BGDB Face and Ear - Early Embryo

From Embryology
Practical 6: Trilaminar Embryo | Early Embryo | Late Embryo | Fetal | Postnatal | Abnormalities

Week 4

During week 4 a number of features appear visible on the embryo surface:

  • Body - heart, liver, somite bulges and limb buds appear.
  • Head - buccopharyngeal membrane breaks down, sensory placodes and pharyngeal arches appear.

Carnegie Stage 12 to 14

Week 4

Stage 11

Stage11 sem13c.jpg Stage11 sem20c.jpg

This is a scanning EM of the embryo superior dorsal view showing the paired otic placodes sinking into the surface at the level of the hindbrain between day 24 and day 25

Human Embryo (Stage 11)
Stage11 sem8.jpg
Stage11 sem81.jpg
Stage11 bf9.jpg Stage11 sem3b.jpg Stage11 sem3b.gif

Stage 12

Stage12 sem1c.jpg Stage12 bf2c.jpgStage12 bf1c.jpg

Stage12 sem4.jpg Stage12 sem5.jpg

Week 5

Stage 13

Stage13 sem1c.jpg Stage13 bf1c.jpg Stage13 sem2c.jpg

Surface view Central Nervous System
<html5media height="620" width="480">File:Stage 13 MRI 3D04.mp4</html5media> <html5media height="600" width="400">File:Stage 13 MRI 3D02.mp4</html5media>

Sensory Placodes

Sensory placodes develop as small patches of ectodermal thickenings.

The placodes are laterally paired and contribute key components to sensory structures of the ear, eye and nose.

Named by the sensory system and components they will form: otic placode, optic (lens) placode and nasal placode.

Stage 13

Identify the structure and position of the otic vesicle (otocyst) relative to other head structures.

Otic placode forms the otocyst

Stage 15

Stage 15

Stage15 sagittal section upper half 01.jpg

Later week 5 development showing a sagittal section upper half of human embryo.

Pharyngeal Arches

Head arches cartoon.jpg Pharyngeal arch structure cartoon.gif

Stage 13 Pharyngeal Arches

Stage13 pharyngeal arch excerpts.gif

Section Images: A6L  A7L  B1L  B2L  B3L  B4L  B5L  B6L

Look through the above cross-sections of the stage 13 embryo observing and identifying structures of the face and ear visible at this stage.

Pharyngeal arch cartilages.jpg

Structures derived from Arches

Pharyngeal Arch Nerve Artery Neural Crest
(Skeletal Structures)
Muscles Ligaments
trigeminal (CN V) maxillary artery (terminal branches) mandible, maxilla, malleus, incus muscles of mastication, mylohyoid, tensor tympanic, ant. belly digastric ant lig of malleus, sphenomandibular ligament
facial (CN VII) stapedial (embryonic)

corticotympanic (adult)

stapes, styloid process, lesser cornu of hyoid, upper part of body of hyoid bone muscles of facial expression, stapedius, stylohyoid, post. belly digastric stylohyoid ligament
3 glossopharyngeal (CN IX) common carotid, internal carotid arteries greater cornu of hyoid, lower part of body of hyoid bone stylopharyngeus
4 vagus (CN X) superior laryngeal branch part of aortic arch (left), part right subclavian artery (right) thyroid, cricoid, arytenoid, corniculate and cuneform cartilages crycothyroid, soft palate levator veli palatini (not tensor veli palatini)
6 vagus (CN X) recurrent laryngeal branch part of left pulmonary artery (left), part of right pulmonary artery (right) thyroid, cricoid, arytenoid, corniculate and cuneform cartilages larynx intrinsic muscles (not cricothyroid muscle)

Early Embryo Interactive Component

Attempt the Quiz - Early Embryo 

Here are a few simple Quiz questions that relate to Early Embryo from the lecture and practical.


1 Which of the following best describes the term "ectomesenchyme":

ectoderm derived from mesoderm
epithelium derived from connective tissue
sensory placodal induction by mesoderm
connective tissue derived from neural crest
none of the above is correct

2 Abnormal or perturbed migration of neural crest cells may result in malformation of structures derived from the:

first pharyngeal arch
second pharyngeal arch
third pharyngeal arch
fourth pharyngeal arch
all of the above

Practical 6: Trilaminar Embryo | Early Embryo | Late Embryo | Fetal | Postnatal | Abnormalities

Practical 6: Trilaminar Embryo | Early Embryo | Late Embryo | Fetal | Postnatal | Abnormalities

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.

Other Sensory Systems

The links below are to additional information providing background about each of the sensory systems. Only hearing is covered in today's class.

Hearing cartoon.jpg Stage 22 image 153.jpg Stage 22 image 209.jpg Tongue - taste cartoon.jpg
Hearing Development
Vision Development
Smell Development
Taste Development
Hearing Links: Introduction | inner ear | middle ear | outer ear | balance | placode | hearing neural | Science Lecture | Lecture Movie | Medicine Lecture | Stage 22 | hearing abnormalities | hearing test | sensory | Student project

  Categories: Hearing | Outer Ear | Middle Ear | Inner Ear | Balance

Historic Embryology - Hearing 
Historic Embryology: 1880 Platypus cochlea | 1892 Vertebrate Ear | 1902 Development of Hearing | 1906 Membranous Labyrinth | 1910 Auditory Nerve | 1913 Tectorial Membrane | 1918 Human Embryo Otic Capsule | 1918 Cochlea | 1918 Grays Anatomy | 1922 Human Auricle | 1922 Otic Primordia | 1931 Internal Ear Scalae | 1932 Otic Capsule 1 | 1933 Otic Capsule 2 | 1936 Otic Capsule 3 | 1933 Endolymphatic Sac | 1934 Otic Vesicle | 1934 Membranous Labyrinth | 1934 External Ear | 1938 Stapes - 7 to 21 weeks | 1938 Stapes - Term to Adult | 1940 Stapes | 1942 Stapes - Embryo 6.7 to 50 mm | 1943 Stapes - Fetus 75 to 150 mm | 1946 Aquaductus cochleae and periotic (perilymphatic) duct | 1946 aquaeductus cochleae | 1948 Fissula ante fenestram | 1948 Stapes - Fetus 160 mm to term | 1959 Auditory Ossicles | 1963 Human Otocyst | Historic Disclaimer
Vision Links: vision | lens | retina | placode | extraocular muscle | cornea | eyelid | lacrima gland | vision abnormalities | Student project 1 | Student project 2 | Category:Vision | sensory
Historic Embryology - Vision 
Historic Embryology: 1906 Eye Embryology | 1907 Development Atlas | 1912 Eye Development | 1912 Nasolacrimal Duct | 1917 Extraocular Muscle | 1918 Grays Anatomy | 1921 Eye Development | 1922 Optic Primordia | 1925 Eyeball and optic nerve | 1925 Iris | 1927 Oculomotor | 1928 Human Retina | 1928 Retina | 1928 Hyaloid Canal | Historic Disclaimer
Smell Links: Introduction | placode | Rhinencephalon | head | respiratory | Student project | taste | sensory | Category:Smell
Historic Embryology - Smell 
Historic Embryology: 1902 Olfactory Structures | 1910 cavum nasi | 1940 Olfactory and Accessory Olfactory Formations | 1941 Olfactory nerve | 1944 Jacobson’s organ | 1980 Staged embryos

Neural Crest

During this period neural crest cells migrate into the pharyngeal arches and other head locations, and have an important contribution to many different head structures. Neural crest cells at other levels contribute to body many structures. There are also many developmental abnormalities associated with abnormal neural crest development and/or migration. This topic is beyond the scope of the current class.

Links: Neural Crest Development
Cranial neural crest skeletal fate 01.jpg Cranial neural crest contribution to skeletal structures

The embryo figure shows colonization of the head and pharyngeal arches by diencephalic, anterior and posterior mesencephalic, and rhombencephalic neural crest cells (NCCs), as indicated by the colour code. The diagram is representative human embryos, although the NCC migratory pathways might differ slightly in different species. The skull drawings show contributions of NCC populations to cranial skeletal elements of humans, based on NCC fate-mapping studies and on extrapolation of avian and mouse data to known homologues in the human.

Some bones, including the squamosal (SQ), alisphenoid (AS), and pterygoid (PT), are shown with mixed contribution from different NCC populations. Note that in mammals the frontal (FR) and parietal (PA) bones have been reported to be of neural crest and mesodermal origin, respectively.

There has been controversy about the neural crest embryonic contribution to the parietal region. A recent transcriptional analysis of second trimester human cranial compartments[1] suggests that "a gene expression signature of neural crest origin still exists in frontal and metopic compartments while gene expression of parietal and sagittal compartments is more similar to mesoderm."[2]

  • BA1-BA3 - pharyngeal arches 1 - 3
  • di - diencephalon
  • FNP - frontonasal process
  • HY - hyoid bone
  • IN - incus
  • MA - malleus
  • mes - mesencephalon
  • MX - maxillary bone
  • NA - nasal bone
  • R1–R7 - rhombomeres 1 – 7
  • ST - stapes
  • ZY - zygomatic bone

  1. Homayounfar N, Park SS, Afsharinejad Z, Bammler TK, MacDonald JW, Farin FM, Mecham BH & Cunningham ML. (2015). Transcriptional analysis of human cranial compartments with different embryonic origins. Arch. Oral Biol. , 60, 1450-60. PMID: 26188427 DOI.
  2. Santagati F & Rijli FM. (2003). Cranial neural crest and the building of the vertebrate head. Nat. Rev. Neurosci. , 4, 806-18. PMID: 14523380 DOI.


Head Terms (expand to view) 
  • branchial arch - see pharyngeal arch.
  • clefting - the way in which the upper jaw forms from fusion of the smaller upper prominence of the first pharyngeal arch leads to a common congenital defect in this region called "clefting", which may involve either the upper lip, the palate or both structures, see palate and head abnormalities.
  • coronal suture - skull term for the fibrous connective tissue joint that connects the frontal bone with the parietal bones.
  • cranial fossae - skull term for the base bones of the cranial vault that form a container and support for the brain.
  • cranial vault - skull term for the space formed by bones of the skull that enclose the brain.
  • cysts - refers to a cervical sinus abnormality, remants of the cervical sinus remains as a fluid-filled cyst lined by an epithelium, see pharyngeal arch and head abnormalities.
  • dolichocephaly - see scaphocephaly.
  • fistula - refers to a pharyngeal membrane abnormality, a tract extends from pharynx (tonsillar fossa) beween the carotid arteries (internal and external) to open on side of neck, see pharyngeal arch and head abnormalities.
  • lambdoid suture (lambdoidal suture) skull term for the fibrous connective tissue joint that connects the parietal bones with the occipital bone, and is continuous with the occipitomastoid suture.
  • metopic suture - skull term for the fibrous connective tissue joint that connects the two fontal bones. In the adult skull this suture is not always present.
  • oxycephaly - (turricephaly) term meaning premature fusion of coronal suture + others, see skull and head abnormalities.
  • pharyngeal arch - (branchial arch) a structure that forms in the cranial region of the embryo having contributions from all germ layers. In humans, the arches appear in week 4 (GA week 6) in a rostra-caudal sequence and are numbered (1, 2, 3, 4, and 6). Each arch contributes a different part of the head and neck and the associated components.
  • pharyngeal cleft - (groove) surface ectoderm that externally separates each pharyngeal arch. In humans, only first pair persist as the outer ear external auditory meatus.
  • pharyngeal groove - see pharyngeal cleft.
  • pharyngeal membrane - surface ectoderm and pharynx endoderm contact region lying between each pharyngeal arch. In humans, only the first membrane pair persist as the tympanic membrane.
  • pharyngeal pouch - pharynx endoderm internal out-pocketing that separates each pharyngeal arch.
  • plagiocephaly - term meaning premature unilateral fusion of coronal or lambdoid sutures, see skull and head abnormalities.
  • Reichardt's cartilage - (pharyngeal arch 2 cartilage) The superior portion of the hyoid forms the ventral portion of this cartilage and the middle ear stapes is thought to form from the ends of this cartilage.
  • sagittal suture - skull term for the fibrous connective tissue joint that connects the two parietal bones in the midline.
  • scaphocephaly - (dolichocephaly) term meaning premature fusion of sagittal suture, see skull and head abnormalities.
  • sinuses - refers to a pharyngeal groove (cleft) abnormality, when a portion of the pharyngeal groove persists and opens to the skin surface, located laterally on the neck, see pharyngeal arch and head abnormalities.
  • squamosal suture - skull term for the fibrous connective tissue joint that connects the squamous portion of the temporal bone with the parietal bones.
  • suture - skull term for a fibrous connective tissue joint. In humans, the main sutures are coronal, sagittal, lambdoid and squamosal sutures, with the metopic suture (frontal suture) occurring as an anatomical variant in the adult skull.
  • turricephaly - see oxycephaly.
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Practical 6: Trilaminar Embryo | Early Embryo | Late Embryo | Fetal | Postnatal | Abnormalities


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Cite this page: Hill, M.A. (2024, April 24) Embryology BGDB Face and Ear - Early Embryo. Retrieved from

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G