The secondary palate is an anatomical structure that divides 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 ...

from the

oral cavity A mouth also referred to as the oral is the body orifice through which many animals ingest food and vocalize. The body cavity immediately behind the mouth opening, known as the oral cavity (or in Latin), is also the first part of the alime ...

in many

vertebrate Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

s. In human

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 ...

, it refers to that portion of the hard palate that is formed by the growth of the two palatine shelves medially and their mutual fusion in the midline. It forms the majority of the adult palate and meets the primary palate at the incisive foramen.

Clinical significance

Secondary palate development The development of the secondary palate commences in the sixth week of human embryonic development. It is characterised by the formation of two palatal shelves on the maxillary prominences, the elevation of these shelves to a horizontal position, ...

begins in the sixth week of

pregnancy Pregnancy is the time during which one or more offspring gestation, gestates inside a woman's uterus. A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Conception (biology), Conception usually occurs ...

and can lead to cleft palate when development goes awry. There are three major mechanisms known to cause this failure: #Growth retardation — Palatal shelves do not grow enough to meet each other. #Mechanical obstruction — Improper mouth size, or abnormal anatomical structures in the embryonic mouth prevent fully grown shelves from meeting each other. #Midline epithelial dysfunction (MED) - The surface mucosa of embryonic shelves is impaired, which causes a failure of palatal fusion.

Evolution

The secondary palate is thought to have a significant role in the development of some

warm-blooded Warm-blooded is a term referring to animal species whose bodies maintain a temperature higher than that of their environment. In particular, homeothermic species (including birds and mammals) maintain a stable body temperature by regulating ...

animals. The separation of the mouth from the nasal cavity also allowed chewing and breathing to occur at the same time. Early creatures with secondary palates include

crocodilians Crocodilia () is an order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorph pseudosuchi ...

(who are cold-blooded), and cynodonts and a few others among the

therapsids Therapsida is a clade comprising a major group of eupelycosaurian synapsids that includes mammals and their ancestors and close relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including li ...

, known from the fossil record in the mid-

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

Mammals A mammal () is a vertebrate animal of the class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle e ...

inherited our hard palates from the cynodonts.

References

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