1.
Which of the choices below is not a functional process performed by the respiratory system?
Correct Answer
B. Transport of respiratory gases
Explanation
The respiratory system is responsible for the exchange of gases between the body and the environment. Pulmonary ventilation refers to the process of breathing, where air is inhaled and exhaled. External respiration involves the exchange of oxygen and carbon dioxide between the lungs and the blood. Pulmonary respiration refers to the exchange of gases between the lungs and the surrounding tissues. Transport of respiratory gases, on the other hand, refers to the movement of oxygen and carbon dioxide through the bloodstream to and from the tissues. This process is primarily carried out by the circulatory system, specifically the cardiovascular system. Therefore, transport of respiratory gases is not a functional process performed by the respiratory system.
2.
The loudness of a persons voice depends on the
Correct Answer
D. Force with which air rushes across the vocal folds
Explanation
The loudness of a person's voice depends on the force with which air rushes across the vocal folds. The vocal folds vibrate when air passes through them, and the force with which the air rushes across the vocal folds determines the amplitude of the sound produced. A stronger force will result in a louder voice, while a weaker force will result in a softer voice. Therefore, the force with which air rushes across the vocal folds directly affects the loudness of a person's voice.
3.
The walls of the alveioli are composed of to types of cells, type I and type II. The function of type II is to _________.
Correct Answer
A. Secrete surfactant
Explanation
Type II cells in the alveoli secrete surfactant. Surfactant is a substance that reduces the surface tension of the alveoli, preventing them from collapsing and sticking together. This helps to maintain the stability and integrity of the alveoli during breathing and allows for efficient gas exchange in the lungs.
4.
Complete the following statement using the choices below. Air moves out of the lungs when the pressure inside the lungs is
Correct Answer
B. Greater than the pressure in the atmospHere
Explanation
When the pressure inside the lungs is greater than the pressure in the atmosphere, air moves out of the lungs. This is because air naturally moves from areas of higher pressure to areas of lower pressure, in order to equalize the pressure. Therefore, when the pressure inside the lungs is greater than the pressure in the atmosphere, the air will flow out of the lungs until the pressures become equal.
5.
Unlike inspiration, expiration is a passive act because no muscular contractions are involved. Expiration, however, depends on two factors. Which of the choices below lists those two factors?
Correct Answer
A. The recoil of elastic fibers that were stretched during inspiration and the inward pull of surface tension due to the film of alveolar fluid
Explanation
Expiration is a passive act because it does not involve muscular contractions. Instead, it relies on two factors: the recoil of elastic fibers that were stretched during inspiration and the inward pull of surface tension due to the film of alveolar fluid. The recoil of elastic fibers helps to push air out of the lungs, while the surface tension of the alveolar fluid creates an inward pull that aids in the process of expiration. These two factors work together to facilitate the passive act of expiration.
6.
Which of the following maintains the patency (openness) of the trachea?
Correct Answer
C. Carilage rings
Explanation
The correct answer is cartilage rings. The trachea is a tube-like structure that allows air to pass into and out of the lungs. The cartilage rings provide support and prevent the collapse of the trachea, maintaining its patency or openness. These rings are C-shaped and are located along the anterior and lateral sides of the trachea. They keep the trachea rigid while still allowing flexibility for movement and expansion during breathing. The surface tension of water, surfactant, and pseudostratified ciliated epithelium are all important for other respiratory functions but do not directly maintain the patency of the trachea.
7.
Intrapulmonary pressure is the
Correct Answer
B. Pressure within the alveoli of the lungs
Explanation
The correct answer is "pressure within the alveoli of the lungs." Intrapulmonary pressure refers to the pressure within the alveoli, which are small air sacs in the lungs where gas exchange takes place. This pressure changes during the respiratory cycle, increasing during inspiration and decreasing during expiration. It is essential for the movement of air in and out of the lungs.
8.
The relationship between the pressure and volume of gases is given by
Correct Answer
A. Boyles law
Explanation
Boyle's law states that the pressure and volume of a gas are inversely proportional when the temperature and amount of gas are kept constant. This means that as the volume of a gas decreases, the pressure increases, and vice versa. Boyle's law is derived from the ideal gas law and is applicable to ideal gases. It helps explain phenomena such as the inflation and deflation of balloons or the compression and expansion of gases in a piston.
9.
The statement "in a mixture of gases, the total pressure is the sum of the individual partial pressures of gases in the mixture" paraphrases
Correct Answer
C. Daltons law
Explanation
Dalton's law states that in a mixture of gases, the total pressure is equal to the sum of the partial pressures of each individual gas in the mixture. This means that each gas in the mixture exerts its own pressure independent of the other gases present. Therefore, the given statement accurately paraphrases Dalton's law.
10.
Surfactant helps to prevent the alveoli from collasping by
Correct Answer
C. Interfering with the conhesiveness of water molecules, thereby reducing the surface tension of alveolar fluid
Explanation
Surfactant is a substance that reduces the surface tension of a liquid. In the case of alveoli, surfactant interferes with the conhesiveness of water molecules, which in turn reduces the surface tension of the alveolar fluid. This reduction in surface tension helps to prevent the alveoli from collapsing by making it easier for the alveoli to expand and stay open during inhalation.
11.
For gas exchange to be efficient, the respiratory membrane must be
Correct Answer
B. 0.5 to 1 micrometer thick
Explanation
The correct answer is 0.5 to 1 micrometer thick. Gas exchange occurs through diffusion across the respiratory membrane, which consists of a thin layer of cells. If the membrane is too thick, diffusion of gases becomes slower and less efficient. Therefore, a thickness of 0.5 to 1 micrometer allows for a rapid and efficient exchange of gases between the respiratory surface and the bloodstream.
12.
With the Bohr effect, more oxygen is released because a(n)
Correct Answer
B. Decrease in pH (acidosis) weakens the hemoglobin-oxygen bond
Explanation
The Bohr effect refers to the phenomenon where a decrease in pH (acidosis) weakens the hemoglobin-oxygen bond, resulting in more oxygen being released by hemoglobin. This occurs because when the pH decreases, the concentration of hydrogen ions increases, which leads to the formation of additional bonds between the hydrogen ions and hemoglobin. These additional bonds cause a conformational change in the hemoglobin molecule, making it more difficult for oxygen to bind to it. As a result, oxygen is more readily released to the tissues that need it.
13.
The most powerful respiratory stimulus for breathing in a healthy person is
Correct Answer
B. Increase of carbon dioxide
Explanation
The increase of carbon dioxide is the most powerful respiratory stimulus for breathing in a healthy person. When carbon dioxide levels rise in the body, it triggers the respiratory centers in the brain to increase the rate and depth of breathing. This response helps to remove excess carbon dioxide and restore the balance of gases in the body. Oxygen levels also play a role in regulating breathing, but the increase in carbon dioxide has a stronger effect on respiratory drive. pH levels (acidosis or alkalosis) can also affect breathing, but they are not as powerful a stimulus as an increase in carbon dioxide.
14.
Nerve impulses from __________________ will result in inspiration
Correct Answer
A. The ventral respiratory group
Explanation
The ventral respiratory group is responsible for generating nerve impulses that result in inspiration. It is a group of neurons located in the medulla oblongata of the brainstem. These neurons send signals to the muscles involved in breathing, causing them to contract and initiate the inhalation process. Therefore, when nerve impulses originate from the ventral respiratory group, it triggers the inspiration phase of breathing.
15.
In the plasma, the quantity of oxygen in solution is
Correct Answer
A. Only about 1.5% of the oxygen carried in dissolved form
Explanation
In the plasma, only about 1.5% of the oxygen is present in a dissolved form. This means that the majority of the oxygen in the plasma is not in a dissolved state, but rather combined with other molecules such as hemoglobin. Therefore, the quantity of oxygen in solution is much smaller compared to the oxygen combined with hemoglobin.
16.
Which of the following statements is incorrect?
Correct Answer
B. Respiratory rate is lowest in newborn infants
Explanation
The statement "respiratory rate is lowest in newborn infants" is incorrect. In fact, the respiratory rate in newborn infants is relatively higher compared to adults. Newborns typically have a respiratory rate of around 30-60 breaths per minute, whereas adults have a lower respiratory rate of around 12-20 breaths per minute.
17.
Which of the choices below describes the forces that act to pull the lungs away from the thorax wall and thus collapse the lungs?
Correct Answer
A. The neural tendency for the lungs to recoil and the surface tension of the alveolar fluid
Explanation
The forces that act to pull the lungs away from the thorax wall and collapse the lungs are the neural tendency for the lungs to recoil and the surface tension of the alveolar fluid. The neural tendency for the lungs to recoil refers to the natural elasticity of the lung tissue, which causes it to want to shrink back to its original size. The surface tension of the alveolar fluid refers to the cohesive forces between the molecules of the fluid lining the alveoli, which creates a force that pulls the alveoli inward and collapses the lungs.
18.
Which of the following does not influence the increase in ventilation that occurs as exercise is initiated?
Correct Answer
B. Decrease in lactic acid levels
Explanation
The decrease in lactic acid levels does not influence the increase in ventilation that occurs as exercise is initiated. During exercise, ventilation increases to meet the increased demand for oxygen and removal of carbon dioxide. This increase in ventilation is primarily regulated by the respiratory center in the brain, which is stimulated by various factors such as psychic stimuli, proprioceptors, and simultaneous cortical motor activation of the skeletal muscles and respiratory center. Lactic acid levels are not directly involved in regulating ventilation during exercise.
19.
Which of the following is not a form of lung cancer?
Correct Answer
B. Kaposi's sarcoma
Explanation
Kaposi's sarcoma is not a form of lung cancer. It is a type of cancer that primarily affects the skin and mucous membranes, but can also involve other organs including the lungs. It is caused by a virus called human herpesvirus 8 (HHV-8) and is most commonly seen in individuals with weakened immune systems, such as those with HIV/AIDS. Adenocarcinoma, small cell carcinoma, and squamous cell carcinoma are all types of lung cancer that arise from different cell types within the lungs.
20.
Which of the following is not an event necessary to supply the body with O2 and dispose of CO2?
Correct Answer
B. Blood pH adjustment
Explanation
Blood pH adjustment is not an event necessary to supply the body with O2 and dispose of CO2. The primary function of blood pH adjustment is to maintain the acid-base balance in the body. This process is regulated by the kidneys and involves the excretion or retention of hydrogen ions (H+) and bicarbonate ions (HCO3-). While maintaining proper blood pH is important for overall health, it is not directly involved in the process of oxygen supply and carbon dioxide removal, which primarily occurs through pulmonary ventilation, internal respiration, and external respiration.
21.
Which of the following is not true of the respiratory tract from the medium bronchi to the aveoli?
Correct Answer
B. Resistance to air flow increases due to the increase in cross sectional diameter
Explanation
The statement that resistance to air flow increases due to the increase in cross-sectional diameter is not true. In reality, resistance to air flow decreases as the cross-sectional diameter increases. This is because a larger diameter allows for a greater volume of air to flow through the respiratory tract, reducing the resistance to airflow.
22.
Which of the following determines lung compliance?
Correct Answer
D. Alveolar surface tension
Explanation
Lung compliance refers to the ability of the lungs to expand and stretch during inspiration. Alveolar surface tension plays a crucial role in determining lung compliance. Alveoli are lined with a thin layer of fluid, and the surface tension of this fluid can affect the ease with which the alveoli can expand. High surface tension can make it more difficult for the alveoli to expand, resulting in decreased lung compliance. Therefore, alveolar surface tension is a key factor in determining lung compliance.
23.
Tidal volume is air
Correct Answer
B. Exchanged during normal breathing
Explanation
Tidal volume refers to the amount of air that is exchanged during normal breathing. It represents the volume of air that is inhaled and exhaled during each breath without any forced expiration or inspiration. This volume of air is essential for maintaining proper gas exchange in the lungs and ensuring a steady supply of oxygen to the body.
24.
Which of the choices below determines the direction of respiratory gas movement?
Correct Answer
B. Partial pressure gradient
Explanation
The direction of respiratory gas movement is determined by the partial pressure gradient. This means that gases will move from an area of higher partial pressure to an area of lower partial pressure. The difference in partial pressure creates a concentration gradient that drives the movement of gases. Solubility in water, temperature, and molecular weight and size of the gas molecule may affect the rate of gas movement, but they do not determine the direction of movement.
25.
Possible causes of hypoxia include
Correct Answer
A. Too little oxygen in the atmospHere
Explanation
Hypoxia refers to a condition where there is an inadequate supply of oxygen to the body's tissues. The given answer, "too little oxygen in the atmosphere," is a possible cause of hypoxia. If the surrounding environment has a low oxygen concentration, it can lead to a reduced oxygen intake by the lungs, resulting in insufficient oxygen reaching the tissues. This can occur in high-altitude areas or in enclosed spaces with limited ventilation.
26.
The lung volume that represents the total volume of exchangeable air is the
Correct Answer
B. Vidal capacity
Explanation
The vital capacity represents the total volume of exchangeable air in the lungs. It is the maximum amount of air that can be exhaled after a maximum inhalation. It is calculated by adding the tidal volume, inspiratory reserve volume, and expiratory reserve volume. The tidal volume is the amount of air inhaled and exhaled during normal breathing, while the inspiratory capacity is the maximum amount of air that can be inhaled after a normal exhalation. The expiratory reserve volume is the additional amount of air that can be exhaled forcefully after a normal exhalation. Therefore, the vital capacity encompasses all of these volumes and represents the total volume of exchangeable air.
27.
Because the lungs are filled with fluid during fetal life, which of the following statements is true regarding repiratory exchange?
Correct Answer
C. Respiratory exchanges are made through the placenta
Explanation
During fetal life, the lungs are filled with fluid and are not functional for respiratory exchange. Instead, oxygen and nutrients are exchanged between the fetus and the mother through the placenta. The placenta acts as a barrier between the fetal and maternal blood supply, allowing for the exchange of gases and nutrients. This is necessary for the fetus to receive oxygen and eliminate carbon dioxide. Therefore, the statement that respiratory exchanges are made through the placenta is true.
28.
Which of the following is not a stimulus for breathing?
Correct Answer
B. Rising blood pressure
Explanation
Rising blood pressure is not a stimulus for breathing. The respiratory system is primarily regulated by the levels of carbon dioxide in the blood, as well as the arterial oxygen levels and pH. When carbon dioxide levels rise or arterial oxygen levels decrease, the body responds by increasing the rate and depth of breathing. Similarly, when the arterial pH becomes acidic due to CO2 retention, the body increases breathing to remove excess carbon dioxide. However, rising blood pressure does not directly stimulate the respiratory system.
29.
Respiratory control centers are located in the
Correct Answer
B. Medulla and pons
Explanation
The respiratory control centers are responsible for regulating breathing. They monitor the levels of oxygen and carbon dioxide in the blood and adjust the rate and depth of breathing accordingly. These control centers are located in the medulla and pons, which are regions of the brainstem. The medulla plays a crucial role in controlling the basic rhythm of breathing, while the pons helps to fine-tune and coordinate the breathing process. Together, the medulla and pons ensure that breathing is properly regulated to maintain the body's oxygen and carbon dioxide levels.
30.
The amount of air that can be inpired above the tidal volume is called
Correct Answer
C. Inspiratory reserve
Explanation
The inspiratory reserve refers to the additional amount of air that can be inhaled after a normal tidal volume breath. This extra air can be taken in during deep inhalation and is used during activities that require increased oxygen intake, such as exercise. It is an important measure of lung function and respiratory capacity. The other options, reserve air, expiratory reserve, and vital capacity, do not accurately describe this specific amount of air that can be inspired above the tidal volume.
31.
Which statement about CO2 is incorrect?
Correct Answer
C. More CO2 dissolves in the blood plasma that is carried in the RBCs
Explanation
CO2 is mostly transported in the blood in the form of bicarbonate ions (HCO3-) rather than being dissolved in the blood plasma or carried by red blood cells (RBCs). Only a small fraction of CO2 is dissolved in the blood plasma, while the majority is converted to bicarbonate ions in the red blood cells and transported to the lungs to be exhaled. Therefore, the statement that more CO2 dissolves in the blood plasma that is carried in the RBCs is incorrect.
32.
Oxygen and carbon dioxide are exchanged in the lungs and through all cell membranes by
Correct Answer
B. Diffusion
Explanation
Diffusion is the process by which molecules move from an area of high concentration to an area of low concentration. In the case of oxygen and carbon dioxide, they are exchanged in the lungs and through cell membranes by diffusion. Oxygen, which is in higher concentration in the lungs or in the blood, will diffuse into the cells where it is in lower concentration. Similarly, carbon dioxide, which is in higher concentration in the cells, will diffuse out of the cells into the blood or lungs where it is in lower concentration. Therefore, diffusion is the correct answer for the exchange of oxygen and carbon dioxide.
33.
Select the correct statement about pharynx
Correct Answer
B. The auditory tube drains into the nasopHarynx
Explanation
The correct statement about the pharynx is that the auditory tube drains into the nasopharynx. The auditory tube, also known as the Eustachian tube, connects the middle ear to the nasopharynx and helps equalize pressure between the middle ear and the atmosphere. This allows for proper functioning of the ear and helps prevent ear infections.
34.
The larynx contains
Correct Answer
A. The thyroid cartilage
Explanation
The larynx contains various structures, including the thyroid cartilage, which is a prominent feature commonly referred to as the Adam's apple. This cartilage helps protect the vocal cords and provides support to the larynx. It is the largest cartilage in the larynx and can be easily felt in the front of the neck. The other structures mentioned, such as the true vocal folds and false vocal folds, are also present in the larynx and play important roles in producing sound and protecting the airway.
35.
Which respiratory associated muscles would contract if you were to blow up a balloon?
Correct Answer
B. Internal intercostals and abdominal muscles would contract
Explanation
When blowing up a balloon, the internal intercostals and abdominal muscles would contract. The internal intercostals help in the process of exhalation by pulling the ribs downward and decreasing the size of the thoracic cavity. The abdominal muscles, including the rectus abdominis and external obliques, contract to increase intra-abdominal pressure, which assists in the forceful exhalation needed to blow up the balloon.
36.
How is the bulk of carbon dioxide carried in blood?
Correct Answer
B. As the bicarbonate ion in the plasma after first entering the red blood cells
Explanation
When carbon dioxide enters the red blood cells, it combines with water to form carbonic acid. Carbonic acid then dissociates into bicarbonate ions and hydrogen ions. The majority of carbon dioxide is carried in the blood as bicarbonate ions in the plasma. This allows for efficient transport of carbon dioxide from the tissues to the lungs, where it can be eliminated through exhalation.
37.
Which of the following is not found on the right lobe of the lung?
Correct Answer
B. Cardiac notch
Explanation
The cardiac notch is not found on the right lobe of the lung. It is a feature of the left lung, where it is a concave space on the medial surface of the lung that accommodates the heart. The right lung, on the other hand, has three lobes (upper, middle, and lower) and is characterized by a horizontal fissure and an oblique fissure, which separate the lobes.
38.
Which of the choices below is not a role of the pleura?
Correct Answer
D. Aids in blood flow to and from the heart because the heart sits between the lungs
Explanation
The pleura is a double-layered membrane that surrounds the lungs and lines the chest cavity. Its main roles include allowing the lungs to inflate and deflate without friction, helping to divide the thoracic cavity into three chambers, and helping to limit the spread of local infections. However, it does not directly aid in blood flow to and from the heart. The heart sits between the lungs, but its blood flow is facilitated by the coronary arteries and veins, not the pleura.
39.
Factors that influence the rate and depth of breathing include
Correct Answer
B. Voluntary coritcal control
Explanation
Voluntary cortical control refers to the ability of an individual to consciously control their breathing rate and depth. This means that a person can choose to breathe faster or slower and take deeper or shallower breaths. Factors such as stress, physical activity, and emotions can influence this voluntary control. The other factors mentioned, thalamic control, stretch receptors in the alveoli, and composition of alveolar air, do not directly involve conscious control and are more related to automatic regulation of breathing.
40.
Which of the following provide the greatest surface area for gas exchange?
Correct Answer
B. Alveoli
Explanation
The alveoli provide the greatest surface area for gas exchange. Alveoli are tiny, thin-walled sacs located at the ends of the respiratory bronchioles. They are surrounded by a network of capillaries, which allows for efficient exchange of oxygen and carbon dioxide between the lungs and the bloodstream. The large number and small size of the alveoli greatly increase the surface area available for gas exchange, making them the primary site for this crucial process in the respiratory system.
41.
The respiratory membrane is a combination of
Correct Answer
B. Alveolar and capillary walls and their fused basement membranes
Explanation
The respiratory membrane is responsible for the exchange of gases between the alveoli and the capillaries in the lungs. It consists of the thin walls of the alveoli and the capillaries, as well as their fused basement membranes. This arrangement allows for efficient diffusion of oxygen from the alveoli into the bloodstream and carbon dioxide from the bloodstream into the alveoli. By having a thin membrane and close proximity between the alveoli and capillaries, the respiratory membrane maximizes the surface area available for gas exchange.
42.
Gas emboli may occur because a
Correct Answer
B. Diver holds his breath upon ascent
Explanation
When a diver holds their breath upon ascent, the pressure decreases rapidly as they rise to the surface. This causes the air in their lungs to expand, potentially leading to the formation of gas emboli. Gas emboli are bubbles of gas that can block blood vessels and cause serious health issues, such as decompression sickness or arterial gas embolism. It is important for divers to exhale continuously during ascent to prevent the buildup of pressure in the lungs and minimize the risk of gas emboli.
43.
Inspiratory capacity is
Correct Answer
A. The total amount of air that can be inspired after a tidal expiration
Explanation
Inspiratory capacity refers to the maximum amount of air that can be inspired by a person after a normal tidal expiration. It represents the sum of tidal volume (the amount of air inhaled and exhaled during normal breathing) and inspiratory reserve volume (the additional amount of air that can be inhaled after a normal inhalation). Therefore, it is the total volume of air that can be taken in by the lungs during a deep breath following a regular exhalation.
44.
Which center is located in the pons?
Correct Answer
A. Pontine respirator group (PRG)
Explanation
The correct answer is the pontine respirator group (PRG). The PRG is a center located in the pons, which is a region in the brainstem. It plays a crucial role in controlling and coordinating the respiratory rhythm, specifically the timing and pattern of breathing. The PRG receives input from various sensory and motor pathways and adjusts the activity of the inspiratory and expiratory muscles accordingly. It acts as a pacemaker neuron center, regulating the breathing rate and depth.
45.
The nose serves all of the following functions except
Correct Answer
B. As the initiator of the cough reflex
Explanation
The nose serves as a passageway for air movement, warming and humidifying the air, and cleansing the air. However, it does not serve as the initiator of the cough reflex. The cough reflex is initiated by irritation of the respiratory tract, usually in the throat or lungs, and is a protective mechanism to clear the airways of any foreign particles or mucus. The nose plays a role in filtering and conditioning the air, but it is not directly involved in initiating the cough reflex.
46.
A premature baby usually has difficulty breathing. However, the respiratory system is developed enough for survival by
Correct Answer
C. 28 weeks
Explanation
At 28 weeks, the respiratory system of a premature baby is developed enough for survival. By this stage, the lungs have developed the necessary structures to support breathing, such as the alveoli and surfactant production. While a premature baby may still have some difficulty breathing, they have a higher chance of survival compared to earlier stages of development.
47.
Which of the following statements is true regarding the respiratory rate of a newborn?
Correct Answer
D. The respiratory rate of a newborn is at ist highest rate approximatley 40-80 respirations per minute
Explanation
The respiratory rate of a newborn is at its highest rate approximately 40-80 respirations per minute. This is because newborns have a faster respiratory rate compared to adults. As they are adjusting to life outside the womb, their respiratory system needs to work harder to supply oxygen to their developing organs. This higher respiratory rate helps ensure that their oxygen needs are met and their body functions properly.
48.
Select the correct statement about the neural mechanisms of respiratory control
Correct Answer
A. The pons is thought to be intstrumental in the smooth transition from inspiration to expiration
Explanation
The statement "the pons is thought to be instrumental in the smooth transition from inspiration to expiration" is correct. The pons, a region in the brainstem, plays a crucial role in regulating the transition between inspiration (breathing in) and expiration (breathing out). It contains neurons that control the timing and coordination of respiratory muscles, allowing for a smooth transition between these two phases of the breathing cycle.
49.
Which of the choice below is not a factor that promotes oxygen binding to and dissociation from hemoglobin?
Correct Answer
D. Number of red blood cells
Explanation
The number of red blood cells is not a factor that promotes oxygen binding to and dissociation from hemoglobin. Oxygen binding to hemoglobin is primarily influenced by the partial pressure of oxygen, which determines the concentration gradient for oxygen to diffuse into the red blood cells. Temperature also affects oxygen binding, as higher temperatures promote oxygen release from hemoglobin. Additionally, the partial pressure of carbon dioxide affects oxygen binding, as an increase in carbon dioxide decreases the affinity of hemoglobin for oxygen, promoting oxygen release to tissues. However, the number of red blood cells does not directly affect oxygen binding or dissociation.
50.
The factors responsible for holding the lungs to the thorax wall are
Correct Answer
D. Surface tension from pleural fluid and negative pressure in the pleural cavity
Explanation
The correct answer is surface tension from pleural fluid and negative pressure in the pleural cavity. The pleural cavity is the space between the lungs and the thorax wall, and it is filled with pleural fluid. The surface tension created by this fluid helps to hold the lungs against the thorax wall. Additionally, the pleural cavity has a negative pressure, which means that the pressure inside the cavity is lower than the atmospheric pressure. This negative pressure also contributes to keeping the lungs attached to the thorax wall.