Post on 14-Jan-2016
description
Peter A. Jezewski, DDS, PhDSTEVEN J. ZEHREN, PH.D.
Craniofacial Embryology; PHARYNGEAL APPARATUS, TONGUE &THYROID GLAND
NBDE Part I• Is a comprehensive exam• 400 questions
– Anatomic sciences (100):• Gross anatomy (49)• Histology (23)• Oral Histology (16)• Developmental Biology (11)• Professional Ethics/Patient Management (1)
– Biochemistry-physiology (100)– Dental Anatomy (100)– Microbiology-Pathology (100)
Axial Patterning Outline of CF Development
• to make it all more obvious• First ANTERIOR to POSTERIOR
– Early definition of head versus tail end. • Animal pole versus vegetal pole: ORAL always at animal pole.
– Gastrulation (in deuterostomes):• We are deuterostomes (Second mouth)
– Gastrulation (gut formation) = First mouth– Stomation (mouth formation) = second mouth
• From posterior (vegetal) pole of egg towards the animal pole or future anterior end.
• Defines germ layers– Ectoderm, mesoderm, endoderm
Axial patterning continued• Gastrulation: also DORSAL to VENTRAL
– Asymmetric gastrulation• Defines Dorsal to ventral axis, (and L and R too)
– Defines dorsal neural domain– Eventually defines dorsal anterior (cranial) region– Defines early neural crest specification; laterally to neural plate. Cranial
placodes are formed just ventrally to neural crest cells.
• Neurulation– Neural plate, CNCC, Cranial Placodes
• Pharyngeal stage– Pharyngeal arches 1, 2 and jaw formation: Primary, Secondary palate. – Tongue– Thyroid gland
A to P Axis
Deuterostomy• Primary AP axis, determined in the egg.• Mouth formation always at the Animal Pole,
coincident with the Anterior.
Ant
Post
Ani
Veg
Protostomes: Deuterostomes:
Diploblasts: Triploblasts:
Deuterostomy• Anterior mouth, Posterior Gut:• Protostomes = Common mouth and anus• Deuterostomes = Second mouth
– Gut at Posterior – Mouth at Anterior
Protostomes: Deuterostomes: Ant
Post
Diploblasts: Triploblasts:
Gastrulation => Posterior Gut formation =>
Germ layers• Ectoderm
– Skin, nervous system.
• Endoderm– Gut, liver, lungs.
• Mesoderm– Skeleton, muscles, heart, blood.
• A tissue centric hypothesis focusing upon cell types.
Human gastrulation
Anterior-Posterior Axial Differentiation: Hox genes
• Gene expression colinear between phyla.
D to V Axis too
Asymmetric Gastrulation => Dorsal and Ventral Tissues
• Dorsal Anterior Ectoderm– Neural tissue
• Dorsal Mesoderm– Notochord
• Ventral Mesoderm– Blood, muscle, bone
A lancelet - cephalochordate
Neurulation
• Neural plate is most dorsal neural tissue– Induced by dorsal mesoderm (notochord)
• Lateral to that is “less neural” tissue– Like regions that will form the neural crest, from
the lateral aspects of the neural plate
• Lateral to this are the regions that will induce the cranial placodes or preplacodal ectoderm
Epidermis Epidermis
Helms J A et al. Development 2005;132:851-861
Neurulation, CNCC formation
• existence of a common pre-placodal region• it seems that an initial step common to all placodes involve signals from the mesendoderm,
while later, more region-specific signals confer placode-specific properties.• induction of the pre-placodal domain
– Endoderm or mesoderm or neural plate
Cranial Placodes
Cranial Placodes
PHARYNGEAL ARCHES
Cranial Neural Crest Cells
Hox and Pharyngeal arches
R1 R2 R3 R4 R5 R6 R7 R8
CN V.
CN VII.
Cranial Neural Crest Cell Migration
AP and DV pharyngeal codes
End of Gastrulation => Phylotypic Stage
• Follows the blastula, gastrula, neurula stages.• At pharyngula stage, all vertebrates show remarkable
similarities:– notochord, – dorsal, hollow nerve cord, – post-anal tail,– series of paired branchial arches.
Comparative Embryology:Common Pharyngula Stage?
chicken
frog zebrafish
Non-mammalianMammalian
mouse
Mouth Formation
A
Site of midbrain
Lens placode
Nasal placode
Stomodeum Heart
Somites
Pharyngeal(branchial) arches
12
3 4
Slide 10.1
PHARYNGEAL ARCHES FORM DURING 4TH WEEK.ECTODERMAL GROOVES SEPARATE ARCHES ON OUTSIDE.
Max. prom.
Mand.prom.
Oropharyngeal membrane
Stomodeum(primitive oral cavity)
Ectoderm
Endoderm of pharynx
STOMODEUM & OROPHARYNGEAL MEMBRANE
Development of the craniofacial primordia.
Helms J A et al. Development 2005;132:851-861
Human primary, secondary palate formation
Mouse primary palate formation
Secondary palate formation
Frontonasalprominence
Umbilical vein
Spinal cord
Eye
Entrance to stomodeum
Entrance to intraembryonic coelom
Mandibular prominence
Second pharyngeal arch
Third pharyngeal arch
Fourth pharyngeal arch
Maxillary prominence
Slide 10.31 SCANNING EM OF EMBRYO (5TH WEEK)
B
Midbrain
1st pharyngeal pouch Aortic arches(1st to 4th)
Esophagus
Lung bud
Thyroid diverticulum(primordium of thyroid gland)
HeartTruncus arteriosus (commonarterial trunk from heart)
Esophagus
Dorsal aorta
Level ofsection C
Ectoderm Endoderm Mesoderm
Germ Layer Derivatives
Slide 10.2 ENDODERMAL PHARYNGEAL POUCHES SEPARATE ARCHES ON INSIDE
1st arch(Meckel)
2nd arch(Reichert)
Cartilages
Muscle
Nerve
Mandibular (1st) arch
1st pharyngeal(branchial) membrane
2nd pharyngeal pouch
3rd pharyngeal pouch
Mesodermal core of 4th arch
3rd aortic arch
Hyoid (2nd) arch
Germ Layer Derivatives
Ectoderm Endoderm Mesoderm
C
Slide 10.3 COMPONENTS OF A PHARYNGEAL ARCH
Human Pharyngeal Arch Cartilages
Pharyngeal arches
PHARYNGEL ARCH CARTILAGES: DERIVATIVES
NCC + and mesoderm boundary• NCC makes all anterior structures of face: including cartilage, bone, muscle.
• Mesoderm makes all those posterior to the pituitary gland
Pink = paraxialmesoderm derived.Blue = neural crest Cells derived.
MEMBRANE BONES OF ARCH 1
ZYGOMATIC
MAXILLA
MANDIBLE
SQUAMOUS TEMPORAL
Ear development
PHARYNGEAL ARCH MUSCLES: DERIVATIVES
• The muscles derived from arch 1 (green) include the muscles of mastication (eg, temporalis and masseter) and the mylohyoid and anterior belly of the digastric. Also derived from arch 1 are the tensor palati m. (soft palate) and tensor tympani m. (middle ear)(not shown).• All of the muscles of mastication insert into the mandible (also from arch 1).• The mylohyoid and anterior belly of the digastric also attach to the mandible. • The muscles derived from arch 2 (salmon) include the muscles of facial expression, stylohyoid m. and posterior belly of the digastric. Also derived from arch 2 is the stapedius m. (middle ear)(not shown).• 5. The muscle derived from arch 3 (purple) is the stylopharyngeus m.• The muscles derived from arch 4 (light blue) include most of the muscles of the pharynx and soft palate, as well as the cricothyroid m.• The muscles derived from arch 6 (dark blue) include most of the muscles of the larynx and the striated musculature of the esophagus (not shown).
PHARYNGEAL ARCH NERVES
(Arch 1)
(Arch 1)
(Arch 2)
(Arch 3)
(Arches 4 &6)
(Superior laryngeal br. and pharyngealbr. to arch 4; recurrent laryngeal br. to arch 6)
3rd, 4th, and 6th aortic arches
Spinal cord
Dorsal aorta
Pulmonary artery
Yolk stalk
Yolk sac
Midbrain
C
Slide 14.56PHARYNGEAL ARCH ARTERIES (AORTIC ARCHES)
Aortic sac
3rd aortic arch
Left dorsal aorta
Aortic arches
Right subclavian artery
Left subclavian artery
Truncus arteriosus(partly dividedaortic and pulmonaryarteries)
External carotid artery
Left dorsal aorta
Internal carotid artery
Aortic sac
3
4
Ductus arteriosus
Left dorsal aorta
4th aortic arch 6th aortic arch
Truncus arteriosus Aortic sac
Aortic sac
Dorsal aortae
3
45 6
5
6
A
7th intersegmental artery
B
Pulmonary arteries
Slide 14.57TRANSFORMATION OF AORTIC ARCHES (VENTRAL VIEW)
6 WKS 7 WKS
Right
3rd aortic arch
Left subclavian artery
Arch of aorta
Ligamentum arteriosum
Internal carotid arteries
Ascendingaorta
Pulmonary trunk
Brachiocephalic artery
Subclavian arteries
Right pulmonary artery
Ductus arteriosus
Descending aorta
Ascending aorta
External carotid arteries
Left common carotid artery
Left pulmonary artery
4th aortic arch 6th aortic arch
Truncus arteriosus Aortic sac Dorsal aortae
C D
Slide 14.58
8 WKS 6 MO. INFANT
TRANSFORMATION OF AORTIC ARCHES (VENTRAL VIEW)
Right
PHARYNGEAL POUCHES, GROOVES & MEMBRANES
A B
Opercular flap
(becomes incorporated into the thyroid gland and forms the parafollicular cells: secretes Calcitonin)
PHARYNGEAL POUCHES, GROOVES & MEMBRANES
Tongue
Foramen cecum of tongue
Tonsillar sinus and surface epitheliumof palatine tonsil(pouch II)
Larynx
Thymus (pouch III)
Auditory tube(pharyngotympanic tube)and tympanic cavity (pouch I)
Tract ofthyroglossal duct
Ultimobranchialbody (pouch IV)
Thyroid gland
Pouch III
Pouch IVParathyroidglands
Slide 10.1320 WEEK FETUS SHOWING DERIVATIVES OF PHARYNGEAL POUCHES
Undescendedparathyroid gland
Hyoid bone
Accessorythymic tissue
Thyroidcartilage
Superiorparathyroidglands
Persistent cordof thymic tissue
Ectopic inferiorparathyroid gland
Persistentthyroglossal duct
Thyroid gland
Trachea
Manubriumof sternum
Retrosternalthymus
Body of sternumSlide 10.19 CONGENITAL ANOMALIES OF THYROID, THYMUS & PARATHYROID GLANDS
LATERAL CERVICAL CYSTS(REMNANTS OF CERVICAL SINUS)
A BC
Epicardial ridge(SCM develops in it)
Sternocleidomastoidmuscle
Swelling formed bybranchial cyst
Tendon ofsternocleidomastoidmuscle
Slide 10.16
LATERAL CERVICALCYST. NOTE ITS
POSITION ANTERIORTO SCM MUSCLE.
TONGUE
A
Arches: Distal tongue bud
Median tongue bud
Foramen cecumof tongue
Copula
Hypobranchialeminence
Hypobranchialeminence
Rima glottidis(opening to vocalapparatus)
Median sulcus
Circumvallatepapillae
Terminal sulcus
Foramen cecum of tongue
Epiglottis
Pharyngeal part of tongue
Oral partof tongue
Migration of thirdarch mesoderm1
2
34
Esophagus Laryngotracheal groove
B
C
Arch Derivatives of Tongue
1st pharyngeal arch(CN V-mandibular division)
2nd pharyngeal arch(CN VII-chorda tympani)
3rd pharyngeal arch(CN IX-glossopharyngeal)
4th pharyngeal arch(CN X-vagus)
Slide 10.26 DEVELOPMENT OF TONGUE
4 WKS5 WKS
ADULT
Occipital myotomes
Orbicularis oculi Temporalis
Occipitalis
Auricularis
Stylohyoid
Stylopharyngeus
Anterior and posterior bellies of digastric muscle
Platysma
Orbicularis oris
Masseter
Mylohyoid
Pharyngealmuscles
SternocleidomastoidClavicle
Frontalis
Buccinator
A B
First archmuscles
Second archmuscles
Third archmuscles
Fourth and sixtharch muscles
Slide 10.9
ALL TONGUE MUSCLES (EXCEPT PALATOGLOSSUS)DEVELOP FROM OCCIPITAL MYOTOMES
(PA4)
1. Muscles of tongue (except palatoglossus) develop from occipital myotomes (palatoglossus derived from arch 4) (A).2. Myoblasts from these myotomes migrate into the tongue (arrow in Fig. A).3. XII accompanies the myoblasts during their migration and innervates the tongue mm.
THYROID GLAND
Slide 10.20
DEVELOPMENT OF THYROID GLAND (EARLY)
Esophagus
A
B
Pharyngeal pouches
Pharyngealarches
Laryngotrachealdiverticulum
Primordialpharynx
Thyroiddiverticulum
Esophagus
Oropharyngealmembrane
Tongue
Foramen cecum of tongue
Thyroglossal duct
Thyroid diverticulum
Developinghyoid bone
StomodeumFormer site oforopharyngealmembrane
Heart
4 WKS
5 WKS
1. Thyroid gland is 1st endocrine gland to appear (4 weeks) (A).2.Thyroid gland develops as a median, endodermal thickening in the floor of the pharynx; this thickening soon forms a down growth known as the thyroid diverticulum (A).3. Thyroid diverticulum descends in neck, anterior to developing hyoid bone (B).•Thyroid diverticulum remains connected to floor of pharynx (in region of tongue) by thyroglossal duct. The opening of the duct onto the tongue is the foramen cecum (B).
Slide 10.21
DEVELOPMENT OF THYROID GLAND (LATER)
C
D
Tongue
Foramen cecum
Thyroglossal duct
Site of atrophyof duct
Thyroid gland
Soft palateHard palateForamen cecumof tongue
Former tract ofthyroglossal duct
Hyoid bone
Larynx
Thyroid glandPyramidal lobeof thyroid gland
Hyoid bone
Trachea
6 WKS
ADULT
1. By 7 weeks (slightly later than stage shown in Fig. C), thyroid gland has assumed its adult shape and position and the thyroglossal duct has atrophied.2. In adult (D), thyroid gland has two lateral lobes connected by an isthmus. Dashed line represents former tract of thyroglossal duct. Distal part of duct may persist (~50%) as a pyramidal lobe.
A
Thyroglossal duct cyst
Opening of thyroglossal duct sinus Cervical thyroglossal duct cyst
BThyroid gland
Foramen cecum of tongue
Hyoid bone
Hyoid bone
Lingualthyroglossalduct cyst
Thyroid cartilage
Slide 10.22
THYROGLOSSAL DUCT CYSTS AND FISTULA (SINUS)NOTE MIDLINE POSITION OF CYSTS
1. Thyroglossal duct normally degenerates but a portion of it may persist to form a thyroglossal duct cyst (A,B).2.These cysts may occur anywhere along the former tract of the thyroglossal duct (dashed lines in Figs. A & B). However, these cysts are always located close to, or in, the midline (vs. lateral cervical cysts).3.If a cyst communicates w/ the surface of the neck it is termed a thyroglossal duct fistula (sinus) (A). Usually such a fistula occurs secondarily (after rupture of an infected cyst).4. Most thyroglossal duct cysts are observed by 5 years of age.
END OF LECTURE