BGDB Face and Ear - Late Embryo

From Embryology
BGDsmall.jpg
Practical 6: Trilaminar Embryo | Early Embryo | Late Embryo | Fetal | Postnatal | Abnormalities | Quiz

Week 6

Primary Palate

  • Beginning week 6 there is fusion of the upper lip.
  • Formed by the maxillary prominences of of the first pharyngeal arch and the frontonasal prominence.
  • Failure of this embryonic process leads to cleft lip.


Stage16-18 face.jpgBailey140.jpg

Above images show face development through week 6 to week 7 (1mm scale markings).

The animation shows the early fusion of the primary palate in the human embryo between stage 17 and 18, going from an epithelial seam to the mesenchymal bridge.

Face animation.gifFace Development Movie | MP4 movie

This animation shows a ventral view of development of the human face from approximately week 5 through to neonate.


The separate embryonic components that contribute to the face have been colour coded.

  • Frontonasal Prominence - frontal central (white)
  • Frontonasal Prominence - Lateral nasal (purple)
  • Frontonasal Prominence - Medial nasal (green)
  • Pharyngeal Arch 1 - Maxillary prominence (yellow)
  • Pharyngeal Arch 1 - Mandibular prominence (orange)
  • Stomodeum (black)

Week 8

Stage 22 image 159.jpg Stage 22 image 103.jpg

Stage 22 image 159.jpg Selected Head Images: B4 - Choroid Plexus | B5 - Cochlea | B6 - Cochlea

Palate

Stage 22 image 219.jpg The dark "pear-shaped" central structure at the top is the developing tongue. The two pale regions either side are the palatal shelves, note that they have not yet fused in the midline (failure of this process is cleft palate).

Tongue

Week 7 to 8 tongue and oral cavity.

Stage 19 Stage 21 Stage 23
Human embryonic tongue 09.jpg Human embryonic tongue 10.jpg Human embryonic tongue 11.jpg

Hearing

Stage 22 image 219.jpg Behind that a pale cartilagenous region (that later ossifies) encloses the structuctures of the inner ear, beside which middle ear bones are forming. On the righthand side of the head the external ear is visible. The lower half of the image shows the developing brainstem with a large ventricular space occupied in part by an extensive choroid plexus (manufacturer of cerebrospinal fluid).
Stage 22 - Oral Cavity and Inner Ear

Stage 22 image 011.jpg

 ‎‎Mobile | Desktop | Original

Stage 22 | Embryo Slides
Streeter1906 plate01.jpg

Embryonic development of the human membranous labyrinth.

Streeter1906 plate02.jpg

Membranous labyrinth and acoustic complex model reconstructed from week 8 human embryo (CRL 30 mm). Note that by the end of the embryonic period the adult external structure has been achieved, internal development continues through the fetal period.

Embryonic External Ear

Shown below are the changes in external ear development between week 5 to week 8. Development changes from a series of 6 hillocks on arch 1 and arch 2 (week 5) to a structure resembling the adult ear (week 8).

External ear stages-14-23-adult.jpg


BGDsmall.jpg
Practical 6: Trilaminar Embryo | Early Embryo | Late Embryo | Fetal | Postnatal | Abnormalities | Quiz

Additional Information

Additional Information - Content shown under this heading is not part of the material covered in this class. It is provided for those students who would like to know about some concepts or current research in topics related to the current class page.
Palate Development (expand to see terms)  
  • cleft - An anatomical gap or space occuring in abnormal development in or between structures. Most commonly associated with cleft lip and cleft palate. Term is also used to describe the external groove that forms between each pharyngeal arch during their formation.
  • cleft lip - An abnormality of face development leading to an opening in the upper lip. Clefting of the lip and or palate occurs with 300+ different abnormalities. Depending on many factors, this cleft may extend further into the oral cavity leading to a cleft palate. In most cases clefting of the lip and palate can be repaired by surgery.
  • cleft palate - An abnormality of face development leading to an opening in the palate, the roof of the oral cavity between the mouth and the nose. Clefting of the lip and or palate occurs with 300+ different abnormalities. In most cases clefting of the lip and palate can be repaired by surgery. Palate formation in the embryo occurs at two distinct times and developmental processes called primary and secondary palate formation. This leads to different forms (classifications) and degrees of clefting.
  • hard palate - anterior part of the palate that becomes ossified. The posterior palate part is the soft palate.
  • epithelial mesenchymal transition - (EMT, epitheliomesenchymal transformation) conversion of an epithelium into a mesenchymal (connective tissue) cellular organization. Process required during lip and palate developmental fusion.
  • epitheliomesenchymal transformation - (epithelial mesenchymal transition) conversion of an epithelium into a mesenchymal (connective tissue) cellular organization.
  • incisive papilla - anterior midline palate near the incisors lying at the end of the palatine raphe.
  • levator veli palatini - Muscle forming part of the soft palate, elevates the soft palate for swallowing.
  • mastication - (chewing) Process of crushing and grinding food within the mouth.
  • maxilla - (pl. maxillae) upper jaw bone forming from the maxillary process of the first pharyngeal arch.
  • medial edge epithelial - (MEE) opposing palatal shelves adhere to each other to form this epithelial seam.
  • musculus uvulae Small muscle forming part of the soft palate lying within the uvula, shortens and broadens the uvula.
  • palatine raphe (median raphe) palate midline ridge (seam) of the mucosa, from the incisive papilla to the uvula.
  • palatal rugae - (palatine rugae, rugae) Transverse series of ridges forming on the secondary hard palate that are sequentially added during development as the palate grows. Involved in the process of mastication.
  • palatal vault - (palatine vault) Term describing the curved "arch" shape of the palate that mainly develops postnatally.
  • palate - The roof of the mouth (oral cavity) a structure which separates the oral from the nasal cavity. Develops as two lateral palatal shelves which grow and fuse in the midline. Initally a primary palate forms with fusion of the maxillary processes with the nasal processes in early face formation. Later the secondary palate forms the anterior hard palate which will ossify and separate the oral and nasal cavities. The posterior part of the palate is called the soft palate (velum, muscular palate) and contains no bone. Abnormalities of palatal shelf fusion can lead to cleft palate.
  • palatine bones - Two bones that with the maxillae form the hard palate.
  • palatogenesis - The process of palate formation, divided into primary and secondary palate development.
  • palatoglossus - (glossopalatinus, palatoglossal muscle) Small muscle forming part of the soft palate required for swallowing.
  • palatopharyngeus - (palatopharyngeal or pharyngopalatinus) Small muscle forming part of the soft palate required for breathing.
  • pharyngeal arch - (branchial arch, Greek, branchial = gill) These are a series of externally visible anterior tissue bands lying under the early brain that give rise to the structures of the head and neck. In humans, five arches form (1,2,3,4 and 6) but only four are externally visible on the embryo. Each arch has initially identical structures: an internal endodermal pouch, a mesenchymal (mesoderm and neural crest) core, a membrane (endoderm and ectoderm) and external cleft (ectoderm). Each arch mesenchymal core also contains similar components: blood vessel, nerve, muscular, cartilage. Each arch though initially formed from similar components will differentiate to form different head and neck structures.
  • philtrum - (infranasal depression, Greek, philtron = "to love" or "to kiss") Anatomically the surface midline vertical groove in the upper lip. Embryonically formed by the fusion of the frontonasal prominence (FNP) with the two maxillary processes of the first pharyngeal arch. Cleft palate (primary palate) occurs if these three regions fail to fuse during development. Fetal alcohol syndrome is also indicated by flatness and extension of this upper lip region.
  • soft palate - (velum, muscular palate) posterior part of the palate that becomes muscular. Forms 5 muscles: tensor veli palatini, palatoglossus, palatopharyngeus, levator veli palatini, musculus uvulae. The anterior palate part is the hard palate.
  • T-box 22 - (TBX22) a transcription factor that cause X-linked cleft palate and ankyloglossia in humans. Tbx22 is induced by fibroblast growth factor 8 (FGF8) in the early face while bone morphogenic protein 4 (BMP4) represses and therefore restricts its expression. (More? OMIM - TBX22)
  • tensor veli palatini - (tensor palati, tensor muscle of the velum palatinum) Small muscle forming part of the soft palate required for swallowing.
  • Transforming Growth Factor-beta - (TGFβ) factors induces both epithelial mesenchymal transition and/or apoptosis during palatal medial edge seam disintegration.
  • uvula - (Latin = a little grape) a pendulous posterior end of soft palate used to produce guttural consonants. First named in 1695.
  • Van der Woude syndrome - common syndromic cause of clefting (2% of cleft lip and palates). Van der Woude syndrome 1 1q32.2 Van der Woude syndrome 2 1p36.11
  • velopharyngeal insufficiency - (VPI) associated with cleft palate repair, describes the velum and lateral and posterior pharyngeal walls failing to separate the oral cavity from the nasal cavity during speech.
Other Terms Lists  
Terms Lists: ART | Birth | Bone | Cardiovascular | Cell Division | Gastrointestinal | Genetic | Hearing | Heart | Immune | Integumentary | Neural | Oocyte | Palate | Placenta | Renal | Respiratory | Spermatozoa | Ultrasound | Vision | Historic | Glossary

Historic

Streeter GL. On the development of the membranous labyrinth and the acoustic and facial nerves in the human embryo. (1906) Amer. J Anat. 6:139-165.

Streeter1906 plate01.jpg


Gray0924.jpg

Adult Membranous Labrynth

The Membranous Labyrinth

The membranous labyrinth is lodged within the bony cavities just described, and has the same general form as these; it is, however, considerably smaller, and is partly separated from the bony walls by a quantity of fluid, the perilymph. In certain places it is fixed to the walls of the cavity. The membranous labyrinth contains fluid, the endolymph, and on its walls the ramifications of the acoustic nerve are distributed.

Within the osseous vestibule the membranous labyrinth does not quite preserve the form of the bony cavity, but consists of two membranous sacs, the utricle, and the saccule.

The Utricle

The utricle, the larger of the two, is of an oblong form, compressed transversely, and occupies the upper and back part of the vestibule, lying in contact with the recessus ellipticus and the part below it. That portion which is lodged in the recess forms a sort of pouch or cul-de-sac, the floor and anterior wall of which are thickened, and form the macula acustica utriculi, which receives the utricular filaments of the acoustic nerve. The cavity of the utricle communicates behind with the semicircular ducts by five orifices. From its anterior wall is given off the ductus utriculosaccularis, which opens into the ductus endolymphaticus.

The Saccule

The saccule is the smaller of the two vestibular sacs; it is globular in form, and lies in the recessus sphæricus near the opening of the scala vestibuli of the cochlea. Its anterior part exhibits an oval thickening, the macula acustica sacculi, to which are distributed the saccular filaments of the acoustic nerve. Its cavity does not directly communicate with that of the utricle. From the posterior wall a canal, the ductus endolymphaticus, is given off; this duct is joined by the ductus utriculosaccularis, and then passes along the aquæductus vestibuli and ends in a blind pouch (saccus endolymphaticus) on the posterior surface of the petrous portion of the temporal bone, where it is in contact with the dura mater. From the lower part of the saccule a short tube, the canalis reuniens of Hensen, passes downward and opens into the ductus cochlearis near its vestibular extremity.

The Semicircular Ducts

(ductus semicirculares; membranous semicircular canals), The semicircular ducts are about one-fourth of the diameter of the osseous canals, but in number, shape, and general form they are precisely similar, and each presents at one end an ampulla. They open by five orifices into the utricle, one opening being common to the medial end of the superior and the upper end of the posterior duct. In the ampullæ the wall is thickened, and projects into the cavity as a fiddle-shaped, transversely placed elevation, the septum transversum, in which the nerves end.

The utricle, saccule, and semicircular ducts are held in position by numerous fibrous bands which stretch across the space between them and the bony walls.




BGDsmall.jpg
BGDB: Lecture - Gastrointestinal System | Practical - Gastrointestinal System | Lecture - Face and Ear | Practical - Face and Ear | Lecture - Endocrine | Lecture - Sexual Differentiation | Practical - Sexual Differentiation | Tutorial


Glossary Links

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols



Cite this page: Hill, M.A. 2017 Embryology BGDB Face and Ear - Late Embryo. Retrieved September 25, 2017, from https://embryology.med.unsw.edu.au/embryology/index.php/BGDB_Face_and_Ear_-_Late_Embryo

What Links Here?
© Dr Mark Hill 2017, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G