Hy Embryology 12 Part 2

Front 1

Describe the development of the oral part of the tongue (anterior 2/3)

Back 1

1. Forms from the median tongue bud and two distal tongue buds that develop in the floor of the pharynx associated with pharyngeal arch 1

2. The distal tongue buds overgrow the median tongue bud and fuse in the midline, forming the median sulcus

3. The oral part is characterized by filiform papillae (no taste buds), fungiform papillae (taste buds present), foliate papillae (taste buds present), circumvallate papillae (taste buds present)

4. General sensation from the mucosa is carried by the lingual branch of the trigeminal nerve (CN V)

5. Taste sensation from the mucosa is carried by the chorda tympani branch of the facial nerve (CN VII)

Front 2

What carries taste sensation from the mucosa of the anterior 2/3 of the tongue?

Back 2

The chorda tympani branch of the facial nerve (CN VII)

Front 3

What carries general sensation from the mucosa of the anterior 2/3 of the tongue?

Back 3

The lingual branch of the trigeminal nerve (CN V)

Front 4

What does the anterior 2/3 of the tongue form from?

Back 4

Forms from the median tongue bud and two distal tongue buds that develop from the floor of the pharynx associated with pharyngeal arch 1

Front 5

Describe the formation of the median sulcus

Back 5

The distal tongue buds overgrow the median tongue bud and fuse in the midline, forming the median sulcus

Front 6

What characterizes the oral part of the tongue/anterior 2/3?

Back 6

-Filiform papillae (no taste buds)
-Fungiform papillae (taste buds present)
-Folate papillae (taste buds present)
-Circumvallate papillae (taste buds present)

Front 7

Describe the development of the pharyngeal part of the tongue (Posterior 1/3)

Back 7

1. Forms from the copula and hypobranchial eminence that develop in the floor of the pharynx associated with pharyngeal arches 2-4

2. The hypobranchial eminence overgrows the copula, thereby eliminating any contribution of pharyngeal arch 2 in the formation of the definitive adult tongue

3. The line of fusion between the oral and pharyngeal parts of the tongue is indicated by the terminal sulcus

4. The pharyngeal part is characterized by the lingual tonsil, which forms along with the palatine tonsil and pharyngeal tonsil (adenoids), Waldeyer's ring

5. General sensation fromt he mucosa is carried primarily by the glossopharyngeal nerve (CN IX)

6. Taste sensation from the mucosa is carried predominantly by the glossopharyngeal nerve (CN IX)

Front 8

What carries taste sensation from the mucosa of the posterior 1/3 of the tongue?

Back 8

Taste sensation from the mucosa is carried predominantly by the glossopharyngeal nerve (CN IX)

Front 9

What carries general sensation from the mucosa of the posterior 1/3 of the tongue?

Back 9

General sensation from the mucosa is carried primarily by the glossopharyngeal nerve (CN IX)

Front 10

What does the terminal sulcus indicate?

Back 10

The line of fusion between the oral and pharyngeal parts of the tongue

Front 11

What does the posterior 1/3 of the tongue form from?

Back 11

Forms from the copula and hypobranchial eminence that develop in the floor of the pharynx associated with pharyngeal arches 2-4

Front 12

What do the muscles of the tongue derive from?

Back 12

The intrinsic muscles and extrinsic muscles (styloglossus, hyoglossus, genioglossus, and palatoglossus) are derived from the myoblasts that migrate into the tongue region from occipital somites

Front 13

What are the extrinsic muscles of the tongue?

Back 13

1. Styloglossus
2. Hyoglossus
3. Genioglossus
4. Palatoglossus

Front 14

What supplies motor innervation to the muscles of the tongue?

Back 14

Motor innervation is supplied by the hypoglossal nerve (CN XII), except for the palatoglossus muscle, which is innervated by CN X

Front 15

Describe the development of the face

Back 15

1. The face is formed by three swellings: the frontonasal prominence, the maxillary prominence (pharyngeal arch 1), and the mandibular prominence (pharyngeal arch 1)

2. Bilateral ectodermal thickenings called nasal placodes develop on the ventrolateral aspects of the frontonasal prominence

3. The nasal placodes invaginate into the underlying mesoderm to form the nasal pits, thereby producing a ridge of tissue that forms the medial nasal prominence and the lateral nasal prominence

4. A deep groove called the nasolacrimal groove forms between the maxillary prominence and the lateral nasal prominence and eventually forms the nasolacrimal duct and lacrimal sac

Front 16

What swellings form the face?

Back 16

The face is formed by three swellings: the frontonasal prominence, the maxillary prominence (pharyngeal arch 1), and the mandibular prominence (pharyngeal arch 1)

Front 17

Describe the nasolacrimal groove

Back 17

A deep groove called the nasolacrimal groove forms between the maxillary prominence and the lateral nasal prominence and eventually forms the nasolacrimal duct and lacrimal sac

Front 18

Describe the nasal placodes

Back 18

1. Bilateral ectodermal thickenings called nasal placodes develop on the ventrolateral aspects of the frontonasal prominence

2. The nasal placodes invaginate into the underlying mesoderm to form the nasal pits, thereby producing a ridge of tissue that forms the medial nasal prominence and the lateral nasal prominence

Front 19

Describe the development of the intermaxillary segment

Back 19

1. Forms when the medial growth of the maxillary prominences causes the two medial nasal prominences to fuse together at the midline

2. The intermaxillary segment forms the philtrum of the lip, four incisor teeth, and primary palate

Front 20

What does the intermaxillary segment form?

Back 20

-Philtrum of the lip
-Four incisor teeth
-Primary plate

Front 21

Describe the development of the secondary plate

Back 21

1. Forms from outgrowths of the maxillary prominences called the palatine shelves

2. Initially the palatine shelves project downward on either side of the tongue but later attain a horizontal position and fuse along the palatine raphe to form the secondary plate

3. The primary and secondary palate fuse at the incisive foreman to form the definitive palate. Bone develops in both the primary palate and the anterior part of the secondary palate.

4. Bone does not develop in the posterior part of the secondary palate, which eventually forms the soft palate and uvula

5. The nasal septum develops from the medial nasal prominences and fuses with the definitive palate

Front 22

What does the secondary plate form from?

Back 22

1. Forms from outgrowths of the maxillary prominences called the palatine shelves

2. Initially the palatine shelves project downward on either side of the tongue but later attain a horizontal position and fuse along the palatine raphe to form the secondary plate

Front 23

Describe the formation of the definitive plate

Back 23

The primary and secondary palate fuse at the incisive foreman to form the definitive palate. Bone develops in both the primary palate and the anterior part of the secondary palate.

Front 24

Where do the primary and secondary palates fuse?

Back 24

The incisive foramen

Front 25

Describe the formation of soft palate

Back 25

The soft palate forms where bone does not develop in the posterior part of the secondary palate

Front 26

Describe the formation of uvula

Back 26

The soft palate forms where bone does not develop in the posterior part of the secondary palate

Front 27

Describe the develop of the nasal septum

Back 27

The nasal septum develops from the medial nasal prominences and fuses with the definitive palate

Front 28

Describe first arch syndrome

Back 28

1. First arch syndrome results from abnormal development of pharyngeal arch 1

2. Produces various facial anomalies

3. It is caused by a lack of migration of neural crest cells into pharyngeal arch 1

4. Two well-described syndromes are Treacher Collins syndrome (mandibulofacial dysostosis) and Pierre Robin Syndrome

Front 29

Describe Treacher Collins syndrome

Back 29

1. A first arch syndrome

2. Also called mandibulofacial dysostosis

3. Characterized by underdevelopment of the zygomatic bones, mandibular hypoplasia, lower eyelid colobomas, downward-slanting palpebral fissures, and malformed external ears

4. An autosomal dominant genetic disorder caused by a mutation in the TCOF1 gene on chromosome 5q32.3-q33.1 for the treacle protein

Front 30

Describe pharyngeal fistulas

Back 30

1. Pharyngeal fistulas occur when pharyngeal pouch 2 and pharyngeal groove 2 persist, thereby forming a patent opening from the internal tonsillar area to the external neck.

2. It is generally found along the anterior border of the sternocleidomastoid muscle

Front 31

Describe pharyngeal cysts

Back 31

1. Pharyngeal cysts occurs when parts of the pharyngeal grooves 2-4 that are normally obliterated persist, thereby forming a cyst

2. Generally found near the angle of the mandible

Front 32

Where are pharyngeal cysts normally found?

Back 32

Generally found near the angle of the mandible

Front 33

Where are pharyngeal fistulas generally found

Back 33

Generally found along the anterior border of the sternocleidomastoid muscle

Front 34

Describe ectopic thymus, parathyroid, or thyroid tissue?

Back 34

1. Result from the abnormal migration of these glands from their embryonic position to their definitive adult location.

2. Glandular tissue may be found anywhere along their migratory path

Front 35

Describe thyroglossal duct cysts

Back 35

1. Thyroglossal duct cysts occur when parts of the thyroglossal duct persist and thereby form a cyst

2. It is most commonly located in the midline near the hyoid bone, but it may also be located at the base of the tongue, in which case it is then called a lingual cyst

3. Thyroglossal duct cyst is one of the most frequent congenital anomalies in the neck and is found along the midline most frequently below the hyoid bone

Front 36

Describe congenital hypothyroidism (cretinism)

Back 36

1. Congenital hypothyroidism (cretism) occurs when a thyroid deficiency exists during the early fetal period due to a severe lack of dietary iodine, thyroid agenesis, or mutations involving the biosynthesis of thyroid hormone

2. This condition causes impaired skeletal growth and mental retardation

3. Characterized by coarse facial features, a low set hair line, sparse eyebrows, wide-set eyes, periorbital puffiness, a flat, broad nose, an enlarged, protuberant tongue, a hoarse cry, umbilical hernia, dry and cold extermities, dry, rough skin (myxedema), and mottled skin

4. Infants are screened for depressed thyroxin or elevated TSH

Front 37

What characterizes congenital hypothyroidism?

Back 37

Characterized by:
1. Coarse facial features
2. A low set hair line
3. Sparse eyebrows
4. Wide-set eyes
5. Periorbital puffiness
6. A flat, broad nose
7. An enlarged, protuberant tongue
8. A hoarse cry
9. Umbilical hernia
10. Dry and cold extermities
11. Dry, rough skin (myxedema)
12. Mottled skin

Front 38

Describe orofacial clefting

Back 38

1. Orofacial clefing is a multifactorial genetic disorder involving the DLX gene family, SHH gene, TGFα gene, TGFβ gene, and the IRF-6 gene along with some putative environmental (eg, phenytoin, sodium valproate, methotrexate)

2. The most common craniofacial birth defect is the orofacial cleft, which consists of a cleft lip with or without cleft palate (CL/P) or an isolated cleft palate (CP)

Front 39

Describe the genes associated with orofacial clefting

Back 39

Orofacial clefing is a multifactorial genetic disorder involving the DLX gene family, SHH gene, TGFα gene, TGFβ gene, and the IRF-6 gene along with some putative environmental (eg, phenytoin, sodium valproate, methotrexate)

Front 40

Describe cleft lips

Back 40

1. A multifactorial genetic disorder that involves neural crest cells.

2. Cleft lip results from the following:
-The maxillary prominence fails to fuse with the medial nasal prominence
-The underlying mesoderm and neural crest fail to expand, resulting in a persistent labial groove

Front 41

Describe cleft palate

Back 41

1. Cleft palate is a multifactorial genetic disorder that involves neural crest cells

2. Cleft palate is classified as anterior or posterior

3. The anterior landmark that distinguishes an anterior cleft palate from the posterior cleft palate is in the incisive foramen

Front 42

When does anterior cleft palate occur?

Back 42

Occurs when the palatine shelves fail to fuse with the primary palate

Front 43

When does posterior cleft palate occur?

Back 43

Occurs when the palatine shelves fail to fuse with each other and with the nasal septum

Front 44

When does anteroposterior cleft palate?

Back 44

Occurs when there is a combination of birth defects

Front 45

Describe DiGeorge syndrome

Back 45

1. DiGeorge syndrome occurs when pharyngeal pouches 3 and 4 fail to differentiate into the thymus and parathyroid glands

2. DiGeorge syndrome is usually accompanied by facial anomalies resembling first arch syndrome (micrognathia, low-set ears) due to abnormal neural crest cell migration, CV anomalies due to abnormal neural crest cell migration during formation of the aorticopulmonary septum, immunodeficiency due to absence of thymus gland, and hypocalcemia due to absence of parathyroid glands

Front 46

What is DiGeorge syndrome accompanied by?

Back 46

DiGeorge syndrome is usually accompanied by:
1. Facial anomalies resembling first arch syndrome (micrognathia, low-set ears) due to abnormal neural crest cell migration,

2. CV anomalies due to abnormal neural crest cell migration during formation of the aorticopulmonary septum

3. Immunodeficiency due to absence of thymus gland

4. Hypocalcemia due to absence of parathyroid glands