Pleural cavity
Encyclopedia
In human anatomy
, the pleural cavity is the potential space between the two pleura (visceral and parietal) of the lungs. The pleura is a serous membrane
which folds back onto itself to form a two-layered, membrane structure. The thin space between the two pleural layers is known as the pleural cavity; it normally contains a small amount of pleural fluid. The outer pleura (parietal pleura
) is attached to the chest wall
. The inner pleura (visceral pleura) covers the lungs and adjoining structures, viz. blood vessel
s, bronchi
and nerve
s.
The parietal pleura is highly sensitive to pain, while the visceral pleura is not, due to its lack of sensory innervation.
. The pleural cavity also contains pleural fluid, which allows the pleurae to slide effortlessly against each other during ventilation
. Surface tension
of the pleural fluid also leads to close apposition of the lung surfaces with the chest wall. This physical relationship allows for optimal inflation of the alveoli during respiration. The pleural cavity transmits movements of the chest wall to the lungs, particularly during heavy breathing. This occurs because the closely opposed chest wall transmits pressures to the visceral pleural surface and hence to the lung itself.
, the other lung will still function normally unless there is a tension pneumothorax or simultaneous bilateral pneumothorax, which may collapse the contralateral parenchyma, blood vessels and bronchi.
The visceral pleura receives its blood supply from the bronchial circulation.
cavities. The diaphragm and the paired pleuropericardial membranes separate the coelomic cavity into four parts. From the splanchnopleura (the visceral mesodermal layer) develops the Visceral pleura and from the somatopleura (parietal mesodermal layer) develops the parietal pleura.
produced by the normal pleurae. Most fluid is produced by the parietal circulation (intercostal arteries
) via bulk flow and reabsorbed by the lymphatic system
. Thus, pleural fluid is produced and reabsorbed continuously. In a normal 70 kg human, a few milliliters of pleural fluid is always present within the intrapleural space. Larger quantities of fluid can accumulate in the pleural space only when the rate of production exceeds the rate of reabsorption. Normally, the rate of reabsorption increases as a physiological response to accumulating fluid, with the reabsorption rate increasing up to 40 times the normal rate before significant amounts of fluid accumulate within the pleural space. Thus, a profound increase in the production of pleural fluid—or some blocking of the reabsorbing lymphatic system—is required for fluid to accumulate in the pleural space.
Localized pleural fluid effusion noted during pulmonary embolism (PE
) results probably from increased capillary permeability due to cytokine or inflammatory mediator release from the platelet-rich thrombi.
When accumulation of pleural fluid is noted, cytopathologic evaluation
of the fluid, as well as clinical microscopy, microbiology, chemical studies, tumor markers, pH determination and other more esoteric tests are required as diagnostic
tools for determining the causes of this abnormal accumulation. Even the gross appearance, color, clarity and odor can be useful tools in diagnosis. The presence of heart failure, infection or malignancy within the pleural cavity are the most common causes that can be identified using this approach.
In spite of all the diagnostic tests available today, many pleural effusions remain idiopathic
in origin. This can be quite vexing to the patient, family and physicians involved. If severe symptoms persist, more invasive techniques may be required. In spite of the lack of knowledge of the cause of the effusion, treatment may be required to relieve the most common symptom, dyspnea
, as this can be quite disabling. Thoracoscopy
has become the mainstay of invasive procedures as closed pleural biopsy has fallen into disuse.
Human anatomy
Human anatomy is primarily the scientific study of the morphology of the human body. Anatomy is subdivided into gross anatomy and microscopic anatomy. Gross anatomy is the study of anatomical structures that can be seen by the naked eye...
, the pleural cavity is the potential space between the two pleura (visceral and parietal) of the lungs. The pleura is a serous membrane
Serous membrane
In anatomy, serous membrane is a smooth membrane consisting of a thin layer of cells which secrete serous fluid. Serous membranes line and enclose several body cavities, known as serous cavities, where they secrete a lubricating fluid which reduces friction from muscle movement...
which folds back onto itself to form a two-layered, membrane structure. The thin space between the two pleural layers is known as the pleural cavity; it normally contains a small amount of pleural fluid. The outer pleura (parietal pleura
Parietal pleura
The portion of the pleura external to the pulmonary pleura lines the inner surface of the chest wall, covers the diaphragm, and is reflected over the structures occupying the middle of the thorax; this portion is termed the parietal pleura....
) is attached to the chest wall
Thoracic wall
The thoracic wall is the boundary of the thoracic cavity.The bony portion is known as the thoracic cage. However, the wall also includes muscle, skin, and fascia....
. The inner pleura (visceral pleura) covers the lungs and adjoining structures, viz. blood vessel
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...
s, bronchi
Bronchus
A bronchus is a passage of airway in the respiratory tract that conducts air into the lungs. The bronchus branches into smaller tubes, which in turn become bronchioles....
and nerve
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...
s.
The parietal pleura is highly sensitive to pain, while the visceral pleura is not, due to its lack of sensory innervation.
Functions
The pleural cavity, with its associated pleurae, aids optimal functioning of the lungs during respirationRespiration (physiology)
'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...
. The pleural cavity also contains pleural fluid, which allows the pleurae to slide effortlessly against each other during ventilation
Ventilation (physiology)
In respiratory physiology, ventilation is the rate at which gas enters or leaves the lung. It is categorized under the following definitions:-Sample values:...
. Surface tension
Surface tension
Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...
of the pleural fluid also leads to close apposition of the lung surfaces with the chest wall. This physical relationship allows for optimal inflation of the alveoli during respiration. The pleural cavity transmits movements of the chest wall to the lungs, particularly during heavy breathing. This occurs because the closely opposed chest wall transmits pressures to the visceral pleural surface and hence to the lung itself.
Structure
In humans, there is no anatomical connection between the left and right pleural cavities. Therefore, in cases of pneumothoraxPneumothorax
Pneumothorax is a collection of air or gas in the pleural cavity of the chest between the lung and the chest wall. It may occur spontaneously in people without chronic lung conditions as well as in those with lung disease , and many pneumothoraces occur after physical trauma to the chest, blast...
, the other lung will still function normally unless there is a tension pneumothorax or simultaneous bilateral pneumothorax, which may collapse the contralateral parenchyma, blood vessels and bronchi.
The visceral pleura receives its blood supply from the bronchial circulation.
Development
Initially the intraembryonic coelom is one continuous space. During development this space partitions to form the pericardial, pleural and peritonealcavities. The diaphragm and the paired pleuropericardial membranes separate the coelomic cavity into four parts. From the splanchnopleura (the visceral mesodermal layer) develops the Visceral pleura and from the somatopleura (parietal mesodermal layer) develops the parietal pleura.
Pleural fluid
Pleural fluid is a serous fluidSerous fluid
In physiology, the term serous fluid is used for various bodily fluids that are typically pale yellow and transparent, and of a benign nature, that fill the inside of body cavities. Serous fluid originates from serous glands, with secretions enriched with proteins and water. Serous fluid may also...
produced by the normal pleurae. Most fluid is produced by the parietal circulation (intercostal arteries
Intercostal arteries
The intercostal arteries are a group of arteries that supply the area between the ribs , called the intercostal space.* Highest intercostal artery - first and second intercostal spaces...
) via bulk flow and reabsorbed by the lymphatic system
Lymphatic system
The lymphoid system is the part of the immune system comprising a network of conduits called lymphatic vessels that carry a clear fluid called lymph unidirectionally toward the heart. Lymphoid tissue is found in many organs, particularly the lymph nodes, and in the lymphoid follicles associated...
. Thus, pleural fluid is produced and reabsorbed continuously. In a normal 70 kg human, a few milliliters of pleural fluid is always present within the intrapleural space. Larger quantities of fluid can accumulate in the pleural space only when the rate of production exceeds the rate of reabsorption. Normally, the rate of reabsorption increases as a physiological response to accumulating fluid, with the reabsorption rate increasing up to 40 times the normal rate before significant amounts of fluid accumulate within the pleural space. Thus, a profound increase in the production of pleural fluid—or some blocking of the reabsorbing lymphatic system—is required for fluid to accumulate in the pleural space.
Localized pleural fluid effusion noted during pulmonary embolism (PE
Pulmonary embolism
Pulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...
) results probably from increased capillary permeability due to cytokine or inflammatory mediator release from the platelet-rich thrombi.
When accumulation of pleural fluid is noted, cytopathologic evaluation
Cytopathology
Cytopathology is a branch of pathology that studies and diagnoses diseases on the cellular level. The discipline was founded by Rudolf Virchow in 1858. A common application of cytopathology is the Pap smear, used as a screening tool, to detect precancerous cervical lesions and prevent cervical...
of the fluid, as well as clinical microscopy, microbiology, chemical studies, tumor markers, pH determination and other more esoteric tests are required as diagnostic
Medical diagnosis
Medical diagnosis refers both to the process of attempting to determine or identify a possible disease or disorder , and to the opinion reached by this process...
tools for determining the causes of this abnormal accumulation. Even the gross appearance, color, clarity and odor can be useful tools in diagnosis. The presence of heart failure, infection or malignancy within the pleural cavity are the most common causes that can be identified using this approach.
In spite of all the diagnostic tests available today, many pleural effusions remain idiopathic
Idiopathic
Idiopathic is an adjective used primarily in medicine meaning arising spontaneously or from an obscure or unknown cause. From Greek ἴδιος, idios + πάθος, pathos , it means approximately "a disease of its own kind". It is technically a term from nosology, the classification of disease...
in origin. This can be quite vexing to the patient, family and physicians involved. If severe symptoms persist, more invasive techniques may be required. In spite of the lack of knowledge of the cause of the effusion, treatment may be required to relieve the most common symptom, dyspnea
Dyspnea
Dyspnea , shortness of breath , or air hunger, is the subjective symptom of breathlessness.It is a normal symptom of heavy exertion but becomes pathological if it occurs in unexpected situations...
, as this can be quite disabling. Thoracoscopy
Thoracoscopy
Thoracoscopy is a medical procedure involving internal examination, biopsy, and/or resection of disease or masses within the pleural cavity and thoracic cavity...
has become the mainstay of invasive procedures as closed pleural biopsy has fallen into disuse.
See also
- Bronchioles
- BronchusBronchusA bronchus is a passage of airway in the respiratory tract that conducts air into the lungs. The bronchus branches into smaller tubes, which in turn become bronchioles....
- Capillaries
- EpiglottisEpiglottisThe epiglottis is a flap that is made of elastic cartilage tissue covered with a mucous membrane, attached to the entrance of the larynx. It projects obliquely upwards behind the tongue and the hyoid bone, pointing dorsally. The term, like tonsils, is often incorrectly used to refer to the uvula...
- LarynxLarynxThe larynx , commonly called the voice box, is an organ in the neck of amphibians, reptiles and mammals involved in breathing, sound production, and protecting the trachea against food aspiration. It manipulates pitch and volume...
- MesotheliomaMesotheliomaMesothelioma, more precisely malignant mesothelioma, is a rare form of cancer that develops from the protective lining that covers many of the body's internal organs, the mesothelium...
- PharynxPharynxThe human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...
- Pleural diseasePleural diseasePleural diseases include:* Pneumothorax: a collection of air within the pleural cavity, arising either from the outside or from the lung. Pneumothoraces may be traumatic, iatrogenic, or spontaneous. A tension pneumothorax is a particular type of pneumothorax where the air may enter on...
- PleurisyPleurisyPleurisy is an inflammation of the pleura, the lining of the pleural cavity surrounding the lungs. Among other things, infections are the most common cause of pleurisy....
- PleurodesisPleurodesisPleurodesis is a medical procedure in which the pleural space is artificially obliterated. It involves the adhesion of the two pleura.- Uses :Pleurodesis is done to prevent recurrence of pneumothorax or recurrent pleural effusion...
- Pleuropulmonary blastomaPleuropulmonary blastomaPleuropulmonary blastoma is a rare cancer originating in the lung or pleural cavity. It occurs most often in infants and young children but also has been reported in adults...
- Rings of cartilage
- Solitary fibrous tumorSolitary fibrous tumorSolitary fibrous tumor is a rare mesenchymal tumor originating in the pleura or at virtually any site in the soft tissue. Approximately 78% to 88% of SFT's are benign and 12% to 22% are malignant....
- Tension pneumothorax
- Thoracic cavityThoracic cavityThe thoracic cavity is the chamber of the human body that is protected by the thoracic wall ....
- Vertebrate tracheaVertebrate tracheaIn tetrapod anatomy the trachea, or windpipe, is a tube that connects the pharynx or larynx to the lungs, allowing the passage of air. It is lined with pseudostratified ciliated columnar epithelium cells with goblet cells that produce mucus...
External links
- Photo of dissection at kenyon.edu