Name: how pressure drives breathing in the lungs
Uploaded: 2024-09-12T13:22:46.000Z
Duration: 1 min 24 s
Channel: JoVE

K12 Standards

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Ohio’s Learning Standards and Model Curriculum

9-12

Human Anatomy and Physiology

Absorption And Excretion

Respiratory System

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Pressure Relationships in Thoracic Cavity

Healthy respiration in humans requires proper air pressure levels in different respiratory organs.
These pressures are expressed relative to the atmospheric pressure, equivalent to 760 mm Hg or one atmospheric pressure.
First, intrapulmonary pressure is the pressure in the alveoli. It fluctuates with each breath but eventually equalizes with the atmospheric pressure.
Second, intrapleural pressure is the pressure in the pleural cavity. It is typically 4 mm Hg lower than the atmospheric pressure.
The negative intrapleural pressure results from opposing forces in the thorax. The surface tension in alveolar fluid and the lungs&#39; natural tendency to recoil try to collapse the lungs completely during exhalation.
But, the elasticity of the chest wall counters this, and a strong adhesive bond between the pleurae keeps the lungs from deflating completely.
The difference between intrapulmonary pressure and intrapleural pressure, also known as transpulmonary pressure, is pivotal in preventing lung collapse by keeping the air sacs open.
As a result, when the difference between the intrapulmonary pressure and the intrapleural pressure is larger, the lungs are more inflated.

pressure relationships in thoracic cavity

Breathing, otherwise known as pulmonary ventilation, is the process of air movement into and out of the lungs. The main mechanisms propelling pulmonary ventilation are atmospheric pressure (Patm), intra-pulmonary (Ppul ) or intra-alveolar pressure (Palv) within the alveoli, and intrapleural pressure (Pip) within the pleural cavity.
Breathing Mechanisms
Both intra-alveolar and intrapleural pressures rely on specific lung properties. The ability to breathe&#8212;allowing air to enter the lungs during inhalation and leave during expiration&#8212;depends on the air pressure inside the lungs relative to the atmospheric pressure.
Pressure Dynamics
Inhalation (inspiration) and exhalation (expiration) hinge on the pressure differences between the atmosphere and the lungs. In a gas, pressure arises from the movement of confined gas molecules. For instance, due to the reduced volume, the same amount of gas molecules will exert more pressure in a one-liter container than in a two-liter container. This relationship between volume and pressure in a gas at a constant temperature is described by Boyle&#39;s Law, which states that pressure and volume are inversely proportional (P = k/V); a volume increase results in pressure decrease and vice versa.
Three types of pressure&#8212;atmospheric, intra-alveolar, and intrapleural&#8212;dictate pulmonary ventilation. Atmospheric pressure represents the force exerted by air gases surrounding a particular surface. It can be expressed as an atmospheric unit (atm) or in millimeters of mercury (mm Hg), where 1 atm equates to 760 mm Hg, the sea-level atmospheric pressure. Other pressure values, such as atmospheric pressure, are typically discussed in respiration.
Intra-alveolar pressure (intrapulmonary pressure) denotes the air pressure within the alveoli, which fluctuates during different breathing stages. As the alveoli are connected to the atmosphere via the airways, the intrapulmonary pressure constantly equalizes with the atmospheric pressure.
Intrapleural pressure is the air pressure within the pleural cavity between the visceral and parietal pleurae. It fluctuates during different breathing stages, and due to specific lung properties, it always stays negative compared to the intra-alveolar pressure.&#160; The intrapleural pressure remains approximately &#8211;4 mm Hg throughout the breathing cycle. It is maintained by the inward recoil of the lung&#39;s elastic fibers and the outward pull of the chest wall. . The balance between these opposing forces determines the &#8211;4 mm Hg intrapleural pressure relative to the intra-alveolar pressure. Transpulmonary pressure, the difference between intrapleural and intra-alveolar pressures, determines lung size.
Factors Influencing Ventilation
Apart from pressure differences, respiration depends on the contraction and relaxation of the diaphragm and thoracic muscle fibers. The diaphragm and intercostal muscle movements primarily cause pressure changes responsible for inspiration and expiration.
Other lung properties also affect respiration. Resistance is a force that slows down motion, in this context, the flow of gases. Airway size is the main factor affecting resistance. Smaller tube diameter forces air through a smaller space, causing more collisions of air molecules with the airway walls. The formula F=&#916;P/R describes the relationship between pressure changes and airway resistance.
Surface tension within the alveoli, caused by the water present in the alveoli lining, tends to restrict alveoli expansion. Pulmonary surfactant, secreted by type II pneumocytes, mixes with water, reducing this surface tension and preventing alveoli collapse during expiration.
Thoracic wall compliance, the thoracic wall&#39;s ability to stretch under pressure, affects the effort required for breathing. The thoracic cavity must expand for inspiration to occur, directly influencing lung capacity. If the thoracic wall lacks compliance (cannot expand), fetal development of the thorax and the lungs becomes challenging.

Healthy respiration in humans requires proper air pressure levels in different respiratory organs.
These pressures are expressed relative to the ...

Education

JoVE Core

Anatomy and Physiology

Unit 1

The Respiratory System

KEY TERMS AND CONCEPTS

how pressure drives breathing in the lungs

Breathing depends on pressure changes in the lungs, chest, and airways. Pulmonary ventilation is the movement of air into and out of the lungs. It is driven by atmospheric pressure, intra-alveolar pressure inside the alveoli, and intrapleural pressure in the pleural cavity.

Inhalation and exhalation rely on pressure differences between the atmosphere and the lungs. Gas pressure comes from the movement of confined molecules. Boyle’s law explains that pressure and volume are inversely proportional at a constant temperature. When volume increases, pressure decreases. When volume decreases, pressure increases.

Three pressure values are important in respiration. Atmospheric pressure is the force exerted by surrounding air. It is often measured in atm or mm Hg, and 1 atm equals 760 mm Hg at sea level. Intra-alveolar pressure, also called intrapulmonary pressure, is the air pressure in the alveoli. It changes during breathing but stays equal to atmospheric pressure because the alveoli connect to the outside air through the airways. Intrapleural pressure is the pressure in the pleural cavity between the visceral and parietal pleurae. It stays negative compared with intra-alveolar pressure and is usually about -4 mm Hg throughout the breathing cycle.

That negative intrapleural pressure is maintained by two opposing forces. The lungs tend to recoil inward because of their elastic fibers. The chest wall pulls outward. Their balance sets the pressure in the pleural cavity. Transpulmonary pressure is the difference between intrapleural and intra-alveolar pressure, and it helps determine lung size.

Breathing also depends on the diaphragm and intercostal muscles. When these muscles contract and relax, they change the volume of the thoracic cavity and create the pressure shifts needed for inspiration and expiration. Airway resistance also affects ventilation. Smaller airway diameter increases resistance because air molecules collide more often with the airway walls. The relationship between pressure change and resistance is described by F = ΔP/R.

Two other factors shape how easily air moves. Surface tension in the alveoli, caused by water in the lining, tends to limit alveolar expansion. Pulmonary surfactant, secreted by type II pneumocytes, mixes with that water and lowers surface tension. This helps prevent alveoli from collapsing during expiration. Thoracic wall compliance, or the ability of the chest wall to stretch under pressure, also matters because the thoracic cavity must expand for inspiration. If the thoracic wall cannot expand well, fetal development of the thorax and lungs becomes difficult.

How Pressure Drives Breathing in the Lungs

how-pressure-drives-breathing-in-the-lungs

overview of respiratory system

How Breathing Moves Air and Gases

The respiratory system moves air in and out of the body and exchanges oxygen and carbon dioxide with the environment. This gas exchange is part of respiration, which is essential for life. The system supplies the blood with oxygen so it can carry that oxygen to the rest of the body. Breathing starts when air enters through the nose or mouth. The nose and nasal cavity form the main external opening and the first part of the airway. Air then passes through the pharynx, or throat, which is shared...

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How the Nose Filters and Senses Air

The nose filters, warms, moistens, and senses the air that enters the body. It also helps shape speech as sound vibrations pass through its large air spaces. The nose has an external part that is visible on the face and an internal part called the nasal cavity. The external nose is built from bone and hyaline cartilage, which gives it flexibility. It is covered by skin and muscle and lined with a mucous membrane. The frontal bone, nasal bones, and maxillary bone support this structure. The...

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Pharynx Pathways for Air and Food

The pharynx is a muscular tube lined with mucous membrane that connects the nasal cavities to the throat. It is divided into three parts: the nasopharynx, oropharynx, and laryngopharynx. Each part has a different role in moving air and food through the upper throat. The nasopharynx sits behind the nasal cavity and serves only as an air passage. Its upper region contains the pharyngeal tonsils, also called adenoids. These are clusters of lymphoid reticular tissue, similar to a lymph node, and...

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Voice Box Anatomy and Function

The larynx is the voice box in the neck. It carries air into the lungs and helps produce voice. Its structure is complex because it must support both breathing and sound production. The larynx contains cartilage, muscles, and the vocal cords, also called vocal folds. It includes three large unpaired cartilages: the thyroid, cricoid, and epiglottis. It also includes three paired cartilages: the arytenoids, corniculates, and cuneiforms. Ligaments and membranes hold these parts together. The...

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Trachea: Layers, Rings, and Airflow

The trachea is the windpipe, and it is a key airway in the human respiratory system. It carries air between the larynx and the bronchi so oxygen can reach the lungs. About half of the trachea lies in the neck, and it sits in front of the esophagus. In an average adult, the trachea is about 10 to 12 cm long. It extends from the larynx at the level of the sixth cervical vertebra to the level of the fifth thoracic vertebra. Its wall is supported by C-shaped cartilaginous rings. The back side is...

the bronchial tree

Bronchial Branching and Airflow Control

The bronchial tree carries air from the trachea into the lungs and helps control breathing. The trachea, or windpipe, connects the larynx to the bronchi. At the carina, the trachea splits into two primary bronchi. The right primary bronchus is wider, shorter, and more vertical than the left. Because of that shape, foreign objects and infections are more likely to enter the right lung. The carina is a cartilaginous ridge at the split in the airway. It helps keep the airway open. It also has...

alveoli and alveolar ducts

How Alveoli Enable Gas Exchange

The respiratory zone of the human body is where gas exchange happens. It begins when the terminal bronchioles branch into respiratory bronchioles, the smallest bronchiole type. These then lead into alveolar ducts and finally into clusters of alveoli. Alveoli are tiny air sacs that look like bunches of grapes. They connect to alveolar ducts, and a group of alveoli forms an alveolar sac. A single alveolus is about 200 μm wide, and its elastic shape lets it expand during inhalation. Nearby...

gross anatomy of the lungs

Lung Lobes, Airways, and Blood Flow

The lungs are paired organs that connect to the trachea through the left and right bronchi. Their base rests against the diaphragm, the dome-shaped muscle below the lungs. The lungs are covered by the pleurae and sit next to the mediastinum, the central space in the chest. The right lung is shorter and wider than the left lung, and it has a larger volume. The left lung has a cardiac notch, which is an indentation for the heart. The top of each lung is the apex, and the lower part is the base.

pleura of the lungs

Pleura Layers and Lung Protection

The pleura are membranes that protect the lungs inside the chest cavity. They are a type of serous membrane and wrap around each lung. The pleura have two layers: the visceral pleura and the parietal pleura. The visceral pleura covers the surface of the lung. The parietal pleura is the outer layer. It lines the thoracic wall, the mediastinum, and the diaphragm. The hilum is the point where the visceral and parietal layers connect. The space between these layers is called the pleural cavity. <br...

Breathing depends on pressure changes in the lungs, chest, and airways. Pulmonary ventilation is the movement of air into and out of the lungs. It is driven by atmospheric pressure, intra-alveolar pressure inside the alveoli, and intrapleural pressure in the pleural cavity. Inhalation and exhalation rely on pressure differences between the atmosphere and the lungs. Gas pressure comes from the movement of confined molecules. Boyle’s law explains that pressure and volume are inversely...

pulmonary ventilation: inhalation

Pulmonary Ventilation and Breathing Pressures

Pulmonary ventilation depends on breathing movements and the pressure changes that move air into and out of the lungs. It supports the exchange of oxygen and carbon dioxide by letting the body take in oxygen and remove waste carbon dioxide. Boyle's law is important here because changes in volume and pressure affect how air moves in the respiratory system. Several respiratory volumes help describe how much air the lungs move. Tidal volume is the air inspired or expired during normal, quiet...

pulmonary cycle: exhalation

Exhalation and Lung Pressure Changes

Exhalation is the process of expelling air from the lungs. It depends on pressure differences between the lungs and the atmosphere. During normal quiet breathing, exhalation is passive and does not require muscle contraction. The elastic recoil of the lungs and chest wall helps both structures return to their resting positions after inhalation. When the muscles used for inhalation stop working, the diaphragm and external intercostal muscles relax. The diaphragm moves upward, and the ribs move...

factors affecting pulmonary ventilation

What Changes Breathing Ease in the Lungs

Breathing ease in the lungs depends on alveolar surface tension, lung compliance, and airway resistance. These factors affect how hard it is to move air during pulmonary ventilation, along with the pressure difference between the outside environment and the lungs. Alveolar surface tension comes from the fluid lining the inside of the alveoli. Water molecules in this fluid attract each other more strongly than they attract the air, so the liquid tends to pull the alveoli inward. That force must...

respiratory volumes and capacities

Lung Volume Measurements in Breathing

Lung volume measurements show how air moves in and out of the respiratory system during breathing. They help explain how the body takes in oxygen and removes carbon dioxide. Respiratory volumes and capacities also give useful information about lung function. Tidal volume is the air breathed in and out during normal, quiet breathing. Inspiratory reserve volume is the extra air that can be forcefully inhaled beyond tidal volume. Expiratory reserve volume is the extra air that can be forcefully...

physical principles governing gas exchange

physical-principles-governing-gas-exchange

Gas Laws in Lung Gas Exchange

Gas laws explain how oxygen and carbon dioxide move during respiration. External respiration is the exchange of gases in the lungs. Oxygen diffuses into the blood, and carbon dioxide diffuses out. Internal respiration happens in body tissues, where the gases move in the opposite directions. Two gas laws guide this process: Dalton's law of partial pressures and Henry's law. Dalton's law says the total pressure of a gas mixture equals the sum of the pressures of each gas acting alone. The...

external and internal respiration

Gas Exchange in Lungs and Tissues

Gas exchange in the lungs and body tissues moves oxygen into the blood and removes carbon dioxide. External respiration happens in the lungs, where inhaled oxygen enters the alveoli, the tiny air sacs that provide a large surface area for diffusion. Oxygen moves across the thin alveolar membrane into the pulmonary capillaries because its partial pressure is higher in the alveoli than in the blood. At the same time, carbon dioxide moves in the opposite direction and is later breathed out during...

oxygen transport in the blood

How Hemoglobin Loads and Releases Oxygen

Hemoglobin is the main molecule that carries oxygen in blood. It is found in red blood cells and has four polypeptide chains, each attached to an iron-containing heme group. This structure lets one hemoglobin molecule bind up to four oxygen molecules quickly and reversibly. When hemoglobin is fully loaded with oxygen, it is called oxyhemoglobin. When it has released oxygen, it is called reduced hemoglobin, or deoxyhemoglobin. As hemoglobin binds oxygen, its shape changes, which helps it pick...

carbon dioxide transport in the blood

How Blood Carries Carbon Dioxide

Carbon dioxide is carried in the blood from body tissues to the lungs. Cells make about 200 mL of CO2 each minute, and the lungs remove about the same amount. The blood moves this waste gas in three main forms. A small amount, about 7-10%, stays dissolved in the plasma. Just over 20% binds to hemoglobin and forms carbaminohemoglobin. In this case, CO2 attaches to the amino acids of globin, not to the heme part of hemoglobin. The rest, about 70%, is carried as bicarbonate ions, or HCO3-. CO2...

hypoxia

Hypoxia: Types and Carbon Monoxide Poisoning

Hypoxia is a medical condition in which body tissues do not get enough oxygen. It can cause a bluish color in the skin and mucosae, especially in fair-skinned people. This sign is often seen when hemoglobin (Hb) saturation drops below 75%. Hypoxia can happen for several different reasons. Anemic hypoxia occurs when there are too few red blood cells (RBCs) or when RBCs have abnormal or too little Hb. Ischemic hypoxia comes from poor blood circulation or blocked blood flow, so blood becomes...

neural control of respiration

Brainstem Centers That Control Breathing

Breathing is controlled by nerve centers in the brainstem. These respiratory centers send nerve signals to the muscles that move the lungs. The main centers are in the medulla oblongata and the pons.

chemical factors affecting respiration centers

chemical-factors-affecting-respiration-centers

How Blood Gases Control Breathing Rate

Blood gases and blood pH help control breathing rate and depth. Changes in carbon dioxide, oxygen, and hydrogen ion levels in arterial blood are detected by chemoreceptors, which are special sensors in the body. Central chemoreceptors are found throughout the brain stem, including the ventrolateral medulla. Peripheral chemoreceptors are located in the aortic arch and carotid arteries. Together, these sensors help the respiratory system respond to chemical changes in the blood. Carbon dioxide...

other factors affecting respiration centers

other-factors-affecting-respiration-centers

Respiratory Reflexes That Change Breathing

Breathing is controlled by the brainstem, but it can also be changed by the nervous system and by body signals. The cerebral motor cortex can override the medullary respiratory centers and send signals directly to the breathing muscles. This makes voluntary actions like holding your breath or taking deeper breaths possible. That control is limited. When carbon dioxide, or CO2, builds up in the blood to a critical level, the brainstem respiratory centers start breathing again. This is why a...

hyperpnea and hyperventilation

Breathing Changes in Exercise and Anxiety

Breathing changes in exercise and anxiety can look similar, but they do not have the same cause. Hyperventilation is a higher-than-normal rate and depth of breathing. It often happens during anxiety attacks and can push out more carbon dioxide than the body needs to remove. When too much carbon dioxide is lost, the blood develops hypocapnia, which means an unusually low level of carbon dioxide. Hypocapnia can narrow cerebral blood vessels and reduce blood flow to the brain. This may cause...

chronic obstructive pulmonary disease

COPD Signs, Causes, and Lung Damage

COPD is a lung condition that causes ongoing breathing problems. It leads to shortness of breath, cough, and sputum production because the airways become blocked and airflow is reduced. Smoking is the main risk factor for COPD, and more than 80% of patients have a history of it. People with COPD often develop worsening dyspnea, or labored breathing. They may also cough often and get repeated lung infections. Many patients with COPD can develop respiratory failure. This happens when...

other pulmonary disorders

Asthma, TB, Lung Cancer, and Sleep Apnea

Asthma, lung cancer, tuberculosis, and sleep apnea are major pulmonary disorders. They affect breathing in different ways. Some are chronic, some are infectious, and some can become life-threatening if not found and treated early. Asthma is marked by chronic airway inflammation and hypersensitivity. It can cause airway obstruction from bronchial spasms, mucosal edema, increased mucus secretion, or epithelial damage. Triggers vary and can include allergens or emotional upset. Treatment often...

key terms and concepts

Explore how atmospheric, alveolar, and intrapleural pressure work together with Boyle’s law, surfactant, and muscle action to move air in and out of the lungs.

How Pressure Drives Breathing in the Lungs | JoVE K12

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How Pressure Drives Breathing in the Lungs

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