leading to a buildup of carbon dioxide and a decrease in oxygen levels. Therefore, alveolar hypoventilation is the cause of these gas tensions.

An increase in the pH of blood will decrease P50. P50 refers to the partial pressure of oxygen at which hemoglobin is 50% saturated with oxygen. A decrease in P50 indicates an increase in the affinity of hemoglobin for oxygen, meaning that hemoglobin will bind to oxygen more readily at lower oxygen pressures. This shift in the oxyhemoglobin dissociation curve to the left allows for more efficient oxygen uptake by the blood and delivery to tissues.

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High ventilation/perfusion ratio in many lung units is not a cause of hypoxemia. Hypoxemia refers to low levels of oxygen in the blood, and it can be caused by various factors. Low ventilation/perfusion ratio in many lung units can lead to hypoxemia because it means that there is inadequate airflow or blood flow to certain areas of the lungs. Diffusion impairment in the alveolar wall can also cause hypoxemia as it affects the exchange of oxygen and carbon dioxide. Decreased PIO2 (partial pressure of inspired oxygen) can result in hypoxemia as well. However, a high ventilation/perfusion ratio in many lung units does not directly contribute to hypoxemia.

The correct answer states that in quadrupeds, pulmonary blood flow is distributed so that the dorsal-caudal regions of the lung receive the most blood flow. This is because the action of gravity causes blood to pool in the lower regions of the lung, resulting in increased blood flow to the dorsal-caudal regions. This distribution of blood flow helps to optimize gas exchange in the lung, as the dorsal-caudal regions have a larger surface area for gas exchange.

The brochial circulation drains into the pulmonary circulation and azygos vein. This means that the blood from the bronchial circulation is collected by the pulmonary circulation, which then carries it back to the heart for oxygenation. Additionally, some of the blood from the bronchial circulation can also drain into the azygos vein, which is a large vein that carries deoxygenated blood from the chest and abdominal walls.

After birth, the first event that occurs is the baby taking its first breath. This is followed by a decrease in pulmonary arterial pressure, which happens as the baby starts breathing and the lungs expand. Finally, the closure of the foramen ovale takes place. The foramen ovale is a hole in the heart that allows blood to bypass the lungs during fetal development, but it closes after birth as the lungs take over the oxygenation of blood.

Type II cells, which produce surfactant, are not present within the first few days of gestation in sheep. Surfactant production begins later in gestation, around the 24th week in humans. Therefore, this statement does not correctly describe the lung in utero.

At high altitudes, such as the top of Mount McKinley, the partial pressure of oxygen in the air decreases. This leads to hypoxia, causing the dog to breathe faster and deeper in order to compensate for the low oxygen levels. The increased respiratory rate results in excessive elimination of carbon dioxide, leading to a decrease in the partial pressure of carbon dioxide in the blood. This decrease in carbon dioxide causes a shift towards alkalinity in the blood, resulting in respiratory alkalosis. Therefore, respiratory alkalosis is the most likely acid-base disturbance to be found in a dog at the top of Mount McKinley.

During exercise, recruitment of muscle capillaries that are unperfused in the resting animal leads to several physiological changes. These include an increase in the surface area for gas diffusion between tissues and blood, a decrease in the distance between tissue capillaries, and maintenance of tissue PO2 in the presence of increased demand for oxygen. However, it does not result in an increase in the velocity of capillary blood flow. The recruitment of additional capillaries allows for a larger total cross-sectional area, which actually slows down the velocity of blood flow, allowing for more efficient gas exchange and nutrient delivery to the tissues.

Particles greater than 5 um in diameter are deposited in the respiratory tract by inertial deposition in large airways. This means that as the particles move through the airways, their inertia causes them to continue moving in a straight line, even when the air changes direction. This leads to the particles impacting and depositing in the larger airways of the respiratory tract. Sedimentation in airways and alveoli, as well as diffusion in the alveoli, are not the primary mechanisms for deposition of particles greater than 5 um in diameter.

Phagocytosis of inhaled particles can sometimes require both macrophages and neutrophils. This means that in certain cases, both types of cells may be involved in the process of engulfing and removing particles that have been inhaled. It is not always exclusively accomplished by alveolar macrophages or accentuated by alveolar hypoxia.

Pigs have the lowest value for lung compliance compared to dogs, cats, and horses. Lung compliance refers to the ability of the lungs to expand and stretch. A lower lung compliance means that the lungs are less elastic and have difficulty expanding, which can affect breathing. Pigs have thicker lung tissue and less elastic lungs compared to other animals, resulting in lower lung compliance.

A normal tidal volume refers to the amount of air that is inhaled and exhaled during a normal breath. In dogs, a normal tidal volume is typically around 15 ml per kilogram of body weight. This means that for every kilogram of the dog's weight, it would inhale and exhale 15 ml of air. This is considered to be a normal range for dogs and helps to ensure proper oxygenation and ventilation of the lungs.

The question provides information about the oxygen capacity of hemoglobin (1.36 mL of oxygen per 1 g of hemoglobin) and the blood PO2 (70 mmHg). However, it does not provide any information about the volume of blood or the concentration of hemoglobin in the blood. Without this information, it is not possible to calculate the oxygen content of the blood. Therefore, the correct answer is that it cannot be calculated from the information provided.

Horse has a diffuse, epitheliochorial placenta in which fetal and maternal blood flow is countercurrent in the microcotyledons.

The correct answer is "None of the above" because the rhythmicity of breathing is not solely originated in any of the mentioned options. The process of breathing involves a complex interaction between various brain regions, including the medulla oblongata, pons, and other respiratory centers. The ventral respiratory group of medullary neurons and the apneustic center play a role in regulating the depth and rate of breathing, but they are not solely responsible for the rhythmicity of breathing. Additionally, rapidly adapting pulmonary stretch receptors are involved in regulating lung inflation, but they do not solely control the rhythmicity of breathing.

After a vagotomy, the duration of inhalation becomes independent of chemical drive. This means that the process of inhalation is no longer influenced by the levels of chemicals in the body that would typically trigger the need to breathe. Vagotomy is a surgical procedure that involves cutting or removing a portion of the vagus nerve, which plays a role in regulating various bodily functions, including respiration. By severing this nerve, the connection between chemical drive and inhalation is disrupted, resulting in inhalation occurring independently of chemical signals.

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The left ventricle receives oxygenated blood from the lungs and pumps it out to the body, making it the structure with the highest PO2. The aorta carries this oxygenated blood to the rest of the body, the ductus arteriosus shunts blood away from the lungs, the pulmonary artery carries deoxygenated blood to the lungs, and the umbilical artery carries deoxygenated blood from the fetus to the placenta.