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COT 1 (WPH) > 3.3 lecture - embryology - development of body plan - MacNeil > Flashcards

3.3 lecture - embryology - development of body plan - MacNeil Flashcards

1
Q

which conceptus layer is always adjacent to maternal blood supply?

A

syncytiotrophoblast

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2
Q

where is the chorionic cavity in relation to the yolk sac and the amnionic cavity?

A

chorionic is outside surrounding both yolk sac and amnionic cavity. the chorion is connected to the embryo via the connecting stalk (becomes umbilical cord)

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3
Q

what layers are present in each primary villus extending from the chorion into the decidua? secondary villus?
tertiary villus?

A
  • primary - syncytiotrophoblast and cytotrophoblast
  • secondary - syncitiotrophoblast, cytotrophoblast, mesoderm core
  • tertiary - synciciotrophoblast, cytotrophoblast, mesoderm core, villous capillaries within mesoderm core
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4
Q

why is week 3 of embryo development the “week of threes” ?

A

3 cavities - chroionic, definitive yolk sac, amnionic
3 placental layers - syncytiotrophoblast, cytotrophoblast, extraembryonic mesoderm
3 germ layers - ecto, meso, endoderm
3 body axes - craniocaudal, dorsoventral, R/L

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5
Q

function of the:

  • amnion
  • yolk sac
A

amnion - line fluid filled amnionic cavity

yolk sac - transfer agent for nutrients, site of primordial germ cells, source of blood cells and blood vessels

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6
Q

epiblast cells that migrate through the primitive groove and migrate cranially in the mesoderm along the cranial caudal axis will form the __

A

notochord

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7
Q

what cells is the notochord derived from?

A

epiblast cells that migrate through the primitive groove and migrate cranially in the mesoderm along the cranial caudal axis

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8
Q

what germ layer is the notochord derived from?

A

mesothelium

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9
Q

another name for the notochord is the…

A

axial mesoderm

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10
Q

the notochord is important for 3 reasons:

A
  • signals induction of neural tube, somites, and surrounding structures
  • vertebral column and base of skull develop around it
  • degenerates to leave behind nucleus pulposus of the intervertebral disc
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11
Q

this structure signals the induction of the neural tube, somites, and surrounding structures

A

notochord

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12
Q

the vertebral column and base of the skull develop around this structure

A

notochord

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13
Q

this structure ultimately degenerates to leave behind nucleus pulposus of the intervertebral discs in adults

A

notochord

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14
Q

the location and function of the nucleus pulposus

A
  • located in center of intervertebral discs in adults

- jelly-like structure that functions to distribute compressive loads through hydraulic pressure

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15
Q

T/F during gastrulation, the cells in the ectoderm that will ultimately form the heart migrate to just below the oropharyngeal membrane

A

false - the heart will be derived from cells of the Mesoderm that migrate Above the oropharyngeal membrane during gastrulation (this cranial end will ultimately fold over so these heart deriving cells are located caudally to oropharyngeal membrane)

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16
Q

what 2 germ layers are fused at the oropharyngeal and cloacal membranes?

A

ectoderm and endoderm are fused (no mesoderm)

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17
Q

~ what day do the oropharyngeal and cloacal membranes break down?

A

~ day 26

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18
Q

a solid cord of cells that underlies the developing neural tube forming a midline axis and serves as a basis for the axial skeleton. induces the neural plate and sclerotome portion of the somite

A

notochord

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19
Q

describe 7 key structures in the sequence in which they arise in the process of neurulation

A
  • neural plate
  • axial neural groove / neural folds
  • neural crests
  • neural tube
  • neural crest cells
  • primitive brain
  • primitive spinal cord
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20
Q

neurulation is…

A

the process by which the neural tube forms

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21
Q

neurulation begins on day __

A

day 18

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22
Q

when the notochord thickens and expands mitotically it forms the…

A

neural plate

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23
Q

folding of the neural plate gives rise to these 2 structures

A
  • axial neural groove

- neural crests

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24
Q

this is where the neuroectoderm merges with the somatic ectoderm during neurulation

A

neural crests

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25
Q

fusion of neural folds in neurulation results in the formation of…

A

the neural tube

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26
Q

neural crest cells arise when…

A

around the time of neural fold fusion to form the neural tube during neurulation, the neural crests detach from the neural tube and migrate into the mesoderm layer

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27
Q

the neural crests detach from the neural tube and migrate into the mesoderm to become…

A

neural crest cells

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28
Q

describe the fusion that gives rise to the neural tube

A
  • neural folds approach each other
  • somatic ectoderm fuses at surface (beginning somewhere mid-axial and zipping up cranially and down caudally)
  • neural crest cells detach, migrate into paraxial mesoderm
  • neural tube sinks into mesoderm layer
  • neural tube folds ventrally to close tube
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29
Q

neural crest cell detachment and migration into mesoderm during gastrulation is an example of what kind of transition?

A

epithelial to mesenchymal transition

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30
Q

mesenchyme is..

A

embryonic connective tissue in the mesoderm

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31
Q

T/F fusion of neural folds is due to genetic factors (genes such as sonic hedgehog) and environmental factors (cholesterol and folic acid)

A

true

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32
Q

what day does closure of the neural tube at each neuropore occur?

A

Anterior/cranial neuropore: ~day 25

Posterior/caudal neuropore: ~day 28

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33
Q

name the four subdivisions of neural crest derivatives

A
  • cranial
  • cardiac
  • vagal
  • trunk
34
Q

examples of neural crest derivatives include:

A
  • connective tissue of bones, neck, face skull
  • cranial nerve ganglia
  • heart septum (cavity wall enclosing heart)
  • dentin of tooth
  • dermis of head and neck
  • dorsal root ganglia
  • enteric nervous system
  • sympatheitic chain
  • adrenal medulla
  • Schwann cells (myelin forming cells in PNS)
  • glial cells
  • malanocytes of skin
  • smooth muscle of head region blood vessels
35
Q

the following are examples of derivatives of what 3rd week structure?

  • connective tissue of bones, neck, face skull
  • cranial nerve ganglia
  • heart septum (cavity wall enclosing heart)
  • dentin of tooth
  • dermis of head and neck
  • dorsal root ganglia
  • enteric nervous system
  • sympatheitic chain
  • adrenal medulla
  • Schwann cells (myelin forming cells in PNS)
  • glial cells
  • malanocytes of skin
  • smooth muscle of head region blood vessels
A

derivatives of neural crest cells

36
Q

what are the 2 types of ectoderm in week 3 of development

A
  • neuroectoderm

- surface ectoderm

37
Q

name some derivatives of the surface ectoderm

A
  • epidermis
  • nails
  • hair
  • subcutaneous glands
  • mammary glands
  • anterior pituitary
  • enamel
  • lens of the eye
38
Q

name some derivatives of the neuroectoderm

A
  • central nervous system
  • retina
  • posterior pituitary gland
  • pineal body
39
Q 
the following are all derivatives of what 3rd week structure?
• epidermis
• nails
• hair
• subcutaneous glands
• mammary glands
• anterior pituitary
• enamel 
• lens of the eye
A

surface ectoderm

40
Q 
the following are all derivatives of what 3rd week structure?
• central nervous system
• retina
• posterior pituitary gland
• pineal body
A

neuroectoderm

41
Q

what are 2 key regions of the axial mesoderm and why are they important

A
  • cardiogenic mesoderm - at cranial end of embryo, forms heart tubes
  • axial rod of mesoderm - forms notochord, which strongly influences formation of nervous system and vertebral column
42
Q

what is the importance of the cardiogenic mesoderm?

A

it is the part of the axial mesoderm that forms the heart tubes at cranial and of embryo

43
Q

what is the importance of the axial rod of the mesoderm?

A

forms notochord, which strongly influences formation of nervous system and vertebral column

44
Q

from medial to lateral, what are 4 key longitudinal regions of the mesoderm and what do they give rise to?

A
  • axial mesoderm (heart tubes, notochord)
  • paraxial mesoderm (somites)
  • intermediate mesoderm (urogenital system)
  • lateral plate mesoderm (coelum, viscera)
45
Q

what does the paraxial mesoderm give rise to?

A

somites

46
Q

what does the intermediate mesoderm give rise to?

A

urogenital system

47
Q

what does the lateral plate mesoderm give rise to?

A
  • coelum (body cavity)
  • connective tissue and muscle of the viscera
  • serous membranes
48
Q

what does the coelum refer to?

A

the body cavity

49
Q

what does the viscera refer to?

A

the internal organs in the main cavities of the body, esp. those in the abdomen, e.g., the intestines

50
Q

what cells undergo ectodermal to mesenchymal differentiation during neurulation?

A

neural plate cells

51
Q

which longitudinal region of the mesoderm is continuous with the extraembryonic mesoderm covering the yolk sac and amnion?

A

lateral mesoderm

52
Q

where do first somites arise from the paraxial mesoderm?

A

in the occipital region

53
Q

in what kind of sequence to new somites develop from the paraxial mesoderm? until how many somites?

A
  • from cranial to caudal

- until 42 pairs of somites

54
Q

how is the paraxial mesoderm correlated to age of the embryo during week 3 of development?

A

age is correlated to the number of somite pairs present

55
Q

from inner to outer, what 3 structures does each somite form?

A
  • sclerotome -> bone (axial skeleton)
  • myotome -> muscle (skeletal muscle)
  • dermatome -> connective tissue (dermis of skin)
56
Q

what is a scleratome derived from and what does it give rise to?

A
  • from somite (from paraxial mesoderm)

- creates axial skeleton (vertebrae, ribs, occipital bone of skull)

57
Q

what is a myotome derived from and what does it give rise to?

A
  • from somite (from paraxial mesoderm)

- creates skeletal muscle of body, head/neck, and limbs

58
Q

what is a dermatome derived from and what does it give rise to?

A
  • from somite (from paraxial mesoderm)

- contributes to dermis of skin (connective tissue layer of skin)

59
Q

what is a key component that migrates with each sclerotome, myotome, and dermatome derived from a somite?

A

each has its own segmental nerve component migrating with the developing cells

60
Q

somites and their developing sclerotomes, myotomes, and dermatomes can be classed into what 4 groups?

A
  • occipital
  • cervical
  • thoracic
  • lumbar
61
Q

what is a dermatomal pattern

A

area of skin supplied by a single spinal nerve

62
Q

what happens to the lateral mesoderm in the trunk ~day 17 of development

A

develops clefts that eventually split it into two layers associated with the endoderm and ectoderm, and the space between the two layers

  • splanchnic mesoderm - mesothelial coverings (gut wall)
  • somatic mesoderm - (body wall)
  • intraembryonic coelum - primitive body cavity
63
Q

splanchnic mesoderm

A

formed from the splitting of the lateral mesoderm in the trunk ~day 17, associated with endoderm,, gives rise to mesothelial coverings

64
Q

intraembryonic coelum

A

primitive body cavity formed from the splitting of the lateral mesoderm in the trunk into splanchnic mesoderm and somatic mesoderm

65
Q

what organ system develops from the intermediate mesoderm

A

urinary & reproductive systems

66
Q

what is the intermediate mesoderm

A

in 2-3 week embryo, intermediate mesoderm is mesodermal layer between lateral mesoderm (which is splitting into somatic and splanchnic mesoderms) and the somites / neural tube
-develops into the urinary & reproductive systems

67
Q

as folding of the intraembryonic coleum forms a horseshoe pointing up, where is the…

  • pericardial cavity
  • pleural cavity
  • peritoneal cavity
A
  • pericardial cavity - bottom of horseshoe ring
  • pleural cavity - lateral extensions
  • peritoneal cavity - lateral extensions
68
Q

summarize week 3 development formations

A

-gastrulation
-major body axes
-notochord
-primordial nervous system (neural tube)
-somites
-cardiogenic area
-primordial body cavity
(still flat trilaminar disk)

69
Q

summarize completion of embryonic period (weeks 4-8)

A

morphogenesis
organogenesis
body folding

70
Q

in what week of development does body folding initiate?

A

week 4

71
Q

in embryonic body folding, the oropharyngeal membrane, cardiogenic area, pericardial cavity, and septum transversum (contributes to diaphragm) are relocated to their appropriate positions by what folding process

A

head folding

72
Q

in embryonic folding, the cloacal membrane, connecting stalk, and hindgut are relocated to their appropriate positions by what folding process

A

tail folding

73
Q

what causes head folding?

A

differential growth at the neural plate

74
Q

what causes tail folding?

A

growth of spinal cord

75
Q

what causes lateral folding?

A

growth of somites

76
Q

as abdominal wall form through lateral folding, part of the endoderm of the yolk sac is incorporated into the embryo as the __

A

midgut

77
Q

what is the yolk stalk

A

connects midgut (part of yolk sac incorporated into body cavity as lateral folding occurs) to yolk sac (hangs outside folding until abdominal wall closes and disconnects yolk sac

78
Q

3 body cavities in adults

A

pleural
pericardial
peritoneal

79
Q

T/F the connecting stalk, which becomes the umbilical cord, is an extension of the yolk sac

A

false

it is an extension of the chorion

80
Q

at the end of body folding in the embryonic period, the entire embryo is surrounded by the __, which is itself surrounded by the __

A

amnionic fluid and amnion

chorionic fluid and chorion

COT 1 (WPH) (25 decks)

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