Kuehn - neurulation and fate of mesoderm

Question 1

what is neurulation

Answer 1

process of neural tube formation (differentiates from ectoderm overlying the notochord)

Question 2

what thickens into the neural plate

Answer 2

the receptive area (oval patch stretching from oral plate to primitive node)

Question 3

what is expressed by notochord to activate the folding of the neural tube

Answer 3

SHH (sonic hedgehog)

Question 4

what contracts inducing the neural plate to fold

Answer 4

actin filaments at apical surface contract until edges fuse together = neural groove -> neural tube

Question 5

what are the edges of the neural folding called

Answer 5

neural fold

Question 6

after the neural folds fuse together, what forms around the neural tube

Answer 6

ectoderm

Question 7

what happens at 20 days

Answer 7

folds begin to form at center of embryo and somites form on either side

Question 8

what happens at 22 days

Answer 8

center folds have fused - zippering from center to edges

Question 9

what day are there 2 small connections/openings between the amnion and neural tube

Answer 9

day 23

Question 10

what day does the rostral neuropore close at

Answer 10

day 25

Question 11

what happens at day 27

Answer 11

the caudal neuropore closes

Question 12

what happens if the rostral neuropore has a delay in closing

Answer 12

exencephaly - failure to develop occipital/parietal bones -> dural and brain herniation

Question 13

what is spina bifida

Answer 13

if there is a delay in the caudal neuropore closing - failure of formation of lamina and spine in lower thoracic/upper lumbar vertebral column

Question 14

what develops between the two neuropores at the proximal part of the neural tube

Answer 14

brain and brainstem (prosencephalon, mesencephalon, and rhombencephalon)

Question 15

what is primary neurulation

Answer 15

period of time where there is neural folding

Question 16

what is secondary neurulation

Answer 16

neural tube (lower sacral) forms by development of medullary core - cannulates and joins with rest of neural tube

Question 17

what 2 things does the umbilicus arise from

Answer 17

umbilical vesicle and connecting stalk

Question 18

when is the umbilicus detached

Answer 18

at 6 weeks

Question 19

what is the fate of the ectoderm

Answer 19

skin, epidermal glands, hair, nails, eye (lens and corneal epithelium), inner ear labyrinth, anterior pituitary, and tooth enamel

Question 20

what is neuroectoderm

Answer 20

specialized ectoderm

Question 21

what arises from neuroectoderm

Answer 21

brain, brainstem, spinal cord, eye (retina, pigmented epithelium, optic nerve, part of iris) and pars nervosa of pituitary gland

Question 22

what is continuous with the endoderm

Answer 22

yolk sac membrane (extra-embryonic mesoderm, yolk-sac epithelium)

Question 23

what is the original endoderm (hypoblast) replaced with

Answer 23

mesodermal cells

Question 24

what epithelia arises from endoderm

Answer 24

epithelium of alimentary canal, parenchyma of pancreas and liver, thyroid, parathyroid, thymus, lung, trachea, middle ear epithelium, urinary bladder, urethral epithelia, and vaginal epithelium

Question 25

what is the septum transversum

Answer 25

it migrates with heart during folding - separates throrax from abdomen and then participates in venous cardiac development

Question 26

what does the intermediate mesoderm give rise to

Answer 26

kidney, ureter, ductus deferens and gonads

Question 27

where does the neural crest layer come from

Answer 27

the neural folds

Question 28

what does the neural crest layer give rise to

Answer 28

melanocytes, PNS, adrenal medulla, bulbar ridges of heart- semilunar valves, meninges, and near head can form- bone, cartilage and other connective tissue of pharyngeal arches, odontoblasts and ear ossicles

Question 29

what 2 types of mesoderm come from the lateral plate mesoderm

Answer 29

somatic mesoderm (somatopleure) and splanchinic mesoderm (splanchonopleure)

Question 30

what 2 layers does the somatic mesoderm differentiate into

Answer 30

dermomyotome and sclerotome

Question 31

what does the somatic mesoderm give rise to

Answer 31

bones, cartilage, fascia, and other connective tissue around periphery of body

Question 32

what does the dermomyotome give rise to

Answer 32

dermis of skin and muscles

Question 33

what does the sclerotome give rise to

Answer 33

vertebral bones and intervertebral disks

Question 34

what does the splanchinic mesoderm give rise to

Answer 34

visceral smooth muscle, fascia, and connective tissue of viscera and associated vasculature

Question 35

when does the mesenchymal migration occur for endochondral bone development

Answer 35

4th-5th week

Question 36

what happens in the 5th-6th week for endochondral bone development

Answer 36

condensation of mesoderm

Question 37

what happens at the beginning of the 6th week for endochondral bone development

Answer 37

chondrification

Question 38

what happens weeks 7-12 for endochondral bone development

Answer 38

primary ossification

Question 39

what happens from birth - 9th year for endochondral bone formation

Answer 39

secondary ossification

Question 40

when do the epiphyseal plates fuse together

Answer 40

years 18-25

Question 41

From what do vertebra develop

Answer 41

arise from sclerotome - each segment is derived from 2 seperate somites - come together to form single vertebra

Question 42

From what are intervertebral disks formed

Answer 42

mesoderm remaining behind after mesodermal migration

Question 43

what are the steps for muscle formation starting at the 15th week

Answer 43

migrating myoblasts - fusion of myoblasts - primary myotube - myotube growing - secondary myotube - mature skeletal muscle fiber

Question 44

how do the upper and lower limbs grow

Answer 44

with middle joint facing laterally and ventral surfaces facing medially