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EMBRYOLOGY (foundation B) > Intro 29: Development of neural tube and somites and embryo folding > Flashcards

Intro 29: Development of neural tube and somites and embryo folding Flashcards

1
Q

what is NEURULATION

A

formation of NEURAL TUBE

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2
Q

when does NEURULATION take place

A

WEEK 3 AND 4

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3
Q

How many stages of NEURULATION

A

4

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4
Q

What is the 1st stage of NEURULATION

A

transformation of ectoderm into THICKENED NEURAL PLATE

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5
Q

what does the Notochord do in relation to the Neural Plate

A

Supports neural plate

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6
Q

2nd stage of NEURULATION

A

ELONGATION of NEURAL PLATE
- shaping so becomes narrower and longer

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7
Q

3rd stage of NEURULATION

A

(lateral) FOLDING of neural plate into NEURAL FOLDS

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8
Q

4th stage of NEURULATION

A

FUSION of neural folds to form NEURAL TUBE

(fusion of the two most lateral apical surfaces of the neural folds)

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9
Q

what is also happening simultaneously with NEURULATION at Day 18-21 (week 3)

A

NOTOCHORD FORMATION

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10
Q

As the NOTOCHORD ELONGATES, the neural plate…

A

NEURAL PLATE BROADENS and EXTENDS to the OROPHARYNGEAL MEMBRANE (future site of oral cavity) in CRANIAL end of embryo

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11
Q

on approx DAY 18, the NEURAL PLATE…

A

INVAGINATES along its central axis to form the NEURAL GROOVE

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12
Q

by the end of the 3rd week (DAY 21) the lateral edges of the NEURAL PLATE become…

A

elevated to form NEURAL FOLDS

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13
Q

at DAY 19 what can you see at DORSAL end of embryo

A

NEURAL PLATE
NEURAL GROOVE

primitive streak
primitive node

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14
Q

at DAY 20 what can you see at DORSAL end of embryo

A

NEURAL FOLD
neural groove

primitive streak

SOLOMITES

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15
Q

Derivatives of the ECTODERM

A

NEUROECTODERM
-NEURAL TUBE
-NEURAL CREST

SURFACE ECTODERM

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16
Q

how is the NEURAL CREST formed

A

Masses of cells DETACH themselves from the lateral side of the NEURAL PLATE
and form the NEURAL CREST

(neural crest cells migrate into mesoderm

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17
Q

Neural Crest gives rise to…

A

melanocytes, iris muscle and pigment cells, chromaffin cells of the adrenal
medulla, connective tissue of H&N glands etc.

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18
Q

How is the neural tube formed

A

By the end of the third week, the neural folds have begun to move together and fuse,
converting the neural plate into a neural tube

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19
Q

NEURAL TUBE soon SEPARATES from the SURFACE ECTODERM.
what then happens to the surface ectoderm

A

SURFACE ECTODERM
- fuses
-DIFFERENTIATES into EPIDERMIS of the SKIN

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20
Q

when is NEURULATION completed

A

4th week

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21
Q

what causes the changes in the ectoderm

A

signals from the notochord

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22
Q

around day 23:
Until the fusion is complete, the cranial (cephalic) and caudal ends of the NEURAL TUBE COMMUNICATE with the AMNIOTIC CAVITY by way of the…

A

anterior (cranial) and posterior (caudial)
NEUROPORES

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23
Q

when do we have CLOSING of the CRANIAL NEUROPORE

A

approx DAY 25

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24
Q

when do we have CLOSING of the CAUDAL NEUROPORE

A

approx DAY 28

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25
Q

upon CLOSURE of the CAUDAL NEUROPORE on DAY 28, the embryo has established..

A

caudally:
rudimentary SPINAL CORD

cranially:
BRAIN VESICLES

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26
Q

the NEURAL TUBE is the basis for the…

A

entire CENTRAL NERVOUS SYSTEM

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27
Q

Neural tube defects (NTDs) occur when

A

neural tube closure fails to occur.

28
Q

Examples of Neural Tube Defects (NTDs)

A
  • Anencephaly:
    Occurs when the neural tube fails to close in the cranial region,
    as a result of this most of the brain fails to form.
  • Spina bifida:
    Occurs when the neural tube fails to close
    anywhere from the cervical region caudally.

However, the most common site for spina bifida to occur is the lumbosacral region.

50-70 % of all NTDs can be prevented by daily intake of vitamin folic acid.

29
Q

Derivatives of the ectoderm

A
  • Central nervous system
  • Peripheral nervous system
  • Sensory epithelium of the ear, nose and eye
  • The epidermis including both hair and nails
  • Subcutaneous glands, mammary glands,
    pituitary gland, enamel of the teeth
30
Q

What does the MESODERM differentiate into

A

HEAD
PARAXIAL MESODERM
INTERMEDIATE MESODERM
LATERAL MESODERM

31
Q

Which type of mesoderm differentiates into SOLOMITES

A

PARAXIAL MESODERM

32
Q

During gastrulation, specific regions of the EPIBLAST migrate through different parts of the … and … to form mesoderm

A

node
primitive streak

33
Q

EPIBLAST cells migrating at the
CENTRAL and MOST CRANIAL part of the node will form the

A

NOTOCHORD

34
Q

EPIBLAST cells migrating LATERALLY form the… (3)

A

PARAXIAL MESODERM
INTERMEDIATE MESODERM
LATERAL PLATE MESODERM

35
Q

Paraxial mesoderm is where in relation to notochord

A

next to

36
Q

What are derived from SOMITES

A

Axial Skeleton,
Voluntary Musculature,
Dermis

37
Q

By the beginning of the 3RD WEEK, PARAXIAL MESODERM starts to be organised into…

A

segments,
SOMITOMERES

38
Q

Toward the end of the third week, SOMITOMERES further organise into

A

SOMITES
on each side of the neural tube

39
Q

new SOMITES appear in… at what rate

A

appear in CRANIO-CAUDAL SEQUENCE

at rate of approx 3 pairs of somites per day

40
Q

at the end of the fifth week how many pairs of SOMITES are present

A

42-44 pairs

41
Q

How are SOMITES formed (somitogenesis)

A

PARAXIAL MESODERM organised to SOMITOMERES organised into SOMITES

42
Q

when are SOMITES formed

A

3RD WEEK

43
Q

What do SOMITES undergo

A

DIFFERENTIATION

44
Q

As the somite matures, various regions become committed to forming only certain cell types.
2 Regions/ Derivatives of SOMITE:

A

SCLEROTOME
DERMAMYOTOME

45
Q

What is the SCLEROTOME region of the Somite and what does it do

A

-ventro-medial region
- give rise to cartilage cells (CHONDROCYTES) of the vertebrae
and ribs
- FORM BONE OF THE AXIAL SKELETON
(the skull bones, the ossicles of the middle ear, the rib cage, sternum and the vertebral column)

46
Q

What is the DERMAMYOTOME of a Somite and what does it consist of:

A

double layered structure that consists of:
DEMATOME
MYOTOME

47
Q

what is the DEMATOME of the dermamyotome of the somite, and what does it generate?

A

-the central region of the dorsal layer of the dermamyotome

  • generates DERMIS of the BACK SKIN
48
Q

what is the MYOTOME of the dermamyotome of the somite, and what does it generate?

A

-lower layer of the dermamyotome
- contains cells that will divide to produce MYOBLASTS that will give rise to
AXIAL and APPENDICULAR (LIMB) SKELETAL MUSCLE

49
Q

Somites determine the migration pattern of… (2)

A

NEURAL CREST CELLS
& SPINAL NERVE AXONS

50
Q

As somites appear NEURAL CREST CELLS simultaneously… (3)

A
  • MIGRATE from DORSAL NEURAL TUBE into SOMITES

-DIFFERENTIATE into MELANOCYTES

-contribute to development of DORSAL ROOT GANGLIA

51
Q

Each myotome and dermatome retains its innervation from..

A

its segment of origin
(original somite)

52
Q

SOMITES are the BUILDING BLOCKS of

A

the VERTEBRATE BODY PLAN

  • essential for segmentation (dermatomes),
  • bone and musculature development,
  • creating a template for the nervous system
53
Q

Although all somites look identical they will form..

A

different structures at different positions along the anterior-posterior axis

54
Q

Distinct regions of each somite become

A

specific tissue and cell types as the body develops

55
Q

Dermatome is defined as..

A

an area of skin in which
sensory nerves derive from
a single spinal nerve root

56
Q

Derivatives of the mesoderm

A
  • The skeleton
  • Most voluntary muscle groups
  • Most of the dermis
  • The circulatory system
  • The linings of all major cavities of
    the body
  • The urogenital system
57
Q

When does EMBRYONIC FOLDING take place

A

WEEK 4

58
Q

FOLDING of the FLAT TRI-LAMINAR EMBRYO forms

A

CYCLINDRICAL SHAPED EMBRYO (tube)

59
Q

EMBRYO FOLDS in 2 DIRECTIONS simultaneously:

A

LATERAL FOLDING (in transverse direction)

LONGITUDINAL FOLDING (cephalo-caudal flexion / sagittal)

forming a C-SHAPE with distinct head and tail ends

60
Q

folding of embryo laterally and longitudinally leads to formation of..

A

abdominal wall

61
Q

embryonic folding:
the embryo ENVELOPS a portion of the…

this will become the…

A

YOLK SAC
- PROTUDES with the UMBILICAL CORD

  • will become the ABDOMEN
62
Q

What does the AMNIOTIC SAC (that was sitting on top of the flat embryo) do as the EMBRYO FOLDS

A

ENVELOPS the EMBRYO

63
Q

FOLDING of EMBRYO essentially creates a tube called..

A

the PRIMITIVE GUT

-lined by the ENDODERM

64
Q

the PRIMITIVE GUT (foregut, hindgut, midgut) is formed by the FOLDING of the…

A

ENDODERM

(endoderm moves towards midline and fuses, causing dorsal part of yolk sac to create primitive gut tube)

hindgut at caudal end. temporarily closed by cloacal membrane (later becomes anus)

65
Q

Derivatives of the endoderm

A
  • Digestive tract
  • Epithelial lining of the respiratory tract
  • Epithelial lining of urinary bladder,
    urethra, tympanic membrane and auditory
    tube
  • Essential tissues of the thyroid,
    parathyroid, liver and pancreas
  • Connective tissues of thymus and tonsils
66
Q

amniotic sac derived from

A

epiblast

67
Q

yolk sac derived from

A

hypoblast

EMBRYOLOGY (foundation B) (4 decks)

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