Changes

*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, 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''.

*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.

[[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.

**Rostral Conchae - lined with Stratified Squamous Epithelium

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

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

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

*Birds lack a soft palate.

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

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

Birds vocalise using a [[Syrinx - Anatomy & Physiology|syrinx]].

Birds vocalise using a [[Syrinx - Anatomy & Physiology|syrinx]].