Topic 7: Chpt 17-18 Flashcards
Why do human lungs have such a large surface area?
Human lungs have a gas exchange surface area equivalent to about 75 square meters to efficiently supply oxygen to trillions of cells and remove CO2. This large surface area, comparable to a racquetball court, is compressed into a small volume to maximize gas exchange.
How do humans meet the challenge of dehydration in respiration?
Humans have internalized lungs within the chest cavity, creating a humid environment protected from external air, which helps maintain the necessary moisture for gas exchange.
What are the main components of a complex respiratory system in humans?
The respiratory system in humans consists of a muscular pump (thorax musculoskeletal structure) for moving air and a thin, moist exchange surface (lung epithelium and blood vessels) for gas exchange.
What are the four primary functions of the respiratory system?
- Gas exchange between the atmosphere and blood. 2. Regulation of body pH by managing CO2 levels. 3. Protection from inhaled pathogens and irritants. 4. Vocalization through air movement across the vocal cords.
How does the respiratory system contribute to homeostasis beyond gas exchange?
The respiratory system helps in regulating body temperature and water balance through heat and moisture loss, which must be compensated for by homeostatic mechanisms.
What principles govern the flow of air in the respiratory system?
Air flow in the respiratory system follows from regions of higher pressure to lower pressure, driven by a muscular pump, and is primarily influenced by the diameter of the air passages.
What are the different meanings of respiration in physiology?
In physiology, respiration refers to cellular respiration, the biochemical process producing ATP by reacting oxygen with organic molecules, and external respiration, which is the exchange of gases between the environment and body cells, involving ventilation and gas transport.
What are the four processes of external respiration?
- Ventilation (air exchange between the atmosphere and lungs). 2. Gas exchange between lungs and blood. 3. O2 and CO2 transport by the blood. 4. Gas exchange between blood and cells.
What is ventilation and what are its mechanisms?
Ventilation, or breathing, involves inspiration (inhalation) to move air into the lungs and expiration (exhalation) to move air out, governed by the mechanics of breathing involving thoracic and abdominal structures.
What are the main components of the respiratory system?
he respiratory system includes conducting airways leading to the lungs, alveoli for gas exchange, and thorax and abdomen muscles that assist in breathing.
What is the role of alveoli in the respiratory system?
Alveoli are interconnected sacs lined with pulmonary capillaries where oxygen is transferred from inhaled air to the blood, and CO2 is transferred from the blood to air being exhaled.
How is the respiratory system anatomically divided?
The upper respiratory tract includes the mouth, nasal cavity, pharynx, and larynx. The lower respiratory tract, or thoracic portion, includes the trachea, primary bronchi, their branches, and the lungs.
How are the respiratory and cardiovascular systems coordinated in external respiration?
External respiration requires coordination between the respiratory system (air movement and gas exchange) and the cardiovascular system (transport of gases), ensuring efficient oxygen delivery and CO2 removal.
What are the components of the thoracic cage?
The thoracic cage consists of the spine, rib cage, and associated muscles, forming a protective structure around the chest cavity. The ribs and spine form the sides and top, while the diaphragm acts as the floor.
What muscles assist in the movement of the thoracic cage during breathing?
Two sets of intercostal muscles (internal and external) connect the ribs. Additional muscles like the sternocleidomastoids and scalenes extend from the head and neck to the sternum and first two ribs, aiding in respiratory movements.
What is the functional role of the thorax?
Functionally, the thorax acts as a sealed container with membranous sacs: one pericardial sac for the heart and two pleural sacs, each surrounding a lung. It also allows passage for the esophagus, thoracic blood vessels, and nerves.
Describe the structure and position of the lungs within the thoracic cavity.
The lungs are light, spongy organs that nearly fill the thoracic cavity, resting on the diaphragm. They connect to the trachea via semi-rigid bronchi and are encased in double-walled pleural sacs
What is the structure and function of the pleural sacs surrounding the lungs?
Each lung is encased in a pleural sac with double-walled membranes lined with elastic connective tissue and capillaries. Pleural fluid between the membranes allows lung movement, holds the lungs tight against the thoracic wall, and keeps them partially inflated.
What is the purpose of pleural fluid in the respiratory system?
Pleural fluid lubricates the space between the pleural membranes, allowing them to slide easily during breathing. It also creates a cohesive force that keeps the lungs expanded against the thoracic wall, similar to two wet glass panes sticking together.
How does air enter the respiratory system and what is the role of the pharynx?
Air enters through the mouth and nose, passing into the pharynx, which serves as a common pathway for food, liquids, and air, connecting to the larynx and trachea
What are the functions of the larynx and vocal cords in the respiratory system?
The larynx directs air into the trachea and houses the vocal cords, which vibrate to create sound when air passes through them.
Describe the structural features of the trachea.
The trachea is a semiflexible tube supported by 15 to 20 C-shaped cartilage rings, ensuring it remains open for air passage into the primary bronchi.
Explain the branching pattern of the bronchial tree within the lungs.
The trachea divides into primary bronchi, which branch into smaller bronchi and then into bronchioles, ending in respiratory bronchioles that connect to the alveoli.
How does the diameter of airways change from the trachea to the bronchioles, and what is its effect on air flow?
Airway diameter decreases from the trachea to the bronchioles, but the total cross-sectional area increases due to the geometric rise in the number of airways, decreasing the velocity of air flow as it progresses deeper into the lungs.
Compare the changes in airway cross-sectional area with changes in the circulatory system.
Similar to the increase in cross-sectional area from the aorta to the capillaries in the circulatory system, the respiratory system increases in total cross-sectional area from the trachea to the bronchioles, reducing air flow velocity analogous to blood flow.
What are the three components of air conditioning in the respiratory system?
The three components are warming the air to body temperature, adding water vapor to reach 100% humidity, and filtering out foreign material to protect the alveoli.
How are inhaled air warmed and humidified in the respiratory system?
Air is warmed by heat from the body and humidified by water evaporating from the mucosal lining of the airways, reaching 100% humidity and 37 °C by the time it enters the trachea.
What is the difference in air conditioning between breathing through the mouth and the nose?
Breathing through the nose is more effective in warming and humidifying air than mouth breathing, which can cause chest ache from cold air when exercising in cold weather.
Describe the air filtration mechanism in the trachea and bronchi.
Air is filtered through ciliated epithelium, which traps particles in a mucus layer moved by the cilia in an upward motion toward the pharynx, a system known as the mucociliary escalator.
How do mucus and cilia contribute to protecting the respiratory system?
Mucus secreted by goblet cells traps particles and pathogens, which are then moved by cilia through the mucociliary escalator toward the pharynx for expulsion or swallowing.
How does cystic fibrosis affect the mucociliary escalator and airway conditioning?
Cystic fibrosis leads to inadequate ion secretion, reducing the watery saline layer essential for cilia function. This results in thick, sticky mucus that traps cilia and prevents mucus clearance, increasing the risk of lung infections.
What is the primary function of the alveoli in the lungs?
The primary function of the alveoli is the exchange of gases between the air in the lungs and the blood, facilitated by their air-filled structure.
Describe the characteristics and role of Type I alveolar cells.
Type I alveolar cells make up about 95% of the alveolar surface area and are very thin, optimizing them for rapid gas diffusion. They are primarily responsible for the gas exchange function of the alveoli.
What is the function of Type II alveolar cells?
Type II alveolar cells synthesize and secrete surfactant, which reduces surface tension and aids lung expansion during breathing. They also help minimize fluid in the alveoli by transporting solutes and water out of the alveolar air space.
How is the alveolar structure adapted to facilitate gas exchange with the blood?
The alveolar walls are extremely thin and closely associated with an extensive network of capillaries, allowing for efficient gas exchange due to minimal diffusion distances between air and blood.
What is the role of elastic and collagen fibers in the lungs?
Elastic and collagen fibers in the connective tissue between alveolar cells provide elastic recoil, helping the lungs return to their original shape after being stretched during inhalation.
Explain the interaction between the respiratory and cardiovascular systems at the alveoli.
The alveoli are embedded within a dense network of capillaries. This close proximity ensures that the capillary blood can rapidly exchange gases with the air in the alveoli, demonstrating the tight integration of these two systems for optimal gas exchange.
What is the pulmonary circulation and where does it begin?
The pulmonary circulation begins with the pulmonary trunk, which receives low-oxygen blood from the right ventricle. It includes the journey of blood through the lungs where it is oxygenated, and back to the heart.
How are the pulmonary arteries and veins structured in relation to the lungs?
The pulmonary trunk divides into two pulmonary arteries, one for each lung. Oxygenated blood returns to the left atrium via pulmonary veins, ensuring efficient gas exchange in the lungs.
How much blood is contained within the pulmonary circulation?
About 0.5 liters, which is 10% of the total blood volume. Approximately 75 mL is in the capillaries for gas exchange, with the remainder in the pulmonary arteries and veins.
How does the rate of blood flow through the lungs compare to other tissues?
The blood flow rate through the lungs is exceptionally high at 5 L/min, equal to the entire cardiac output of the right ventricle, ensuring that as much blood flows through the lungs in one minute as through the rest of the body.
What are the characteristics of pulmonary arterial pressure?
Pulmonary arterial pressure averages 25/8 mm Hg, significantly lower than systemic arterial pressure, due to the low resistance in pulmonary circulation.
Why is the resistance in the pulmonary circulation low?
The low resistance is due to the shorter total length of the pulmonary vessels and the distensibility and large cross-sectional area of pulmonary arterioles.
How does the lymphatic system affect the pulmonary circulation?
The lymphatic system efficiently removes filtered fluid from the lung interstitial space, keeping interstitial fluid volume minimal and ensuring short distances for gas diffusion between alveoli and capillaries.
What is the primary difference between blood and air as fluids in physiological systems?
Blood is a noncompressible liquid, whereas air is a compressible mixture of gases. This affects how each behaves under pressure and during flow.
What units are used to measure air and blood pressure in respiratory physiology?
Pressure is typically reported in millimeters of mercury (mm Hg), but respiratory physiologists sometimes use centimeters of water (1 mm Hg = 1.36 cm H₂O) or kiloPascals (760 mm Hg = 101.325 kPa).
What convention do respiratory physiologists use for atmospheric pressure?
Atmospheric pressure at sea level is conventionally designated as 0 mm Hg in respiratory physiology to simplify comparisons of pressure differences during ventilation, regardless of altitude
How does air flow occur in ventilation?
Air flow results from pressure gradients, moving from areas of higher pressure to lower pressure. This bulk flow is facilitated by changes in thoracic cavity volume during breathing.
How does Boyle’s law relate to respiratory physiology?
Boyle’s law states that the pressure of a gas is inversely proportional to its volume (P₁V₁ = P₂V₂). In respiration, increasing chest volume decreases alveolar pressure (drawing air in), and decreasing it increases pressure (pushing air out).
What are the mechanisms by which gases move in and out of the lungs?
Gases move by bulk flow and diffusion. Bulk flow moves the entire gas mixture due to pressure changes, while diffusion moves individual gases down their partial pressure gradients.
How are the gas laws applied in respiratory physiology?
Gas laws govern the behavior of gases in the lungs and airways, explaining phenomena like the exchange of oxygen and carbon dioxide between alveoli and blood, based on pressure and volume changes.
What is Tidal Volume (V T)?
Tidal Volume is the amount of air moved during a single inspiration or expiration during quiet breathing, typically about 500 mL in a healthy adult.
How do you measure Inspiratory Reserve Volume and what does it represent?
Inspiratory Reserve Volume is the additional air inhaled after a normal inhalation. Measured by inhaling as much air as possible after a normal inhalation, averaging about 3000 mL in a 70-kg man.
What is Expiratory Reserve Volume and how is it measured?
Expiratory Reserve Volume is the amount of air that can be forcefully exhaled after the end of a normal expiration, averaging about 1100 mL in a healthy adult.
What is Residual Volume and why can’t it be directly measured?
Residual Volume is the air remaining in the lungs after maximal exhalation, about 1200 mL, which helps keep the lungs inflated against the chest wall. It cannot be measured directly by spirometry because it involves air that remains in the lungs after forceful exhalation.
Define Vital Capacity and how is it calculated?
Vital Capacity is the total amount of air that can be voluntarily moved in or out of the respiratory system with one breath. It is the sum of Inspiratory Reserve Volume, Tidal Volume, and Expiratory Reserve Volume.
What does Total Lung Capacity comprise?
Total Lung Capacity is the sum of Vital Capacity and Residual Volume. It represents the total volume of air the lungs can hold.
What are Inspiratory Capacity and Functional Residual Capacity?
Inspiratory Capacity is the total amount of air a person can inspire from a resting expiratory level, calculated as Tidal Volume plus Inspiratory Reserve Volume. Functional Residual Capacity is the volume of air remaining in the lungs after a normal exhalation, calculated as Expiratory Reserve Volume plus Residual Volume.
What creates the pressure gradient necessary for breathing?
Muscle contraction in the thoracic cage and diaphragm expands the lungs, creating a negative pressure inside the chest relative to atmospheric pressure, which draws air into the lungs.
How does Boyle’s Law explain the movement of air in and out of the lungs?
Boyle’s Law states that the pressure of a gas is inversely proportional to its volume. During inhalation, lung volume increases, decreasing internal pressure below atmospheric pressure, drawing air in. During exhalation, lung volume decreases, increasing pressure, and pushing air out.
Which muscles are primarily involved in quiet breathing?
The diaphragm, external intercostals, and scalene muscles are the primary muscles involved in quiet breathing, contracting to increase the thoracic cavity’s volume and decrease its internal pressure.
What happens during forced breathing?
During forced breathing, such as during intense exercise or blowing a balloon, additional chest and abdominal muscles are recruited to increase the volume change and pressure gradient for greater air movement.
What is the formula that describes airflow in the respiratory system?
Airflow (∆P/R) is directly proportional to the pressure gradient (∆P) and inversely proportional to the resistance (R) in the respiratory pathways.
What factors can increase resistance in the respiratory system?
Resistance can increase due to narrowed or obstructed airways, such as from inflammation, mucus buildup, or structural changes, which impedes airflow and requires greater pressure gradients to maintain air movement.
Describe the diaphragm’s mechanical action and its impact on thoracic volume during quiet breathing.
In quiet breathing, the diaphragm contracts, moving downwards approximately 1.5 cm towards the abdomen, thus increasing the thoracic volume significantly. This diaphragmatic movement is responsible for 60% to 75% of the volume change during inspiration, making it the primary driver of air intake
How do the external intercostal and scalene muscles contribute to thoracic expansion during inspiration?
The external intercostal and scalene muscles contract to elevate the ribs upwards and outwards. This action enlarges the thoracic cavity in both the vertical and lateral dimensions, accounting for 25-40% of the volume change during inspiration, complementing the diaphragm’s function.
What is the revised understanding of the scalene muscles’ role in quiet breathing?
Recent studies have revealed that scalene muscles actively participate in quiet breathing by lifting the sternum and the upper ribs. This action prevents the lower ribs from moving inward during diaphragmatic contraction, ensuring an efficient increase in thoracic volume.
What is the current understanding of the role of external intercostal muscles in breathing?
The external intercostal muscles are now understood to play a minor role in quiet breathing but become increasingly important in elevating rib cage expansion during more forceful respiratory activities like deep breathing or physical exertion.
What is the alveolar pressure just before inspiration begins?
Just before inspiration starts, alveolar pressure is at atmospheric level, assigned a value of 0 mm Hg. This equilibrium state where alveolar and atmospheric pressures are equal ensures that there is no air flow into the lungs at this moment.
Describe the changes in alveolar pressure at the onset of inspiratory muscle contraction.
As inspiratory muscles contract, thoracic volume begins to increase around Time 0 to 2 seconds. This volume increase causes alveolar pressure to decrease to about -1 mm Hg below atmospheric pressure (point A2), initiating the flow of air into the lungs.
When does alveolar pressure reach its minimum during inspiration, and what is this pressure?
Midway through the inspiration phase, approximately 1 second after the onset, alveolar pressure reaches its lowest point, slightly more negative than -1 mm Hg. This lowest pressure corresponds with the maximum rate of air entering the lungs.
What happens to alveolar pressure at the end of the inspiratory phase?
By the end of inspiration, as the thoracic volume expansion ceases (around 2 seconds), alveolar pressure rises back to equal atmospheric pressure (0 mm Hg). Airflow stops because the pressure gradient between the atmosphere and the alveoli has been neutralized.
Explain the significance of alveolar pressure equilibration at the end of inspiration.
The equilibration of alveolar pressure with atmospheric pressure marks the completion of the inspiratory phase. It ensures that no more air enters the lungs until the next cycle of inspiration begins, maintaining the rhythmic pattern of breathing.
How can you practically demonstrate that alveolar pressure equilibrates with atmospheric pressure at the end of inspiration?
By inhaling deeply and then abruptly stopping any further chest or diaphragm movement without holding the breath, you will notice that air flow ceases almost instantly. This cessation demonstrates that alveolar pressure has reached atmospheric level, stopping the airflow.
What initiates passive expiration in the respiratory system?
Passive expiration begins when impulses from somatic motor neurons to the inspiratory muscles cease, allowing these muscles to relax. This relaxation triggers the elastic recoil of the lungs and thoracic cage, returning the diaphragm and rib cage to their pre-inspiration positions.
How does the volume and pressure of the lungs change during passive expiration?
During passive expiration, the volume of the lungs and thoracic cage decreases due to elastic recoil. This decrease in volume leads to an increase in air pressure inside the lungs. When alveolar pressure surpasses atmospheric pressure, air flows out of the lungs.
What are the specific changes in alveolar pressure during passive expiration, and how long does this phase last?
Passive expiration typically occurs from 2 seconds to 4 seconds. Alveolar pressure rises to about 1 mm Hg above atmospheric pressure, facilitating the reversal of air flow out of the lungs. By 4 seconds, alveolar pressure equalizes with atmospheric pressure, halting air movement and marking the end of the respiratory cycle.
Which muscles are involved in active expiration, and what actions do they perform?
Active expiration, necessary during vigorous activities or forced breathing, involves the internal intercostal muscles and the abdominal muscles. The internal intercostals help decrease thoracic volume by pulling the ribs inward. Abdominal muscles contract to compress the abdominal cavity, pushing the diaphragm upwards and further reducing lung volume.
How can neuromuscular diseases affect respiratory ventilation?
Neuromuscular diseases like myasthenia gravis and poliomyelitis can weaken or paralyze the respiratory muscles, reducing ventilation efficiency. This leads to diminished air exchange, impaired cough reflex, and increased risk of respiratory infections.
What is ventilation, and how is it facilitated in the human body?
Ventilation, or breathing, involves the bulk flow exchange of air between the atmosphere and the alveoli. It requires movement of the lungs in association with the thoracic cage. The lungs, encased in fluid-filled pleural sacs, adhere to the thoracic cage due to cohesive forces in the intrapleural fluid. This adhesion allows the lungs to move with the thoracic expansions and contractions during breathing.
What creates subatmospheric intrapleural pressure, and what is its significance?
Subatmospheric intrapleural pressure is created during fetal development when the thoracic cage grows more rapidly than the lungs, stretching the lungs to conform to the thoracic volume. This pressure, typically around -3 mm Hg, is crucial as it helps the lungs to adhere tightly to the thoracic wall, facilitating their expansion during inspiration.
What is pneumothorax, and how can it affect lung function?
Pneumothorax occurs when air enters the pleural cavity due to trauma or spontaneous events like a ruptured congenital bleb. This disrupts the fluid bond between the lung and chest wall, causing the lung to collapse (like a deflated balloon) and fail to function properly. Treatment involves removing air from the pleural cavity and sealing any openings
How does intrapleural pressure change throughout the respiratory cycle?
Intrapleural pressure starts around -3 mm Hg and becomes more negative during inspiration (down to -6 mm Hg or lower during deep breaths) as the lungs expand against the elastic recoil. During expiration, as the lungs recoil to a resting state, the pressure returns to approximately -3 mm Hg, maintaining a subatmospheric level to keep the lungs inflated.
How does the syringe analogy explain the mechanics of intrapleural pressure?
A syringe filled with water and sealed can mimic the thoracic cavity’s mechanics. Pulling the plunger (like the diaphragm during inspiration) creates a negative pressure that resists further pulling, similar to lung expansion against elastic recoil. Releasing the plunger mimics expiration, showing how lung volume and pressure return to baseline.
How much energy does the body normally use for quiet breathing, and how does this change during exercise?
Normally, about 3–5% of the body’s total energy expenditure is dedicated to quiet breathing. This percentage increases substantially during exercise, reflecting the greater demand for oxygen and the increased effort required to move larger volumes of air.
What are the two main factors that influence the work required for breathing?
The work of breathing is primarily influenced by the stretchability (compliance) of the lungs and the resistance of the airways to airflow. These factors determine how much force the respiratory muscles need to exert during the breathing process.
What is lung compliance, and how is it clinically relevant?
Lung compliance measures the ease with which the lungs can be expanded, calculated as the change in lung volume (∆V) per unit of pressure change (∆P). High compliance indicates that the lungs stretch easily, requiring less force to expand. Low compliance, conversely, means the lungs are stiff and more force is needed for expansion. Compliance is critical in diagnosing and managing respiratory conditions.
What is elastance, and how does it affect expiration?
Elastance is the ability of the lungs to resist deformation and return to their original shape after being stretched. It’s the reciprocal of compliance. High elastance means the lung effectively returns to its resting state after expansion, aiding passive expiration. Low elastance, as seen in conditions like emphysema, results in ineffective passive expiration, requiring active effort to expel air.
How does emphysema affect lung compliance and elastance?
Emphysema destroys the elastin fibers in lung tissue, leading to high compliance (easy to stretch lungs) but low elastance (poor recoil). This alteration means that although lungs can inflate easily, they don’t effectively recoil during expiration. Patients often need to actively use their expiratory muscles to force air out, similar to squeezing air out of an inflated plastic bag.
What role does surface tension play in the mechanics of lung expansion?
Surface tension in the lungs is created by the thin fluid layer between alveolar cells and the air, and contributes significantly to the resistance to lung stretch. It acts like a thin membrane being stretched at the air-fluid interface, increasing the work needed to expand the lungs.
How does the law of LaPlace relate to alveolar pressure?
The law of LaPlace describes how the pressure inside a fluid-lined sphere (like an alveolus) is influenced by surface tension and radius, with the equation
𝑃 = 2𝑇 / 𝑟 . It predicts that smaller alveoli would have higher inward pressure and thus require more force to expand, compared to larger alveoli, if all else is equal.
