22.2 The Lungs
3 min read•june 18, 2024
Lungs are vital organs that enable breathing and . They take in oxygen and expel carbon dioxide, regulate blood pH, and even play a role in speech and smell. Understanding anatomy is crucial for grasping how we breathe.
The lungs are part of a complex circulatory system. Blood flows through , capillaries, and veins, allowing for gas exchange. Pleural membranes surround the lungs, helping them move smoothly during breathing and maintaining their expanded state.
Lung Anatomy and Function
Functions of lungs in respiration
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- Gas exchange enables oxygen to diffuse from into and carbon dioxide to diffuse from into (oxygen and carbon dioxide)
- Regulate blood pH by removing excess carbon dioxide from the blood, which forms carbonic acid ( enzyme)
- Vocalization occurs when air passing through the larynx enables speech production ()
- Olfaction allows inhalation through the nose, enabling odorant molecules to reach olfactory receptors ()
- Filtration removes small blood clots and traps and removes small air bubbles via pulmonary capillary beds ()
Blood flow in pulmonary circulation
- Deoxygenated blood enters the pulmonary trunk from the right ventricle and divides into left and right
- Pulmonary arteries carry deoxygenated blood to the lungs, dividing into arterioles and pulmonary capillaries surrounding alveoli
- Gas exchange occurs between alveoli and pulmonary capillaries, oxygenating the blood
- Oxygenated blood returns to the heart via , which merge to form
- Four (two from each lung) carry oxygenated blood to the left atrium (oxygenated blood)
Blood vessels of the lungs
- Pulmonary trunk carries deoxygenated blood from the right ventricle to the lungs (deoxygenated blood)
- Pulmonary arteries (left and right) carry deoxygenated blood from the pulmonary trunk to the lungs
- Pulmonary capillaries surround alveoli and allow gas exchange between alveolar air and blood (diffusion)
- Pulmonary venules merge to form pulmonary veins and carry oxygenated blood away from the lungs
- Pulmonary veins (four in total, two from each lung) carry oxygenated blood from the lungs to the left atrium of the heart
Structure of pleural membranes
- Pleural membranes are serous membranes that enclose each lung, consisting of two layers:
- directly adheres to the lung surface
- lines the thoracic cavity
- is the space between visceral and parietal pleurae containing a small amount of pleural fluid to reduce friction during breathing (serous fluid)
- Purposes of pleural membranes:
- Allow the lungs to move smoothly during inhalation and exhalation
- Maintain contact between the lungs and thoracic wall
- Help maintain the lungs' expanded state by coupling lung movement to the thoracic wall (surface tension)
- within the is slightly negative compared to atmospheric pressure, keeping the lungs expanded and preventing their collapse ()
Respiratory Physiology and Gas Exchange
- is the number of breaths taken per minute, influenced by factors such as exercise, stress, and disease
- refers to the lungs' ability to expand and contract during breathing, affected by lung elasticity and surface tension
- of gases in the alveoli and blood plays a crucial role in determining the direction and rate of gas exchange
- , a condition of inadequate oxygen supply to tissues, can result from various factors affecting the respiratory system
Key Terms to Review (60)
Alveoli: Alveoli in the context of the ovarian reproductive system refer to the small, sac-like structures within the mammary glands where milk is produced and secreted during lactation. Each alveolus is lined with milk-producing epithelial cells and surrounded by myoepithelial cells that help expel milk into the ducts leading to the nipple.
Alveoli: Alveoli are the tiny air sacs located at the end of the respiratory tree in the lungs. They are the functional units of the respiratory system, responsible for the exchange of gases between the air and the bloodstream.
Bronchi: The bronchi are the primary airways that branch off from the trachea and carry air into and out of the lungs. They play a crucial role in the respiratory system by facilitating the movement of air during the process of breathing and enabling gas exchange within the lungs.
Bronchial artery: The bronchial artery is a blood vessel that supplies oxygenated blood to the lungs, supporting the tissues of the lungs outside of the alveoli where gas exchange occurs. Unlike the pulmonary arteries, which carry deoxygenated blood to the alveoli for oxygenation, bronchial arteries provide nutrients and oxygen to the lung tissue itself.
Bronchoconstriction: Bronchoconstriction is the narrowing of the bronchi in the lungs due to the tightening of surrounding smooth muscle. This process reduces airflow and can lead to breathing difficulties.
Carbonic Anhydrase: Carbonic anhydrase is a zinc-containing enzyme that catalyzes the reversible conversion between carbon dioxide and carbonic acid, playing a crucial role in the regulation of pH and the transport of respiratory gases within the body.
Carbonic anhydrase (CA): Carbonic anhydrase is an enzyme found primarily in red blood cells, facilitating the rapid conversion of carbon dioxide and water into carbonic acid, which then dissociates into hydrogen ions and bicarbonate. This process is crucial for transporting CO2 from tissues to the lungs and for maintaining acid-base balance in the blood.
Conducting zone: The conducting zone consists of all the respiratory pathways that carry air to the sites of gas exchange but do not themselves participate in the exchange of gases. These include structures such as the nose, pharynx, larynx, trachea, bronchi, and bronchioles up to the terminal bronchioles.
Conducting Zone: The conducting zone of the respiratory system is responsible for the transport of air between the atmosphere and the gas exchange region of the lungs. It consists of a series of structures that guide air flow and prepare the air for efficient gas exchange.
Diaphragm: The diaphragm is a dome-shaped sheet of muscle and tendon that serves as the primary muscle for respiration, separating the thoracic (chest) cavity from the abdominal cavity. It contracts and flattens when you inhale, allowing the lungs to expand and fill with air, and relaxes and domes upwards during exhalation, pushing air out of the lungs.
Diaphragm: The diaphragm is a dome-shaped muscle that separates the thoracic and abdominal cavities. It is the primary muscle of respiration, playing a crucial role in the process of breathing and gas exchange within the body.
Diffusion Capacity: Diffusion capacity, also known as diffusing capacity, is a measure of the ability of the lungs to transfer gases, such as oxygen and carbon dioxide, between the alveoli and the bloodstream. It is a crucial parameter in evaluating lung function and overall respiratory health.
Emphysema: Emphysema is a chronic lung disease characterized by the destruction and enlargement of the air sacs (alveoli) within the lungs, leading to impaired lung function and breathing difficulties. This condition is closely linked to the topics of the lungs, the process of breathing, and gas exchange.
Gas exchange: Gas exchange is the biological process by which oxygen is transported from the environment into the bloodstream and carbon dioxide is transferred from the bloodstream to the environment. This crucial exchange primarily occurs in the lungs, where specialized structures facilitate the movement of gases through diffusion, allowing for the replenishment of oxygen in the blood and the removal of waste gases.
Hering-Breuer Reflex: The Hering-Breuer reflex is a negative feedback mechanism that helps regulate the depth and rate of breathing. It is triggered by the stretch receptors in the lungs and airways, and it plays a crucial role in maintaining the balance of gas exchange within the body.
Hilum: The hilum of the lung is an indented region on its mediastinal surface through which bronchi, blood vessels, lymph vessels, and nerves enter and exit the lung. It acts as a critical hub for the respiratory system's plumbing and wiring.
Hypoxia: Hypoxia is a condition in which the body or a region of the body is deprived of adequate oxygen supply at the tissue level. It can result from various factors, including low oxygen levels in the blood, inadequate blood flow, or an inability of the cells to use oxygen effectively.
Hypoxia: Hypoxia is a condition in which the body or a region of the body is deprived of adequate oxygen supply, leading to various physiological and pathological consequences. This term is particularly relevant in the context of requirements for human life, the functioning of the lungs, and the role of the urinary system in maintaining homeostasis.
Intercostal muscles: Intercostal muscles are groups of muscles found between the ribs that help form and move the chest wall. They are primarily involved in the mechanical aspect of breathing, assisting with the expansion and contraction of the thoracic cavity to facilitate respiration.
Intercostal Muscles: The intercostal muscles are a group of skeletal muscles located between the ribs that play a crucial role in the mechanics of breathing and the structural integrity of the thoracic cavity. These muscles are closely associated with the respiratory system, the thoracic cage, and the abdominal wall.
Intrapleural Pressure: Intrapleural pressure is the pressure that exists in the pleural cavity, the space between the lungs and the chest wall. This pressure is crucial for the proper functioning of the respiratory system, as it helps to maintain the shape and position of the lungs during breathing.
Lung: The lung is a pair of spongy, air-filled organs located on either side of the chest (thorax), responsible for removing carbon dioxide from and bringing oxygen into the blood. They play a crucial role in the respiratory system by facilitating gas exchange with the external environment.
Lung Compliance: Lung compliance is a measure of the lung's ability to stretch and expand during inhalation. It is a key factor in determining the work required to breathe and the overall efficiency of the respiratory system.
Nasal cavity: The nasal cavity is a large air-filled space above and behind the nose in the middle of the face, part of the respiratory system that warms, moistens, and filters air entering the body before it reaches the lungs. It also plays a significant role in olfaction (sense of smell) and in forming vocal sounds.
Nasal Cavity: The nasal cavity is the air-filled space within the nose, serving as the primary respiratory passageway and playing a crucial role in the respiratory system. It is the initial entry point for air entering the body and is responsible for filtering, warming, and humidifying the air before it reaches the lungs.
Parietal pleura: The parietal pleura is a thin membrane that lines the inner surface of the chest wall and diaphragm in the thoracic cavity, but does not directly cover the lungs. It provides a smooth, frictionless surface that facilitates lung movement during respiration.
Parietal Pleura: The parietal pleura is the outer layer of the pleural membrane that lines the inner surface of the thoracic cavity. It works in conjunction with the visceral pleura to facilitate the smooth movement of the lungs during respiration.
Partial pressure: Partial pressure is the pressure exerted by a single type of gas in a mixture of gases. It's crucial in determining how gases diffuse across biological membranes, such as during gas exchange in the respiratory system.
Partial Pressure: Partial pressure is the pressure exerted by a specific gas within a mixture of gases. It is a crucial concept in understanding the behavior and movement of gases, particularly in the context of the respiratory system and gas exchange processes.
Pleura: The pleura are thin, double-layered membranes that surround the lungs and line the thoracic cavity, playing a critical role in respiratory function. These membranes facilitate smooth movement of the lungs during breathing while also providing a barrier against infection and helping to maintain the pressure necessary for proper lung inflation. The pleura consists of two layers: the visceral pleura, which covers the lungs, and the parietal pleura, which lines the chest wall.
Pleural cavity: The pleural cavity is a thin fluid-filled space between the two layers of the pleura, which are membranes surrounding each lung. This cavity provides lubrication and space for the lungs to expand and contract during breathing.
Pleural Cavity: The pleural cavity is the space between the two layers of the pleural membrane that surrounds the lungs. It is a fluid-filled space that allows the lungs to slide smoothly against the chest wall during breathing. This cavity is an essential component of the respiratory system, as it facilitates the expansion and contraction of the lungs during inhalation and exhalation.
Pneumonia: Pneumonia is a respiratory infection that causes inflammation and fluid buildup in the lungs, making it difficult to breathe. It can be caused by various pathogens, including bacteria, viruses, and fungi, and can range in severity from mild to life-threatening.
Pneumothorax: Pneumothorax is a medical condition characterized by the presence of air in the pleural cavity, which can lead to lung collapse. This condition affects the lungs' ability to expand fully during breathing, resulting in respiratory distress and decreased oxygen levels in the bloodstream. Understanding pneumothorax is crucial, as it directly impacts lung function and the mechanics of breathing.
Pulmonary arteries: Pulmonary arteries are the large blood vessels that transport deoxygenated blood from the right ventricle of the heart to the lungs for oxygenation. Unlike most arteries which carry oxygenated blood, pulmonary arteries carry blood rich in carbon dioxide to the lungs where it releases carbon dioxide and absorbs oxygen.
Pulmonary Arteries: The pulmonary arteries are the blood vessels responsible for transporting deoxygenated blood from the right ventricle of the heart to the lungs, where the blood becomes oxygenated. These arteries play a crucial role in the circulatory system and the respiratory system by facilitating the exchange of gases between the blood and the alveoli in the lungs.
Pulmonary capillaries: Pulmonary capillaries are tiny blood vessels located in the lungs that facilitate the exchange of oxygen and carbon dioxide between the blood and the air in the lung's alveoli. They form a network around the alveolar sacs, ensuring efficient gas exchange essential for respiration.
Pulmonary Capillaries: Pulmonary capillaries are the smallest blood vessels located within the lungs that facilitate the exchange of gases between the blood and the alveoli. They play a crucial role in the circulatory system by allowing oxygen to be absorbed into the bloodstream and carbon dioxide to be expelled from the body.
Pulmonary Embolism: A pulmonary embolism is a blockage in one of the pulmonary arteries in the lungs, usually caused by a blood clot that travels to the lungs from elsewhere in the body. This disruption in blood flow can be life-threatening if not treated promptly.
Pulmonary plexus: The pulmonary plexus is a network of nerve fibers located at the root of the lungs, involved in the autonomic regulation of respiratory functions. It comprises both sympathetic and parasympathetic nerves that control bronchoconstriction, vasodilation, and mucous secretion within the lungs.
Pulmonary surfactant: Pulmonary surfactant is a complex mixture of lipids and proteins produced by cells in the lungs, which reduces surface tension within the alveoli to prevent their collapse during exhalation. This substance is crucial for efficient gas exchange and lung stability.
Pulmonary veins: Pulmonary veins are blood vessels that carry oxygenated blood from the lungs back to the left atrium of the heart. Unlike most veins, which carry deoxygenated blood, pulmonary veins are unique because they transport blood rich in oxygen.
Pulmonary Veins: The pulmonary veins are blood vessels that carry oxygenated blood from the lungs to the heart's left atrium. They play a crucial role in the cardiovascular and respiratory systems, facilitating the exchange of gases and the circulation of blood throughout the body.
Pulmonary Venules: Pulmonary venules are small blood vessels that carry deoxygenated blood from the alveolar capillaries in the lungs back to the pulmonary veins. They play a crucial role in the circulatory system's gas exchange processes, facilitating the transport of carbon dioxide-rich blood from the body's tissues to the lungs for oxygenation.
Respiratory rate: Respiratory rate is the number of breaths a person takes per minute, which is a critical measure of respiratory health and function. It can vary with age, physical condition, and health status.
Respiratory Rate: Respiratory rate refers to the number of breaths a person takes per minute. It is a vital sign that provides important information about an individual's respiratory and overall health status.
Respiratory zone: The respiratory zone is the part of the respiratory system where gas exchange between air and blood occurs, primarily within the alveoli. It consists of structures including the respiratory bronchioles, alveolar ducts, and alveolar sacs.
Respiratory Zone: The respiratory zone is the portion of the respiratory system where gas exchange occurs between the air and the blood. It includes the alveoli and the surrounding capillaries, facilitating the transfer of oxygen and carbon dioxide between the lungs and the circulatory system.
Spirometry: Spirometry is a common pulmonary function test that measures how much air a person can inhale and exhale, as well as how quickly they can do so. This test is crucial for assessing lung function and diagnosing respiratory conditions, allowing healthcare providers to evaluate the effectiveness of treatments and monitor the progression of diseases affecting the lungs.
Surfactant: Surfactant is a complex mixture of lipids and proteins produced by type II alveolar cells in the lungs. It plays a critical role in the respiratory system by reducing surface tension within the alveoli, facilitating gas exchange, and preventing alveolar collapse during exhalation.
Surfactant Protein: Surfactant proteins are a group of specialized proteins found in the alveoli of the lungs that play a crucial role in maintaining the structural integrity and functional efficiency of the respiratory system. These proteins work in conjunction with phospholipids to form a surfactant that reduces the surface tension within the alveoli, facilitating efficient gas exchange and preventing alveolar collapse during exhalation.
Tidal Volume: Tidal volume is the amount of air that is inhaled and exhaled during normal, quiet breathing. It is one of the key measurements used to assess respiratory function and is an important factor in the overall process of breathing and gas exchange within the body.
Tidal volume (TV): Tidal Volume is the amount of air that moves in or out of the lungs during a normal breath at rest. It's a crucial measurement in respiratory physiology, indicating the efficiency of pulmonary ventilation.
Type I pneumocytes: Type I pneumocytes are thin, flat epithelial cells that line the alveoli in the lungs, playing a crucial role in gas exchange. These cells comprise about 95% of the alveolar surface area and facilitate the diffusion of oxygen and carbon dioxide between the air in the alveoli and the blood in the capillaries. Their structure allows for efficient gas exchange and provides a barrier that is necessary for maintaining the integrity of the alveolar air space.
Ventilation: Ventilation is the process of moving air into and out of the lungs, facilitating the exchange of oxygen and carbon dioxide between the body and the external environment. This essential respiratory function is crucial for maintaining proper gas exchange and supporting various physiological processes throughout the body.
Visceral pleura: The visceral pleura is a thin membrane that directly covers the lungs' surface, playing an essential role in providing lubrication and facilitating the lungs' movement during breathing. It is part of the pleural sac that encloses the lungs within the thoracic cavity.
Visceral Pleura: The visceral pleura is the thin, innermost layer of the pleural membrane that directly covers the surface of the lungs. It is responsible for providing a smooth, lubricated surface to facilitate the sliding motion of the lungs during breathing.
Vital Capacity: Vital capacity is the maximum volume of air that can be expelled from the lungs after a maximum inhalation. It is a key measurement of lung function and respiratory capacity, and is an important indicator of overall respiratory health.
Vital capacity (VC): Vital capacity is the maximum amount of air a person can exhale after a maximum inhalation, measuring the strength and health of respiratory function. It combines tidal volume, inspiratory reserve volume, and expiratory reserve volume.
Vocal Cords: Vocal cords, also known as vocal folds, are a pair of elastic membranes located within the larynx that vibrate to produce sound during speech. They play a crucial role in the production of voice and are essential for various functions related to the head, neck, and respiratory system.