Lecture 10- Embryology of the head and neck

Question 1

Label

Answer 1

Question 2

how many pharangeal arches

Answer 2

• 5 (1 to 6 (5^th doesn’t form in humans))
• 1^st arch is the largest- get progressively smaller

Question 3

• Each arch associated with

Answer 3

artery, cranial nerve and cartilage

Question 4

what forms the ehad and neck region

Answer 4

frontal nasal prominence and pharangeal arches

• (over ½ of embryo at week 4)

Question 5

structure of a pharangeal arch

Answer 5

• Structure
  
  • Core= mesenchyme
  • Outer covering= ectoderm (epidermic of skin)
  • Inner covering= endoderm in the pharynx

Question 6

helpful images to help get your head around the pharangeal arches

Answer 6

Question 7

Development of pharyngeal region

Answer 7

• Segmental
• Each arch (body segment) has a neurovascular plan
  
  • Develops muscles and skeletal elements and associated with particular nerve

Question 8

Development of the gut tube in the pharynx

Answer 8

• Endoderm tube
  
  • Modification
  • Glandular development
    
    • Parathyroids, thymus, palatine tonsils, thyroid

Question 9

Grooves and clefts

Answer 9

Simultaneously, a number of outpocketings appear on the lateral wall of the pharynx – the pharyngeal pouches. The pouches separate the arches on the internal (endodermal) surface whilst the clefts separate the arches on the external (ectodermal) surface.

Question 10

Clefts=

Answer 10

grooves on the outside

Question 11

what happens to pharangeal clefts during development

Answer 11

Most clefts will obliterate (2ND PHARNGEAL ARCH grows down to cover THE other CLEFTS)

1st cleft is the only one to persist

Question 12

failure to obliterate clefts gives rise to

Answer 12

branchial cysts and fistual

Question 13

branchial cysts

Answer 13

• Branchial cysts (fluid filled remnant of 1^st pharyngeal cleft) or branchial fistulae (opening of fluid filled remnant into neck) can occur if there are remnants
• Key landmark for looking for these abnormalities = SCM
  
  • E.g. anterior border= branchial cyst

Question 14

what does the 1st cleft that persists become

Answer 14

external auditory meatus

Question 15

Pouches

Answer 15

• First one- ET and middle ear
• Glandular tissue e.g. palatine tonsil, PT and thymus, thyroid etcccccc

Question 16

Each arch associated with a

Answer 16

CN, cartilaginous structures, blood vessels and muscles ​

Question 17

gross anatomy of Ph A1 (pharangeal arch 1)

Answer 17

Made up of 2 bumps- first bump (dorsal- maxillary), second bump (ventral- mandibular)

Question 18

Maxillary prominence

Answer 18

• Dorsal portion
• Becomes future maxilla zygomatic bone and temporal bone
• Associated with maxillary cartilage- gives rise to incus

Question 19

Mandibular prominence

Answer 19

• Ventral portion
• Becomes future mandible
• Associated with Meckel’s cartilage

Question 20

summarise Ph A1 cartilage

Answer 20

• Maxillary cartilage (first bump)
  
  • Gives rise to incus
• Meckel’s cartilage (second bump)
  
  • Mandible cartilage
    
    • Gives rise to malleus

Question 21

arterial supply of Ph A1

Answer 21

• Becomes the terminal portion of the maxillary artery- branch of external carotid

Question 22

CN associated with Ph A1

Answer 22

• CN 5- trigeminal
  
  • Sensory filed
    
    • Skin on face
    • Lining of mouth and nose
  • General sensation
    
    • Anterior 2/3 of tongue

Question 23

Ph A1 Associated muscles

Answer 23

• Muscles of mastication
• Mylohyoid
• Anterior belly of digastric
• Tensor veli palatani
• Tensor tympani

Question 24

summarise Ph A2 cartilage

Answer 24

• Reichert’s
  
  • Stapes
  • Styloid process
  • Stylohyoid ligament
  • Upper part of hyoid

Question 25

arterial supply of Ph A2

Answer 25

* Stapedial artery- **regresses before birth** * Hyoid artery- gives rise to corticotympanic artery in adult

Question 26

CN associated with Ph A2

Answer 26

* CN 7 – facial nerve * Special sensory- taste of anterior 2/3 of tongue (via chorda tympani)

Question 27

Ph A2 associated muscles

Answer 27

* Muscles of facial expression * Stapedius (nerve to stapedius) * Stylohyoid * Platysma * Posterior belly of digastric

Question 28

Summarise Ph A3 cartilage

Answer 28

* Remainder of hyoid

Question 29

arterial suppy of Ph A3

Answer 29

* Internal carotid

Question 30

CN associated with Ph A3

Answer 30

* CN 9- glossopharyngeal * Sensory function- taste and general sensation to posterior 1/3^rd of tongue

Question 31

Ph A3 associated muscles

Answer 31

Stylopharngeus

Question 32

**Ph A4 Cartilage** *

Answer 32

* Cartilage of the larynx * Thyroid cartilage * Corniculate cartilage * Cuneiform cartilage

Question 34

Ph A4 arterial supply

Answer 34

* Arch of aorta (L) and subclavian artery(R)

Question 35

Ph A4 CN

Answer 35

* CN 10- Vagus (superior laryngeal branch)

Question 36

Ph A4 associated muscles

Answer 36

* Pharyngeal constrictors * Cricothyroid * Levator palatini

Question 37

**Ph A6 Cartilage**

Answer 37

Cartilage of the larynx

Question 38

**Ph A6 Arterial supply**

Answer 38

* Pulmonary arch * Pulmonary arteries (R) * Ductus arteriosus (L)

Question 39

Ph A6 associated CN

Answer 39

* CN 10- Vagus * Recurrent laryngeal branch * Sensory field * Taste sensation from epiglottis and pharynx * General sensation in pharynx, larynx, oesophagus, tympanic membrane, externa auditory meatus and part of the external ear * Gag reflex * Parasympathetic innervation to viscera

Question 40

Ph A6 associated muscles

Answer 40

* Pharyngeal constrictors * Intrinsic muscle of the larynx (except cricothyroid)

Question 41

pharangeal pouch associated with 1st arch derivatives

Answer 41

eustachian tube and middle ear cavity

Question 42

pharangeal pouch associated with 2st arch derivatives

Answer 42

lining of the palatine tonsils

Question 43

pharangeal pouch associated with 3rd arch derivatives

Answer 43

* dorsal- inferior parathyroid gland * ventral- thymus

Question 44

pharangeal pouch associated with 4th arch derivatives

Answer 44

dorsal- supeiror parathyroid glands ventral- ultimobranchial body (C cells)

Question 45

**What does the 1st pharyngeal cleft form?**

Answer 45

External auditory meatus

Question 46

## Footnote **Which pharyngeal arch contributes to Reichert’s cartilage?**

Answer 46

* 2^nd

Question 48

**Which of the following is NOT associated with the 4th pharyngeal arch?** * Aortic arch * Laryngeal cartilages * Superior laryngeal nerve * Recurrent laryngeal nerve

Answer 48

* Aortic arch * Laryngeal cartilages * Superior laryngeal nerve * **Recurrent laryngeal nerve**

Question 49

summary of the cartilages associated with each arch

Question 50

1.

Answer 50

development of head and neck

Question 51

Answer 51

B

Question 52

CN associated with arches 1-6

Answer 52

to feel good so regularly arch 1: CN V (trigeminal) arch 2: CN VII (facial) arch 3: CN IX (glossopharyngeal) arch 4: CN X (superior laryngeal branch of the vagus) arch 6: CN X (recurrent laryngeal branch of the vagus)