Samacheer Class 11 Bio Zoology - Respiration

Airway resistance is typically low due to two main reasons. First, the diameter of most airways in the respiratory system is relatively large, which allows air to flow through with minimal resistance according to the principle that resistance is inversely proportional to the fourth power of the radius. Second, although the smaller airways have narrower individual diameters, they are arranged in parallel to one another, which means their combined cross-sectional area becomes very large. This parallel arrangement significantly reduces the total resistance to airflow. Additionally, air has a low viscosity compared to other fluids, which further contributes to the low resistance encountered during breathing and allows for efficient ventilation of the lungs.

• When a person travels from sea level to elevations where the atmospheric pressure and partial pressure of O 2 lowered there is a poor binding of O 2 with haemoglobin leads to acute mountain sickness.
• When the person lives there for a long time the kidney synthesizes the erythropoietin which stimulates the bone marrow to produce more RBCs

Pneumonia is a dangerous disease because it involves inflammation of the lungs due to infection caused by bacteria or viruses. The condition leads to the accumulation of fluid or pus in the alveoli, which are the functional units responsible for gas exchange in the lungs. This accumulation severely impairs the ability to breathe and reduces the efficiency of oxygen uptake into the bloodstream. Patients experience symptoms including sputum production, nasal congestion, shortness of breath, and sore throat. The formation of lung abscesses further compromises respiratory function. If left untreated, pneumonia can lead to respiratory failure and become life-threatening, particularly in young children, elderly individuals, and immunocompromised persons. The severity depends on the causative agent and the extent of lung involvement.

Diffusion of gases occurs specifically in the alveolar region and not in other parts of the respiratory system because the other parts of the respiratory tract, including the nasal cavity, trachea, bronchi, and bronchioles, function primarily to conduct air into the lungs rather than to facilitate gaseous exchange. Real respiration, meaning the actual exchange of oxygen and carbon dioxide between air and blood, takes place only between the alveoli and the blood capillaries surrounding them. The alveolar region is uniquely specialized for this function because the diffusion membrane consists of three thin layers: the thin squamous epithelial cells of the alveoli themselves, the basement substance or basement membrane lying between the epithelium and capillary endothelium, and the endothelium of the alveolar capillaries. These three layers together form an extremely thin barrier that allows gases to diffuse rapidly and efficiently. The thin squamous epithelial cells of the alveoli are particularly important as they provide an enormous surface area for gaseous exchange while maintaining minimal thickness, enabling oxygen to diffuse into the blood and carbon dioxide to diffuse out into the alveolar air for exhalation.

When a person travels quickly from sea level to elevations above 8000 ft, where the atmospheric pressure and partial pressure of oxygen are lowered, the individual responds with symptoms of acute mountain sickness (AMS)- headache, shortness of breath, nausea, and dizziness due to poor binding of O 2 with hemoglobin. When the person moves on a long-term basis to mountains from sea level his body begins to make respiratory and hematopoietic adjustments.
To overcome this situation kidneys accelerate the production of the hormone erythropoietin, which stimulates the bone marrow to produce more RBCs. When a person descends deep into the sea, the pressure in the surrounding water increases which causes the lungs to decrease in volume.
This decrease in volume increases the partial pressure of the gases within the lungs. This effect can be beneficial, because it tends to drive additional oxygen into the circulation, but this benefit also has a risk, the increased pressure can also drive nitrogen gas into the circulation.
This increase in blood nitrogen content can lead to a condition called nitrogen narcosis. When the diver ascends to the surface too quickly a condition called ‘bends’ or decompression sickness occurs and nitrogen comes out of solution while still in the blood-forming bubbles. Small bubbles in the blood are not harmful, but large bubbles can lodge in small capillaries, blocking blood flow or can press on nerve endings.
Decompression sickness is associated with pain in joints and muscles and neurological problems including stroke. The risk of nitrogen narcosis and bends is common in scuba divers. During carbon dioxide poisoning, the demand for oxygen increases. As the 02 level in the blood decreases it leads to suffocation and the skin turns bluish-black.
Part II
11th Bio Zoology Guide Respiration Additional Important Questions and Answers
(1 Mark)
I. Choose The Best Options

Tobacco smoke contains several toxic substances that cause significant harm to human health. The major toxic substances present in tobacco include nicotine, tar, carbon monoxide, ammonia, arsenic, and sulfur dioxide. These substances have multiple ill-effects on the body. Carbon monoxide and nicotine damage the cardiovascular system by reducing oxygen supply to the heart and increasing heart rate and blood pressure. Nicotine stimulates the heart to beat faster and causes narrowing of blood vessels, resulting in elevated blood pressure and increased risk of coronary heart diseases. Tar damages the gaseous exchange system by coating the alveoli and reducing their efficiency in oxygen and carbon dioxide exchange. Smoking is a major risk factor for various cancers, including lung cancer, stomach cancer, pancreatic cancer, and bladder cancer. Additionally, smoking lowers sperm count in men, affecting fertility. The cumulative effects of these toxic substances make smoking a serious threat to respiratory, cardiovascular, and overall health.

• Smoking can cause lung diseases by damaging the airways and alveoli and results in emphysema and chronic bronchitis.
• These two diseases along with asthma are referred to as a chronic obstructive pulmonary disease.
• When a preson smokes 85% of the smoke released is inhaled by the smoker himself and others in the vicinity called passive smokers are also affected indirectly.

• In the alveoli high PO 2 low PCO 3 Low temperature and less H + Concentration favours the formation of oxyhemoglobin wjiere as in the tissues low PO 2 high PCO 2 high H and high-temperature favoures the dissocation of O 2 from oxyhemoglobin.
• A sigmoid curve is obtained when the percentage saturation of haemoglobin with O 2 is plotted against PO 2.
• This S, Shaped curve has a steep slope for PO 2 valuer between 10 and 50 mm Hg and then flattens between 70 and 100 mm Hg.
• Under normal physiological conditions, every 100 ml of oxygenated blood can deliver about 5 ml of O 2 to the tissues.

The partial pressures of oxygen (PO2) and carbon dioxide (PCO2) vary significantly across different locations in the respiratory and circulatory systems. During inspiration, the inspired air contains PO2 of 159 mm Hg and PCO2 of 0.3 mm Hg. During expiration, the expired air has PO2 of 120 mm Hg and PCO2 of 127 mm Hg. In the alveoli, where gas exchange occurs, PO2 is 104 mm Hg and PCO2 is 40 mm Hg. In the pulmonary artery carrying deoxygenated blood from the heart to the lungs, PO2 is 40 mm Hg and PCO2 is 45 mm Hg. In the pulmonary vein returning oxygenated blood from the lungs to the heart, PO2 is 95 mm Hg and PCO2 is 40 mm Hg. Oxygenated blood in the systemic circulation maintains PO2 of 95 mm Hg and PCO2 of 40 mm Hg. Deoxygenated blood returning to the lungs has PO2 of 40 mm Hg and PCO2 of 45 mm Hg. These gradients in partial pressures drive the diffusion of gases across the respiratory membranes and tissues.

The rate of breathing in aquatic animals is faster than that of terrestrial animals because the amount of dissolved oxygen available in water is significantly lower compared to the amount of oxygen present in air. Water contains only about 5 to 10 milliliters of dissolved oxygen per liter, whereas air contains approximately 210 milliliters of oxygen per liter. To obtain sufficient oxygen for their metabolic needs, aquatic animals must ventilate their respiratory surfaces more frequently and move larger volumes of water across their gills or other respiratory organs. This increased ventilation rate compensates for the lower oxygen availability in the aquatic environment. Additionally, the solubility of oxygen in water decreases with increasing temperature, further reducing oxygen availability in warmer aquatic habitats and necessitating even faster breathing rates.

The epiglottis is a thin elastic flap of cartilage located at the junction between the nasopharynx and larynx. Its primary function is to prevent food and liquids from entering the larynx and trachea during swallowing, thereby avoiding choking. When a person swallows, the epiglottis folds downward to cover the entrance to the larynx, directing food and water into the esophagus instead. This protective mechanism is essential for maintaining a patent airway and preventing aspiration of food particles into the respiratory tract. The epiglottis also plays a role in voice production by helping to modulate airflow through the larynx during phonation.

The lungs are protected by the thoracic cavity, which is a rigid bony framework that encloses and shields these delicate organs. The thoracic cavity is bounded dorsally by the vertebral column, which provides structural support and protection to the posterior aspect of the lungs. Ventrally, the sternum or breastbone protects the anterior surface of the lungs and heart. Laterally, the ribs form a cage-like structure that surrounds the lungs and provides additional protection against external trauma. The lower boundary of the thoracic cavity is formed by the dome-shaped diaphragm, a muscular structure that separates the thoracic cavity from the abdominal cavity. The lungs themselves are light and spongy tissues that are enclosed within an air-tight space formed by the pleural membranes. This anatomical arrangement provides comprehensive protection while allowing the lungs to expand and contract during breathing.

Minute respiratory volume is the total amount of air that moves into and out of the respiratory passage per minute during normal breathing. It is calculated by multiplying the tidal volume by the respiratory rate. In a healthy adult, the normal tidal volume is approximately 500 milliliters, and the normal respiratory rate is approximately 12 breaths per minute. Therefore, the minute respiratory volume is calculated as 500 ml multiplied by 12, which equals 6000 milliliters or 6 liters per minute. This value represents the total volume of air ventilated through the lungs in one minute under resting conditions and is an important measure of overall respiratory efficiency and ventilation capacity.

The respiratory surface possesses several characteristic features that make it ideally suited for efficient gas exchange. The surface area of the respiratory surface is large, which maximizes the area available for gas diffusion, and it is richly supplied with blood vessels to facilitate rapid transport of gases. The respiratory surface is extremely thin, typically consisting of a single layer of cells, which reduces the diffusion distance and allows gases to move quickly between the environment and the blood. It is kept moist at all times, as the presence of moisture is essential for gases to dissolve and diffuse across the membrane. The respiratory surface is in direct contact with the environment, whether it be air in terrestrial organisms or water in aquatic organisms, ensuring immediate access to oxygen. Finally, it is permeable to respiratory gases, meaning oxygen can easily diffuse into the blood while carbon dioxide diffuses out, making it an effective barrier for selective gas exchange while remaining impermeable to other substances.

• The surface area must be very large and richly supplied with blood vessels.
• Should be extremely thin and kept moist.
• Should be in direct contact with the environment.
• Should be permeable to the respiratory gases.

• Healthy lungs contain large amounts of elastic connective tissue around the alveoli containing elastin which makes the lung tissue elastic.
• People with emphysema and bronchitis have difficulty in exhaling because the enzyme elastase destroys the elastin around the alveoli and reduces the elasticity of the lungs.

• Allergy is caused by allergens, it may be due to dust, pollens some seafood.
• Allergens provoke an inflammatory response. The allergens affect our respiratory tracts and we immediately start sneezing and coughing.

Snoring is a breathing phenomenon that occurs during sleep and is characterized by a hoarse, rattling sound produced by the vibration of soft tissues in the upper airway. The condition results from a partially closed or narrowed upper airway in the nose and throat region, which restricts the passage of air to the lungs. As air is forced through this narrowed passage during breathing, the surrounding tissues, particularly the soft palate and uvula, vibrate and produce the characteristic snoring sound. The narrowing of the airway can be caused by various factors including relaxation of throat muscles during sleep, anatomical abnormalities such as a deviated septum or enlarged tonsils, obesity, nasal congestion, or sleeping position. Snoring is more common in males and increases with age. While occasional snoring may be harmless, chronic snoring can indicate sleep apnea, a serious condition in which breathing is repeatedly interrupted during sleep, leading to oxygen deprivation and potential health complications.

• The oesophagus and trachea lies in the pharynx During swallowing a thin elastic flap called epiglottis prevent the food from entering in to the larynx.
• If we talk or laugh during swallowing the closing of trachea becomes disturbed and hence the food may enter in to trachea.

• There are more dust and microbes in the air. If we breathe through the mouth there is a possibility of entering these microbes and dust in to the stomach through oesophagus.
• When we breathe through the nose the dust will be filtered by the bristles. The dust particular is trapped by the mucous membrane of the nasal cavity.

• The diffusion membrane of the alveolus is made up of three layers. The thin squamous epithelial cells.
• The endothelium of the alveolar capillaries
• The basement substance found in between them. The thin requamous epithelial cells of alveoli are composed of Type-I and Type-II cells.
• The Type-I cells are very thin so that gases can diffuse rapidly through them. Type-II cells are thicker synthesize and secrete a substance called surfactant.

Dead space refers to the volume of the respiratory system where air is present but gas exchange does not occur. This includes the air-filled passages such as the nose, nasal cavity, pharynx, larynx, trachea, bronchi, and bronchioles. Some of the inspired air never reaches the alveoli, which are the functional units responsible for gas exchange, but instead fills these respiratory passages. The dead space is not involved in gaseous exchange and therefore does not contribute to the uptake of oxygen or the elimination of carbon dioxide. The anatomical dead space amounts to approximately 150 milliliters in an average adult human. This means that during each breath, a portion of the inspired air is wasted in ventilating the dead space rather than participating in gas exchange. The concept of dead space is important in understanding respiratory physiology and the efficiency of ventilation.

• Hemoglobin belongs to the class of conjugated protein.
• The iron-containing pigment portion haem constitutes only 4% and the rest colourless protein of the histone class globin.
• The molecular weight of Hb is 68000
• These four Iron atoms can combine with a molecule of oxygen.

Methaemoglobin is an abnormal form of hemoglobin in which the iron component of the haem group is in the ferric state (Fe³⁺) instead of the normal ferrous state (Fe²⁺). In normal hemoglobin, the iron is in the ferrous state, which allows it to bind reversibly with oxygen molecules to form oxyhemoglobin. However, in methaemoglobin, the iron is oxidized to the ferric state, which prevents the binding of oxygen. Consequently, methaemoglobin cannot carry oxygen and therefore cannot participate in oxygen transport. The presence of methaemoglobin in the blood reduces the oxygen-carrying capacity of hemoglobin and can lead to tissue hypoxia. Methaemoglobin can be formed through exposure to certain chemicals such as nitrites, aniline dyes, and some medications. The body normally maintains methaemoglobin at very low levels through the action of methaemoglobin reductase enzymes. Elevated levels of methaemoglobin can cause a condition called methaemoglobinemia, which results in cyanosis and reduced oxygen delivery to tissues.

Newborn respiratory distress syndrome (NRDS) is a serious condition that affects premature babies who have insufficient levels of surfactant in their alveoli. The synthesis of surfactants begins only after the 25th week of gestation, so infants born before this time have inadequate surfactant production. Without sufficient surfactant, the surface tension in the alveoli remains high, making it extremely difficult for the newborn to inflate the lungs and breathe properly. This leads to respiratory distress, characterized by rapid and labored breathing, and can be life-threatening if not treated promptly. Modern medical interventions include artificial surfactant replacement therapy to help affected infants breathe more easily.

Yawning is a reflex action triggered by the body's need to maintain adequate oxygen levels. When there is a shortage of oxygen in the blood, specialized chemoreceptors in the brain sense this imbalance and send signals to the central nervous system. The CNS then triggers the yawning reflex to correct the oxygen-carbon dioxide imbalance. During a yawn, the mouth opens wide and a deep breath is taken, which allows more air to enter the lungs and increases oxygen intake. This deep inhalation during yawning helps to re-oxygenate the blood and remove accumulated carbon dioxide, thereby restoring the proper balance of respiratory gases in the body. Yawning is also contagious, suggesting it may have social or evolutionary significance beyond its primary physiological function.

Respiration is essential for all living organisms because it provides the energy required for all bodily activities and functions. Every process in the body, from muscle contraction to nerve impulse transmission to biosynthesis, requires energy in the form of ATP. This energy is obtained from the breakdown of food molecules, particularly glucose and other organic compounds. Oxygen is utilized by the cells to oxidize these biomolecules through aerobic respiration, a process that releases large amounts of energy stored in chemical bonds. Without respiration, cells cannot produce sufficient ATP to maintain vital functions such as metabolism, growth, reproduction, and homeostasis. Therefore, respiration is a fundamental life process necessary for the survival and proper functioning of all organisms.

The rate of respiration in aquatic animals is significantly higher than in terrestrial animals because the amount of dissolved oxygen available in water is very low compared to the concentration of oxygen in air. Water contains only about 5-10 milligrams of dissolved oxygen per liter, whereas air contains approximately 210 milligrams of oxygen per liter. To obtain sufficient oxygen for their metabolic needs, aquatic organisms must process much larger volumes of water through their respiratory organs, such as gills, resulting in a much faster breathing rate. This higher respiratory rate is essential for aquatic animals to extract enough dissolved oxygen to meet their energy requirements for survival and activity.

Mucus plays a vital protective role in the respiratory tract. The goblet cells present in the mucous membrane secrete mucus, a slimy material rich in glycoproteins that coats the inner surfaces of the respiratory passages. This mucus layer acts as a defense mechanism by trapping microorganisms, dust particles, and other foreign substances that are inhaled with air. Once trapped in the sticky mucus film, these particles are prevented from reaching the delicate alveoli where gas exchange occurs. The mucus-particle complex is then continuously moved upward by the coordinated beating of cilia lining the respiratory tract, eventually reaching the pharynx where it is swallowed and passes down the gullet into the digestive system. This mucociliary clearance mechanism is an important part of the body's innate immune defense against respiratory infections and pollution.

Dead space refers to the volume of air in the respiratory system that does not participate in gas exchange. Some of the inspired air fills the respiratory passages such as the trachea, bronchi, and bronchioles, where no gas exchange occurs because these structures lack alveoli. This non-functional air is called dead space and amounts to approximately 150 milliliters in an adult human. During each breath, a portion of the inspired air remains in these passages and is exhaled without contributing to oxygen uptake or carbon dioxide removal. The remaining inspired air that actually reaches the alveoli and participates in gas exchange is called alveolar ventilation. Understanding dead space is important for calculating the actual amount of fresh air that reaches the gas exchange surfaces during respiration.

The villager is suffering from a respiratory condition caused by inhalation of particulate pollutants, which has triggered an allergic and inflammatory response in his respiratory tract. Upon exposure to the polluted urban environment, he began experiencing symptoms such as sneezing and coughing as his immune system reacted to the allergens and particulate matter in the air. The pollutants irritate the respiratory tract and provoke an inflammatory response characterized by swelling, mucus production, and airway constriction. If exposure to these particulate pollutants continues over a prolonged period, the chronic inflammatory response can lead to the development of asthma, a chronic respiratory disease characterized by reversible airway obstruction, bronchial hyperresponsiveness, and inflammation. Prevention involves minimizing exposure to polluted air through the use of masks, air purifiers, and avoiding heavily polluted areas when possible.

Kumar's mother is affected with silicosis, a chronic occupational lung disease caused by prolonged inhalation of crystalline silica dust particles in the stone grinding factory. When silica particles are inhaled, they deposit in the lungs and trigger an inflammatory response. Over time, this chronic inflammation leads to pulmonary fibrosis, a condition in which lung tissue becomes scarred and thickened, reducing the lungs' ability to expand and contract properly. This results in progressive breathing difficulty and reduced oxygen exchange. Treatment involves hospitalization and administration of medications to manage symptoms and slow disease progression. Anti-inflammatory medications may be prescribed to reduce inflammation, and in some cases, medications like imatinib may be used to combat fibrosis. Additionally, the patient should be removed from further exposure to silica dust, and supportive care including oxygen therapy may be necessary to maintain adequate oxygenation. Prevention through proper workplace safety measures, including dust control and use of protective equipment, is essential for workers in such industries.

• It helps in the exchange of O 2 and CO 2 between the atmosphere and the blood.
• It maintains homeostatic regulation of body pH.
• It protects us from inhaled pathogens and pollutants.
• It maintains the vocal cords for normal communication.
• It removes the heat produced during cellular respiration through breathing.

• The trachea is semiflexible tube supported by cartilaginous rings.
• It starts from the pharynx and ends in the lungs there it divides into right and left primary bronchi.
• With in the lungs the bronchi divided repeatedly into secondary and tertiary bronchi.
• That further divides into terminal bronchioles and respiratory bronchioles.
• Bronchi have ‘c’ shaped curved cartilage plates.
• This plate helps in preventing collapsing as the air pressure changes during breathing.
• There is no cartilaginous stingray the brarichioles,
• The rigidity of the bronchioles prevents them from collapsing.

Inspiration occurs if the pressure inside the lungs is less than the atmospheric pressure.
Inspiration:
* There is a contraction of diaphragm muscles and external intercostal muscles which pulls the ribs and sternum upwards and downwards and increases the volume of the thoracic chamber in the dorsoventral axis.
* Hence the pulmonary pressure is less than the atmospheric pressure.
* This forces the fresh air from outside to enter the air passages into the lungs to equalize the pressure.
Expiration:
* Expiration takes place when the pressure within the lungs is higher than the atmospheric pressure.
* Relaxation of the diaphragm leads to its original dome-shaped nature.
* The internal intercostal muscles contract pulling the ribs downward reducing the thoracic volume and pulmonary volume.
* Thin results in an increase in the intrapulmonary pressure slightly above the atmospheric pressure causing the expulsion of air from the lungs.

• The lungs are light spongy tissue.
• It is enclosed inthe thoracic cavity surrounded by an air-tight space.
• The thoracic cavity is bound dorsally by the ventral column and ventrally by the sternum. laterally by the ribs and on the lower side by the dome-shaped diaphragm.
• The lungs are covered by a double walled pleural membrane and the plural cavity is filled with pleural fluid which reduces friction.
• The trachea is a semi-flexible tube supported by cartilaginous rings which extends upto the 5th thoracic vertebra.
• It divides into right and left bronchi and enters in to the lungs. There it divides further many times and ends in alveoli.

Molecular oxygen is carried in blood in two ways: bound to haemoglobin within the red blood cells and dissolved in plasma. Oxygen is poorly soluble in water, so only 3% of the oxygen is transported in the dissolved form. 97% of oxygen binds with haemoglobin in a reversible manner to form oxyhaemoglobin (Hb0 2 ). The rate at which haemoglobin binds with O 2 is regulated by the partial pressure of O 2.
Each haemoglobin carries maximum of four molecules of oxygen. In the alveoli high pO 2, low pCO 2, low temperature and less H+ concentration, favours the formation of oxyhaemoglobin, whereas in the tissues low p02, high pCO 2, high H+ and high temperature favours the dissociation of oxygen from oxyhaemoglobin.
A sigmoid curve (S-shaped) is obtained when percentage saturation of haemoglobin with oxygen is plotted against pO 2. This curve is called oxygen haemoglobin dissociation curve. This S-shaped curve has a steep slope for pO 2 values between 10 and 50 mm Hg and then flattens between 70 and 100 mm Hg. Under normal physiological conditions, every 100 mL of oxygenated blood can deliver about 5 mL of O 2 to the tissues.

* 7-10% of CO 2 is transported in a dissolved form in the plasma.
* 20-25% of dissolved CO 2 is bound and carried in the RBCs as carbamino haemoglobin.
CO 2 + H 6 ⇌ H 6 CO 2
* About 70% of CO 2 is transported as bicarbonate ions.
* At the tisoues the PCO 2 is high due to catabolism and diffuses in the blood to form HCO – 3 and H +
* When CO 2 diffuses into RBCs it combines with water forming carbonic acid catalyzed by carbonic anhydrase.
* Carbonic acid is dissociated into hydrogen and bicarbonate.
* Every 100 ml of deoxygenated blood delivers 4ml CO 2 to the alveoli for elimination.

• Medulla oblongata is a repiratory regulation centre.
• The pneumotaxic centre present in the pons varoli is the respiratory rhythm centre.
• The chemosensitive area found close to the rhythm centre is highly sensitive to CO 2 and H +
• H + are eliminated out by respiratory process.
• Receptiors associated with the aortic arch and carotid artery send signals to the rhythm centre for remedial action.

The respiratory system is affected by environmental occupational personal and social factors.
Following are some of the respiratory disorders:
Asthma: It is characterized by narrowing and inflammation of bronchi and bronchioles and difficulty in breathing.
Causes: Allergens like dust drugs pollen grains, certain food items like fish.
Emphysema: It is chronic breathlessness. It is caused by gradual breakdown of the thin wall of the alveoli decreasing the total surface area of a gaseous exchange.
Causes: The widening of the alveoli is called Emphysema.
Cigarette smoking reduces the respiratory surface of the alveolar walls.
Bronchitis: It is the inflammation of the bronchi.
Causes: Pollution smoke ciagratte smoking.
Symptoms: Cough shortness of breath sputum in the lungs.
Pneumonia: It is the inflammation of the lungs.
Causes: Bacteria and virus
Symptoms
* Sputum production Nasal congestion, Shortness of breath sore throat.
* Tuberculosis
Causes
* Tuberculosis is caused by mycobacterium tubercular.
* Infection mainly occurs in the lungs and bones.
Symptoms
Collection of fluid between the lungs and the chest wall is the main complication of this

• It increases the heartbeat rate.
• It narrows the blood vessels results in raised blood pressure and leads to coronary heart diseases.
• Smoking can cause lung diseases by damaging the airways and alveoli and results in emphysema and chronic bronchitis.

Different organisms have evolved specialized respiratory organs suited to their habitats and lifestyle. Sponges and coelenterates rely on their body surface for gas exchange due to their simple body structure and small size. Earthworms utilize their moist skin as a respiratory surface, which requires the skin to remain damp for effective oxygen diffusion. Insects possess a complex system of trachea and tracheoles that deliver oxygen directly to cells throughout their body. Aquatic arthropods and mollusks have developed gills, which are highly efficient organs for extracting dissolved oxygen from water. Fish also use gills as their primary respiratory organs, with water flowing over the gill filaments for gas exchange. Amphibians such as frogs have lungs for air breathing but also retain the ability to respire through their moist skin, allowing them to utilize both aquatic and terrestrial environments. Reptiles, birds, and mammals have evolved lungs as their primary respiratory organs, with varying degrees of complexity and efficiency adapted to their specific metabolic demands and environmental conditions.

The respiratory process involves several interconnected steps that work together to ensure efficient oxygen delivery to cells and removal of carbon dioxide. The first step is the exchange of air between the atmosphere and the lungs, which occurs through the process of ventilation or breathing, where air moves in and out of the lungs. The second step is the exchange of oxygen and carbon dioxide between the lungs and the blood across the alveolar membrane, a process called external respiration or pulmonary gas exchange. The third step involves the transport of oxygen and carbon dioxide by the blood through the circulatory system, with oxygen being carried by hemoglobin in red blood cells and carbon dioxide being transported in various forms including dissolved gas and as bicarbonate ions. The fourth step is the exchange of gases between the blood and the body cells, known as internal respiration, where oxygen diffuses from the blood into the cells and carbon dioxide diffuses from the cells into the blood. Finally, the cells take up oxygen for various metabolic activities and energy production through aerobic respiration, while simultaneously releasing carbon dioxide as a waste product of metabolism. This coordinated sequence ensures continuous supply of oxygen to tissues and removal of metabolic wastes.

Respiratory system disorders are conditions that impair normal breathing and gas exchange. Pulmonary embolism occurs when a blood clot lodges in the lung blood vessels, obstructing blood flow. Bronchitis involves inflammation of the bronchial tube linings, causing persistent cough and mucus production. Asthma is characterized by swelling and narrowing of airways with excess mucus secretion, leading to breathing difficulty. Lung cancer is primarily caused by smoking and involves malignant growth in lung tissue. Pneumonia is an infection causing inflammation of the lungs and alveoli, impairing gas exchange. Pulmonary edema results from fluid accumulation in lung tissue and air spaces, reducing oxygen absorption. Emphysema involves permanent widening and damage to alveoli, causing shortness of breath and reduced elastic recoil. Atelectasis is the collapse of alveoli and lung tissue, preventing proper ventilation. Tuberculosis is an infectious disease affecting lungs and bones, often causing effusion or fluid accumulation in the lungs. Pleurisy is inflammation of the pleura, the membrane surrounding the lungs, causing chest pain during breathing. Each disorder disrupts normal respiratory function through different mechanisms, ranging from structural damage to infection to obstruction.

When a person travels from sea level to elevations above 8000 ft there is a poor binding of O 2 with haemoglobin.
* There is a symptom of headache shortness of breath nausea and dizziness develop. (Acute mountain sickness)
* To overcome this situation kidneys accelerate the production of the hormone erythropoietin which stimulates the synthesis of RBCs.
II. Inthedeepsea
* When a person descends deep in to the sea the pressure in the water increases which causes the lungs to decrease in volume.
* There is an increased nitrogen level in the blood lead to nitrogen narcosis.
* When the diver ascends to the surface a condition called decompression sickness occurs. As nitrogen comes out of solution while still in the blood-forming bubbles.
* The large bubbles can block the blood flowor can press on the nerve ending. This also causes pain in joints, muscles and causes neurological problems.