Development of the Face, Palate and Tongue Flashcards
Name the three facial prominences that form around the stomodeum (primordial mouth) and which give rise to the structures of the face.
✔ frontonasal prominence
✔ maxillary prominence
✔ mandibular prominence
✔ [Diagram] [Electron photomicrograph]
Give a brief account of the developmental events of the frontonasal prominence.
- The frontonasal prominence develops a thickening termed the nasal placode.
- The placodes invaginate to form nasal pits.
- The pits separate the lateral and medial nasal prominences.
- The frontal process gives rise to the forehead and the bridge of the nose.
- [Electron photomicrograph]
Give a brief account of the developmental events of the maxillary prominence.
Give a brief account of the developmental events of the medial nasal prominence.
The medial nasal prominences are displaced medially by the maxillary prominences.
The right and left medial nasal prominences fuse in the middle to form the intermaxillary segment.
The intermaxillary segment contributes to the formation of the:
✔ philtrum of the upper lip
✔ nasal tip and crest
✔ primary palate
✔ incisor regions of the upper jaw
What do the lateral nasal processes give rise to?
alae of the nose
Give a brief account of the developmental events of the mandibular prominence.
The right and left mandibular prominences grow and merge across the midline.
They contribute to the formation of the:
✔ lower lip
✔ lower jaw
What is the nasolacrimal groove? Briefly state its developmental fate.
Outline the development of the primary palate.
✔ Early in the sixth week, the primary palate/palatine process begins to develop from the intermaxillary segment of the maxilla.
Initially this segment is formed by merging of the medial nasal prominences.
✔ The primary palate forms the premaxillary part of the maxilla.
✔ [Diagram]
Outline the development of the secondary palate.
✔ Follow along with this diagram: [Diagram].
✔ It begins to develop early in the sixth week from two mesenchymal projections that extend from the internal aspects of the maxillary prominences.
✔ Initially, the lateral palatine processes or palatal shelves project inferomedially on each side of the developing tongue.
✔ As the jaws develop, the tongue becomes relatively smaller and moves inferiorly.
✔ During the 7th and 8th weeks, the lateral palatine processes elongate and ascend to a horizontal position superior to the tongue.
✔ Gradually, these processes approach each other and fuse in the median plane.
✔ The palatine processes also fuse with the nasal septum and the posterior part of the primary palate.
✔ The nasal septum develops as a downgrowth from internal parts of the merged medial nasal prominences.
✔ Bone gradually develops in the primary palate, forming the premaxillary part of the maxilla, which lodges the incisor teeth. Concurrently bone extends from the maxillae and palatine bones into the lateral palatine processes to form the hard palate.
✔ The posterior part of these processes do not ossify.
✔ They extend posteriorly beyond the nasal septum and fuse to form the soft palate.
✔ Its soft conical projection is called the uvula.
Further notes:
[The fusion between the nasal septum and the palatine processes begins anteriorly during the ninth week and is completed posteriorly by the twelfth week.]
The tongue form from a series of ventral swellings on the ________________.
floor of the pharynx
Briefly outline the development of the anterior 2/3 of the tongue.
✓ derived from the tissues of the 1st pharyngeal arch
✓ begin as two (lateral) lingual swellings and a median swelling called the tuberculum impar
✓ the lingual swellings outgrow the tuberculum impar and merge, forming mucosa of anterior 2/3 of tongue
✓ it’s innervated by the lingual branch of mandibular nerve
✓ [Diagram]
[Part of tissues from the 2nd arch migrate ventrally, and could be the reason why the chorda tympani of facial nerve is responsible for taste sensation to most of anterior 2/3 of tongue.]
Briefly outline the development of the posterior 1/3 of the tongue.
✓ derived from the tissues of the 2nd to 4th pharyngeal arches, but tissues from the 3rd arch are largely involved (most tissues from the 2nd arch migrate ventrally, while most tissues from the 4th arch develop the mucosa of the epiglottis)
✓ the swellings consist of:
■ copula (associated with 2nd arch)
■ a large hypobranchial eminence (associated by 3rd, 4th arch)
✓ hypobranchial eminence overgrows the copula
✓ the tongue separates from the floor of the mouth by a down growth of ectoderm around its periphery, which degenerates to form lingual sulcus and gives the tongue mobility.
✓ posterior 1/3 of tongue is separated from anterior 2/3 by sulcus terminalis
✓ posterior 1/3 of tongue is supplied by glossopharyngeal nerve
✓ [Diagram]
Outline the development of the tongue musculature.
✓ predominantly derived from the occipital myotomes
✓ migrate ventrally with their innervation (hypoglossal nerve)
✓ palatoglossus is derived from the mesenchyme of the 4th pharyngeal arch
Identify the congenital anomaly and state its embryological basis: [Click here].
unilateral cleft lip and palate: failure of fusion of the palatal shelf with the intermaxillary segment and the other palatal shelf
[Image: bilateral cleft lip and palate]
