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==Introduction==

==Introduction==

[[Image:PleuralMembranesSchematic.jpg|right|thumb|350px|'''Schematic Diagram of the Pleural Membranes''' (Cross section through thoracic cavity at the level of the heart)]]

[[Image:PleuralMembranesSchematic.jpg|right|thumb|350px|'''Schematic Diagram of the Pleural Membranes''' (Cross section through thoracic cavity at the level of the heart)]]

*Each [[Lungs - Anatomy & Physiology|lung]] is placed within a separate layer of membrane, thus there are two pleural sacs.

Each [[Lungs - Anatomy & Physiology|lung]] is placed within a separate layer of membrane, thus there are two pleural sacs. The space between the two sacs is known as the [[Mediastinum - Anatomy & Physiology|mediastinum]], and is almost in the midline of the thorax. The pleura covering the surface of the lung is known as '''pulmonary pleura''' or '''visceral pleura'''. This becomes continuous with the '''mediastinal pleura''', as it wraps around the [[Lungs - Anatomy & Physiology|lung]]. The '''diaphragmatic''' and '''costal pleura''' are continuous with the mediastinal pleura. Together, these three membranes are the '''parietal pleura'''.

*The space between the two sacs is known as the [[Mediastinum - Anatomy & Physiology|Mediastinum]], and is almost in the midline of the thorax.

 

*The pleura covering the surface of the lung is known as '''Pulmonary Pleura''' or '''Visceral Pleura'''. This becomes continuous with the '''Mediastinal Pleura''' as it wraps around the [[Lungs - Anatomy & Physiology|lung]].

Between the parietal and visceral pleura is the '''intrapleural space''', or '''pleural cavity'''. This contains a small amount of serous fluid which establishes adhesion between the layers and allows smooth movement between the lung and chest wall, and between individual lobes of the [[Lungs - Anatomy & Physiology|lungs]]. The [[Heart - Anatomy & Physiology|heart]] is invested in a parietal and visceral layer of [[Heart Structure - Anatomy & Physiology#Pericardium|'''pericardium''']] with the '''pericardial space''' separating the two membranes. Cranially, the costal and mediastinal pleura adjoin to form a 'dome' of pleura which extends to the thoracic inlet. This is known as the '''cupulae pleurae'''. This region is only protected by soft tissue, and thus is vulnerable to injury.

*The '''Diaphragmatic''' and '''Costal Pleura''' are continuous with the Mediastinal Pleura. Together, these three membranes are the '''Parietal Pleura'''.

 

*Between the Parietal and Visceral Pleura is the '''Intrapleural Space''', or '''Pleural Cavity'''. This contains a small amount of serous fluid which establishes adhesion between the layers and allows smooth movement between the lung and chest wall, and between individual lobes of the [[Lungs - Anatomy & Physiology|lungs]].

Within the pleural sac encasing the right [[Lungs - Anatomy & Physiology|lung]], there is a fold which encases the vena cava. It is known as the '''Plica Venae Cavae'''. The pleural membranes are larger than the [[Lungs - Anatomy & Physiology|lungs]] which they encase, thus there are areas where the facing surfaces of parietal pleura touch each other. These are known as '''pleural recesses'''. One example is the '''costodiaphragmatic recess''', the space between the costal and diaphragmatic pleura. The volume of the recess varies to a point due to the phase of [[Ventilation - Anatomy & Physiology#Inspiration|inspiration]]/[[Ventilation - Anatomy & Physiology#Expiration|expiration]].

*The [[Heart - Anatomy & Physiology|Heart]] is invested in a Parietal and Visceral layer of [[Heart Structure - Anatomy & Physiology#Pericardium|'''Pericardium''']] with the '''Pericardial Space''' separating the two membranes.

*Cranially the Costal and Mediastinal Pleura adjoin to form a 'dome' of pleura which extends cranially to the thoracic inlet. This is known as the '''Cupulae Pleurae'''. This region is only protected by soft tissue, and thus is vulnerable to injury.

*Within the pleural sac encasing the right [[Lungs - Anatomy & Physiology|lung]], there is a fold which encases the Vena Cava. It is known as the '''Plica Venae Cavae'''.

*The Pleural Membranes are larger than the [[Lungs - Anatomy & Physiology|lungs]] which they encase, thus there are areas where the facing surfaces of parietal pleura touch each other. These are known as '''Pleural Recesses'''. One example is the '''Costodiaphragmatic Recess''', the space between the costal and [[Diaphragm - Anatomy & Physiology|diaphragm]]atic pleura. The volume of the recess varies to a point due to the phase of [[Ventilation - Anatomy & Physiology#Inspiration|inspiration]]/[[Ventilation - Anatomy & Physiology#Expiration|expiration]].

===Pleural Membrane Function===

===Pleural Membrane Function===

*The Pleural Cavity is filled with a small amount of serous fluid which forms a thin film of liquid between the pleural layers. This is vital in that it prevents separation of the two pleural layers and lubricates the surface, so the [[Lungs - Anatomy & Physiology|lungs]] can move easily within the thoracic cavity.

The Pleural Cavity is filled with a small amount of serous fluid which forms a thin film of liquid between the pleural layers. This is vital in that it prevents separation of the two pleural layers and lubricates the surface, so the [[Lungs - Anatomy & Physiology|lungs]] can move easily within the thoracic cavity. The pleural fluid also provides surface tension, keeping the lung suitably close to the wall of the thorax, despite the lungs not being directly fixed to it. The pleurae thus allow the volume of the [[Lungs - Anatomy & Physiology|lungs]] to change with the volume of the thoracic cavity, enabling [[Ventilation - Anatomy & Physiology|ventilation]]. The left and right pleural sacs are separate so that in the event of one being punctured, the other lung can continue to function effectively.

*The Pleural Fluid also provides surface tension, keeping the [[Lungs - Anatomy & Physiology|lung]] suitably close to the wall of the thorax, despite the the lungs not being directly fixed to it. The pleurae thus allow the volume of the [[Lungs - Anatomy & Physiology|lungs]] to change with the volume of the thoracic cavity, enabling [[Ventilation - Anatomy & Physiology|ventilation]].

*The left and right pleural sacs are separate so that in the event of one being punctured, the other [[Lungs - Anatomy & Physiology|lung]] can continue to function effectively.

==Vasculature==

==Vasculature==

*The Pleural membranes are supplied by the '''Bronchial''' and '''Pulmonary Arteries'''.

The pleural membranes are supplied by the '''bronchial''' and '''pulmonary arteries'''.

==Innervation==

==Innervation==

*'''Parietal Pleura''' is innervated by the intercostal nerves, with the Mediastinal and Diaphragmatic pleura also innervated by the Phrenic Nerve.

'''Parietal Pleura''' is innervated by the intercostal nerves, with the mediastinal and diaphragmatic pleura also innervated by the phrenic nerve. '''Visceral pleura''' is innervated by the vagus nerve and sympathetic fibres. It is insensitive to pain stimuli.

*'''Visceral pleura''' is innervated by the Vagus nerve and sympathetic fibres. It is insensitive to pain stimuli.

==Species Differences==

==Species Differences==

[[Image:Dogthorax1.jpg|right|thumb|350px|''The mediastinum is visible in this dog dissection, left lung removed. ©RVC 2008]]

[[Image:Dogthorax1.jpg|right|thumb|350px|''The mediastinum is visible in this dog dissection, left lung removed. ©RVC 2008]]

*In '''cattle''' the [[Mediastinum - Anatomy & Physiology|Mediastinum]] is a tough membrane, in contrast to '''horses, dogs''' and '''cats''' where it is rather thin and more delicate.

In '''cattle''', the [[Mediastinum - Anatomy & Physiology|mediastinum]] is a tough membrane, in contrast to '''horses, dogs''' and '''cats''' where it is rather thin and more delicate.

*Birds do not have a pleural cavity as [[Avian Respiration - Anatomy & Physiology|Avian lungs]] do not have the capacity to inflate.

 

*The [[Respiration in Non-Homeotherms - Anatomy & Physiology|Respiratory Systems of non-Homeotherms]] are also very different to that of mammals.

'''Birds''' do not have a pleural cavity as [[Avian Respiration - Anatomy & Physiology|avian lungs]] do not have the capacity to inflate. The [[Respiration in Non-Homeotherms - Anatomy & Physiology|respiratory systems of non-homeotherms]] are also very different to that of mammals.

==Links==

==Links==

[[Pleural Cavity and Membranes - Pathology]]

Click here for information on [[:Category:Pleural Cavity and Membranes - Pathology|pathology of pleural cavity membranes]].

 

==References==

==References==

*{{citation|initiallast = Dyce|initialfirst = K.M|2last = Sack|2first = W.O|finallast = Wensing|finalfirst = C.J.G|year = 2002|title = Textbook of Veterinary Anatomy|ed =3rd|city = Philadelphia|pub = Saunders}}

{{citation|initiallast = Dyce|initialfirst = K.M|2last = Sack|2first = W.O|finallast = Wensing|finalfirst = C.J.G|year = 2002|title = Textbook of Veterinary Anatomy|ed =3rd|city = Philadelphia|pub = Saunders}}

 

*{{citation|initiallast = Budras|initialfirst = K.D|2last = McCarthy|2first = P.H|3last = Fricke|3first = W|finallast = Richter|finalfirst = R|year = 2002|title = Anatomy of the Dog|ed =4th|city = Hannover|pub = Schlutersche GmbH & Co. KG, Verlag und Druckerei}}

[[Category:Respiratory System - Anatomy & Physiology]]

[[Category:Respiratory System - Anatomy & Physiology]]

[[Category:To Do - A&P]]

[[Category:A&P Done]]