In the first-year class, Unit 13 on Gaseous Exchange Notes is a pivotal topic within the field of biology and physiology. This unit delves into the intricate mechanisms by which living organisms, including humans, exchange vital gases such as oxygen and carbon dioxide with their environment. Students explore the anatomy and physiology of the respiratory system, from the upper airways to the microscopic alveoli, gaining insights into the crucial role played by these structures in oxygen uptake and carbon dioxide elimination.
Additionally, the unit explores the physiological principles governing respiration, including gas diffusion, the role of hemoglobin in oxygen transport, and the control mechanisms regulating breathing. Understanding these fundamentals is essential not only for academic knowledge but also for appreciating the profound importance of efficient gaseous exchange in sustaining life and overall health.
Short Questions Notes from Unit 13 Gaseous Exchange of 1st Year Biology
What are the two levels at which respiration occurs in living organisms?
Respiration occurs at two levels: organismic and cellular.
What is the primary function of cellular respiration in organisms?
Cellular respiration is directly involved in the production of energy necessary for all living activities.
Why is air considered a better respiratory medium than water for organisms?
Air is considered a better respiratory medium than water because it has a higher oxygen content per liter and oxygen diffuses about 8000 times more quickly in air than in water.
Where does gaseous exchange take place in plants?
Gaseous exchange in plants primarily occurs through stomata in leaves and lenticels in older stems.
- 1st Year Biology Unit No.1 Introduction Notes
- 1st Year Biology Unit No. 2 Biological Molecules Notes
- 1st Year Biology Unit No. 3 Enzymes Notes
- 1st Year Biology Unit No. 4 The Cell Notes
- 1st Year Biology Unit No. 5 Variety of Life Notes
What is photorespiration, and how does it affect plant growth?
Photorespiration is a process in plants during which oxygen is absorbed and carbon dioxide is released. It reduces the overall rate of carbon dioxide fixation and plant growth because it competes with the Calvin cycle, where carbon dioxide is normally fixed into carbohydrates.
Why does photorespiration exist in plants, even though it appears to hinder photosynthesis?
Photorespiration exists because the active site of rubisco, an essential enzyme in photosynthesis, can bind both carbon dioxide and oxygen. Originally, when there was little oxygen in the atmosphere, this was not a problem. However, as the quantity of oxygen increased, photorespiration became more prevalent.
What are the properties of respiratory surfaces in animals?
The properties of respiratory surfaces in animals include large surface area with moisture, thin epithelium for short diffusion distance, ventilation to maintain a diffusion gradient, and an extensive capillary network for rapid gas exchange.
How does gas exchange occur in Hydra?
In Hydra, gas exchange occurs through the entire general surface in contact with water, including the cells lining the digestive cavity. There are no specialized respiratory organs in Hydra.
How does gas exchange take place in Earthworms?
Gas exchange in Earthworms primarily occurs through their skin, which is richly supplied with blood capillaries and kept moist by mucous gland secretions and coelomic fluid. Oxygen dissolves on the wet skin surface and enters the bloodstream, where it combines with hemoglobin. Carbon dioxide is removed from tissues and transported to the skin for excretion. Earthworms lack specialized respiratory organs as well.
What is the specialized respiratory system of a cockroach composed of?
The respiratory system of a cockroach consists of branching systems of air tubules called tracheae lined by chitin.
How do cockroaches exchange gases with their environment?
Gaseous exchange in cockroaches occurs through tiny tubules called tracheoles, which are filled with fluid. Oxygen dissolves in this fluid and is directly supplied to the living cells. A concentration gradient allows oxygen to diffuse into the trachea from outside air.
How do cockroaches control the movement of air for respiration?
Cockroaches use the expansion and contraction of their abdominal muscles (dorsoventral muscles) to pump air in and out of the tracheae. When the abdomen expands, the first four pairs of spiracles open to allow air in, and when the abdomen contracts, the anterior four pairs of spiracles close, forcing air through the tubes and out of the body.
What role does blood play in cockroach respiration?
Blood is not involved in the transport of gases during cockroach respiration. Gaseous exchange occurs directly between the tissue cells and the air in the tracheoles.
Where are the spiracles located on a cockroach’s body?
Cockroaches have 10 pairs of spiracles, with two pairs located in the thorax and the remaining eight pairs in each of the eight abdominal segments.
How does the respiratory system of fish differ from that of cockroaches?
Fish respire through gills, which are paired structures located on either side of the body, near the junction of the head and trunk. Gills have a large surface area for gaseous exchange and are ventilated by a constant flow of water.
How does the blood flow in the circulatory system of fish during respiration?
In fish, oxygenated blood is pumped from the gills to all parts of the body by the heart. Deoxygenated blood from different parts of the body is received by the heart, creating a single circuit with blood flowing in one direction.
How does water play a role in fish respiration?
Water enters through the fish’s mouth, passes over the gills, and then exits the body through the gill openings, providing a constant flow of oxygen for gaseous exchange in the gills.
How does gaseous exchange occur in frogs?
Gaseous exchange in frogs occurs through the lungs, skin, and buccal chamber, which are richly supplied with blood vessels. Cutaneous respiration refers to gaseous exchange through the skin, while pulmonary respiration occurs through the lungs.
What is the process of inhalation in frogs?
During inhalation in frogs, air enters through the nostrils when they are open. The mouth remains closed. The floor of the buccal cavity is raised, pushing air into the lungs.
What is the term for the intake of air in frogs?
The intake of air in frogs is known as inhalation or inspiration.
Describe the process of exhalation in frogs.
Exhalation in frogs occurs in the reverse order of inspiration. The consumed air, after gaseous exchange, moves out of the lungs through the nostrils. This is called exhalation or expiration.
Where is the main site for gaseous exchange in frog lungs?
The main site for gaseous exchange in frog lungs is the thin-walled air chambers that increase the inner surface of the lungs. These chambers are richly supplied with capillaries.
What is the respiratory system like in birds?
The respiratory system in birds is highly efficient and elaborate due to their high metabolic rate. It involves a one-way flow of air through the lungs, constant air renewal, and the presence of parabronchi instead of alveoli.
What are parabronchi, and where is gaseous exchange facilitated in birds?
Parabronchi are tiny, thin-walled ducts in bird lungs that facilitate gaseous exchange. The walls of parabronchi are the chief sites for gaseous exchange.
How does the direction of blood flow in bird lungs differ from the air flow through parabronchi?
In bird lungs, the direction of blood flow is opposite to that of the air flow through parabronchi, creating a counter-current exchange mechanism that enhances oxygen absorption.
What role do air sacs play in bird respiration?
Air sacs in birds act as bellows and reach all parts of the body, even penetrating some bones. They help in ventilation and send air into the parabronchi for gaseous exchange.
How many air sacs do most birds have, and how do they inlate?
Most birds have nine air sacs, which become inflated by air at atmospheric pressure when the rib articulations are rotated forward and upward.
What are the components of the respiratory system in humans?
The respiratory system in humans includes lungs and air passages.
List the different air passage ways in the human respiratory system.
The air passage ways consist of nostrils, nasal cavities, pharynx, larynx, trachea, bronchi, bronchioles, and alveolar ducts.
How does air become prepared for respiration while passing through the nasal cavity?
Air becomes moist, warm, and filtered of smaller foreign particles by the mucous membrane in the nasal cavity.
What is the function of the epiglottis in the larynx?
The epiglottis serves as a lid that covers the opening of the larynx during swallowing to prevent the entry of food or liquids into the larynx.
What are the structures that help in voice production in the larynx?
Vocal cords, thin-edged fibrous bands in the glottis, help in voice production when vibrated by air.
What prevents the trachea from collapsing and keeps the air passage open?
C-shaped cartilage rings in the wall of the trachea prevent it from collapsing.
What is the functional unit of the lungs?
The functional unit of the lungs is the air-sac, which consists of several microscopic single-layered structures called alveoli.
What is the role of the diaphragm in the respiratory system?
The diaphragm, a muscular sheet, plays a crucial role in breathing by contracting and relaxing to change the volume of the chest cavity.
How many phases are involved in the breathing process?
The breathing process consists of two phases: inspiration (inhalation) and expiration (exhalation).
What is the rhythmic frequency of breathing during rest in humans?
During rest, breathing occurs rhythmically at a frequency of 15 to 20 times per minute in humans.
How does inspiration increase the space inside the chest cavity, and what are the two main factors contributing to it?
Inspiration increases the space inside the chest cavity by elevating the ribs upwards and forwards through the contraction of rib muscles, and by making the diaphragm less domelike through the contraction of diaphragm muscles.
What causes the expansion of the lungs during inspiration, and what is the resulting effect on pressure?
The expansion of the lungs during inspiration is caused by the increase in the chest cavity’s size. This expansion reduces the pressure within the lungs. When the pressure decreases in the lungs, air rushes in from the outside due to higher atmospheric pressure, resulting in inspiration.
How does expiration differ from inspiration in terms of muscle activity and chest cavity size?
During expiration, the muscles of the ribs are relaxed, causing the ribs to move downward and inward. Simultaneously, the diaphragm muscles relax, making the diaphragm more domelike. This reduction in chest cavity space exerts pressure on the lungs, causing air to move out of the lungs, which is known as expiration.
What is the primary cause of respiratory distress syndrome in premature infants, and how does it relate to surfactant production?
Respiratory distress syndrome in premature infants is primarily caused by insufficient surfactant production. Surfactant is a mixture of lipoprotein molecules that reduce the surface tension within the alveoli. In premature infants, there may not be enough surfactant produced, which increases the tendency of the lungs to collapse, leading to respiratory distress.
What factors facilitate the intake of oxygen and release of carbon dioxide by blood in the capillaries of alveoli during respiration?
Several factors facilitate the intake of oxygen and release of carbon dioxide by blood in the capillaries of alveoli during respiration:
- Diffusion driven by differences in partial pressures of oxygen and carbon dioxide.
- The presence of a rich network of capillaries surrounding the alveoli, exposing the blood to a large alveolar surface.
- The separation of blood in the lungs from alveolar air by extremely thin membranes of capillaries and alveoli.
What is the respiratory pigment in human beings?
The respiratory pigment in human beings is hemoglobin, which is contained in red blood corpuscles.
What is formed when hemoglobin combines with oxygen?
Hemoglobin readily combines with oxygen to form bright red oxyhemoglobin.
Under what conditions does oxyhemoglobin split into normal purple-red colored hemoglobin and oxygen?
Oxyhemoglobin splits into normal purple-red colored hemoglobin and oxygen in conditions of low oxygen concentration and less pressure, facilitated by the carbonic anhydrase enzyme present in red blood cells.
What is the maximum amount of oxygen that normal human blood can absorb at sea level?
Normal human blood can absorb about 20 ml of oxygen per 100 ml of blood at sea level, which is its maximum capacity for oxygen when fully oxygenated.
At what oxygen tension is hemoglobin 98 percent saturated in the lungs?
Hemoglobin is 98 percent saturated when the oxygen tension is 115 mm mercury in the lungs.
How does the capacity of hemoglobin to combine with oxygen change with an increase in carbon dioxide pressure?
An increase in carbon dioxide pressure decreases the capacity of hemoglobin to hold oxygen, favoring the greater liberation of oxygen from the blood to the tissue.
What happens to the oxygen-carrying capacity of blood when there is a rise in temperature?
A rise in temperature causes a decrease in the oxygen-carrying capacity of blood, such as during increased muscular activity.
How does pH affect the binding of oxygen to hemoglobin?
Decreased pH (acidic conditions) results in a decrease in the ability of hemoglobin to bind oxygen, while increased pH (alkaline conditions) increases the ability of hemoglobin to bind oxygen.
How is carbon dioxide transported in the blood?
Carbon dioxide is transported in the blood in several different states, including as carboxyhemoglobin, carried by other plasma proteins, and as bicarbonate ion combined with sodium.
What is the role of carbonic anhydrase in carbon dioxide transport?
Carbonic anhydrase facilitates the conversion of carbon dioxide and water into carbonic acid, which then splits into hydrogen ions and bicarbonate ions in the blood.
How is most of the carbon dioxide carried in the blood when it leaves the capillary bed?
Most of the carbon dioxide is carried as bicarbonate ions when blood leaves the capillary bed.
What is the difference in carbon dioxide concentration between arterial and venous blood?
Arterial blood contains about 50 ml of carbon dioxide per 100 ml of blood, while venous blood has 54 ml of carbon dioxide per 100 ml of blood.
What is lung cancer, and what is one of its primary causes?
Lung cancer is a malignant tumor that can develop in the respiratory system, primarily in the lungs. Smoking, especially in young adults, is one of the main causes of lung cancer.
What percentage of lung cancer cases is estimated to be caused by smoking?
It is estimated that 90% of lung cancer cases are caused by smoking.
What bacterium is responsible for tuberculosis, and how does it affect the respiratory system?
Mycobacterium tuberculosis is responsible for tuberculosis. It damages the inside of the lungs, leading to symptoms such as cough and fever.
What conditions can facilitate the growth of Mycobacterium tuberculosis in the respiratory system?
Malnutrition and poor living conditions can facilitate the growth of Mycobacterium tuberculosis in the lungs.
What is asthma, and what are some common triggers for asthma attacks?
Asthma is a respiratory disease characterized by severe episodes of difficult breathing. Common triggers for asthma attacks include pollen, spores, cold air, humidity, and pollution.
How does asthma affect the bronchiole tubes, and what causes the symptoms of asthma?
Asthma causes spasmodic contraction of small bronchiole tubes, leading to difficulty in breathing. Inflammatory chemicals like histamines are released, contributing to bronchiole constriction.
What is emphysema, and why is it more common among smokers?
Emphysema is a breakdown of the alveoli in the lungs. It is more common among smokers because the substances in tobacco smoke weaken the alveolar walls, reducing lung function.
What happens to the alveolar sacs in patients with emphysema?
In patients with emphysema, alveolar walls degenerate, and small alveoli combine to form larger alveoli. This results in fewer alveoli with increased volume but decreased surface area, leading to impaired gas exchange.
What is the role of respiratory pigments like hemoglobin and myoglobin in the blood?
Respiratory pigments like hemoglobin increase the blood’s oxygen-carrying capacity. Hemoglobin, found in many animals, including humans, can increase oxygen carrying capacity by about 75 times. Myoglobin, present in muscle fibers, serves as an intermediate compound for oxygen transfer and storage in muscles.
How does myoglobin differ from hemoglobin in terms of its affinity for oxygen?
Myoglobin has a higher affinity for oxygen compared to hemoglobin, allowing it to combine with oxygen more readily.
How long can aquatic mammals, especially cetaceans, stay submerged in the ocean without coming up for air?
They can stay submerged for about two hours.
What is the significance of the volume of blood in diving mammals compared to non-divers?
Diving mammals have almost twice the volume of blood in relation to their body weight as compared to non-divers.
What is the role of myoglobin in diving mammals’ muscles?
Myoglobin binds extra oxygen in the muscles of diving mammals.
What happens to a mammal’s body when it reaches its diving limit?
The diving reflex is activated, which includes the cessation of breathing, a significant slowdown in heart rate (to one-tenth of the normal rate), reduced oxygen and energy consumption, and redistribution of blood flow.
Which parts of the body receive the most blood during a dive, and why?
Most of the blood goes to the brain and heart because these organs can least withstand anoxia (lack of oxygen).
Why do skin, muscles, digestive organs, and other internal organs receive very little blood when an animal is submerged?
These areas can survive with less oxygen.
What type of respiration do muscles shift to during a dive?
Muscles shift from aerobic to anaerobic respiration.
What is the total lung capacity in an adult human when fully inflated?
The total lung capacity in an adult human when fully inflated is about 5 litres.
How much air is exchanged during normal breathing when at rest or asleep?
During rest or sleep, the exchange of air is about half a litre.
What volume of air is typically taken inside the lungs and expelled during exercise?
During exercise, the volume of air taken inside the lungs and expelled is about 3.5 litres.
What is the residual volume of air in the lungs even during exercise?
There is a residual volume of 1.5 litres in the lungs even during exercise that cannot be expelled.
How many times per minute do adults normally inhale and exhale at rest?
Adults normally inhale and exhale 15-20 times per minute at rest.
What can happen to the breathing rate during exercise?
During exercise, the breathing rate may rise to 30 times per minute.
Why is deep and fast breathing important during exercise?
Deep and fast breathing during exercise allows more oxygen to dissolve in the blood and be supplied to the active muscles, while also removing extra carbon dioxide produced by the muscles.
How long can aquatic mammals, like cetaceans, stay submerged in the ocean without coming up for air?
Aquatic mammals, especially cetaceans, can stay submerged in the ocean for about two hours without coming up for air.
What physiological changes occur when a diving mammal reaches its limit while diving?
When a diving mammal reaches its limit, the diving reflex is activated, causing the breathing to stop, the heart rate to slow down, and a redistribution of blood flow to prioritize the brain and heart. Muscles shift from aerobic to anaerobic respiration, reducing oxygen consumption and energy usage.
How does breathing differ from respiration?
Breathing differs from respiration in that breathing is the physical process of inhaling and exhaling air, while respiration is the chemical process that occurs within cells to produce energy (in the form of ATP) by using oxygen and generating carbon dioxide as a waste product.
How much carbon dioxide is present in venous and arterial blood?
The amount of carbon dioxide present in venous blood is higher than in arterial blood. In venous blood, the carbon dioxide concentration is typically around 45 mmHg (millimeters of mercury), whereas in arterial blood, it is around 40 mmHg.
How does air always remain in the lungs of human beings?
Air always remains in the lungs of human beings due to the presence of a thin layer of mucus that lines the respiratory passages. This mucus helps trap and humidify the air, ensuring that the lungs stay moist and that the airways do not collapse.
What are the products which are produced during photorespiration?
During photorespiration in plants, the primary products produced are glycolate and ammonium ions. This process occurs when oxygen competes with carbon dioxide for the active site of the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) in the Calvin cycle, leading to the formation of glycolate instead of glucose.
How much denser is a water medium than air medium for exchange of respiratory
gases?
Water is approximately 800 times denser than air, which can significantly impact the exchange of respiratory gases, making it more challenging for organisms to extract oxygen from water compared to air.
Long Questions Notes from Unit 13 Gaseous Exchange of 1st Year Biology
Question: In what ways is air a better respiratory medium than water?
Air is a better respiratory medium than water for many terrestrial animals, including humans, for several reasons:
Oxygen Availability: The concentration of oxygen (O2) in air is much higher than in water. Oxygen is essential for aerobic respiration, the process by which cells generate energy. This higher oxygen content in air makes it more efficient for animals to extract oxygen for respiration.
Reduced Buoyancy: In water, the buoyant force makes it more difficult for organisms to move and stay in one place. In contrast, air provides less buoyant force, allowing organisms to move more freely and easily.
Energetic Efficiency: Extracting oxygen from water requires more energy than extracting it from air. This is because water molecules are denser and contain fewer oxygen molecules per unit volume compared to air. Therefore, organisms would need to expend more energy to extract the same amount of oxygen from water.
Water Loss: Air does not cause water loss through respiration, which is important for terrestrial animals that need to conserve water. In contrast, aquatic organisms can lose water through their respiratory surfaces due to the constant contact with water.
Gas Exchange: Air-breathing organisms typically have specialized respiratory structures like lungs or gills that are more efficient at gas exchange in air. These structures are adapted to maximize the diffusion of gases like oxygen and carbon dioxide between the respiratory surface and the surrounding medium.
Question: What is photorespiration? Give its consequences.
Photorespiration is a metabolic process that occurs in plants, especially in C3 plants (plants that initially fix carbon dioxide into a three-carbon compound during photosynthesis). It is a side reaction that can occur when the concentration of carbon dioxide (CO2) is low and the concentration of oxygen (O2) is high in the leaf cells.
Consequences of photorespiration include
Energy Waste: Photorespiration consumes energy in the form of ATP (adenosine triphosphate) and reduces the efficiency of photosynthesis. Instead of producing sugars, which are the primary products of photosynthesis, photorespiration leads to the release of CO2 and consumes ATP.
Reduced Carbon Fixation: Photorespiration competes with the Calvin cycle, the primary pathway for carbon fixation during photosynthesis. When photorespiration occurs, less carbon dioxide is fixed into organic molecules, reducing the plant’s ability to produce carbohydrates.
Oxygen Toxicity: High oxygen concentrations within plant cells, as can occur during photorespiration, can lead to the formation of harmful reactive oxygen species (ROS). ROS can damage cellular components and lead to oxidative stress.
Reduced Plant Growth: Overall, photorespiration reduces the efficiency of photosynthesis and limits plant growth and productivity, particularly in conditions where CO2 levels are low or O2 levels are high, such as hot and dry environments.
Question: Describe briefly the properties of respiratory surfaces in cockroach.
In cockroaches, respiratory surfaces are specialized structures that facilitate gas exchange, allowing them to breathe and obtain oxygen while expelling carbon dioxide. These respiratory surfaces have several unique properties:
Tracheal System: Cockroaches have a network of tiny tubes called tracheae that extend throughout their body. These tracheae branch into smaller tracheoles, which are in direct contact with cells, ensuring efficient gas exchange.
Spiracles: Small openings called spiracles are distributed along the sides of the cockroach’s body, usually one pair in each abdominal segment. These spiracles serve as entry and exit points for air to enter and leave the tracheal system.
Moisture Requirement: The inner lining of the tracheae must remain moist for effective gas exchange. This moisture prevents the tracheae from drying out, ensuring that oxygen can dissolve in the liquid film and diffuse into the cells while allowing carbon dioxide to diffuse out.
Limitations: Cockroaches rely on passive diffusion for gas exchange, which limits the rate of exchange. They do not possess specialized respiratory organs like lungs or gills, which are more efficient at extracting oxygen from the environment.
Adaptation to Terrestrial Life: Cockroaches are adapted to terrestrial environments, and their respiratory system is designed to conserve water. By having a closed tracheal system with spiracles that can be tightly sealed, they can reduce water loss through respiration.
Question: In what ways is respiration in birds the most eicient and elaborate?
Respiration in birds is highly efficient and elaborate, adapted to meet the high oxygen demands required for their energy-intensive activities, such as flying. Here are several ways in which avian respiration is particularly efficient and elaborate:
Unidirectional airflow: Birds have a unique respiratory system that allows for a unidirectional flow of air through their lungs. Air enters the respiratory system through the trachea and then flows into a network of air sacs before reaching the lungs. This unidirectional flow ensures that fresh, oxygen-rich air is constantly supplied to the gas exchange surfaces in the lungs, maximizing oxygen uptake and carbon dioxide removal.
Air sacs: Birds have a system of air sacs that serve as bellows, allowing for a continuous flow of air through the lungs. These air sacs act as reservoirs for air, ensuring a constant supply of oxygen to the blood during both inhalation and exhalation. The two cycles of inhalation and exhalation (tidal breathing) in mammals are separated into four cycles in birds due to the presence of these air sacs.
Crosscurrent exchange: The avian lung has a highly efficient crosscurrent exchange system. Oxygenated air in the posterior air sacs flows in a direction opposite to the flow of deoxygenated blood in the lung capillaries. This counterflow arrangement ensures a steep concentration gradient for oxygen, facilitating efficient oxygen diffusion into the bloodstream.
High metabolic rate: Birds have a high metabolic rate, and their respiratory system is adapted to meet this demand. The efficient gas exchange mechanisms in their lungs allow for rapid oxygen uptake and carbon dioxide removal, supporting the energy requirements of flight and other strenuous activities.
Thin-walled, parabronchial tubes: Avian lungs are composed of numerous thin-walled, tubular structures called parabronchi. These parabronchi are highly vascularized and provide a large surface area for gas exchange. This design allows for efficient diffusion of gases across the respiratory membranes.
Air sacs for buoyancy: In addition to their role in respiration, air sacs also help birds control buoyancy. By adjusting the volume of air in the sacs, birds can alter their overall body density, making it easier for them to maintain stable flight.
Reduced dead space: The avian respiratory system minimizes dead space, which is the volume of air that remains in the respiratory system and does not participate in gas exchange. This reduction in dead space ensures that a higher proportion of inspired air is utilized for gas exchange, improving respiratory efficiency.
Question: Discuss the mechanical aspects of breathing in man.
Breathing in humans is a complex process involving various mechanical aspects that ensure the exchange of oxygen and carbon dioxide between the body and the external environment. This process primarily relies on the respiratory system, which includes the lungs, diaphragm, and various muscles and structures. Let’s discuss the mechanical aspects of breathing in detail:
Respiratory Muscles
Diaphragm: The diaphragm is the primary muscle responsible for breathing. It separates the chest (thoracic) cavity from the abdominal cavity. When it contracts, it flattens, increasing the volume of the thoracic cavity and creating a negative pressure that draws air into the lungs during inhalation.
Intercostal Muscles
The intercostal muscles are located between the ribs and are divided into external and internal muscles. They assist in expanding and contracting the ribcage during breathing.
Inhalation:
When you inhale, the diaphragm contracts and moves downward, while the external intercostal muscles contract, lifting the ribcage up and outward.
This expansion of the thoracic cavity increases its volume, which leads to a decrease in air pressure inside the lungs. As a result of this pressure difference, air is drawn into the lungs through the nose or mouth.
Exhalation
Exhalation is typically a passive process during rest. When the diaphragm and external intercostal muscles relax, the chest cavity’s volume decreases.
This reduction in thoracic cavity volume increases the air pressure inside the lungs, causing air to be pushed out.
During forceful exhalation, such as during exercise or coughing, the internal intercostal muscles and abdominal muscles can contract to further decrease the thoracic cavity’s volume, expelling air more rapidly.
Lung Elasticity
The lungs themselves play a crucial role in breathing mechanics. They are elastic and tend to recoil to their smaller size when not actively filled with air. This natural elasticity assists in passive exhalation as the lungs return to their resting state.
Compliance and Resistance
Lung compliance refers to how easily the lungs can expand when subjected to pressure changes. High compliance means the lungs are easy to expand, while low compliance indicates resistance to expansion.
Airway resistance can also impact breathing. Diseases like asthma or chronic obstructive pulmonary disease (COPD) can increase resistance, making it more difficult to inhale and exhale.
Surfactant
Surfactant is a substance produced by the alveoli (tiny air sacs in the lungs) that reduces surface tension within the alveoli. This helps prevent the alveoli from collapsing during exhalation, making it easier to breathe.
Thoracic Cage
The thoracic cage, comprised of the ribs and sternum, provides structural support to the chest cavity. Its flexibility allows for the expansion and contraction necessary for breathing.
Nervous Control
The process of breathing is also controlled by the nervous system. The medulla oblongata in the brainstem plays a central role in regulating the rhythm and depth of breathing. It sends signals to the respiratory muscles to control the rate of inhalation and exhalation based on the body’s needs, such as increased breathing during exercise.
Question: Write a detailed note on respiratory pigments.
Respiratory pigments are specialized molecules found in various organisms, including humans and animals, that play a crucial role in transporting oxygen from the respiratory organs to the tissues where it is needed for metabolic processes. These pigments are essential for efficient oxygen uptake and delivery, as they significantly enhance the oxygen-carrying capacity of blood and other bodily fluids. In this detailed note, we will explore the types, functions, and characteristics of some of the most well-known respiratory pigments.
Hemoglobin (Hb)
Structure: Hemoglobin is the most well-known and extensively studied respiratory pigment in humans and many other vertebrates. It consists of four subunits: two alpha chains and two beta chains. Each subunit contains a heme group, which is a complex molecule consisting of an iron atom (Fe2+) bound to a porphyrin ring.
Function: Hemoglobin binds with oxygen in the lungs, forming oxyhemoglobin. This reversible binding allows Hb to pick up oxygen efficiently in areas of high oxygen concentration (the lungs) and release it where it is needed in tissues with lower oxygen levels.
Characteristics: Hemoglobin gives blood its red color when oxygenated, and it turns dark red when deoxygenated. The iron in heme is critical for oxygen binding. Carbon monoxide (CO) can also bind to hemoglobin, but with a much higher affinity than oxygen, which can lead to carbon monoxide poisoning.
Myoglobin (Mb)
Structure: Myoglobin is a monomeric protein found in muscle tissues, particularly skeletal and cardiac muscles. It also contains a heme group similar to that in hemoglobin.
Function: Myoglobin’s primary role is to store oxygen within muscle cells. It has a higher affinity for oxygen than hemoglobin, which enables it to efficiently extract oxygen from hemoglobin when needed during muscle contraction.
Characteristics: Myoglobin is responsible for the reddish-brown color of muscle tissue. It can also serve as an oxygen reserve, providing oxygen to muscle cells when demand increases during strenuous physical activity.
Occurrence: Myoglobin is found in muscles of vertebrates, particularly in skeletal and cardiac muscle.
Hemocyanin
Occurrence: Hemocyanin is found in mollusks (like snails and octopuses) and some arthropods (like horseshoe crabs) as well as certain crustaceans and some spiders.
Structure: Hemocyanin contains copper ions (Cu2+) instead of iron and exists as large, multi-subunit complexes. When oxygen binds to it, it turns blue, which gives the blood of some organisms a blue color.
Function: Hemocyanin plays a role in oxygen transport in invertebrates. It becomes oxygenated when it contacts oxygen-rich environments and releases oxygen as it encounters tissues with lower oxygen levels.
Hemerythrin
Occurrence: Hemerythrin is found in some marine invertebrates like certain annelids, brachiopods, and priapulids.
Structure: Hemerythrin contains iron ions (Fe2+) and has a pinkish color when oxygenated.
Function: Hemerythrin functions as an oxygen carrier and is particularly effective in low-oxygen environments, such as marine sediments. It reversibly binds and releases oxygen as needed.
Significance of Respiratory Pigments
Efficient Oxygen Transport: Respiratory pigments increase the oxygen-carrying capacity of the blood, allowing organisms to meet their oxygen demands, especially in larger and more complex animals.
Adaptation to Environmental Conditions: Different respiratory pigments are adapted to varying oxygen levels. For example, hemocyanin and hemerythrin are suited for low-oxygen environments, while hemoglobin is more efficient in oxygen-rich environments.
Temperature Regulation: In some cold-blooded animals, like fish and reptiles, changes in the oxygen-binding properties of hemoglobin can help regulate body temperature by adjusting the rate of oxygen release in response to temperature changes.
Muscle Oxygen Storage: Myoglobin stores oxygen in muscles, helping organisms endure periods of high physical activity or oxygen deprivation.
Question: List the air passage way in sequence from nostrils to alveoli. Describe the structure of alveolus in detail.
The air passage from the nostrils to the alveoli can be described in sequence, starting from the external nostrils and ending at the microscopic alveoli within the lungs. Here is a step-by-step description of the airway passages:
Nostrils (Nasal Cavities)
The journey begins as air is inhaled through the nostrils, also known as the external nares.
The nostrils lead into the nasal cavities, which are lined with mucous membranes.
The nasal cavities are separated by a nasal septum and contain structures like conchae, which help humidify, filter, and warm the incoming air.
Pharynx
From the nasal cavities, the air passes into the pharynx, a common passageway for both air and food. The pharynx is divided into three sections: the nasopharynx (connected to the nasal cavities), the oropharynx (connected to the mouth), and the laryngopharynx (leading to the larynx and esophagus).
Larynx
The airway then enters the larynx, commonly known as the voice box.
The larynx contains vocal cords and plays a crucial role in speech production and preventing food or foreign objects from entering the trachea.
Trachea (Windpipe)
Below the larynx, the airway becomes the trachea, a tube reinforced with C-shaped cartilage rings to keep it open. The trachea serves as the main passage for air as it travels down into the chest.
Bronchi
The trachea branches into two bronchi, one for each lung (right and left bronchus).
The bronchi further divide into smaller bronchioles, which continue to branch out and get progressively smaller.
Bronchioles
The bronchioles are smaller airways within the lungs that lack cartilage support.
They are lined with smooth muscle, which can contract or relax to control the flow of air to different parts of the lungs.
Alveoli
- The bronchioles eventually lead to the alveoli, which are the tiny air sacs where gas exchange occurs.
- Alveoli are the functional units of the respiratory system and are surrounded by a network of capillaries.
- These microscopic structures have a thin, single-layered epithelium that allows for efficient gas exchange between the lungs and the bloodstream.
Now, let’s describe the structure of an alveolus in detail:
Structure of Alveolus
Alveoli are small, balloon-like structures located at the distal ends of the respiratory bronchioles within the lungs.
Each lung contains millions of alveoli, providing a vast surface area for gas exchange.
Key structural features of an alveolus;
Epithelial Cells
Alveoli are lined with a thin layer of epithelial cells, primarily consisting of two main types: type I and type II alveolar cells.
Type I Alveolar Cells
These are squamous epithelial cells that form a delicate, single-cell-thick lining of the alveolus.
Type I cells are responsible for the majority of gas exchange, as their thin structure allows oxygen and carbon dioxide to pass easily between the alveolus and the adjacent capillaries.
Type II Alveolar Cells
These cuboidal cells secrete a surfactant, a fluid that coats the inner surface of the alveoli.
Surfactant reduces surface tension within the alveoli, preventing their collapse during exhalation and facilitating lung expansion during inhalation.
Capillaries
Alveoli are surrounded by an extensive network of tiny blood vessels called capillaries.
Capillaries enable the exchange of oxygen from inhaled air into the bloodstream and the removal of carbon dioxide from the bloodstream into the alveoli.
Basement Membrane
Between the alveolar epithelium and the capillaries, there is a thin basement membrane that provides structural support.
Interstitium
Surrounding the alveoli, there is a connective tissue framework known as the interstitium, which helps maintain the alveolar structure.