The pulmonary pleurae (''sing.'' pleura) are the two opposing layers of
serous membrane
The serous membrane (or serosa) is a smooth tissue membrane of mesothelium lining the contents and inner walls of body cavities, which secrete serous fluid to allow lubricated sliding movements between opposing surfaces. The serous membrane ...
overlying the
lungs and the inside of the surrounding
chest walls.
The inner pleura, called the visceral pleura, covers the surface of each lung and dips between the
lobes of the lung
The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...
as ''fissures'', and is formed by the
invagination
Invagination is the process of a surface folding in on itself to form a cavity, pouch or tube. In developmental biology, invagination is a mechanism that takes place during gastrulation. This mechanism or cell movement happens mostly in the vegeta ...
of
lung buds
The lung bud sometimes referred to as the respiratory bud forms from the respiratory diverticulum, an embryological endodermal structure that develops into the respiratory tract organs such as the larynx, trachea, bronchi and lungs. It arises from ...
into each
thoracic sac during
embryonic development. The outer layer, called the parietal pleura, lines the inner surfaces of the
thoracic cavity
The thoracic cavity (or chest cavity) is the chamber of the body of vertebrates that is protected by the thoracic wall (rib cage and associated skin, muscle, and fascia). The central compartment of the thoracic cavity is the mediastinum. There ...
on each side of the
mediastinum, and can be subdivided into ''mediastinal'' (covering the side surfaces of the
fibrous pericardium
The pericardium, also called pericardial sac, is a double-walled sac containing the heart and the roots of the great vessels. It has two layers, an outer layer made of strong connective tissue (fibrous pericardium), and an inner layer made of ...
,
oesophagus
The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to th ...
and
thoracic aorta
The descending thoracic aorta is a part of the aorta located in the thorax. It is a continuation of the aortic arch. It is located within the posterior mediastinal cavity, but frequently bulges into the left pleural cavity. The descending thoracic ...
), ''diaphragmatic'' (covering the upper surface of the
diaphragm), ''costal'' (covering the inside of
rib cage
The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels.
The sternum, together known as the thoracic cage, is a sem ...
) and cervical (covering the underside of the
suprapleural membrane) pleurae. The visceral and the mediastinal parietal pleurae are connected at the
root of the lung
The root of the lung is a group of structures that emerge at the hilum of each lung, just above the middle of the mediastinal surface and behind the cardiac impression of the lung. It is nearer to the back (posterior border) than the front (ant ...
("hilum") through a smooth fold known as ''pleural reflections'', and a
bell sleeve-like extension of visceral pleura hanging under to the hilum is known as the
pulmonary ligament
The root of the lung is a group of structures that emerge at the hilum of each lung, just above the middle of the mediastinal surface and behind the cardiac impression of the lung. It is nearer to the back (posterior border) than the front (ant ...
.
Between two pleurae is a
potential space
In anatomy, a potential space is a space between two adjacent structures that are normally pressed together (directly apposed). Many anatomic spaces are potential spaces, which means that they are potential rather than realized (with their realiz ...
called the
pleural cavity
The pleural cavity, pleural space, or interpleural space is the potential space between the pleurae of the pleural sac that surrounds each lung. A small amount of serous pleural fluid is maintained in the pleural cavity to enable lubrication b ...
(also pleural space), which is normally collapsed and filled with only a tiny amount of
serous fluid
In physiology, serous fluid or serosal fluid (originating from the Medieval Latin word ''serosus'', from Latin ''serum'') is any of various body fluids resembling serum, that are typically pale yellow or transparent and of a benign nature. The fl ...
(''pleural fluid'')
secreted 440px
Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classical ...
by the pleurae, and is clinically considered
vacuum
A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or " void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often di ...
ous under healthy conditions. The two lungs bounded by parietal pleura, almost fill the
thoracic cavity
The thoracic cavity (or chest cavity) is the chamber of the body of vertebrates that is protected by the thoracic wall (rib cage and associated skin, muscle, and fascia). The central compartment of the thoracic cavity is the mediastinum. There ...
.
Anatomy
Each pleura comprises a superficial
serosa
The serous membrane (or serosa) is a smooth tissue membrane of mesothelium lining the contents and inner walls of body cavities, which secrete serous fluid to allow lubricated sliding movements between opposing surfaces. The serous membrane ...
made of a simple
monolayer of flat (squamous) or cuboidal
mesothelial cell
The mesothelium is a membrane composed of simple squamous epithelial cells of mesodermal origin, which forms the lining of several body cavities: the pleura (pleural cavity around the lungs), peritoneum (abdominopelvic cavity including the mesent ...
s with
microvilli up to long. The mesothelium is without
basement membrane, and supported by a well-vascularized underlying
loose connective tissue
Loose connective tissue, sometimes called areolar tissue, is a cellular connective tissue with thin and relatively sparse collagen fibers. Its ground substance occupies more volume than the fibers do. It has a viscous to gel-like consisten ...
containing two poorly defined layers of
elastin-rich laminae. The costal parietal pleurae also have
adipocytes in the
subserosa, which present as ''subpleural/extrapleural fats'' and are
histologically considered belonging to the
endothoracic fascia
The endothoracic fascia is the layer of loose connective tissue deep to the intercostal spaces and ribs, separating these structures from the underlying pleura. This fascial layer is the outermost membrane of the thoracic cavity. The endothor ...
that separates the subserosa from the inner
periosteum
The periosteum is a membrane that covers the outer surface of all bones, except at the articular surfaces (i.e. the parts within a joint space) of long bones. Endosteum lines the inner surface of the medullary cavity of all long bones.
Structu ...
of the
ribs. Both pleurae are quite firmly attached to their underlying structures, and are usually covered by surface
glycocalyces that limit fluid loss and reduce friction.
The enclosed space between the parietal and visceral pleurae, known as the
pleural space
The pleural cavity, pleural space, or interpleural space is the potential space between the pleurae of the pleural sac that surrounds each lung. A small amount of serous pleural fluid is maintained in the pleural cavity to enable lubrication bet ...
, is normally filled only by a tiny amount (less than ) of
serous fluid
In physiology, serous fluid or serosal fluid (originating from the Medieval Latin word ''serosus'', from Latin ''serum'') is any of various body fluids resembling serum, that are typically pale yellow or transparent and of a benign nature. The fl ...
secreted from the apical region of the parietal pleura. The combination of
surface tension,
oncotic pressure
Oncotic pressure, or colloid osmotic-pressure, is a form of osmotic pressure induced by the proteins, notably albumin, in a blood vessel's plasma (blood/liquid) that causes a pull on fluid back into the capillary. Participating colloids displace ...
, and the
fluid pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
drop caused by the inward
elastic recoil of the
lung parenchyma
Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms.
Etymology
The term ''parenchyma'' is New Latin from the word π ...
and the rigidity of the
chest wall, results in a normally negative pressure of -5 cm (approximately ) within the pleural space, causing it to mostly stay collapsed as a
potential space
In anatomy, a potential space is a space between two adjacent structures that are normally pressed together (directly apposed). Many anatomic spaces are potential spaces, which means that they are potential rather than realized (with their realiz ...
that acts as a functionally
vacuum
A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or " void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often di ...
ous
interface
Interface or interfacing may refer to:
Academic journals
* ''Interface'' (journal), by the Electrochemical Society
* '' Interface, Journal of Applied Linguistics'', now merged with ''ITL International Journal of Applied Linguistics''
* '' Int ...
between the parietal and visceral pleurae. Contracting the
respiratory muscles
The muscles of respiration are the muscles that contribute to inhalation and exhalation, by aiding in the expansion and contraction of the thoracic cavity. The diaphragm and, to a lesser extent, the intercostal muscles drive respiration during q ...
expands the
chest cavity, causing the attached parietal pleura to also expand outwards. If the pleural functional vacuum stays intact, the pleural space will remain as collapsed as possible and cause the visceral pleura to be pulled along outwards, which in turn draws the underlying lung also into expansion. This transmits the pressure negativity into the
alveoli and
bronchioli, thus facilitating
inhalation.
Visceral pleura
The visceral pleura (from la, viscera, lit=organ) covers the
lung surfaces and the
hilar structures and extends
caudally from the hilum as a
mesentery-like band called the
pulmonary ligament
The root of the lung is a group of structures that emerge at the hilum of each lung, just above the middle of the mediastinal surface and behind the cardiac impression of the lung. It is nearer to the back (posterior border) than the front (ant ...
. Each lung is divided into
lobes by the infoldings of the pleura as fissures. The fissures are double folds of pleura that section the lungs and help in their expansion,
allowing the lung to
ventilate more effectively even if parts of it (usually the basal
segments) fail to expand properly due to
congestion or
consolidation.The function of the visceral pleura is to produce and reabsorb fluid. It is an area that is insensitive to pain due to its association with the lung and innervation by visceral sensory neurons.
Visceral pleura also forms interlobular septa (that separates secondary pulmonary lobules). Interlobular septa contains connective tissue, pulmonary veins, and lymphatics.
Parietal pleura
The parietal pleura (from la, paries, lit=wall) lines the inside of the
thoracic cavity
The thoracic cavity (or chest cavity) is the chamber of the body of vertebrates that is protected by the thoracic wall (rib cage and associated skin, muscle, and fascia). The central compartment of the thoracic cavity is the mediastinum. There ...
which is set apart from the
thoracic wall
The thoracic wall or chest wall is the boundary of the thoracic cavity.
Structure
The bony skeletal part of the thoracic wall is the rib cage, and the rest is made up of muscle, skin, and fasciae.
The chest wall has 10 layers, namely (from sup ...
by the endothoracic fascia. The Parietal includes the inner surface of the
rib cage
The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels.
The sternum, together known as the thoracic cage, is a sem ...
and the upper surface of the
diaphragm, as well as the side surfaces of the
mediastinum, from which it separates the pleural cavity. It joins the visceral pleura at the
pericardial base of the
pulmonary hilum and pulmonary ligament as a smooth but
acutely angled circumferential junction known as the ''hilar reflection''.
The parietal pleura is subdivided according to the surface it covers.
* The ''costal pleura'' is the pleural portion covering the inner surfaces of the
rib cage
The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels.
The sternum, together known as the thoracic cage, is a sem ...
, and is separated from the
ribs/
cartilages and
intercostal muscles
Intercostal muscles are many different groups of muscles that run between the ribs, and help form and move the chest wall. The intercostal muscles are mainly involved in the mechanical aspect of breathing by helping expand and shrink the size of ...
by the
endothoracic fascia
The endothoracic fascia is the layer of loose connective tissue deep to the intercostal spaces and ribs, separating these structures from the underlying pleura. This fascial layer is the outermost membrane of the thoracic cavity. The endothor ...
.
** The apical part of the costal pleura, sometimes referred to as the ''cervical pleura'' or ''cupula of pleura'', bulges beyond the
thoracic inlet into the
posterior triangle of the
neck, where it is covered by an extension of the endothoracic fascia known as the
suprapleural membrane. This is the most superficial (and thus most vulnerable) part of the pleura and can be
punctured by
subclavian catheterization or a
penetrating neck injury.
* The ''diaphragmatic pleura'' is the portion covering the convex upper surface of the
diaphragm. Its junction with the costal pleura at the diaphragmatic margin is a sharp gutter known as the ''
costodiaphragmatic recess'', which has diagnostic significance on
plain radiography.
* The ''mediastinal pleura'' is the portion covering the lateral surfaces of the
mediastinum, predominantly the
fibrous pericardium
The pericardium, also called pericardial sac, is a double-walled sac containing the heart and the roots of the great vessels. It has two layers, an outer layer made of strong connective tissue (fibrous pericardium), and an inner layer made of ...
,
thoracic aorta
The descending thoracic aorta is a part of the aorta located in the thorax. It is a continuation of the aortic arch. It is located within the posterior mediastinal cavity, but frequently bulges into the left pleural cavity. The descending thoracic ...
,
superior vena cava
The superior vena cava (SVC) is the superior of the two venae cavae, the great venous trunks that return deoxygenated blood from the systemic circulation to the right atrium of the heart. It is a large-diameter (24 mm) short length vein th ...
/
azygos vein
The azygos vein is a vein running up the right side of the thoracic vertebral column draining itself towards the superior vena cava. It connects the systems of superior vena cava and inferior vena cava and can provide an alternative path for blo ...
,
esophagus
The esophagus ( American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to ...
and (very rarely) an enlarged
thymus
The thymus is a specialized primary lymphoid organ of the immune system. Within the thymus, thymus cell lymphocytes or ''T cells'' mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. ...
. Its anterosuperior part (especially of the left side) not infrequently can bulge into the
anterior mediastinum behind the
upper sternal body and even touch its contralateral counterpart in forced
inhalation, but the left and right pleurae ''do not'' communicate unless there is a significant
injury (
traumatic or
iatrogenic
Iatrogenesis is the causation of a disease, a harmful complication, or other ill effect by any medical activity, including diagnosis, intervention, error, or negligence. "Iatrogenic", ''Merriam-Webster.com'', Merriam-Webster, Inc., accessed 27 ...
) or
disease
A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...
process (e.g.
malignancy
Malignancy () is the tendency of a medical condition to become progressively worse.
Malignancy is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous ''benign'' tumor in that a malignancy is not s ...
).
Neurovascular supply
As a
rule of thumb, the
blood
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...
and
nerve supply of a pleura comes from the structures under it. The visceral pleura is supplied by the
capillaries
A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter. Capillaries are composed of only the tunica intima, consisting of a thin wall of simple squamous endothelial cells. They are the smallest blood vessels in the body: ...
that supply the lung surface (from both the
pulmonary circulation
The pulmonary circulation is a division of the circulatory system in all vertebrates. The circuit begins with deoxygenated blood returned from the body to the right atrium of the heart where it is pumped out from the right ventricle to the lungs ...
and the
bronchial vessels), and innervated by the
nerve endings from the
pulmonary plexus
The pulmonary plexus is an autonomic plexus formed from pulmonary branches of vagus nerve and the sympathetic trunk. The plexus is in continuity with the deep cardiac plexus.
Structure
It innervates the bronchial tree and the visceral pleura. ...
.
The parietal pleura is supplied by blood from the cavity wall under it, which can come from the
aorta
The aorta ( ) is the main and largest artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen, where it splits into two smaller arteries (the common iliac arteries). The aorta distributes o ...
(
intercostal,
superior phrenic and
inferior phrenic arteries
The inferior phrenic arteries are two small vessels which supply the diaphragm. They present much variety in their origin.
Structure
Origin
The inferior phrenic arteries usually arise between T12 and L2 vertebrae. They may arise separately ...
), the
internal thoracic arteries (
pericardiacophrenic,
anterior intercostal and
musculophrenic
The intercostal arteries are a group of arteries that supply the area between the ribs ("costae"), called the intercostal space. The highest intercostal artery (supreme intercostal artery or superior intercostal artery) is an artery in the human ...
branches), or their
anastomoses
An anastomosis (, plural anastomoses) is a connection or opening between two things (especially cavities or passages) that are normally diverging or branching, such as between blood vessels, leaf veins, or streams. Such a connection may be norm ...
. Similarly, its nerve supply is from its underlying structures — the costal pleura is innervated by the
intercostal nerve
The intercostal nerves are part of the somatic nervous system, and arise from the anterior rami of the thoracic spinal nerves from T1 to T11. The intercostal nerves are distributed chiefly to the thoracic pleura and abdominal peritoneum, and diff ...
s; the diaphragmatic pleura is innervated by the
phrenic nerve in its central portion around the
central tendon, and by the intercostal nerves in its periphery near the
costal margin
The costal margin, also known as the costal arch, is the lower edge of the chest (thorax) formed by the bottom edge of the rib cage.
Structure
The costal margin is the medial margin formed by the cartilages of the seventh to tenth ribs. It attac ...
; the mediastinal pleura is innervated by branches of the phrenic nerve over the
fibrous pericardium
The pericardium, also called pericardial sac, is a double-walled sac containing the heart and the roots of the great vessels. It has two layers, an outer layer made of strong connective tissue (fibrous pericardium), and an inner layer made of ...
.
Development
The visceral and parietal pleurae, like all
mesothelia, both derive from the
lateral plate mesoderm
The lateral plate mesoderm is the mesoderm that is found at the periphery of the embryo. It is to the side of the paraxial mesoderm, and further to the axial mesoderm. The lateral plate mesoderm is separated from the paraxial mesoderm by a narrow ...
s. During the third week of
embryogenesis, each lateral mesoderm splits into two layers. The dorsal layer joins overlying
somite
The somites (outdated term: primitive segments) are a set of bilaterally paired blocks of paraxial mesoderm that form in the embryonic stage of somitogenesis, along the head-to-tail axis in segmented animals. In vertebrates, somites subdivide ...
s and
ectoderm to form the
somatopleure
In the anatomy of an embryo, the somatopleure is a structure created during embryogenesis when the lateral plate mesoderm splits into two layers. The outer (or somatic) layer becomes applied to the inner surface of the ectoderm, and with it (part ...
; and the ventral layer joins the underlying
endoderm to form the
splanchnopleure. The dehiscence of these two layers creates a fluid-filled cavity on each side, and with the ventral infolding and the subsequent midline fusion of the
trilaminar disc, forms a pair of
intraembryonic coelom
In the development of the human embryo the intraembryonic coelom (or somatic coelom) is a portion of the conceptus forming in the mesoderm during the third week of development. During the third week of development, the lateral plate mesoderm split ...
s anterolaterally around the
gut tube during the fourth week, with the splanchnopleure on the inner cavity wall and the somatopleure on the outer cavity wall.
The
cranial end of the intraembryonic coeloms fuse early to form a single cavity, which rotates anteriorly and apparently ''descends'' inverted in front of the thorax, and is later encroached by the growing
primordial heart as the
pericardial cavity
The pericardium, also called pericardial sac, is a double-walled sac containing the heart and the roots of the great vessels. It has two layers, an outer layer made of strong connective tissue (fibrous pericardium), and an inner layer made of ...
. The
caudal portions of the coeloms fuse later below the
umbilical vein
The umbilical vein is a vein present during fetal development that carries oxygenated blood from the placenta into the growing fetus. The umbilical vein provides convenient access to the central circulation of a neonate for restoration of blood v ...
to become the larger
peritoneal cavity
The peritoneal cavity is a potential space between the parietal peritoneum (the peritoneum that surrounds the abdominal wall) and visceral peritoneum (the peritoneum that surrounds the internal organs). The parietal and visceral peritonea are la ...
, separated from the pericardial cavity by the
transverse septum. The two cavities communicate via a slim pair of remnant coeloms adjacent to the upper
foregut called the ''pericardioperitoneal canal''. During the fifth week, the developing
lung bud
The lung bud sometimes referred to as the respiratory bud forms from the respiratory diverticulum, an embryological endodermal structure that develops into the respiratory tract organs such as the larynx, trachea, bronchi and lungs. It arises from ...
s begin to invaginate into these canals, creating a pair of enlarging cavities that encroach into the surrounding somites and further displace the transverse septum caudally — namely the pleural cavities. The mesothelia pushed out by the developing lungs arise from the splanchnopleure, and become the visceral pleurae; while the other mesothelial surfaces of the pleural cavities arise from the somatopleure, and become the parietal pleurae.
Function
As a
serous membrane
The serous membrane (or serosa) is a smooth tissue membrane of mesothelium lining the contents and inner walls of body cavities, which secrete serous fluid to allow lubricated sliding movements between opposing surfaces. The serous membrane ...
, the pleura secretes a
serous fluid
In physiology, serous fluid or serosal fluid (originating from the Medieval Latin word ''serosus'', from Latin ''serum'') is any of various body fluids resembling serum, that are typically pale yellow or transparent and of a benign nature. The fl ...
(pleural fluid) that contains various lubricating
macromolecules such as
sialomucin
Mucins () are a family of high molecular weight, heavily glycosylated proteins (glycoconjugates) produced by epithelial tissues in most animals. Mucins' key characteristic is their ability to form gels; therefore they are a key component in most ...
,
hyaluronan and
phospholipids. These, coupled with the smoothness of the glycocalyces and
hydrodynamic lubrication of the pleural fluid itself, reduces the
frictional coefficient
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction:
*Dry friction is a force that opposes the relative lateral motion of t ...
when the opposing pleural surfaces have to
slide against each other during
ventilation
Ventilation may refer to:
* Ventilation (physiology), the movement of air between the environment and the lungs via inhalation and exhalation
** Mechanical ventilation, in medicine, using artificial methods to assist breathing
*** Ventilator, a m ...
, thus help improving the
pulmonary compliance
The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the vertebral column, backbone o ...
.
The
adhesive property of the pleural fluid to various cellular surfaces, coupled with its
oncotic pressure
Oncotic pressure, or colloid osmotic-pressure, is a form of osmotic pressure induced by the proteins, notably albumin, in a blood vessel's plasma (blood/liquid) that causes a pull on fluid back into the capillary. Participating colloids displace ...
and the negative
fluid pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
, also holds the two opposing pleurae in close sliding contact and keeps the
pleural space
The pleural cavity, pleural space, or interpleural space is the potential space between the pleurae of the pleural sac that surrounds each lung. A small amount of serous pleural fluid is maintained in the pleural cavity to enable lubrication bet ...
collapsed, maximizing the
total lung capacity
Lung volumes and lung capacities refer to the volume of air in the lungs at different phases of the respiratory cycle.
The average total lung capacity of an adult human male is about 6 litres of air.
Tidal breathing is normal, resting breathi ...
while maintaining a functional
vacuum
A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or " void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often di ...
. When
inhalation occurs, the contraction of the
diaphragm and the
external intercostal muscle
The external intercostal muscles, or external intercostals (Intercostales externi) are eleven in number on both sides.
Structure
The muscles extend from the tubercles of the ribs behind, to the cartilages of the ribs in front, where they end ...
s (along with the
bucket
A bucket is typically a watertight, vertical cylinder or truncated cone or square, with an open top and a flat bottom, attached to a semicircular carrying handle called the ''bail''.
A bucket is usually an open-top container. In contrast, a ...
/
pump handle movement
Pump-handle is a movement of the ribs that results in a change in the anteroposterior diameter of the thorax.
Definition
One of the most important functions of the ribs and diaphragm is the change in volume of the thorax that helps inspiration
...
s of the
ribs and
sternum
The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. Sha ...
) increases the
volume
Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). Th ...
of the pleural cavity, further increasing the negative
pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
within the pleural space. As long as the functional
vacuum
A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or " void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often di ...
remains intact, the lung will be drawn to expand along with the chest wall, relaying a negative
airway
The respiratory tract is the subdivision of the respiratory system involved with the process of respiration in mammals. The respiratory tract is lined with respiratory epithelium as respiratory mucosa.
Air is breathed in through the nose to ...
pressure that causes an
airflow
Airflow, or air flow, is the movement of air. The primary cause of airflow is the existence of air. Air behaves in a fluid manner, meaning particles naturally flow from areas of higher pressure to those where the pressure is lower. Atmospheric ...
into the lung, resulting in
inhalation.
Exhalation
Exhalation (or expiration) is the flow of the breath out of an organism. In animals, it is the movement of air from the lungs out of the airways, to the external environment during breathing.
This happens due to elastic properties of the lungs, ...
is however usually passive, caused by
elastic recoil of the
alveolar wall
A pulmonary alveolus (plural: alveoli, from Latin ''alveolus'', "little cavity"), also known as an air sac or air space, is one of millions of hollow, distensible cup-shaped cavities in the lungs where oxygen is exchanged for carbon dioxide. Al ...
s and relaxation of
respiratory muscles
The muscles of respiration are the muscles that contribute to inhalation and exhalation, by aiding in the expansion and contraction of the thoracic cavity. The diaphragm and, to a lesser extent, the intercostal muscles drive respiration during q ...
. In forced exhalation, the pleural fluid provides some hydrostatic cushioning for the lungs against the rapid change of pressure within the pleural cavity.
Clinical significance
Pleuritis
Pleurisy, also known as pleuritis, is inflammation of the membranes that surround the lungs and line the chest cavity (pleurae). This can result in a sharp chest pain while breathing. Occasionally the pain may be a constant dull ache. Other sym ...
or
pleurisy
Pleurisy, also known as pleuritis, is inflammation of the membranes that surround the lungs and line the chest cavity ( pleurae). This can result in a sharp chest pain while breathing. Occasionally the pain may be a constant dull ache. Other sy ...
is a
inflammatory condition of pleurae. Due to the
somatic innervation of the parietal pleura, pleural irritations, especially if from acute causes, often produce a sharp
chest pain that is worse by breathing, known as ''pleuritic pain''.
Pleural disease or
lymphatic
Lymph (from Latin, , meaning "water") is the fluid that flows through the lymphatic system, a system composed of lymph vessels (channels) and intervening lymph nodes whose function, like the venous system, is to return fluid from the tissues to ...
blockages can lead to a build-up of serous fluid within the pleural space, known as a
pleural effusion
A pleural effusion is accumulation of excessive fluid in the pleural space, the potential space that surrounds each lung.
Under normal conditions, pleural fluid is secreted by the parietal pleural capillaries at a rate of 0.6 millilitre per k ...
. Pleural effusion obliterates the pleural vacuum and can collapse the lung (due to
hydrostatic pressure
Fluid statics or hydrostatics is the branch of fluid mechanics that studies the condition of the equilibrium of a floating body and submerged body " fluids at hydrostatic equilibrium and the pressure in a fluid, or exerted by a fluid, on an imm ...
), impairing ventilation and leading to
type 2 respiratory failure. The condition can be treated by mechanically removing the fluid via
thoracocentesis (also known as a "pleural tap") with a
pigtail catheter, a
chest tube
A chest tube (also chest drain, thoracic catheter, tube thoracostomy or intercostal drain) is a surgical drain that is inserted through the chest wall and into the pleural space or the mediastinum in order to remove clinically undesired substance ...
, or a
thoracoscopic procedure. Infected pleural effusion can lead to
pleural empyema
Pleural empyema is a collection of pus in the pleural cavity caused by microorganisms, usually bacteria. Often it happens in the context of a pneumonia, injury, or chest surgery. It is one of the various kinds of pleural effusion. There are three ...
, which can create significant
adhesion
Adhesion is the tendency of dissimilar particles or surfaces to cling to one another ( cohesion refers to the tendency of similar or identical particles/surfaces to cling to one another).
The forces that cause adhesion and cohesion can b ...
and
fibrosis
Fibrosis, also known as fibrotic scarring, is a pathological wound healing in which connective tissue replaces normal parenchymal tissue to the extent that it goes unchecked, leading to considerable tissue remodelling and the formation of perma ...
that require division and
decortication
Decortication is a medical procedure involving the surgical removal of the surface layer, membrane, or fibrous cover of an organ. The procedure is usually performed when the lung is covered by a thick, inelastic pleural peel restricting lung ex ...
. For recurrent pleural effusions,
pleurodesis
Pleurodesis is a medical procedure in which part of the pleural space is artificially obliterated. It involves the adhesion of the visceral and the costal pleura. The mediastinal pleura is spared.
Uses
Pleurodesis is performed to prevent recurre ...
can be performed to establish permanent obliteration of the pleural space.
See also
*
Pleural friction rub
A pleural friction rub, or simply pleural rub, is an audible medical sign present in some patients with pleurisy and other conditions affecting the chest cavity. It is noted by listening to the internal sounds of the body, usually using a stethosc ...
References
Sources
*
External links
*
* - "X-ray, chest, posteroanterior view"
* - "Transverse section through lung"
*
Diagram at kent.edu
{{Authority control
Pleura