Head And Neck Development I

Question 1

Overview: what do the following bony parts enclose/contain?

1. Membrane bones enclose/replace?
2. Chondrocranium enclose/form?
3. Visceral skeleton forms?

Answer 1

1. Enclose cranium and replace cartilage precursors in the jaw
2. Enclose sensory organ capsules, forms base of brain case
3. Form endochondral bones in the jaws and neck

Question 2

Timeline:

1. What develops during 4th week
2. During weeks 5-7, enclosure of __ and migration of __
3. 6th week is development of

Answer 2

1. Branchial arch (aka pharyngeal arch)
2. Branchial grooves and migration of thyroid glands
3. Bony elements

Question 3

Innervation of the following pharyngeal arches:

1. First
2. Second
3. Third
4. Fourth-sixth

Answer 3

1. CN V (maxillary and mandibular)
2. CN VII
3. CN IX
4. CN X

Question 4

Why is there no arch 5?

Answer 4

It either doesn’t develop or it develops and then regresses

Question 5

3 components of each pharyngeal arch

Answer 5

Cartilaginous, nerve and aortic arch

Question 6

Pharyngeal arches are swellings of __ derived from __ and __

Answer 6

Mesenchyme; derived from lateral plate mesoderm and neural crest cells

Question 7

1. Location of pharyngeal grooves (clefts)

2. What are they derived from?

Answer 7

1. Indentions between pharyngeal arches

2. Ectoderm

Question 8

1. Location of pharyngeal pouches

2. What are they derived from?

Answer 8

1. Indentations between pharyngeal arches

2. Endoderm

Question 9

What is a closing membrane

Answer 9

The place where pharyngeal groove meets pharyngeal pouch

Question 10

How does growth of neck occur?

Answer 10

Through migration of neural crest cells (NOT from mesodermal proliferation)

Question 11

What other 3 things form from neural crest migration?

Answer 11

Cartilaginous elements, tendons, and connective tissue of branchial muscles

Question 12

1. Mesoderm core is a combination of what 2 layers?

2. What does it form?

Answer 12

1. Lateral plate and cranial paraxial mesoderm

2. Muscle cell bodies

Question 13

1. What forms the cervical sinus? Is cervical sinus permanent or temporary?
2. All pharyngeal grooves/closing membranes are obliterated except?

Answer 13

1. The second arch growing over the more caudal grooves; should be temporary
2. The ones associated with arch 1

Question 14

1. What happens if cervical sinus is not temporary?
2. How will an external cyst present?
3. 3 possible sites of cervical cysts/fistulas?

Answer 14

1. It forms a cervical cyst; place where second arch grew over and sinus never closed up
2. Pus will come out of your neck
3. On face right next to ear, medial to middle of SCM muscle, medial to where SCM inserts to sternum

Question 15

What provides sensory innervation to 1st arch? Motor?

Answer 15

Sensory= V2
Motor= V3

Question 16

1. What branch of vagus nerve innervates 4th arch?

2. 6th?

Answer 16

1. Superior laryngeal nerve

2. Recurrent laryngeal nerve

Question 17

Cartilaginous derivatives of each arch:

1. First (3)
2. Second (5)
3. Third (2)
4. Fourth/sixth (1)

Answer 17

1. Mandible, malleus, incus
2. Stapes, styloid process, stylohyoid ligament, lesser horn and upper body of hyoid
3. Greater horn and lower body of hyoid
4. Laryngeal cartilages

Question 18

What is the precursor for the mandible?

Answer 18

Meckels cartilage

Question 19

Muscle groups of the arches:

1. 1st (5)
2. 2nd (3)
3. 3rd (1)
4. 4th/6th (2)

Answer 19

1. Muscles of mastication, anterior digastric, mylohyoid, tensor tympani and tensor veli palatini
2. Muscles of facial expression, posterior digastric, stylohyoid
3. Stylopharyngeus
4. Muscles of larynx and pharynx

Question 20

All arches come from 1st somitomere except for? Which comes from?

Answer 20

4th/6th - 1st occipital somite

Question 21

Arteries of the following:

1. 3rd arches
2. Right 4th arch
3. Left 4th arch
4. 6th arches

Answer 21

1. Internal and external carotid
2. Brachiocephalic trunk and right subclavian
3. Aortic arch and left subclavian
4. Pulmonary arteries (and ductus arteriosus on left)

Question 22

Derivatives of the pharyngeal pouches:

1. 1st pouch
2. 2nd pouch
3. 3rd pouch
4. 4th pouch

Answer 22

1. Middle ear and eustachian tube
2. Palatine tonsil
3. Inferior parathyroid and thymus
4. Superior parathyroid and ultimobranchial body (C cells of thyroid)

Question 23

Ear formation: derivatives of the following:

1. 1st groove
2. 1st closing membrane
3. 1st pouch

Answer 23

1. External acoustic meatus
2. Tympanic membrane
3. Middle ear and eustachian tube (repeat)

Question 24

1. Air chamber in the head comes from?
2. Hyomandibular joint evolved into?
3. Articular/quadrate joint evolved into? What kind of cartilage?
4. TMJ is between 2 __ bones. What kind of cartilage?

Answer 24

1. First pharyngeal pouch
2. Stapes
3. Incus and malleus; hyaline
4. Membrane; fibrocartilage

Question 25

Name 3 unpaired structures that develop from floor of pharynx

Answer 25

Thyroid, larynx, and tongue

Question 26

Tongue derivation has what 3 parts

Answer 26

Distal tongue bud, median tongue bud, and hypobranchial eminence

Question 27

Site of development for thyroid?

Answer 27

Foramen cecum

Question 28

How is the larynx developed?

Answer 28

As an outpocketing from pharyngeal floor

Question 29

Tongue is derived from every arch except? However, a branch of this arch __, persists to do what?

Answer 29

2nd Chorda tympani persists to provide taste to anterior 2/3

Question 30

Thyroid development begins where and migrates where? So along this course, what is possible?

Answer 30

Develops in back of tongue and descends to front of trachea Ectopic thyroid is possible

Question 31

What happens if the thyroglossal duct does not degenerate?

Answer 31

Communication between mouth and thyroid will occur

Question 32

1. Which pouch has the tonsil?

Answer 32

2nd pouch