NOrmal AND Abnormal Neck/Face Development

Much of the neck is derived from _____ ____. Facial skin is derived from the ___. What does the ectomesenchyme develop into? What does the endoderm develop into?

Pharyngeal arches 2, 3, 4 and 6.
Ectoderm
Ectomesenchyme deleveops into skeletal tissues (bone, cartilage,) CT
The endoderm develops into most of the oral mucosa

How does the neck achieve its smooth adult contour?

Arch 2 achieves overgrowth down to cover pharyngeal pouches 2-4.

What abnormal development can occur in the neck?

Branchial cyst=lateral visceral cyst=pharyngeal arch cyst

What is Branchial cyst?

It is abnormal development of Pharyngeal grooves/cleft in which the cervical sinus persists.

what are the borders of a branchial cyst?

It often lies along the anterior border of the SCM and often at the mandibular triangle.

Is a branchial cyst noticeable at birth?

No, it is not visible at birth but it appears during childhood.

what sinus provides opening for the branchial cyst?

the cervical sinus if it persists during neck development.

what arches are involved in an external opening?

External opening-Arch 2 and 4 never met

What is the Oropharyngeal membrane? What is it also known as? Where is its origin?

The Oropharyngeal membrane is also known as the buccopharyngeal membrane. This membrane seperates the Stomodeum from foregut. The membrane is derived from ectoderm+endoderm

In what week does oral cavity development begin? what kind of folding is observed?

In week 4, longitudinal folding causes invagination to become stomodeum

what is derived from arch 1 in oral cavity development?
what is derived from arch 2,3,4?

the stomodeum is derived from arch 1(ectoderm)...anterior to membrane
the forgut is derived from arches 2,3,4 (endoderm)...posterior to membrane

How do you get continuity between mouth and the pharynx?

the Oropharyngeal membrane burst.

What week does the development of the thyroid gland begin?Where does it begin?

In week 4, as the oral cavity starts to develop (remember the story of stomodeum), development of the thyroid gland begins at the oropharynx floor (foramen cecum-endoderm)

Describe the development pathway of the thyroid gland.

From the foramen cecum, it invaginates and travels ventrally to anterior neck. It moves down to form the thyroglossal duct and the thyroid diverticulum. The duct elongates and the diverticulum enlarges to become the thyroid gland.

What arches are involved in thyroid development? What becomes C cells? When does the thyroid gland begin to f(x)?

Arches 4 and 5 are involved in thyroid gland development. The thyroid gland joins ultimobranchial body. The ultimobranchial body becomes C cells.
The thyroid is functioning at 3 months

What are the two abnormalities in thyroid development?

Ectopic thyroid aka aberrant thyroid tissue and
Thyroglossal cyst

How does an ectopic thyroid develop? Where is the site of tissue?

It can stop migrating anywhere along migration route. Ectopic thyroid is especially common near the foramen cecum, resulting in a bulge on tongue

How does a thyroglossal cyst develop? Is it visible at birth?

Failure of thyroglossal duct to atrophy and disppear results in thyroglossal cyst. It is not visible at birth but it appears in childhood.

Abnormal development of pharayngeal pouches ___ and ___ can lead to ___ parathyroids.

abnormal development of 3rd and 4th pharayngeal pouches==> ectopic parathyroids

Where are they located? Is an ectopic parathyroid a problem?

They are abnormal migration that end up in/near the thyroid gland and thymus.
Ectopic parathyroid is not a problem unless a surgeon doesn't know where it is before surgery.

What are the two abnormal pharyngeal pouch developments discussed in class? What pouches are involved?

Ectopic parathyroids and DiGeorge's Syndrome.
Pouches 3 and 4 are involved

what is the normal # of parathyroid? Discuss the variation in number of parathyroid glands.

The normal # of parathyroid gland is 4.
This number can vary.
If # <4, 1-2 pouches didn't get the message.
If # >4, pouches made too much parathyroid glands than necessary

In DiGeorge Syndrome, what is effected? What is the end result?

The neural crest is effected by agenesis or hypoplasia in the DiGeorge syndrome.
Short Philtrum, Micrognathia, hypertolerism, abn. ext. ears, +/- cleft lip/palate is the end result

What is agenesis? What is hypoplasia

Agenesis is failure to develop
Hypoplasia-incomplete development

What causes Digeorge Syndrome?

Multifactorial-known genetic abnormality, alcohol and retinoids

Which is incompatible with life?

Complete agenesis of parathyroids and thymus is incompatible with life.

When does tongue development begin? What germ layers, arches and other tissues of origin are involved?

Tongue development begins during week 4( same as oral cavity development and thyroid development)
The oralpharynx floor =ectoderm+endorm of arches 1,2,3,4.
Ectomesenchyme is also involved.

What does arch 1 contribute to tongue formation? Sensory innervation? Special sensory innervation?

3 lingual swellings:
2 lateral=distal--->anterior 2/3 of tongue
1 median =Tuberculum impar=disappears
Sensory innervation-CN 5
Special sensory innervation-CN 7

What does arch 2 contribute to tongue formation? Sensory innervation? Special sensory innervation?

1 midline swelling : Copula--> disappears

what seperates the contributions of arch 1 from that of arches 2, 3, and 4?Sensory innervation? Special sensory innervation?

Foramen cecum
Sensory innervation-
Special sensory innervation-

What does arch 3 contribute to tongue formation?Sensory innervation? Special sensory innervation?

1 midline swelling:
Hypobranchial eminence-->1/3 posterior tongue
Sensory innervation-9
Special sensory innervation-9

What does arch 4 contribute to tongue formation?Sensory innervation? Special sensory innervation?

1 midline swelling:
hypobranchial eminence -->root of tongue
Sensory innervation-10
Special sensory innervation-10

what nerve innervates all the muscles of the tongue?

CN XII

Where do the muscles of tongue originate from?

Occipital myotomes (somites 2-5) form intrinsic and extrinsic muscles of the tongue.

When do salivary glands develop? What do the germ layers give rise to? What does the ectomesenchyme give rise to? When do the salivary glands function?

Salivary glands develop week 6-7. It originates from the oral epithelium.
The ectomesenchyme gives rise to CT of glands
The ectoderm-->parotid gland
Endoderm--->Submandibular and sublingual
The salivary glands are functional at week 18.

Facial development begins during weeks__ to __. 5 regions along with the stomodeum form the face. There is 1 ____prominence, 2___ prominence and 2__mandibular prominence

Facial development begins during weeks 4 to 8. 5 regions along with the stomodeum form the face. There is 1 FRONTALNASAL____prominence, 2 MAX___ prominence and 2_Mand. prominence

The frontal nasal prominence forms?
The two Maxillary prominences form?
The two mandibular prominences form?

Frontal nasal prominence forms superior 1/3 of face
2 Maxillary prominences form middle 1/3 of face (upper lip and jaw) of Arch 1
two mandibular prominences form inferior 1/3 of face. (lower lip and jaw)

Where does the nasal cavity form from? How does the external nose develop?

Nasal Cavity forms from the frontonasal prominence. The development of the external nose begins with Ectodermal thickening.

When ectodermal thickening aka ____occurs during nasal cavity development, to give___ and ___.

Nasal Placode
Nasal Prominence and Nasal pit

The___ develops in area where there's no proliferation.
The Nasal prominence forms the ___ and ___ nasal prominences.

Nasal pit develops in area where there is no proliferation.
Nasal Prominence:
Lateral NP-alae
Medial NP-crest/tip/septum

The nasal cavity forms from the ___ that invaginates into the mesenchyme. This invagination deepens to become ___.

Ectoderm invaginates into mesenchyme to form nasal pit.
The invagination deepens to form nasal sac.

How do you get from nasal sac to nasal cavity?

Upon development of naval sac, the Oronasal membrane develops. It is soon ruptured to allow O2 into pharynx.--->nasal cavity is formed.
olfactory N fibers and primitive choanae are present.

The four paranasal sinuses are? Are these the first or last parts of the nose to develop?

The four paranasal sinuses are the ethmoidal, sphenoidal, frontal and maxillary. These are the last part of nose to develop.

What are the functions of the paranasal sinuses? Are they present at birth?

Paranasal functions to alter size and shape of face, voice resonance and disperse masticatory forces into cranium. At birth sinuses are absent. All expand slowly until adulthood. Growth accelerates during tooth eruption. 6-8 years.

The upper lip and jaw are derived from #___processes and #___ prominences of Arch 1. How many sections is the upper lip broken into? What are they? What forms each section

The upper lip and jaw are derived from 2 median nasal prominence and 2 max prominence. There are 3 sections of the upper lip:
1/3 Philtrum is formed from the median nasal prominence
2 x1/3 lateral is formed from the max prominence
Review:f rontal nasal si

The lower lip and jaw is derived from the___prominence

The lower lip and jaw is derived from the mandible prominence. Skeletal tissues include Meckel's cartilage which is replaced by mandible

What is the premaxilla? It is also known as?

The 2 median nasal prominences fuse to form INTERMAXILLARY SEGMENT aka PREMAXILLA.

What does the premaxilla contain in adults?

It contains 4 incisors and the primary palate

What forms the rest of the maxilla and rest of teeth?

The maxillary prominence

Cleft lip aka___affects 1:___. Discuss the trend observed in Cleft Lip

Anterior cleft affects 1:500-1000 people. Anterior because it is anterior to the incisive canal. It affects Asians>Caucasian>Africans
More common in males than females.

What is cleft lip/anterior cleft? What is the most common cleft lip? What is uncommon?

Anterior cleft is the joining of the medial nasal prominence with the maxillary prominence.
Common cleft lip is med 1/3 and lat 1/3
Uncommon cleft is lower lip and jaw.

A cleft lip that involves the lip, alveolar bone and premaxilla is____. Incomplete cleft lip can involve any depth.

Complete

Is the majority of cleft lip isolated or part of a syndrome?

90% is isolated and 10% is part of a syndrome.

Cleft Lip may affect ___, ___,___

Feeding, breathing and speech
Review craniofacial team

Causes of cleft lip are ____. Some environmental agents include__,__ and ___.

Cleft lip is multifactoral-family history +
Environmental agents include smoking, decrease in folate and Dilantin

The primary palate aka___ aka ___ forms during what week?
The secondary palate forms during what week?
The entire Palate formation is complete by week__?

primary palate=intermaxillary segment=premaxilla (hard palate) forms during week 6
The secondary palate forms during weeks 6-8
The palate formation is complete after 12 weeks.

What forms the secondary palate? Review primary palate formation.

Maxillary prominence-->lateral palatine process--> secondary palate-->hard palate + soft palate and uvula. BEHIND(post.) of incisive canal

When does folding occur with the lateral palatine process? Describe the folding. Is it vertical to horizontal or vice versa?

Lateral palantine folding occurs weeks 7-8.5
It is a vertical to Horizontal folding.
In the vertical position , the tongue lies in between the lateral processes. During folding, tongue gets away so folding can occur.

A cleft palate can occur when

elevation=folding doesn't occur with the lateral palatine processes.

How is the incisive canal formed?

The palatine processes must fuse with the nasal septum to form the incisive canal.
This is the first contact point where median nasal palatine process, secondary palate and nasal septum connect.

Cleft palate aka__? Trend?

Posterior cleft. It is half as common as cleft lip=1:2000
females> males

Cleft palate caused by a number of things. ____ and ___ makes it difficult for tongue to move out of the way of the lateral palatine process when they need to flip from__ to ____. Cleft palate may also be caused by deficient growth of ____ __ ___.

Macroglossia and micrognathia makes it difficult for tongue to move out of way during elevation. Deficient growth of lateral palatine process may also cause posterior cleft.

Complete Cleft lip includes entire hard palate posterior to incisive canal. Incomplete Cleft lip is aka

submucosa clefts.

Is cleft palate isolated or syndromic? What are effects of cleft palate?

75% is isolated and 25% is syndromic. Cleft palate effects include feeding, breathing and speech.

In repairing cleft palate, repair __ first then repair___.

Repair soft palate first then Hard palate.

What week does the eye form?What germ layers and tissue structures are they formed from?

During week 4, the eyes develop.
It is derived from from the diencephalon part of the forebrain(ectoderm),
the ectoderm of the head and mesenchyme ( both ectomesenchyme from neural crest an mesodermal mesenchyme)

What does the diencephalon form?

It expands laterally to form 2 optic stalks(medial) and 2 optic vessicles(lateral)

Optic stalk-->
Optic cup-->
lens placode-->
mesenchyme -->

Optic stalk-->optic nerve
Optic cup-->retina, ciliary body, iris
lens placode--> lens
mesenchyme --> cornea, sclera and chambers

The eyelids shut ___ months and reopen___months

3 and reopen 6 months in utero.

Muscles of the eye are derived from____.

somitomeres 1,2,3 and 5 migrate to form extraocular eye muscles. CN 4,3,6 migrates with somitomeres

In the eye, CN 3 innervates what eye muscles?

superior, medial and ventral racti muscles derinved from somitomere1 and 2

In the eye, CN 4 innervates

Superior olique muscles derived from somitomere 3

In the eye, CN 6 innervates

lateral rectus of the eye derived from somitomere 5

What are other congenital syndrome involving the face?

Fetal Alcohol syndrome
Retinoic Acid syndrome
Fetal hydantoin syndrome
holoprosencephaly

What causes FAS? What are the features of FAS?

Moderate to excessive alcohol intake-->FAS
Features of FAS includes:
Frontonasal prominence-low nasal bridge, short nose , indistinct philtrum
Arch 1-micrognathia, thin upper lip, flat midface, minor ear abnomalities
Other-CNS abnormalities(mental retarda

Excessive vitamin A, usually as Accutane causes? What are the features of this syndrome?

Reitinoic Acid Syndrome
Features:
Arch 1-Micrognathia, cleft palate, microtia
Pharyngeal pouch- thymic apalasia
NTD

ANticonvulsant medications may cause?
Features?

Fetal hydantoin syndrome
features:
frontonasal prominence- hypertolerism, short nose
arch 1,2-abnormal ext ear
other-microcephaly with mental retardation

FAS, retinoids, cocaine may cause? what is the spectrum?

Holoprosencephaly. the spectrum is mild to severe. It can include brain, eyes, nose, philtrum and maxilla

Repair schedule for cleft soft palate is

3-10 months

Repair schedule for cleft hard palate is

12-18 months ( after deciduous teeth erup to minimize growth disturbance to perm teeth)

Repair schedule for cheeks and eyelids is

3 years

Repair schedule for mandible (micrognathia) is

4-5 years

Repair schedule for ears is

5-7 years.

Arch 1 developmental abnormalities include

Treacher Collins Syndrome and Pierre Robin syndrome

Treacher Collins Syndrome aka ___ is likely due to death of ____ prior or after cell migration.

Treacher Collins Syndrome is also known as mandibulofacial dysostosis. This syndrome is likely due to death of the neural crest prior to cell migration.

What is mandibulofacial dysostosis? It is uncommon 1 :10000

Bone malformation in lower 2/3 of face
so it includes maxilla and mandible malformation.
Etiology includes genetics and environmental