Embryology of Face and Ear

BGD Lecture

Dr Mark Hill

UNSW Embryology

Lecture Overview

Face and Neck Pharyngeal Arches origins components structures formed Pharynx Ear Development origins otic placode external, middle, inner ear Abnormalities
(DVD links \| Print)	Pharynx cross-section

The links below require an internet connection
Systems Notes - Head and Neck
Systems Notes - Hearing
For links not requiring internet connection see the DVD notes slide.
For information on printing the slides see Print slide.
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Human Embryo Comparison

Note the great change beween the middle of embryological development to the end.
Human Embryo - Carnegie Stages

Embryo External Appearance


Stage 14	Stage 23

Pharynx

common forgut cavity begins at buccopharyngeal membrane "arched" beneath the brain over the pharyngeal eminence changes orientation as descends

Pharyngeal Arches

derived from pharyngeal or branchial arches
Humans have 5 arches

1, 2, 3, 4, 6
arch 5 either does not form or rapidly regresses

forms in rostro-caudal sequence
Arch 1 to 6 form week 4 onwards
Arch 1 and 2 appear at time of closure of cranial neuropore

Early Pharyngeal Arches

Stage 13/14 pharyngeal arch appearance

Pharyngeal Arch Components

each arch has initially similar components
contributions from all 3 germ layers

Ectoderm - outside surface and Neural Crest of core
Mesoderm - core of mesenchyme
Endoderm - inside pharyngeal surface

Pharyngeal Arch Features

arch
groove/cleft - externally separates each arch

only first pair persist as external auditory meatus

pouch - internally separates each arch

pockets from the pharynx

membrane - ectoderm and endoderm contact regions

only first pair persist as tympanic membrane

Neck and Face

each arch has initially similar components
each arch forms many different structures
Face - mainly arch 1 and 2
Neck - mainly arch 3 and 4

arch 4 and 6 fuse

Pharyngeal Arch Neural Crest

Cranial neural crest (midbrain and hindbrain region) enters pharyngeal arch mesenchyme
Forms connective tissues (cartilage, bone, ligaments):

jaw cartilage and bone
middle ear in mammals
frontonasal process bones
teeth dentine
cranial nerve peripheral neurons and glia

The cranial neural crest therefore contributes much of the underlying structure of the face.
Rhombomeres are the transient segmentation of the hindbrain. Not only visible, but also shown by gene expression boundaries.
For more information about neural crest see the UNSW Embryology Neural Crest Notes.

Pharyngeal Arch Core

Each arch contains

artery (See Chicken - heart and aortic arches Chicken - aortic arches)
cartilage
nerve
muscular component

There are some good images of this shown in the Sadler Image Bank Sadler Image Bank - Pharyngeal Arches | Sadler Image Bank - Pharyngeal Arch Arteries.
The aortic arch vessels are aslo shown on Embryo Images - Aortic Arch Vessels.
For more information about aortic development see the UNSW Embryology Heart Notes.

Pharyngeal Arch 1

Mandibular Arch
has 2 surface prominances
- Upper - smaller, maxillary
  - forms maxilla, zygomatic bone and squamous part of temporal
- Lower - larger, mandibular
  - mandible

See the embryo stage images Embryo Stage 12 | Embryo Stage 13
Embryo Images show both early and late images of teh first two arches Pharyngeal Arch 1 and 2 early | Embryo Images - Pharyngeal Arch 1 and 2 later
If you are interested in the origins of the jaw look at Dev Biol - Jaw structure in the fish, reptile, and mammal

Arch 1 Structures

Nerve
- trigeminal (CN V)
Muscles
- mastication (temporalis, masseter, medial pterygoid, lateral pterygoid)
Skeletal
- Meckel's cartilage, mandible model, malleus, incus
Artery
- maxillary (terminal branches)

Arch 2 Structures

Nerve
- facial (VII)
Muscles
- facial expression (buccinator, platysma, stapedius, stylohyoid, digastric posterior belly)
Skeletal
- Reichert's cartilage, stapes, styloid process, lesser cornu of hyoid, upper part of body of hyoid bone
Artery
- stapedial (embryonic)
- corticotympanic (adult)

Arch 3 Structures

Nerve
- glossopharyngeal (IX)
Muscles
- stylopharyngeus
Skeletal
- greater cornu of hyoid, lower part of body of hyoid bone
Artery
- common carotid, internal carotid (root)

Arch 4/6 Structures

Nerve
- superior laryngeal and recurrent laryngeal branch of vagus (X)
Muscles
- intrinsic muscles of larynx, pharynx; levator palati
Skeletal
- thyroid, cricoid, arytenoid, corniculate and cuneform cartilages
Artery
- 4 - aortic arch, right subclavian
- 6 - ductus arteriosus, pulmonary (roots)

Learn how the neck works from Physiology of oral cavity, pharynx and upper esophageal sphincter
Look at the Cranial Nerves in the brainstem cranial nerve nuclei

All Arches

Arch	Nerve	Muscles	Skeletal	Artery
1 (maxillary/mandibular)	trigeminal (V)	mastication (temporalis, masseter, medial pterygoid, lateral pterygoid)	mandible model malleus, incus Meckel's cartilage	maxillary (terminal branches)
2 (hyoid)	facial (VII)	facial expression ( buccinator, platysma, stapedius, stylohyoid, digastric posterior belly)	stapes, styloid process, lesser cornu of hyoid, upper part of body of hyoid bone Reichert's cartilage	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)

Pouches

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

Grooves and Membranes

Grooves- only 1st groove forms part of the external acoustic meatus
Membranes- only 1st membrane forms the tympanic membrane

Pharyngeal Abnormalities

Sinuses - when a portion of groove persists
Fistula - a tract extending from pharynx to open on side of neck
Cysts - remants of cervical sinus
Vestiges - cartilaginous or bony developmental remnants under skin on side of neck
Major abnormalities of the face are often indirectly due to abnormal neural tube and calveria formation.

Major facial abnormalities arise form abnormal neural tube and calveria formation. In these cases it is generally an indirect effect on face formation and detected by ultrasound. Holoprosencephaly Information
Most pharyngeal abnormalaties arise from incomplete obliteration of developmental pharyngeal clefts and pouches.
Thyroglossal duct cysts are the most common, followed by branchial cleft anomalies, dermoid cysts, and more rarely median cervical clefts.
Many abnormalities do not become evident until infancy or childhood (even though they are present from birth).
Branchial anomalies tend to become infected.
The origin of lymphoepithelial cysts in adults is contentious.

Face

Face develops from week 4 to 10 1 Frontonasal prominence - Nasal (medial, lateral) 2 Maxillary 2 Mandibular

Palate

Ultrasound Movie - Facial Cleft 1

Embryo Images - palate closing

Tongue

Derived from all pharyngeal arches contributing different components
Somites - tongue muscle cells
Somitomeres - muscles of mastication

Ear Development

Origins

otic placode

Major Divisions

external, middle, inner ear

Abnormalities

The links below require an internet connection
Systems Notes - Head and Neck
Systems Notes - Hearing

For links not requiring internet connection see DVD notes links

Embryo External Appearance


Stage 14	Stage 23

Externally the pharyngeal arches are initially the most obvious external feature.
Sensory placodes are present on the surface (but not obvious).
By stage 14 the sensory placode that contributes to hearing (otic placode) has already been lots from the surface and now lies in the mesenchyme in the neck region.
The cervical sinus is a surface landmark shwing the region where arch 2 is growing down over the arches below.
Human Embryo - Carnegie Stages
For links not requiring internet connection see DVD notes links

Ear Major Divisions

inner ear
- otic placode then otocyst
middle ear
- 1st pharyngeal pouch
- 1st and 2nd arch mesenchyme
outer ear
- 1st pharyngeal cleft
- 6 surface hillocks

Otocyst

pair of surface sensory placodes (otic placodes) in the head region
placodes fold inwards forming a depression
pinches off entirely from the surface
fluid-filled sac or vesicle (otic vesicle, otocyst)
vesicle sinks into the head mesenchyme

Stage 13 Embryo

Embryo Images Ear Links

Scanning Electron Microscope Images of Development

Inner Ear Development

vesicle then extends and folds
membranous labrynth
- cochlea
- utricle and saccule
- endolymphatic duct
- semicircular canals
Then
- innervated by CN VIII
- embedded in developing temporal bone

Inner Ear Stage 22

Stage 22

Middle Ear

ossicles (bones) arch 1 - malleus, incus arch 2 - stapes Model muscles (mesoderm) arch 1 - tensor tympani arch 2 - stapedius tympanic cavity first pharyngeal pouch extends as tubotympanic recess

Site showing a model of ossicle movements FEM analysis of the middle ear

Outer Ear

surface hillocks (auricular hillocks)
- three on pharyngeal arch 1
- three on pharyngeal arch 2
external auditory meatus (canal)
- 1st pharyngeal cleft (groove)

Stage 17

Stage 18 Stage 19

External Ear Stages 15 - 23

Abnormalities

There are many different genetic and environmental causes of abnormalities of the face and ear.
Australian Newborn hearing screening program (about 1 in 500 babies are born with a hearing loss Factsheet)
Links:
- Face Abnormalities
- Ultrasound - Cleft Lip
- Head and Neck Abnormalities
- Hearing Abnormalities
- Abnormal Development - Fetal Alcohol Syndrome
- Children's Hospital Cleft lip and palate
- See also the links in Notes for this slide

Western Australian pamphlet PDF: Your Newborn Bab Hearing Test
Children's Hospital at Westmead online pamphlet Can your child hear?
Children's Hospital at Westmead online pamphlet Language development the early years
Australian Prescriber (2003) article on Newborn hearing screening

Movies

Movie of the human head covering the Carnegie stages from 15 to 22. Note the images are not to scale.

Quicktime movie 179 Kb in new window.

Movie of the human head covering the Carnegie stages from 16 to 18.

Movie of stage 13/14 pig embryo sections showing the head region of the nasal placodes.

Face Development Overview (300 Kb)

Fetal Development Overview (800 Kb)

Development of the Tongue (187Kb)

References - Textbooks

Human Embryology (3rd ed.), Larson
- Chapter 12 Head pp 351-378, Hearing pp 392-417
The Developing Human: Clinically, Oriented Embryology (6th ed.) Moore and Persaud
- Chapter 10 Head pp 201- 240, Chapter 19 Hearing pp 491-511
Anatomy of the Human Body, Gray, H. Philadelphia: Lea and Febiger, 1918.

Online - Developmental Biology

Developmental Biology (6th ed.) Gilbert, Scott F. Sunderland (MA): Sinauer Associates, Inc.; c2000.
Head: Cranial neural crest cell migration in the mammalian head | Regions of the neural crest | Jaw structure in the fish, reptile, and mammal | Some derivatives of the pharyngeal arches
Ear: Evolution of the mammalian middle ear bones from the reptilian jaw | Chick embryo rhombomere neural crest cells | Some derivatives of the pharyngeal arches

Online - Textbooks

Eurekah Bioscience Collection: Cranial Neural Crest and Development of the Head Skeleton
Clinical Methods: 63. Cranial Nerves IX and X: The Glossopharyngeal and Vagus Nerves | The Tongue | 126. The Ear and Auditory System | An Overview of the Head and Neck - Ears and Hearing | Audiometry
Neuroscience: The Auditory System | The Inner Ear | The Middle Ear | The External Ear

Online Resources

Embryo Images Unit: Embryo Images Online Craniofacial Development Cell Populations Pharyngeal Arches Tongue Nose and Upper Lip Palate Development Inner Ear Middle Ear External Ear

Journals: GI Motility online (2006) Anatomy and development of oral cavity and pharynx The Cleft Palate Journal

DVD Links

Links on this page function from the UNSW Embryology DVD and do not require an internet connection.
Systems Notes - Head and Neck
Head and Neck Abnormalities
Systems Notes - Hearing
Systems Notes Abnormalities
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BGD: Embryology of Face and Ear

© Dr Mark Hill • 2007

Embryology of Face and Ear

BGD Lecture

Dr Mark Hill

UNSW Embryology

Lecture Overview

Human Embryo Comparison

Embryo External Appearance

Stage 14 Head

Stage 23 Head

Pharynx

Pharyngeal Arches

Early Pharyngeal Arches

Pharyngeal Arch Components

Pharyngeal Arch Features

Neck and Face

Pharyngeal Arch Neural Crest

Pharyngeal Arch Core

Pharyngeal Arch 1

Arch 1 Structures

Arch 2 Structures

Arch 3 Structures

Arch 4/6 Structures

All Arches

Pouches

Grooves and Membranes

Pharyngeal Abnormalities

Face

Palate

Tongue

Ear Development

Embryo External Appearance

Ear Major Divisions

Otocyst

Stage 13 Embryo

Embryo Images Ear Links

Inner Ear Development

Inner Ear Stage 22

Stage 22

Middle Ear

Outer Ear

Stage 17

Stage 18 Stage 19

External Ear Stages 15 - 23

Abnormalities

Movies

References - Textbooks

Online - Developmental Biology

Online - Textbooks

Online Resources

DVD Links

Print Slides