Embryology > Neurulation > Flashcards

Neurulation Flashcards

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1
Q

Week 4

A

Neurulation

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2
Q

Steps of neurulation

A

1.) Neuroectodermal tissues differentiate from the ectoderm and thicken into the neural plate; the neural plate border separates the ectoderm from the neural plate

2.) The neural plate bends dorsally, with the two ends eventually joining at the neural plate borders, which are now referred to as the neural crest

3.) The closure of the neural tube disconnects the neural crest from the epidermis; neural crest cells differentiate to form most of the peripheral nervous system

4.) The notochord degenerates and only persists as the nucleus pulposus of the intervertebral discs; other mesoderm cells differentiate into the somites, the precursors of the axial skeleton and skeletal muscle

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3
Q

Neurulation highlights

A
  • notochord induces overlying ectoderm to develop into the neural plate
  • the neural plate folds into the neural tube and the neural crests are pinched off
  • the neural tube derives the CNS
  • the neural crests derive the PNS and select other cells
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4
Q

During gastrula (week 3 development), the body axis is formed

A
  • bilateral symmetry
  • left and right
  • dorsal and ventral
  • cranial and caudal
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5
Q

Week 3

A
  • triploblastic/trilaminar disc
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6
Q

What germ layers are formed during gastrulation?

A
  • ectoderm
  • mesoderm
  • endoderm
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7
Q

Notochord

A

Sonic Hedge Hog (SHH)

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8
Q

The mesoderm differentiates into how many types?

A

3

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9
Q

Primitive streak becomes

A

primitive groove

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10
Q

Primitive node becomes

A

primitive pit

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11
Q

The notochord secretes SHH, which dictates what?

A

cellular involvement

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12
Q

Neural plate

A
  • neural groove
  • neural folds
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13
Q

During neurulation, the neuroectodermal cells transform into what?

A

neural tube

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14
Q

Neural tube becomes what?

A

brain and spinal cord

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15
Q

The neural tube activates what?

A
  • neural crest cells
  • further differentiation of ectoderm, mesoderm, and endoderm
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16
Q

Central Nervous System (CNS)

A
  • brain
  • brain stem
  • spinal cord
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17
Q

Peripheral Nervous System (PNS)

A
  • cranial nerves
  • peripheral body nerves
  • ganglion
  • sensory and motor
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18
Q

Steps at ectoderm: primitive area makes

A

primitive streak –> groove
primitive node –> pit

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19
Q

Primitive node

A

“Hensen’s node” or “Spemann-Mangold Organizer”
- notochord and SHH and axial mesoderm

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20
Q

Notochord and SHH and Axial mesoderm stimulates what?

A

Neural plate (replaces primitive streak at day 25)

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21
Q

Neural plate makes

A
  • neural groove
  • neural folds

which makes the neural tube

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22
Q

Steps at ectoderm: Cells at primitive NODE (let’s make a tube)

A
  • they direct organization
  • cells that DIVE through groove and travel CRANIALLY become the prechordal plate and notochord (which stimulate neurulation)
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23
Q

Steps at ectoderm: Cells at primitive NODE

Ectoderm: neural plate –> _______ ____

Ectoderm: surrounding plate –> ______

A

neural tube; epidermis

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24
Q

At primitive NODE, what happens to the cells at the cranial end?

A

they proliferate

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25
At the primitive NODE, once plate is formed it undergoes __________ by _______ _______
elongation; convert extension
26
Neural plate
communication
27
How do germ cells communicate at the neural plate?
induction
28
At the neural plate, mesoderm causes overlaying ectoderm to undergo molecular and cellular changes
1.) Cells proliferate (increase mitosis) 2.) Cells express new sets of mRNA's specific for neural development "markers" including CAM's (cell adhesion molecules)
29
If cells transplant incorrectly---
two-headed organism
30
Neural plate -- communication -- cell movement
cells undergo shape and behavioral changes - columnarization - apical constriction - convergent extension - cell crawling
31
Neural plate --> hinge and close --> neural tube
1.) The sheet bends at a median hinge joint, creating neural folds 2.) The sheet bends further at lateral hinge joints, closing at the top to form the neural tube 3.) Neural crest cells detach from the epithelial tube and become wandering mesenchyme cells
32
Neural crest cells "4th germ layer"
- specialized cells within neural tube - migrate outward through the fetus - give rise to NEW tissues
33
Neural crest cells make up the sensory epithelium of what?
- ears - nose - eyes - mouth
34
Neural crest cells make up what glands?
- sweat - mammary - pituitary
35
Movement of cells for neurulation in dorsal view
- neural tube is OPEN - "pores" close --> neural tube is CLOSED - Neural tube is NOW formed
36
Day 18-Day 23
- Cranial (anterior) neuropore - Caudal (posterior) neuropore
37
Otic placode
- otic vesicles - cochlea - inner ear
38
Surface ectoderm
- nose - mouth - epidermis of fetal skin - hair - nails - sweat glands - mammary glands
39
Where are the somites found?
Under ectoderm
40
Lens placode
- lens - cornea
41
Steps at mesoderm: notochord
- secretes SHH protein - tells the cells where they are in 3D space - SHH permeates embryo - day 20: differentiation of 3 mesoderm types
42
3 mesoderm types
1.) Paraxial mesoderm 2.) Intermediate mesoderm 3.) Lateral mesoderm
43
The paraxial mesoderm becomes _________
Somites
44
Somites
PAIRED blocks of mesoderm, closest to Notochord
45
Paraxial mesoderm (somites)
- paired - formed alongside NOTOCHORD - cranial to caudal development - 3 somites per day are formed - can dictate how old embryo is
46
How many somites are formed each day?
3
47
Paraxial mesoderm Somites give rise to what 3 groups of mesodermal tissues?
1.) Dermatome (skin) 2.) Myotome (muscle) 3.) Sclerotome (hard)
48
Sclerotome
- bones - cartilage
49
Intermediate mesoderm
- smaller - lateral to somites ex. adrenal cortex, kidneys, testes and ovaries
50
Lateral mesoderm
- thinnest - most lateral
51
Lateral mesoderm splits into which two layers at week 3?
1.) Dorsal portion: Somatic/Parietal 2.) Ventral portion: Splanchnic/Visceral
52
Somatic/parietal (dorsal) mesoderm
Adheres to ectoderm - parietal pleura; soft tissue of arms and legs
53
Splanchnic/visceral (ventral) mesoderm
Adheres to endoderm - visceral pleura; muscle wall of gut, heart, circulatory system
54
Space between the 2 mesoderm layers is called what?
Intraembryonic coelom
55
Intraembryonic coelom is a space that houses what?
Thoracic and abdominal cavities
56
Paraxial mesoderm (somites) forms
- skin - muscle - bony tissue
57
Intermediate mesoderm forms
- adrenal glands - gonads - kidneys
58
Lateral mesoderm forms
- serous membrane - limb tissue - heart - circulatory system
59
Steps at Endoderm: Endo and Ecto push together to form 2 bilaminar regions called?
1.) Oropharyngeal membrane or buccopharyngeal (head) 2.) Cloacal membrane (rear)
60
Week 4
opening mouth
60
Week 7
opening anus and genitourinary tracts
61
Steps at Endoderm: week 4 Embryo folds in which 2 directions along LONGITUDINAL plane?
1.) Cranial fold 2.) Caudal fold
62
Movement of cells at the endoderm take on a _______ curved appearance, which helps to form ____ _____ and yolk area at middle
"shrimp"; gut tube
63
Steps at Endoderm: Mesoderm follows the endoderm to form ____ layer of that structure
2nd - ex. blood vessels
64
Steps at Endoderm: The two sides of the body will come together at ventral surface and eventually ____, but the yolk sac is in the ___
fuse; way
65
Steps at Endoderm: The gut is divided into which 3 regions?
- foregut - midgut - hindgut
66
Foregut
at week 4: mouth opening connects others at week 5: trachea and lungs
67
Midgut
- stays connected to yolk sac through yolk stalk or vitelline duct - stalk thins over time and collapses - yolk sac dissipates
68
What is a remnant of yolk stalk called in the midgut?
Meckel's Diverticulum
69
Hindgut
- at week 7: anus opening connects anal canals at pectinate line (large intestine/anus junction)
70
Hindgut feature that connects anal canals
pectinate line
71
Endoderm forms the linings of the gastrointestinal tube and respiratory tube...
- tonsils - thyroid - parathyroid glands - thymus - liver - gallbladder - pancreas - parts of ear - epithelium of urethra and urinary bladder - GI tract and pharynx - respiratory tract
72
Pharynx
pectinate line (GI tract endoderm)
73
Primitive streak and node becomes what?
neural tube
74
Notochord
- Transient contributes to nucleus pulposus - influences embryo folding - secretes Sonic Hedge Hog
75
Steps of neurulation
1.) Neural plate (3 types of mesoderm) 2.) Neural groove 3.) Neural folding 4.) Neural tube - 3 pairs a day - by week 5, 42-44 pairs
76
Intermediate mesoderm
- kidneys - adrenal glands - urogenital system
77
Lateral plate mesoderm
- heart - blood vessels - organ muscle - body wall
Embryology
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