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Avian Respiration - Anatomy & Physiology (view source)
Revision as of 11:54, 14 August 2008
, 11:54, 14 August 2008no edit summary
==Introduction==
==Introduction==
The avian respiratory system contains some fundamental changes to the mammalian system.
The avian respiratory system contains some fundamental differences to the mammalian system.
==Avian Nasopharynx and Oropharynx==
==Avian Nasopharynx and Oropharynx==
*The trachea can be palpated on the right side of the neck; it runs alongside the oesophagus.
*The trachea can be palpated on the right side of the neck; it runs alongside the oesophagus.
*The trachea is lined with [[Respiratory Epithelium - Anatomy & Physiology|Respiratory Epithelium]].
*The trachea is lined with [[Respiratory Epithelium - Anatomy & Physiology|Respiratory Epithelium]].
*The trachea bifurcates as in mammals. The [[Syrinx - Anatomy & Physiology|syrinx]] is formed by this terminal part of the trachea.
*The trachea bifurcates into two main bronchi as in mammals. The [[Syrinx - Anatomy & Physiology|syrinx]] is formed by this terminal part of the trachea.
==Avian Lungs==
==Avian Lungs==
*The lungs of birds are relatively small, unlobed and do not have the capacity to expand.
*Avian lungs are relatively small, with a bird's lungs being approximately 50% as large as the lung of a mammal of a similar size. The lungs are unlobed and do not have the capacity to expand.
*The lungs are positioned in the craniodorsal region of the body, and are deeply indented by both the thoracic vertebrae and ribs.
*The lungs are positioned in the craniodorsal region of the body, and are deeply indented by both the thoracic vertebrae and ribs.
*Birds do not have a pleural cavity as the lungs do not expand, thus it is not necessary.
*Birds do not have a pleural cavity as the lungs do not expand, thus it is not necessary.
==Air Sacs==
==Air Sacs==
*Birds lack a diaphragm, and their thoracic and abdominal cavities are continuous.
*The bird has a number of thin walled, easily distensible '''Air Sacs''' which can extend to approximatley 10x the volume of the lungs. These are present within body cavities, and extend into bones, to take the place of marrow. This has the added function of reducing the weight.
*The chicken has 8 air sacs:
**'''Cervical''' - this extends within the cervical and thoracic vertebrae.
**'''Clavicular''' - lies within the thoracic inlet, surrounding the heart, and within the humerus in the [[Forelimb - Anatomy & Physiology|forelimb]].
**'''Cranial Thoracic''' (x2) - are ventral to the lungs.
**'''Caudal Thoracic''' (x2) - between the body wall and the thoracic air sacs
**'''Abdominal''' (x2) - these are the largest air sacs and fill the caudodorsal region of the abdomen, in contact with intestines, kidneys and genital organs. In addition they enter the acetabulum and synsacrum.
===Avian Ventilation===
*Ventilation is birds is strikingly different to that of mammals in that air flows through the lungs in the same direction during both inspiration and expiration.
===Avian Gas Exchange===
*One '''Primary Bronchi''' from the trachea enters each lung, narrowing as it travels through, and communicates with the '''Abdominal Air Sac'''. This bronchi gives off branches as it travels through the lung, known as '''Secondary Bronchi'''. Each of these gives off a further 400-500 '''Parabronchi''' in the walls of which, gaseous exchange takes place.
*Avian Gas exchange takes place not in alveoli, as in mammals, but within '''Air Capillaries''' which are extensions of the parabronchial lumen. They are an interconnecting network of loops, and closely intertwine with Blood Capillaries.
*The Air Capillaries and Blood Capillaries are arranged so that flow is ''crosscurrent''. This makes the gaseous exchange which occurs from one to the other extremely efficient.
==Links==
==Links==