Changes

==Avian Nasopharynx and Oropharynx==

==Avian Nasopharynx and Oropharynx==

*The nostrils of the bird, which lead into the nasal cavity, may have a flap of horn to protect them, known as the ''Operculum''.

*The nostrils of the bird, which lead into the [[Nasal Cavity - Anatomy & Physiology|nasal cavity]], may have a flap of horn to protect them, known as the ''Operculum''.

*The Oral Cavity and the Nasal Cavity of the bird are interconnecting via a slit in the hard palate called the ''Choana''. Birds lack a soft palate.

*The Oral Cavity and the Nasal Cavity of the bird are interconnecting via a slit in the [[Hard Palate - Anatomy & Physiology|hard palate]] called the ''Choana''. Birds lack a [[Soft Palate - Anatomy & Physiology|soft palate]].

[[Image:Avianheadsaggitalsection.jpg|right|thumb|350px|©Nottingham 2008 ''Saggital Section of an Avian skull showing the conchae.]]

[[Image:Avianheadsaggitalsection.jpg|right|thumb|350px|©Nottingham 2008 ''Saggital Section of an Avian skull showing the conchae.]]

*There are Rostral, Middle and Caudal Conchae arising from the lateral wall, filling part of the nasal cavity.

*There are Rostral, Middle and Caudal Conchae arising from the lateral wall, filling part of the [[Nasal Cavity - Anatomy & Physiology|nasal cavity]].

**Rostral Conchae - Vestibular Region - lined with Stratified Squamous Epithelium

**Rostral Conchae - Vestibular Region - lined with Stratified Squamous Epithelium

**Middle Conchae - Respiratory Region - lined with [[Respiratory Epithelium - Anatomy & Physiology|Respiratory Epithelium]].

**Middle Conchae - Respiratory Region - lined with [[Respiratory Epithelium - Anatomy & Physiology|Respiratory Epithelium]].

**Caudal Conchae - Olfactory Region - lined with olfactory epithelium.

**Caudal Conchae - [[Special Senses - Olfactory - Anatomy & Physiology|Olfactory]] Region - lined with [[Special Senses - Olfactory - Anatomy & Physiology|olfactory]] epithelium.

*The '''Infraorbital Sinus''' is a triangular cavity under the skin, rostroventral to the eye.

*The '''Infraorbital Sinus''' is a triangular cavity under the skin, rostroventral to the eye.

*Some marine birds have a ''Salt Gland'' (nasal gland) which excretes sodium.

*Some marine birds have a ''Salt Gland'' (nasal gland) which excretes sodium.

==Avian Larynx==

==Avian Larynx==

*The larynx is on the floor of the oropharynx supported by '''Cricoid''' and paried '''Arytenoid''' Cartilages which are different in structure to those in mammals.

*The [[Larynx - Anatomy & Physiology|larynx]] is on the floor of the [[Oral Cavity - Oropharynx - Anatomy & Physiology|oropharynx]] supported by '''Cricoid''' and paried '''Arytenoid''' Cartilages which are different in structure to those in mammals.

*There is no Epiglottis.

*There is no [[Epiglottis|Epiglottis.]]

*There are no vocal folds - birds vocalise using a [[Syrinx - Anatomy & Physiology|syrinx]].

*There are no vocal folds - birds vocalise using a [[Syrinx - Anatomy & Physiology|syrinx]].

==Avian Trachea==

==Avian Trachea==

*The avian trachea is composed of tightly stacked cartilages which are shaped similarly to signet rings. These are complete with no dorsal space as in the mammalian [[Trachea - Anatomy & Physiology|trachea]]. They overlap considerably.  

*The avian [[Trachea - Anatomy & Physiology|trachea]] is composed of tightly stacked [[Bones and Cartilage - Anatomy & Physiology|cartilages]] which are shaped similarly to signet rings. These are complete with no dorsal space as in the mammalian [[Trachea - Anatomy & Physiology|trachea]]. They overlap considerably.  

*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 - Anatomy & Physiology|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 into two main bronchi as in mammals. The [[Syrinx - Anatomy & Physiology|syrinx]] is formed by this terminal part of the trachea.

*The trachea bifurcates into two main [[Bronchi and Bronchioles|bronchi]] as in mammals. The [[Syrinx - Anatomy & Physiology|syrinx]] is formed by this terminal part of the trachea.

==Avian Lungs==

==Avian Lungs==

*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.

*Avian [[Lungs - Anatomy & Physiology|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 [[Spinal Column - Anatomy & Physiology#Vertebrae and Joints|vertebrae]] and [[Ribs and Sternum - Anatomy & Physiology|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 and Membranes|pleural cavity]] as the lungs do not expand, thus the membranes are not necessary.

==Air Sacs==

==Air Sacs==

*Birds lack a diaphragm, and their thoracic and abdominal cavities are continuous.  

*Birds lack a [[Diaphragm - Anatomy & Physiology|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 bird has a number of thin walled, easily distensible '''Air Sacs''' which can extend to approximatley 10x the volume of the [[Lungs - Anatomy & Physiology|lungs]]. These are present within body cavities, and extend into some specific [[Bones and Cartilage - Anatomy & Physiology|bones]], to take the place of [[Bone Marrow - Anatomy & Physiology|bone marrow]]. This has the added function of reducing the weight of the bone, as they are essentially filled with air.

*The chicken has 8 air sacs:  

*The chicken has 8 air sacs:  

**'''Cervical''' - this extends within the cervical and thoracic vertebrae.

**'''Cervical''' - this extends within the cervical and thoracic [[Spinal Column - Anatomy & Physiology#Vertebrae and Joints|vertebrae]].

**'''Clavicular''' - lies within the thoracic inlet, surrounding the heart, and within the humerus in the [[Forelimb - Anatomy & Physiology|forelimb]].

**'''Clavicular''' - lies within the thoracic inlet, surrounding the [[Heart - Anatomy & Physiology|heart]], and within the humerus in the [[Forelimb - Anatomy & Physiology|forelimb]].

**'''Cranial Thoracic''' (x2) -  these are ventral to the lungs.

**'''Cranial Thoracic''' (x2) -  these are ventral to the [[Lungs - Anatomy & Physiology|lungs]].

**'''Caudal Thoracic''' (x2) - located between the body wall and the thoracic air sacs.  

**'''Caudal Thoracic''' (x2) - located 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 these airsacs utilise space within the acetabulum and synsacrum.  

**'''Abdominal''' (x2) - these are the largest air sacs and fill the caudodorsal region of the abdomen, in contact with [[Small Intestine - Anatomy & Physiology|small]] and [[Large Intestine - Anatomy & Physiology|large intestines]], [[Kidney Basic Anatomy & Physiology|kidneys]] and [[Reproductive System|reproductive]] organs. In addition these airsacs utilise space within the acetabulum and synsacrum.  

*The Cervical, Clavicular and Cranial Thoracic air sacs form one functional group - '''Cranial''', with the Caudal Thoracic and Abdominal Air sacs forming another, '''Caudal''' functional group.  

*The Cervical, Clavicular and Cranial Thoracic air sacs form one functional group - '''Cranial''', with the Caudal Thoracic and Abdominal Air sacs forming another, '''Caudal''' functional group.  

*The air sacs have a vital role in ventilation, but do not have the capacity for gaseous exchange.

*The air sacs have a vital role in [[Ventilation - Anatomy & Physiology|ventilation]], but do not have the capacity for [[Gas Exchange - Anatomy & Physiology|gaseous exchange]].

==Avian Ventilation==

==Avian Ventilation==