Lecture 6: pharyngeal

Question 1

start of bilateral pharyngeal apparatus development

Answer 1

4-5 weeks post fertilization

in a cranial to caudal sequence

Question 2

4 pairs of temporary embryonic structures

Answer 2

• pharyngeal arches
• pharyngeal grooves (clefts)
• pharyngeal pouches
• pharyngeal membranes

Question 3

pharyngeal arches

Answer 3

5 pairs of arches (5th arch almost never forms)
-mesenchymal core (paraxial mesoderm, neural crest cells, and lateral plate) lined on the outside by ectoderm and endoderm on the inside

Question 4

pharyngeal grooves (clefts)

Answer 4

external aspect (ectoderm-epidermis)

Question 5

pharyngeal pouches

Answer 5

4 well defined internal structures formed by outpockting of the endoderm

Question 6

pharyngeal membranes

Answer 6

two layered structures of ectoderm and endoderm

Question 7

each pharyngeal arch contains

Answer 7

• cartilagenous skeletal component (neural crest cell derived)
• connective tissue (neural crest cell derived) and muscle component (paraxial mesoderm)
• cranial nerve
• aortic arch artery

Question 8

intramembranous bone formation

Answer 8

• bone develops in well vascularized mesenchyme
• absence of cartilage model
• develops flat bones of face and skull

Question 9

intra cartilaginous (endochondral) bone formation

Answer 9

-bone formation in a pre-existing cartilage model (limb bones, weight bearing bones, and some bones of the pharyngeal apparatus)

Question 10

2 prominence of the 1st pharyngeal arch

Answer 10

maxillary and mandibular

Question 11

maxillary prominence

Answer 11

• cartilage: palatopterygoquadrate

- cartilage regresses and leaves no adult remnants

Question 12

mandibular prominence

Answer 12

• large contribution to the face

- cartilage: meckel’s cartilage: leaves some adult structures

Question 13

meckel’s cartilage gives rise to

Answer 13

-incus
-malleus
by endochondral ossification

Question 14

perichondrium of meckel’s cartilage forms

Answer 14

• anterior ligament of the malleus

- sphenomandibular ligament

Question 15

intramembranous in the maxillary prominence forms

Answer 15

• squamous portions of the temporal bone
• maxillary bone
• zygomatic bone
• palatine bone
• from mesenchyme derived from neural crest cells

Question 16

intramembranous in the mandibular prominence forms

Answer 16

mandible

*from mesenchyme derived from neural crest cells

Question 17

muscle components of the 1st pharyngeal arch

Answer 17

• 4 muscles of mastication
• tensor veli palatini and tensor tympani
• anterior belly of the digastric
• mylohyoid

Question 18

nerve components of the 1st pharyngeal arch

Answer 18

• mandibular branch of the trigeminal nerve (CN5) supplies muscles
• sensory to the skin of the face is through the ophthalmic, maxillary, and mandibular branches of the trigeminal nerve (CN5)

Question 19

2nd pharyngeal arch (hyoid arch) cartilage

Answer 19

reichert’s cartilage

endochondral ossification

Question 20

reichert’s cartilage gives rise to

Answer 20

• stapes
• styloid process
• stylohyoid ligament
• lesser horn and upper body of the hyoid bone

Question 21

muscle components of the 2nd pharyngeal arch

Answer 21

• muscles of facial expression
• stapedius
• stylohyoid
• posterior belly of the digastric

Question 22

nerve components of the 2nd pharyngeal arch

Answer 22

facial nerve (CN 7)

Question 23

3rd pharyngeal arch gives rise to

Answer 23

lower part of the body and greater horn of the hyoid bone

-endochondral ossification

Question 24

muscle components of the 3rd pharyngeal arch

Answer 24

stylopharyngeus

Question 25

nerve components of the 3rd pharyngeal arch

Answer 25

glossopharyngeal (CN 9)

Question 26

4th and 6th pharyngeal arches

Answer 26

- merge together - form the laryngeal cartilages from lateral plate mesoderm - ossification does not occur in these cartilages

Question 27

muscle components of the 4th and 6th pharyngeal arch

Answer 27

- muscles of the soft palate - muscles of the pharynx - intrinsic muscles of the larynx - muscles of the upper esophagus

Question 28

nerve components of the 4th and 6th pharyngeal arch

Answer 28

vagus nerve (CN10)

Question 29

1st pharyngeal pouch

Answer 29

- forms a stalk like extension (tubotympanic recess) - expands towards the 1st pharyngeal cleft (future external acoustic meatus) - distal portion expands to form the epithelial lining of tympanic cavity, proximal narrow portions forms the auditory tube (eustachian tube) * *tympanic ear cavity and auditory tube

Question 30

2nd pharyngeal pouch

Answer 30

- endoderm proliferates and forms buds that extend into the mesenchyme - buds infiltrated by lymphatic tissue - part of the pouch remains as the palatine fossa * *palatine tonsil

Question 31

3rd pharyngeal pouch

Answer 31

dorsal region: **inferior parathyroid gland (secrete PTH) | ventral: stoma of the **thymus

Question 32

4th pharyngeal pouch

Answer 32

dorsal region: **superior parathyroid gland | ventral region: **ultimobranchial body (cells derived from neural crest cells)

Question 33

1st pharyngeal cleft

Answer 33

external acoustic meatus

Question 34

1st pharyngeal membrane

Answer 34

tympanic membrane

Question 35

tongue development begins

Answer 35

week 4 of development

Question 36

tongue arises from

Answer 36

proliferation of endoderm (and mesenchyme) of the pharyngeal floor -swellings give rise tot ehe mucous membrane (epithelium and CT) of the tongue

Question 37

pharyngeal arch 1 (tongue)

Answer 37

forms anterior 2/3 of the tongue - median swelling midline - two lateral swellings - fuse midline

Question 38

terminal sulcus

Answer 38

location where the anterior and posterior portions of the tongue fuse

Question 39

copula

Answer 39

formed by the endoderm and underlying mesenchyme of the 2nd arch

Question 40

hypobranchial eminence

Answer 40

formed by the endoderm and underlying mesonchyme of the 3rd and 4th arches

Question 41

which arch does not contribute to the mucosa of the adult tongue

Answer 41

2nd arch because the 3rd overgrows the 2nd

Question 42

posterior 1/3 of the tongue

Answer 42

formed by the 3rd and 4th arch endoderm | innervated by CN9 and 10

Question 43

muscles of the tongue arise from..

Answer 43

the myotomes of the occipital somites that migrate forward towards the developing tongue innervated by the hypoglossal nerve (CN12) except the palatonglossus