2009 BGD-B Lecture Face and Ear: Difference between revisions

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Revision as of 21:52, 13 May 2009

Introduction

Please note that this is an early draft version of text only from the online lecture presentation Beginnings, Growth and Development Lecture: Face and Ear. Prepared for easy printing and annotation, on the left hand menu "toolbox" select "Printable version".

1. Lecture Overview

  • Face and Neck
  • Pharyngeal Arches
    • origins
    • components
    • structures formed
  • Pharynx
  • Ear Development
    • origins
    • otic placode
    • external, middle, inner ear
  • Abnormalities


Links: Systems Notes - Head and Neck | Systems Notes - Hearing Lecture Slides (2004) ANAT2300 Head Development | Lecture Slides (2003) ANAM1006 Head Development


2. Human Embryo Comparison

Stage Comparison

More: Note the great change beween the middle of embryological development to the final stage.

Links: Embryo Stages | Stage Comparison | Stage 14 | Stage 23

3. Human Embryo External Appearance

600px stage14.jpg 600px stage23.jpg
Stage 14 Stage 23

More: 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

Links: Embryo Stages | Stage Comparison | Stage 14 | Stage 23

4. Pharynx

  • common forgut cavity
  • begins at buccopharyngeal membrane
  • "arched"
  • beneath the brain
  • over the pharyngeal eminence
  • changes orientation as descends
File:Head arches.jpg
  File:Pb2.gif

5. 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 from week 4 onwards
  • Arch 1 and 2 appear at time of closure of cranial neuropore

6. Early Pharyngeal Arches

  • Stage 13/14 pharyngeal arch appearance

7. 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
File:Head1.gif



File:Head1.gif
 

8. 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

9. Neck and Face

  • each arch has initially similar components
  • each arch though forms many different structures
  • Face - mainly arch 1 and 2
  • Neck - mainly arch 3 and 4
  • arch 4 and 6 fuse

10. 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
File:Head arches.jpgFile:Ba2qt2.gif

More: The cranial neural crest therefore contributes much of the underlying structure of the face. Rhombomeres are the transient segmentation of the hindbrain.

Links: Neural Crest Notes |

11. Pharyngeal Arch Core

Each arch contains
  • artery
  • cartilage
  • nerve
  • muscular component
File:Archcartilage.jpg File:Meckelsm.jpg

File:Head1.gif

More:

Links: Embryo Images - Aortic Arch Vessels |

12. Pharyngeal Arch 1

  • Mandibular Arch
    • has 2 prominances
  • Upper - smaller, maxillary
    • forms maxilla, zygomatic bone and squamous part of temporal
  • Lower - larger, mandibular
    • mandible
File:Pb2.gifFile:Mandible sm.jpg
   

More:

Links: Embryo Stage 12 | Embryo Stage 13 | Embryo Images - Pharyngeal Arch 1 and 2 early | Embryo Images - Pharyngeal Arch 1 and 2 later | Dev Biol - Jaw structure in the fish, reptile, and mammal |

13. Pharyngeal Arch 2 - 4

  • Pharyngeal Arch 2
    • Hyoid Arch
    • forms most of hyoid bone
    • 5 segments: body, two greater cornua, two lesser cornua
  • Arch 3 and 4
    • neck structures
    • hyoid bone, thyroid and cricoid cartilages
File:Archcartilage sm.jpgFile:Hyoid bone sm.jpg
   

More: Hyoid bone ossified from six centres (2 body, 1 for each cornu). Ossiification - late fetal in the greater cornua, then in the body, then postnatally (1-2 years) in the lesser cornua.

Links: Embryo Stage 13 |

14. Pharyngeal Arch Derivatives

Structures derived from 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)

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

More: The above table is not for you to learn by heart but an indication of the structures formed from each arch.

It is easy to remember that:

  • 1st arch - about the mouth (chewing, jaw) and the external and middle ear.
  • 2nd arch - about the face, hyoid and external and middle ear.
  • 3rd arch - about the neck and endocrine.
  • 4th arch- about the neck and endocrine.

Links: Arch Derivatives | Dev Biol - Some derivatives of the pharyngeal arches |

15. 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

More:

Links: Head and Neck Abnormalities | Hearing Abnormalities | Abnormal Development - Fetal Alcohol Syndrome | Abnormal Ultrasound - Cleft Lip |

16. Face

  • Face develops from week 4 to 10
File:Face16to18.jpg File:Face16to18.gif
  • 1 Frontonasal prominence - Nasal (medial, lateral)
  • 2 Maxillary2 Mandibular
  • Face Development cartoon


More:

Links: Face Development | Sadler Image Bank - Frontal aspect of the face 5 week and 6 week embryo | Sadler Image Bank - Frontal aspect of the face 7 week embryo |

17. Palate

File:Primarypalate1718.gif File:CleftPrimaryPalate1619.jpg


File:Cleft1label.jpg File:Cleft2label.jpg
Ultrasound Movie - Facial Cleft 1
Ultrasound Movie - Facial Cleft 2

More: Cleft lip and palate develop between the 4th and 8th week of gestation and is dominated by changes resulting in the formation of the nose. Palatal development occurs between the 7th and 12th week of gestation and is divided into the formation of the primary palate (prolabium), premaxilla and cartilaginous septum) and formation of the secondary palate (hard and soft palate). The animation above 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.

Links: Face Development - Primary Palate | Face Development Abnormalities | Abnormal Ultrasound - Cleft Lip |

18. Tongue

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

More: The tongue develops "inside" the floor of the oral cavity, therefre it is not readily visible in the external views of the embryonic (Carnegie) stages of development. Somitomeres are the unsegmented mesoderm found in the head region, in a similar location to that of somites in the body.

Links: Tongue Development | Sensory Development - Taste

Ear Development

Three divisions of the Ear
  • Ear Development
  • origins
  • otic placode
  • external, middle, inner ear
  • Abnormalities

Links: Systems Notes - Hearing | Systems Notes - Senses

2. Human Embryo External Appearance

File:600stage14.jpg File:600stage23.jpg
* Stage 14 * Stage 23


More: Externally the pharyngeal arches are initially the most obvious external feature. Sensory placodes are present on the surface (but not obvious). By this stage 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.

Links: Embryo Stages | Stage Comparison | Stage 14 | Stage 23

3. Three Ear Parts

  • inner ear
    • otic placode then otocyst
  • middle ear
    • 1st pharyngeal pouch
    • 1st and 2nd arch mesenchyme
  • outer ear
    • 1st pharyngeal cleft
    • 6 surface hillocks
File:Hearingcartoon.jpg
   

4. 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
File:PigA3L.GIF
  • Stage 13 Embryo


5. 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
File:Inner ear2 sm.jpgFile:Innerear sm.jpg
File:HUMB5L.gif
  • Stage 22
File:HumHPB5L.GIF

6. Middle Ear

* ossicles (bones)
  • arch 1 - malleus, incus
  • arch 2 - stapes
  • muscles (mesoderm)
  • arch 1 - tensor tympani
  • arch 2 - stapedius
  • tympanic cavity
  • first pharyngeal pouch
  • extends as tubotympanic recess
File:Archcartilage.jpg
  File:Ear ossicles.jpg

7. Outer Ear

  • Surface hillocks (auricular hillocks)
    • three on pharyngeal arch 1
    • three on pharyngeal arch 2
  • external auditory meatus (canal)
    • 1st pharyngeal cleft (groove)
File:CSt17.gif* Stage 17


File:CSt18.gifFile:CSt19.gif* Stage 18 Stage 19 File:CSt20.gif
File:Hearingcartoon.jpg File:Externalearanatomy.gif
 

Abnormalities

  • Fetal Alcohol Syndrome

More:

Links: Head and Neck Abnormalities | Hearing Abnormalities | Abnormal Development - Fetal Alcohol Syndrome |

Movies

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

References

Textbooks

  • Human Embryology (3rd ed.) Larson Chapter 12 pp Face 351-378, Ear pp 392-417
  • The Developing Human: Clinically Oriented Embryology (6th ed.) Moore and Persaud Face Chapter 10 pp 201- 240, Ear Chapter 19 pp 491-511
  • Before We Are Born (5th ed.) Moore and Persaud Chapter 20 pp 460-479

Online Textbooks=

Face

Ear

Online Resources

Embryo Images Face: Embryo Images Online | Craniofacial Development | Cell Populations | Pharyngeal Arches | Tongue | Nose and Upper Lip | Palate Development

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

Embryo Images Ear: Embryo Images Online | Ear Development | Inner Ear | Middle Ear | External Ear


Terms

branchial arch (= pharyngeal arch) (Greek, branchia = gill) is a misnomer.

buccopharyngeal membrane (= oral membrane), apposition of ectoderm with endoderm with no mesoderm between. Lies at a ventral central depression (stomadeum). This external to internal junctionl region wiil break down, creating an opening and allows amniotic fluid to fill the foregut.

chondrocranium in humans, forms base of skull (in lower vertebrates encases brain).

Glossary

Links back to UNSW Embryology 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

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© Dr M. A. Hill, 2007, Cell Biology Laboratory, School of Medical Sciences, Faculty of Medicine The University of New South Wales, Sydney, Australia. Email UNSW CRICOS Provider Code No. 00098G