CFD5- Pharyngeal arches

Question 1

what are 4 primary germ layers?

Answer 1

• Ectoderm
• Mesoderm
• Endoderm
• neural crest/ ecto-mesenchyme

Question 2

Describe the ectoderm.

Answer 2

skin, neural tube, etc this comes from the Epiblast layer

Question 3

Describe the mesoderm.

Answer 3

forms everything else and is from migratory cells of the epiblast layer

Question 4

Describe the endoderm.

Answer 4

gut- this comes from the hypoblast

Question 5

Describe the neural crest/ echo-mesenchyme.

Answer 5

from the ectoderm that migrates into mesoderm to form structures in head and neck

Question 6

how is neural tube formed?

Answer 6

ectoderm

Question 7

Describe the formation of feotus.

Answer 7

-sperm fusing with egg
-blastocyst formed
-Embryoblast differentiates into two components – epiblast and hypoblast
amniotic fluid seeping in to form the amniotic cavity –gaps formed so nutrients can get to the cells-this layer of animal cells will form ectoderm and endoderm
-The mesoderm forms and migrates in from the sides and forms a divide between the ectoderm and the endoderm
-neuralition
-The ectoderm migrates into the mesoderm and folds

Question 8

what day do the arches form?

Answer 8

4th and 5th week

Question 9

How do the arches change?

Answer 9

Cartilages are made very early and then disappear and replaced by bones

Question 10

how is the stomatodeum (oral cavity) formed?

Answer 10

gap formed by the disintegration of a layer of cells from the oropharyngeal membrane

Question 11

what are the arches separated by externally?

Answer 11

clefts/grooves

Question 12

what are the arches separated by internally?

Answer 12

pouches

Question 13

what is the only arch not lined by endoderm on the inside?

Answer 13

1

Question 14

what lines all the arches on the outside?

Answer 14

ectoderm

Question 15

what does each arch have?

Answer 15

• artery
• nerve
• cartilage
• muscle
• ectoderm (outside)
• endoderm (inside)- except 1st arch

Question 16

what is the 1st arch called?

Answer 16

mandibular arch

Question 17

what does the first arch form?

Answer 17

mandible

Question 18

what is the mandibular arch made of?

Answer 18

mandibular and maxillary process

Question 19

Describe the cartilage: meckel’s cartilage.

Answer 19

-Primitive support, largely disappears
-Forms:
2 bones:
-Incus
-malleus
2 ligaments:
-Sphenomandibular
-Sphenomalleolar

Question 20

what does the 1st pharyngeal arch give rise to?

Answer 20

-Body of tongue
-Muscles of mastication:
Temporalis, masseter, pterygoids
Mylohyoid, anterior body of digastric

Question 21

what nerve innervates the 1st pharyngeal arch?

Answer 21

V (trigeminal)

Question 22

what is the blood supply of the 1st pharyngeal arch?

Answer 22

maxillary and carotid arteries

Question 23

Describe treacher-collins syndrome.

Answer 23

-Genetic-can be a simple as a single polymorphism.
-Failure of neural crest cell migration
-Facial Bone hypoplasia:
Mandible and zygoma
-Ear abnormalities
-Clefts
-Dental anomalies:
Tooth agenesis
Enamel deformities
Misplacement upper 6s

Question 24

what does the 2nd arch called?

Answer 24

hyoid arch

Question 25

what does the reicherts cartilage form?

Answer 25

- Stapes - Lesser horn and superior hyoid body - styloid process, stylohyoid ligament

Question 26

what muscles are in the 2nd arch?

Answer 26

facial expression and posterior belly digastric

Question 27

what other tissues are in the 2nd arch?

Answer 27

thyroid gland and tonsil

Question 28

what nerve innervates the 2nd arch?

Answer 28

VII (facial)

Question 29

what does the 3rd arch form?

Answer 29

- greater horn of hyoid - inferior hyoid body - root of the tongue

Question 30

what muscle is in the 3rd arch?

Answer 30

stylopharyngess muscle

Question 31

what nerve innervates the 3rd arch?

Answer 31

IX (glossopharyngeal)

Question 32

Whats in the 4th arch?

Answer 32

-Forms thyroid cartilage -Pharynx and epiglottis -Muscles: Pharyngeal constrictor soft palate

Question 33

what nerve innervates the 4th arch?

Answer 33

X (vagus)- sup. laryngeal

Question 34

whats in the 6th arch?

Answer 34

- Cricoid + arytenoid cartilages - Larynx - Muscles of larynx

Question 35

what nerve innervates the 6th arch?

Answer 35

X (vagus) -inferior laryngeal nerve

Question 36

what is the 1st cleft/groove?

Answer 36

external auditory meatus and ear drum

Question 37

what happens to 2nd-6th clefts?

Answer 37

disappear -obliterated by the proliferating 2nd arch

Question 38

what is the 1st pouch?

Answer 38

- Eustachian Tube - Middle ear cavity - Tympanic membrane - Ventral part obliterated by the tongue

Question 39

what is the 2nd pouch?

Answer 39

- Tonsillar fossa | - Ventral part obliterated by the tongue

Question 40

what is the 3rd pouch?

Answer 40

inf. parathyroid gland and thymus

Question 41

what is the 4th pouch?

Answer 41

sup. parathyroid gland

Question 42

what is the only groove to persist?

Answer 42

1st as pharyngeal acoustic meatus

Question 43

what are the other grooves obliterated with?

Answer 43

cervical sinus as the neck develops

Question 44

where do the pharyngeal membranes appear?

Answer 44

- in the floor of the pharyngeal grooves | - form where the epithelia of the grooves and pouches approach each other

Question 45

what seperates the endoderm of the pouches and ectoderm of the grooves?

Answer 45

mesenchyme

Question 46

what is the only pharyngeal membrane to not obliterate?

Answer 46

1st- becomes the tympanic membrane

Question 47

Describe how branchial fistula/cyst forms?

Answer 47

- 2nd Arch fails to grow down sufficiently over 2nd-4th Clefts - Along anterior border of sternocleido-mastoid muscle

Question 48

Describe ectopic thyme or parathyroid tissue.

Answer 48

failure to migrate completely