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S1 Anatomy > Embryology > Flashcards

Flashcards in Embryology Deck (48):
1

the presence of _____ beneath the _____, through a process called induction, causes a thickening of the _____ to form a _____

notochord
embryonic ectoderm
ectoderm
neural plate

2

neural plate consists of...

neural ectoderm

3

what does the neural plate do around day 18

invaginates along the midsagittal plane to form a neural groove

4

what happens in the neural plate by the end of the third week

neural folds adjacent to neural groove fuse above neural ectoderm to form a neural tube

5

developing neural tube is open where?
-what are these openings called?

open at the anterior and posterior ends
anterior and posterior neuropores, respectively

6

neural tube eventually separates from...

overlying ectoderm

7

what are the neural crest cells

group of neuroectodermal cells that are "left behind" on the dorsolateral sides as the neural tube is formed

8

when does the neural tube begin to close
-where does it begin

around day 22
at the level of future somite 4-6

9

how does the closure of the neural tube progress

rostrally and caudally

10

which neuropore of the neural tube (rostral or caudal) closes last?
-when does it close

caudal closes last
around day 27

11

failure of the neuropores to close results in...

spina bifida
-deformities of the nervous system and investing skeleton

12

where is the most common area for spina bifida to occur
-cause
-resulting neural tube defects may also involve...

lumbar region
due to failure of the posterior neuropore to close
may also involve
-overlying tissues
-meninges
-vertebral column
-dorsal muscles
-skin

13

neural tube develops into...

central nervous system

14

CNS
-consists of...

brain and spinal cord

15

neural crest cells
-responsible for development of...

peripheral nervous system, including the autonomic nervous system
Schwann cells

16

Schwann cells
-purpose

myelinate the peripheral nervous system and the melanocytes noted in stratum basale of the epithelial lining of the skin

17

development of CNS is marked by rapid proliferation of the ____ end

rostral

18

"head fold" created due to...

overgrowth of the oropharyngeal membrane by the neural plate

19

lumen of neural tube becomes...

ventricular system of CNS

20

due to rapid growth of cranial end of CNS, what occurs
-these are termed

begins to bend
termed flexures

21

what are the flexures?
-where do they occurs

cervical flexure
-between spinal cord and brainstem
cephalic flexure
-between brainstem and cerebral hemispheres

22

brain region expands laterally into three _____

vesicles

23

what are the three vesicles?

rhombencephalon
-hindbrain
mesencephalon
-midbrain
prosencephalon
-forebrain

24

secondary vesicle formation occurs in the...
-what is created in each

rhombencephalon
-myelencephalon
-metencephalon
prosencephalon
-diencephalon
-telencephalon

25

myelencephalon turns into...

medulla

26

metencephalon turns into

pons and cerebellum

27

diencephalon turns into

thalamus
hypothalamus
pineal gland

28

telencephalon turns into

cerebral hemispheres
basal ganglia

29

CNS develops from _____ division and _____ followed by _____

develops from mitotic cell division and proliferation followed by migration of cells lining the neural tube

30

developing cells (that form the CNS) eventually form...
-what do these cells do?

neuroblasts (precursor neurons)
spongioblasts (precursor glial cells)
cells migrate away from the luminal surface to form the structures of the cord and brain

31

neural tube divided into...

alar, basal, roof and floor plate

32

what neural elements do the alar, basal, roof and floor plates turn into?

roof and floor
-do not differentiate into neuronal elements
alar (located dorsally)
-sensory component of the cord and brain
basal (located ventrally)
-motor component of the card and brain

33

neural crest cells form...

sensory peripheral nerves, including
-dorsal root ganglia
-autonomic ganglia
-myelinating cells of the PNS
melanocytes

34

embryonic mesoderm located lateral to the notochord is divided into...

3 divisions
-paraxial
-intermediate
-lateral plate

35

near the cervical flexure, the paraxial mesoderm begins to develop...
-this begins when?
-continues until...

furrows
begins at about 20 days
continues until about 30 days

36

how many somite pairs develop
-how are they classified

42-45
cranial
-4-5
cervical
-8
thoracic
-12
lumbar
-5
sacral
-5
coccygeal
-8-10

37

every somite differentiates into...
-these are precursors to...

sclerotome
dermomyotome
-dermatome
-myotome
precursors for the formation of the various dermal layers of the skin, muscles and bones and are associated with specific segmental levels of the developing nervous system

38

initially, what is the relationship of the specific developing segmental nerve with a somite

direct

39

what occurs to result in the somewhat altered image we have of a dermatome map

changes in the orientation of the limb bud
overlap mixing in the development of the specific muscle and dermal parts of the skin

40

where does limb bud development begin

preaxial and postaxial border

41

in which direction do the limb buds develop

ventrally, with hand and footplates facing each other

42

arm development takes place _____ rapidly than that of the leg

more

43

originally, the flexor aspect of the limbs is _____ and the extemsor aspect is_____, with the preaxial border being _____ and the postaxial border being _____

ventral
dorsal
cranial (rostral)
caudal

44

a rotation begins in the arm that results in a _____
-consequence

lateral 90 degree displacement along the longitudinal axis
consequence
-puts future elbow pointing posteriorly, with the extensor muscles (of the proximal bone) lateral and posterior

45

a rotation begins in the leg that results in a _____
-consequence

medial 90 degree displacement
places bend of knee facing forward, with the extensor compartment of the proximal bone now on the anterior part of the limb

46

critical time of limb bud formation

24-42 days after fertilization

47

day 24 (beginning of critical time of limb bud formation) coincides with _____

differentiation of the somites and the consequent organization of the limb differentiation

48

drugs that disrupt limb bud differentiation may result in_____

deformities including lack of formation of limbs
-thalidomide: drug used in the 50's to control morning sickness