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[[Image:Doglunginflated.jpg|right|thumb|250px|©RVC 2008]]

[[Image:Doglunginflated.jpg|right|thumb|250px|©RVC 2008]]

The lungs are the site for [[Gas Exchange - Anatomy & Physiology|gaseous exchange]], and are situated within the thoracic cavity. They occupy approximately 5% of the body volume in mammals when relaxed, and their elastic nature allows them to expand and contract with the processes of [[Ventilation - Anatomy & Physiology#Inspiration|inspiration]] and [[Ventilation - Anatomy & Physiology#Expiration|expiration]].

The lungs are the site for [[Gas Exchange - Anatomy & Physiology|gaseous exchange]], and are situated within the thoracic cavity. They occupy approximately 5% of the body volume in mammals when relaxed, and their elastic nature allows them to expand and contract with the processes of [[Ventilation - Anatomy & Physiology#Inspiration|inspiration]] and [[Ventilation - Anatomy & Physiology#Expiration|expiration]].  

The lungs, along with the [[Larynx - Anatomy & Physiology|larynx]] and [[Trachea - Anatomy & Physiology|trachea]], develop from a ventral respiratory tract. After separation from the developing [[Oesophagus - Anatomy & Physiology|oesophagus]], two lung buds develop, which undergo divisions as they grow, forming the beginnings of the [[Bronchi and Bronchioles - Anatomy & Physiology|bronchial]] tree. This process is not completed at the time of [[Normal Parturition - Anatomy & Physiology|parturition]].

The lungs, along with the [[Larynx - Anatomy & Physiology|larynx]] and [[Trachea - Anatomy & Physiology|trachea]], develop from a ventral respiratory tract. After separation from the developing [[Oesophagus - Anatomy & Physiology|oesophagus]], two lung buds develop, which undergo divisions as they grow, forming the beginnings of the [[Bronchi and Bronchioles - Anatomy & Physiology|bronchial]] tree. This process is not completed at the time of [[Normal Parturition - Anatomy & Physiology|parturition]].

==Structure==

==Structure==

The left and right lungs lie within their [[Pleural Cavity and Membranes - Anatomy & Physiology|pleural]] sac and are only attached by their roots, to the [[Mediastinum - Anatomy & Physiology|mediastinum]], so they are fairly free within the thoracic cavity. The right lung is always larger than the left, due to the positioning of the [[Heart - Anatomy & Physiology|heart]]. The apex of the lungs is their cranial point.

The left and right lungs lie within their [[Pleural Cavity and Membranes - Anatomy & Physiology|pleural]] sac and are only attached by their roots, to the [[Mediastinum - Anatomy & Physiology|mediastinum]], so they are fairly free within the thoracic cavity. The right lung is always larger than the left, due to the positioning of the [[Heart - Anatomy & Physiology|heart]]. The apex of the lungs is their cranial point.

In most species, the lungs are divided into lobes by the [[Bronchi and Bronchioles - Anatomy & Physiology|bronchial]] tree:

In most species, the lungs are divided into lobes by the [[Bronchi and Bronchioles - Anatomy & Physiology|bronchial]] tree:

'''Left Lung''' = Cranial and Caudal lobes.  

'''Left Lung''' - Cranial and Caudal lobes.  

'''Right Lung''' = Cranial, Caudal, Middle and Accessory lobes. The cranial lobe is further divided by an external fissure.

'''Right Lung''' - Cranial, Caudal, Middle and Accessory lobes. The cranial lobe is further divided by an external fissure.

The bulk of the lung consists of [[Bronchi and Bronchioles - Anatomy & Physiology|bronchi]], [[Anatomy of Blood Vessels - Anatomy & Physiology|blood vessels]] and connective tissue. The terminal [[Bronchi and Bronchioles - Anatomy & Physiology|bronchioles]] have alveoli scattered along their length, and are continued by alveolar ducts, alveolar sacs and finally alveoli.

The bulk of the lung consists of [[Bronchi and Bronchioles - Anatomy & Physiology|bronchi]], [[Anatomy of Blood Vessels - Anatomy & Physiology|blood vessels]] and connective tissue. The terminal [[Bronchi and Bronchioles - Anatomy & Physiology|bronchioles]] have alveoli scattered along their length, and are continued by alveolar ducts, alveolar sacs and finally alveoli.

===Alveolar Ducts===

===Alveolar Ducts===

These have alveoli which open on all of it's sides, they have no 'walls' as such. Openings to individual alveoli are guarded by [[Muscles - Anatomy & Physiology#Smooth Muscle|smooth muscle]].

These have alveoli which open on all of it's sides, they have no 'walls' as such. Openings to individual alveoli are guarded by [[Muscles - Anatomy & Physiology#Smooth Muscle|smooth muscle]].

===Alveolar Sacs===

===Alveolar Sacs===

These are rotunda-like areas on the end of each alveolar ducts which are usually present in clusters.

These are rotunda-like areas on the end of each alveolar ducts which are usually present in clusters.

===Alveoli===

===Alveoli===

These are minute, polygonal chambers, whose diameter changes with the processes of [[Ventilation - Anatomy & Physiology#Inspiration|inspiration]] and [[Ventilation - Anatomy & Physiology#Expiration|expiration]], and varies by species. The wall of the alveoli is extremely thin, consisting of 2 irregular layers of epithelial sheets, 'sandwiching' a network of capillaries. Thus the ''Blood-Gas Barrier'' is just a single basal lamina - ideal for [[Gas Exchange - Anatomy & Physiology|gaseous exchange]]. The alveolar interstitium is formed from connective tissue fibres and cells, which include collagen fibrils and elastin fibres.

Alveoli are minute, polygonal chambers, whose diameter changes with the processes of [[Ventilation - Anatomy & Physiology#Inspiration|inspiration]] and [[Ventilation - Anatomy & Physiology#Expiration|expiration]], and varies by species. The wall of the alveoli is extremely thin, consisting of 2 irregular layers of epithelial sheets, 'sandwiching' a network of capillaries. Thus the ''Blood-Gas Barrier'' is just a single basal lamina - ideal for [[Gas Exchange - Anatomy & Physiology|gaseous exchange]]. The alveolar interstitium is formed from connective tissue fibres and cells, which include collagen fibrils and elastin fibres.

==Function==

==Function==

==Innervation==

==Innervation==

Nervous supply to the lung is via the '''pulmonary plexus''' within the [[Mediastinum - Anatomy & Physiology|mediastinum]].

Nervous supply to the lung is via the '''pulmonary plexus''' within the [[Mediastinum - Anatomy & Physiology|mediastinum]].

The pulmonary plexus consists of sympathetic fibres largely from the '''stellate ganglion''', and parasympathetic fibres from the [[Cranial Nerves - Anatomy & Physiology|vagus nerve]].

The pulmonary plexus consists of sympathetic fibres largely from the '''stellate ganglion''', and parasympathetic fibres from the [[Cranial Nerves - Anatomy & Physiology|vagus nerve]].

==Species Differences==

==Species Differences==

The lungs of the '''horse''' show almost no lobation, and the right lung of the horse lacks a Middle Lobe. Incomparison to this, the lungs of '''ruminants''' and '''pigs''' are obviously lobed. The fissures between the lobes (''Interlobar fissures'') are deeper in the '''dog and cat''' lung compared to other species. [[Avian Respiration - Anatomy & Physiology|Avian Respiration]] has many fundamental differences to mammalian respiration. The [[Respiration in Non-Homeotherms - Anatomy & Physiology|respiratory systems of non-homeotherms]] are also very different to that of mammals.

The lungs of the '''horse''' show almost no lobation, and the right lung of the horse lacks a middle lobe. In comparison to this, the lungs of '''ruminants''' and '''pigs''' are obviously lobed. The fissures between the lobes (''interlobar fissures'') are deeper in the '''dog and cat''' lung compared to other species. [[Avian Respiration - Anatomy & Physiology|Avian respiration]] has many fundamental differences to mammalian respiration. The [[Respiration in Non-Homeotherms - Anatomy & Physiology|respiratory systems of non-homeotherms]] are also very different to that of mammals.

==Links==

==Links==

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

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

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[[Category:A&P Done]]