embryology Embryology (from Ancient Greek, Greek ἔμβρυον, ''embryon'', "the unborn, embryo"; and -λογία, ''-logy, -logia'') is the branch of animal biology that studies the Prenatal development (biology), prenatal development of gametes (sex ...

, the nasal placode (or olfactory placode) gives rise to the

olfactory epithelium The olfactory epithelium is a specialized epithelium, epithelial tissue inside the nasal cavity that is involved in olfaction, smell. In humans, it measures and lies on the roof of the nasal cavity about above and behind the nostrils. The olfact ...

of the

nose A nose is a sensory organ and respiratory structure in vertebrates. It consists of a nasal cavity inside the head, and an external nose on the face. The external nose houses the nostrils, or nares, a pair of tubes providing airflow through the ...

. Two nasal placodes arise as thickened

ectoderm The ectoderm is one of the three primary germ layers formed in early embryonic development. It is the outermost layer, and is superficial to the mesoderm (the middle layer) and endoderm (the innermost layer). It emerges and originates from the o ...

from the frontonasal process. They give rise to the

, the

philtrum The philtrum (, from Ancient Greek , lit. 'love charm') or medial cleft is a vertical indentation in the middle area of the upper lip, common to therian mammals, extending in humans from the nasal septum to the tubercle of the upper lip. Toget ...

of the upper

lip The lips are a horizontal pair of soft appendages attached to the jaws and are the most visible part of the mouth of many animals, including humans. Mammal lips are soft, movable and serve to facilitate the ingestion of food (e.g. sucklin ...

, and the

primary palate Around the 5th week, the intermaxillary segment arises as a result of fusion of the two medial nasal processes and the frontonasal process within the embryo. The intermaxillary segment gives rise to the primary palate. The primary palate will form ...

Development

During the fifth week of

human embryonic development Human embryonic development or human embryogenesis is the development and formation of the human embryo. It is characterised by the processes of cell division and cellular differentiation of the embryo that occurs during the early stages of d ...

, 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 cavity is a large, air-filled space above and behind the nose in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. The nas ...

. 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

, the

of the upper

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 sep ...

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 {{Anatomy-stub