BGDB Face and Ear - Early Embryo

Week 4

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

At the level of the body heart, liver, somite bulges and limb buds appear.
At the level of the head sensory placodes and pharyngeal arches appear.

Carnegie Stage 12 to 14

Week 4

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 (Stage 11)

Week 5

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, lens placode and nasal placode.

Pharyngeal Arches

Stage 13 Pharyngeal Arches

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

Stage 13 Pharynx

Structures derived from Arches

Arch	Nerve	Muscles	Skeletal	Artery
1 (maxillary/mandibular)	trigeminal (V)	mastication (temporalis, masseter, medial pterygoid, lateral pterygoid)	Meckel's cartilage mandible modelmalleus, incus	maxillary(terminal branches)
2 (hyoid)	facial (VII)	facial expression (buccinator, platysma, stapedius, stylohyoid, digastric posterior belly)	Reichert's cartilage stapes, styloid process, lesser cornu of hyoid, upper part of body of hyoid bone	stapedial (embryonic) corticotympanic (adult)
3	glossopharyngeal (IX)	stylopharyngeus	greater cornu of hyoid, lower part of body of hyoid bone	common carotid, internal carotid (root)
4 and 6	superior laryngeal and recurrent laryngeal branch of vagus (X)	intrinsic muscles of larynx, pharynx; levator palati	thyroid, cricoid, arytenoid, corniculate and cuneform cartilages	4 - aortic arch, right subclavian 6 - ductus arteriosus, pulmonary (roots)

Structures derived from Pouches

Pouch	Overall Structure	Specific Structures
1	tubotympanic recess	tympanic membrane, tympanic cavity, mastoid antrum, auditory tube
2	intratonsillar cleft	crypts of palatine tonsil, lymphatic nodules of palatine tonsil
3	inferior parathyroid gland, thymus gland
4	superior parathyroid gland, ultimobranchial body
5	becomes part of 4th pouch

Glossary Links

Glossary: 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 | Term Link

Cite this page: Hill, M.A. (2024, May 19) Embryology BGDB Face and Ear - Early Embryo. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/BGDB_Face_and_Ear_-_Early_Embryo

What Links Here?