The nasal placode (or olfactory placode
) gives rise to the
olfactory epithelium
The olfactory epithelium is a specialized epithelial tissue inside the nasal cavity that is involved in smell. In humans, it measures
9 cm2 and lies on the roof of the nasal cavity about 7 cm above and behind the nostrils. The olfactory ...
of the
nose
A nose is a protuberance in vertebrates that houses the nostrils, or nares, which receive and expel air for respiration alongside the mouth. Behind the nose are the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passe ...
. Two nasal placodes arise as thickened
ectoderm from the
frontonasal process. They give rise to the
nose
A nose is a protuberance in vertebrates that houses the nostrils, or nares, which receive and expel air for respiration alongside the mouth. Behind the nose are the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passe ...
, the
philtrum of the upper
lip
The lips are the visible body part at the mouth of many animals, including humans. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech. Human lips are a tactile sensory organ, and can be ...
, and the primary palate.
Development
During the fifth week of
human embryonic development the placodes increase in size. In the sixth week of development the centre of each placode
grows inwards to form the two nasal pits. The invaginations will give rise to the olfactory epithelium that lines the roof of the
nasal cavity.
The nasal pits are oval shaped and they leave a raised margin which is divided into a
medial nasal process and a
lateral nasal process.
[
The medial and lateral nasal process of each placode gives rise to the ]nose
A nose is a protuberance in vertebrates that houses the nostrils, or nares, which receive and expel air for respiration alongside the mouth. Behind the nose are the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passe ...
, the philtrum of the upper lip
The lips are the visible body part at the mouth of many animals, including humans. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech. Human lips are a tactile sensory organ, and can be ...
and the primary palate
The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity.
A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly sepa ...
.[
]
See also
* Placode
A neurogenic placode is an area of thickening of the epithelium in the embryonic head ectoderm layer that gives rise to neurons and other structures of the sensory nervous system.
Placodes are embryonic structures that give rise to structures such ...
References
External links
* https://web.archive.org/web/20130509194720/http://embryology.med.unsw.edu.au/Notes/week4_3.htm#nose
* https://web.archive.org/web/20060925080120/http://www.ana.ed.ac.uk/database/humat/notes/embryo/sensory/nose.htm
Animal developmental biology
Embryology
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