Embryology

Question 1

what two classes of things does the ectoderm give rise to in the head?

Answer 1

epidermis and special senses

Question 2

placode

Answer 2

where the ectoderm thickens and develops in a special sense

eventually invaginate away from surface and sometimes even from vesicle

Question 3

what structures do the neural crest cells form in the head

Answer 3

bones of the face

Question 4

pharyngeal arches and clefts

Answer 4

mesodermal derivatives are organized with reference to pharyngeal arches, separated pharyngeal clefts

formed as rudimentary gills, there are eventually 6 arches that form

Question 5

myoblasts in pharyngeal arches

Answer 5

skeletal muscles

Question 6

neural crest cells in pharyngeal arches

Answer 6

facial bones

Question 7

which cranial nerves are associated with which arches

Answer 7

1- 5
2- 7
3- 9
4-6- 10

Question 8

how does each arch receive blood?

Answer 8

from aoritic arches

Question 9

derivatives of 1st pharyngeal muscles

Answer 9

muscles- mastication

skeletal- maxilla, zygomatic, mandible, malleus, incus

Question 10

derivatives of 2nd pharyngeal muscles

Answer 10

muscles- facial

skeletal- stapes- part of hyoid

Question 11

derivatives of 3rd pharyngeal muscles

Answer 11

muscles- stylopharyngeus

skeletal- part of hyoid

Question 12

derivatives of 4th pharyngeal muscles

Answer 12

muscles- muscles of palate, pharynx, larynx

skeletal- laryngeal cartilages

Question 13

pharyngeal pouches

Answer 13

gut tube does not stay perfectly cylindrical, “pouches” out towards pharyngeal arch

Question 14

expanding 2nd arch

Answer 14

covers the neck, leaving only 1st pharyngeal cleft

Question 15

remnant of 1st pharyngeal cleft becomes what

Answer 15

external acoustic meatus

Question 16

derivatives of the 4 pouches

Answer 16

1 eustachian tube

2 palantine tonsile

3 inferior parathyroid thymus

4 superior parathyroid

Question 17

describe the development of the eyes

Answer 17

4th week, optic vesicles form (lateral outgrowths from the forebrain, optic vesicle elongates and narrows, forming the optic stalk (eventually becoming the optic nerve).

vesicle comes into contact with the epidermis, forming the invaginating lens placode. as it continues to indent, forms the optic cup.

the inner layer of the optic cup becomes neural retina, outer layer become pigmented layer

Question 18

choroidal fissure

Answer 18

groove forms on inferior optic stalk/cup, where the hyaloid artery passes to supply the lens and vesicle

Question 19

eye structures formed by surface ectoderm

Answer 19

conjunctival sac
epidermis of eyelid
corneal epithelium
lens

Question 20

eye structures formed by surface neuroectoderm

Answer 20

retina
optic nerve
iris
ciliary

Question 21

eye structures formed by surface mesoderm

Answer 21

hyaloid arteries

Question 22

eye structures formed by surface neural crest cells

Answer 22

sclera, cornea, choroid

Question 23

otic placodes

Answer 23

4th week, above 2nd pharyngeal cleft

forms vesicle

forms membranous labyrinth

Question 24

middle ear cavity

Answer 24

distal part of 1st pharyngeal pouch

Question 25

eustachian tube

Answer 25

proximal part of the pouch retains its connection with the pharynx

Question 26

external acoustic meatus

Answer 26

1st pharyngeal cleft

Question 27

which germ layer is the tympanic membrane made of

Answer 27

skin- ectoderm- outer layer fibrous CT- mesenchyme- middle layer mucous membrane- endoderm

Question 28

auricle development

Answer 28

grows on the ear oriented incorrectly, and twists anteriorly and migrates up