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DEVELOPMENT OF THE HEAD. FACIAL, ORAL, AND NASAL REGIONS VISCERAL POUCHES AND GROOVES. Figure 8-2, chicken development, in Carlson. Figure 9-9, pig development, in Carlson. Figure 9-10, human development, in Carlson. Chicken - 3.5 days. Figure 8-2, chicken development, in Carlson.

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DEVELOPMENT OF THE HEAD

FACIAL, ORAL, AND NASAL REGIONS

VISCERAL POUCHES AND GROOVES

slide6

Chicken - 3.5 days

Figure 8-2, chicken development, in Carlson

Pig - 12 days

Figure 9-9, pig development, in Carlson

Human - 28 days

Figure 9-10, human development, in Carlson

slide7

Development of the face and associated structures

Figs. 16-5, 16-7, pp. 518, 520 - Carlson

4 weeks

slide9

Upper jaw:

1. Maxillary processes

2. Nasomedial processes

Lower Jaw:

Lateral and ventro-mesial components of the mandibular arches

Nostrils:

1. Nasolateral processes

2. Nasomedial processes

Nasolacrimal groove:

Between nasolateral process and maxillary process. Will form lacrimal duct (tear duct) in adult. Obstruction causes excessive tearing. Extends from orbit of eye to nasal sinus.

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Take me to your leader

Upper lip:

1. Maxillary processes

2. Nasomedial processes

Lower lip:

Lateral and ventro-mesial components of the mandibular arches

Figs. 16-5, 16-7, pp. 518, 520 - Carlson

slide10

5 weeks

Nares

6 weeks

External nares

7 weeks

(External nares)

Nares

(Internal nares)

(External nares)

Fig. 14-3 on development of the nasal cavities in your lecture packet. Similar to Figs. 16-9, p.524 in Carlson

The formation of the nasal passages begins with the invagination of the olfactory placodes to form the olfactory pit. As development proceeds, this invagination deepens and extends through the head mesenchyme between the telencephalon and the roof of the pharynx. The ectoderm lining of this invagination eventually abuts the endodermal lining of the roof of the pharynx to form the oronasal membrane. This membrane eventually degenerates forming an opening of the nasal passage on each side through the roof of the pharynx.

slide11

Figures on palate formation in lecture packet. Also see Carlson, pp. 521 - 525.

Important structures in the formation of the palate

1. Median palatine process - primary palate

2. Lateral palatine processes - secondary palate + uvula

slide12

Figures on palate formation in lecture packet. Also see Carlson, pp. 521 - 525.

Important structures in the formation of the palate

1. Median palatine process - primary palate

2. Lateral palatine processes - fuse to form the secondary palate and uvula

The hard palate is formed along the suture line between the left and right lateral palatine processes.

slide13

Initially - epithelium lining palatine processes is undifferentiated

Once processes meet along midline, inductive effects cause changes

Cells along suture line between processes either undergo apoptosis (they die), convert to head mesenchyme, or they migrate into the oral epithelium.

Cells of nasal epithelium differentiate into a simple, cuboidal, ciliated epithelium.

Cells of oral epithelium differentiate into stratified squamous epithelium.

P. 523 Carlson

Fig. 14-3 on development of the nasal cavities in your lecture packet. Similar to Figs. 16-9, p.524 in Carlson

cuboidal

slide15

What structures are involved?

Lip

nasomedial processes

maxillary processes

Palate

median palatine process

lateral palatine processes

Types of cleft lip/palate

http://www.lpch.org/diseaseHealthInfo/healthLibrary/craniofacial/cleft.html

slide16

A. (above) Lip - Failure in fusion of nasomedial process with maxillary process and failure in fusion of edges of nasolacrimal groove with nasolateral process.

B. (above) Failure in fusion of posterior portions of maxillary process and mandibular arch on left.

A. & B. (to left)

Lip - Failure in fusion of nasomedial process and maxillary process (A.-on one side, B.-on both sides).

Palate - Failure in fusion of anterior region of lateral palatine processes with median palatine process.

C. (to left) - Lip formation complete.

Palate - failure in fusion of lateral palatine processes with each other.

D. (to left)

Lips - same as A. & B. (to left)

Palate - Failure in fusion of lateral palatine processes with each other and with the median palatine process.

slide17

Cleft Palate

Most of the time, the cause is unknown. Clefts can run in families and be associated with other problems. Some drugs taken during pregnancy are known to cause clefts. Clefts are more common in certain ethnic groups.

In most cases, however, there is no identifiable cause or risk factor.

In the United States, clefts occur once in every 700 to 1000 births, making it a common birth defect.

Many children with clefts have abnormalities of the teeth-this can range from crooked teeth to extra or missing teeth.

Most surgeons repair cleft lip when the baby is 6 to 10 weeks old. Most surgeons repair cleft palate at 6 to 12 months of age. The exact age for repair will depend on the size and health of the child and the surgeon's preference.

Movie - cleft repair

slide18

Correction of cleft lip/palate

Before and after surgery

http://www.smiletrain.org

slide19

6 wks

5 wks

Important structures and landmarks in the formation of the tongue:

1. Lateral lingual swellings - form most of the body of the tongue

2. Tuberculum impar - forms posterior part of the body of the tongue

3. Foramen cecum - pit at the point where the thyroid evagination formed

4. Copula - forms the root of the tongue

See figure 16-10, p. 526 and associated text in Carlson.

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Important structures and landmarks in the formation of the tongue:

1. Lateral lingual swellings - form most of the body of the tongue

2. Tuberculum impar - forms posterior part of the body of the tongue

3. Foramen cecum - pit at the point where the thyroid evagination formed

4. Copula - forms the root of the tongue

Filiform, fungiform, circumvallate, foliate papillae differentiate on the body of the tongue.

The foramen cecum is at the middle of the border between the body and root of the tongue.

See figure 16-10, p. 526 and associated text in Carlson.

slide21

Visceral arches, visceral pouches, and visceral clefts

Visceral arch I - maxilla and mandible, malleus and incus of middle ear, portion of pinna of ear innervation - cranial nerve #5 (trigeminal)

Visceral cleft I - external auditory meatus, ectodermal component of tympanic membrane

Visceral pouch I - middle ear cavity and eustachian tube, endodermal component of tympanic membrane

Visceral arch II - facial bones and cartilage, stapes of middle ear, portion of pinna of ear, innervation - cranial nerve # 7 (facial), “opercular flap” of cervical sinus in embryo

Visceral cleft II - cervical sinus in embryo Visceral pouch II - palatine tonsils

slide22

Development of the pinna of the ear

The pina arises from 6 swellings, called auricular hillocks or tubercles, that border the hyomandibular cleft. Three of these are in the tissues of the mandibular arch and three in the tissues of the hyoid arch.

AH - auricular hillocks, FVA - first visceral arch, FVC - first visceral cleft, SVA - second visceral arch

http://www.ajronline.org/cgi/content/full/178/6/1523

slide23

Development of the pinna of the ear

At 6 weeks of development 6 swellings of tissue, called auricular hillocks or tubercles, form on either side of the hyomandibular cleft.

The tissues of the tubercles proliferate and together form the pinna of the ear. The portions of the pinna close to its attachment with the head are derived from the mandibular arch and the rest from the hyoid arch.

The fact that the pinna is formed by 6 different masses of tissue that merge may explain why there is so much variation in its shape.

6 weeks

Figure 15-20, p. 511, Carlson.

See text and figures, pages 505-511 in Carlson.

slide24

Development of the middle and inner ear

Three ossiclesdevelop from neural crest cells in the mesenchyme of the mandibular and hyoid arch.

These will form the malleus, incus, and stapes.

Most texts say that the malleus and incus form from neural crest cells in the mesenchyme of the mandibular arch and the stapes from neural crest cells in the mesenchyme of the hyoid arch. However, more recent studies suggest that the malleus and incus are actually derived from neural crest cells in both arches.

Get the figures HERE! ------>

http://www.ajronline.org/cgi/content/full/178/6/1523

See text and figures, pages 505-511 in Carlson.

Fig. 12A at web link below.

AH - auricular hillocks, ED - endolymphatic duct, FVC - first visceral cleft, FVP - first visceral pouch, OC - Ossicles, OV - otic vesicle

slide25

Get the figures HERE! ------>

http://www.ajronline.org/cgi/content/full/178/6/1523

Development of the middle and inner ear

The otic vesicle consists of the utricle (upper half) and saccule (lower half). The utricle will form the utriculus and the semicircularcanals. The saccule forms the sacculus and the cochlea.

The hyomandibular pouch thins out and elongates to become the tubotympanicrecess (forms the eustacian tube) and the tympanic cavity(forms the cavity of the middle ear).

Fig. 12B at web link below.

See text and figures, pages 505-511 in Carlson.

ED - endolymphatic duct, CD - cochlear diverticulum, I - incus, M - malleus, MP - meatal plug, S - stapes, SC - semicircuar canals, TC - tympanic cavity, TR - tubotympanic recess

slide26

Get the figures HERE! ------>

http://www.ajronline.org/cgi/content/full/178/6/1523

Development of the middle and inner ear

The hyomandibular cleft forms the external auditory meatus.

The ectodermal lining of the cleft proliferates and for a period of time forms the meatal plug. This structure will eventually degenerate.

The tympanic membrane is formed from the region where the ectoderm lining the meatus meets the endoderm lining the middle ear cavity.

Fig. 12B at web link below.

See text and figures, pages 505-511 in Carlson.

ED - endolymphatic duct, CD - cochlear diverticulum, I - incus, M - malleus, MP - meatal plug, S - stapes, SC - semicircular canals, TC - tympanic cavity, TR - tubotympanic recess

slide27

Get the figures HERE! ------>

http://www.ajronline.org/cgi/content/full/178/6/1523

See text and figures, pages 505-511 in Carlson.

Fig. 12C at web link below.

CD - cochlear diverticulum, EAM - external auditory meatus, ED - endolymphatic duct, ES - endolymphatic sac, ET - epitympanum, EuT - eustatian tube, LSC - lateral semicircular canal, OW - oval window, PSC - posterior semicircular canal, RW - round window, S - sacculus, SSC - superior semicircular canal, TC - tympanic cavity = middle ear cavity, TM - tympanic membrane = ear drum, U - utriculus

slide28

Visceral arch III - neck bones, innervation - cranial nerve # 9 (glossopharyngeal)

Visceral cleft III - cervical sinus in embryo

Visceral pouch III - inferior parathryroid glands III, thymus III

Visceral arch IV - laryngeal cartilages, innervation - cranial nerve # 10 (vagus)

Visceral cleft IV - cervical sinus in embryo

Visceral pouch IV - superior parathyroid glands IV, thymus IV (rudiment in humans), ultimobranchial bodies IV

slide29

Visceral arch V - rudimentary in amniotes

Visceral cleft V - not present in amniotes

Visceral pouch V - not present or a small rudiment that contributes to ultimobranchial bodies

Visceral arch VI - hard to discern in amniotes, aortic arches within these visceral arches contribute to the pulmonary trunk and right and left pulmonary arteries.

slide30

Visceral (branchial) groove 1

external auditory meatus (external ear canal)

Visceral pouch 1 - eustachian tube

Midline of floor of pharynx between second pair of visceral arches - thyroid

Visceral pouch 2 - palatine tonsils

Visceral pouch 3 - parathyroid gland III

thymus III

Visceral pouch 4 - parathyroid gland IV

thymus IV (rudiment in humans)

ultimobranchial bodies IV

(also called postbranchial bodies)

Some texts also say,

Visceral pouch 5 - ultimobranchial bodies V

As the various glands mentioned above differentiate, they move to new (more posterior) positions during 1st - 2nd month in humans. This movement is accomplished by differential growth of surrounding tissues.

Thyroglossal duct forms as thyroid moves posterior. Becomes occluded and breaks up during second month of development.

Sometimes, portions of the duct remain leaving cavities or pockets called cysts. These cysts can fill with fluid or mucus, and may enlarge if they become infected.

slide31

Parathyroid glands - secrete parathyroid hormone (parathormone) - increases calcium levels in the blood.

Removal will cause tetanic seizures

Ultimobranchial bodies (postbranchial bodies)- source of C cells dispersed throughout thyroid that secrete calcitonin - a hormone that decreases calcium levels in blood.

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Endocrines.gif