Head and Neck development

Question 1

Folding of embryo forms these two structures

Answer 1

primitive mouth (stomodeum) and forgut

Question 2

What forms on either side in the floor of the pharynx during formation of foregut and stomodeum

Answer 2

Five pairs of pharyngeal arches

Question 3

What do the pharyngeal arches consist of?

Answer 3

Mesodermal core covered by ectoderm, and lined by pharyngeal endoderm (EXCEPT the first)

Question 4

Each arch appears as a swelling containing a cartilaginous rod form by?

Answer 4

Neural crest cells

Question 5

Sequential swellings are separated by constrictions caused by these invaginations of the ectoderm. How many?

Answer 5

Pharyngeal clefts, 4

Question 6

Evaginations of the endoderm. How many?

Answer 6

Pharyngeal pouches, 4

Question 7

The narrow, constricted areas between clefts and pouches.

Answer 7

Pharyngeal membranes

Question 8

In more primitive vertebrates, the membranes between clefts and pouches function for/form?

Answer 8

Gill slits or functioning gills. This doesn’t occur in humans, and are no longer necessary for breathing and filter feeding. Freed for other uses.

Question 9

Muscle precursors derive from?

Answer 9

Paraxial somitomeres (recall paraxial mesoderm forms somites which go on to form myotome, dermatome, and sclerotome)

Question 10

Arch 1 correlates with which CN?

Answer 10

CN V (Trigeminal, both)

Question 11

Arch 2 correlates with which CN?

Answer 11

CN VII (Facial, both)

Question 12

Arch 3 correlates with which CN?

Answer 12

CN IX (glossopharyngeal, both)

Question 13

Arch 4 and 6 correlate with which CN?

Answer 13

CN X (Vagus, both)

Question 14

Each cartilaginous rod that has migrated into the arch from rhombomeres make up these 4 important structures:

Answer 14

embryonic hindbrain, muscle precursors, aortic arch artery, and associated nerve

Question 15

Transiently divided segment of the developing neural tube, within the hindbrain region in the area that will eventually become the rhombencephalon

Answer 15

Rhombomere, appear as a series of constricted swellings in the neural tube

Question 16

What does the primitive mouth area is lined by what derived epithelium?

Answer 16

Ectodermal

Question 17

The epithelial layer of the pharynx is derived from?

Answer 17

Endoderm

Question 18

In humans the first arch cartilages persist as the Palatopterygoquadrate bars and Meckle’s cartilage (from maxilla and mandible process, respectively). What do their upper ends become?

Answer 18

The incus and malleus bones of the middle ear

Question 19

Membrane bone from the neural crest mesenchyme develops and surrounded the remaining first arch cartilage to form these 4 bones:

Answer 19

Maxillary, Mandibular, zygomatic (cheek bones), and squamous temporal bones.

Question 20

The first arch somitomeric mesoderm yields these 5 muscles:

Answer 20

1. Muscles of mastication
2. Tensor tympani
3. Tensor veli palatini
4. Anterior belly of digastric
5. Mylohyloid

Question 21

Second arch cartilage gives rise to these 3 bones:

Answer 21

1. lesser cornu and upper rim of hyoid bone
2. third ossicle of middle ear (stapes)
3. styloid process

Question 22

Muscles associated with second arch (4)

Answer 22

All muscles of facial expression including:

1. platysma
2. stylohyoid
3. stapedius
4. posterior belly of digastric

Question 23

Third arch cartilage gives rise to this bone:

Answer 23

Greater cornu and lower rim of hyoid bone

Question 24

The only muscle developed from third arch

Answer 24

Stylopharyngeous (innervated by CN IX)

Question 25

What does the artery of the third arch give rise to?

Answer 25

Common carotid and base (first part) of the internal carotid

Question 26

What do the fourth and sixth arches develop into? (1 with 5 parts)

Answer 26

laryngeal cartilage: 1. thyroid 2. cricothyroid 3. arytenoid 4. coniculate 5. cuneiform

Question 27

Muscles derived from the fourth arch mesoderm (3)

Answer 27

1. Pharyngeal constrictors 2. Cricothyroid 3. levator veli palatine + other palatal muscles

Question 28

Muscles derived from the sixth arch (2)

Answer 28

1. intrinsic muscles of larynx | 2. striated muscle of esophagus

Question 29

Primary nerve [of vagus nerve] of the fourth arch derivative

Answer 29

superior laryngeal branch of vagus nerve

Question 30

Innervation of the sixty arch muscles are from which nerve?

Answer 30

Recurrent laryngeal branch of the vagus nerve

Question 31

The vagus nerve also contributes to innervation of the soft palate and pharyngeal constrictors through its contributions to what?

Answer 31

The pharyngeal plexus

Question 32

What happens to the fifth arch?

Answer 32

In humans, it either never forms or is rudimentary and disappears

Question 33

The first pharyngeal pouch expands to form these two structures

Answer 33

1. Tubotympanic recess- gives rise to tympanic cavity of the middle ear 2. Pharyngotympanic tube (eustachian tube/auditory tube) connecting the middle ear cavity and nasal pharynx

Question 34

What does the pharyngeal membrane between the first clefts and pouches form?

Answer 34

The tympanic membrane (eardrum)

Question 35

What does the second pouch form?

Answer 35

The palatine tonsils

Question 36

The third pouch gives rise to what two regions?

Answer 36

A solid dorsal region and a hollow elongated ventral region

Question 37

Where does the thymus originate from?

Answer 37

Ventral regions of the third pouches

Question 38

Solid cords that break their connection with the pharynx migrate bilaterally and eventually form what?

Answer 38

The thorax, fuse into a single gland

Question 39

Where does the inferior parathyroid gland originate from?

Answer 39

The dorsal region of the third pouch

Question 40

Which pouch in addition to the third pouch has dorsal and ventral regions?

Answer 40

The fourth pouches

Question 41

What two important structures does the fourth pouch form?

Answer 41

1. Superior parathyroid (dorsal) | 2. Ultimobranchial body (ventral)

Question 42

Of neural crest origin, these cells give rise to the calcitonin secreting C cells of the parafollicular thyroid

Answer 42

Ultimobranchial body (small organ found in the neck region)

Question 43

The last 3 pharyngeal clefts usually disappear and become covered by the second arch, however the first cleft becomes these two structures:

Answer 43

1. external acoustic meatus (ear canal) | 2. External layer of tympanic membrane

Question 44

This develops by proliferation of cells in the floor of the pharynx between the first and second pouches

Answer 44

Thyroid gland

Question 45

The most common congenital malformation of the head and neck

Answer 45

Unilateral cleft lip (failure of one of maxillary prominence to fuse with medial nasal prominence of same side)

Question 46

Cleft palate, a defect distinct from cleft lip, is usually classified as anterior or posterior, distinguishable by their relationship to what?

Answer 46

The incisive foramen

Question 47

First arch syndrome, the lumping together of first arch, is usually a result from failure of what?

Answer 47

Failure of neural crest cells to migrate into the arch

Question 48

DiGeorge Syndrome

Answer 48

complex constellation of anomalies caused by deletion of chromosome 22 (first arch anomalies, immunological deficiencies with thymus, deficiencies of thyroid and parathyroid glands, cardiovascular anomalies)

Question 49

Common denominator for DiGeorge syndrome

Answer 49

Impaired neural crest migration into the third and fourth arches

Question 50

The hard palate is formed in how many stages?

Answer 50

2

Question 51

This segment contributes to the upper lip (philtrum) and a jaw component carrying the incisor teeth, forming the triangular primary palate

Answer 51

Intermaxillary segment (has deep palatal compartments)

Question 52

What forms the secondary palate?

Answer 52

Formed by paired outgrowth of the maxilla

Question 53

Ventrally, what undergoes endochondrial ossification to form the hard palate?

Answer 53

Mesenchymal condensations

Question 54

Posteriorly, what condenses to form the soft palate?

Answer 54

Myogenic mesenchyme

Question 55

Expansion of the face continues after birth by development and expansion of

Answer 55

paransal sinuses

Question 56

Paransal sinues (air filled spaces) develop as diverticular of the lateral nasal wall and invade and expand within which 4 bones?

Answer 56

1. Maxillary 2. Ethmoid 3. Sphenoid 4. Frontal

Question 57

Mandibulofacial dysostosis, genetic basis, inherited as autosomal dominant (first arch syndrome)

Answer 57

Treacher Collins

Question 58

The tongue develops from which arch?

Answer 58

1, 3, and 4

Question 59

What forms the intrinsic and extrinsic muscles of the tongue?

Answer 59

migrating occipital somite mesoderm

Question 60

What innervate the muscles in tongue derived from occipital somites?

Answer 60

hypoglossal nerve CN XII

Question 61

The mucosa of the anterior two-thirds of the tongue receives general sensory innervation from which nerve?

Answer 61

CN V

Question 62

The posterior third of the tongue received its innervation for both general and taste from which nerve?

Answer 62

CN IX (glossophyrangeal)

Question 63

A small area on the dorsal most part of the root or pharyngeal part of tongue receives general and taste sensation from?

Answer 63

superior laryngeal branch of CN X (vagus)

Question 64

Taste to the anterior two-thirds is from what nerve?

Answer 64

Chorda tympani branch of CN VII (facial)

Question 65

Most recent evidence is that taste buds form independtly in this, but survive only if what are present?

Answer 65

Form in lingual epithelium, need nerves to survive

Question 66

All "glossus" muscles (muscles of palate) are innervated by CN XII, except for this muscle

Answer 66

Palatoglossus

Question 67

The five facial swellings

Answer 67

An unpaired frontonasal prominence on anterior end of developing embryo, and paired maxillary and mandibular prominences (form from growth and division of the paired first pharyngeal arches)

Question 68

The five prominences form this major facial feature

Answer 68

The nose

Question 69

What forms the bridge of the nose?

Answer 69

The frontonasal prominence

Question 70

Formation of the tongue

Answer 70

Pharyngeal arches 1, 3, and 4

Question 71

The thyroid develops from an invagination of the tongue endoderm between what two structures? Later indicated by what foramen?

Answer 71

Tuberculum impar and copula linguae. Foramen cecum

Question 72

Through where does the thyroid migrate to its porper position?

Answer 72

Thyroglossal duct

Question 73

Unilateral cleft lip can result from these two factors:

Answer 73

- maxillary prominence fails to fuse with medial nasal prominence - underlying somitomeric mesoderm and neural crest fail to expand, resulting in a "persistent labial groove"

Question 74

What does the intermaxillary segment form?

Answer 74

The philtrum of the lip, the incisors (4), and the primary palate

Question 75

Palatine shelves

Answer 75

outgrowths of maxillary prominences

Question 76

The secondary palate forms from outgrowths of these structures

Answer 76

palatine shelves, maxillary promimences

Question 77

palatine shelves project downward on either side of tongue but later attain a horizontal postition and fuse along the ________ to form the ______

Answer 77

palatine raphe, secondary palate

Question 78

Where do the primary and secondary palates fuse? to form what?

Answer 78

incisive foramen, definitive palate