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Embryology > Trilaminar Embryo (week 3) > Flashcards

Trilaminar Embryo (week 3) Flashcards

1
Q

when does hemangiogenesis begin?

A

end of week 3

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2
Q

where does hemangiogenesis begin?

A

in the extraembryonic mesoderm

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3
Q

what are blood islands?

A

hemangiogenic mesorderm within the wall of the yolk sac

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4
Q

what are hemangioblasts?

A

progenitor cells capable of differentiating into angioblasts and hematopoeitic stem cells

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5
Q

what are angioblasts precursors to?

A

endothelial cells of the blood vessels

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6
Q

what are the precursors of blood cells?

A

hematopoitic cells

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7
Q

what is angiogenesis

A

formation of new blood vessels by fusion of pre-existing blood vessels,

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8
Q

what does the blood island give rise to

A

angioblasts and hematopoeitic stem cells

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9
Q

when does primitive hemangiogenesis start?

A

beginning of week 3 in the yolk sac

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10
Q

when does definitive hemangiogenesis start?

A

2 days after primitive hemangiogenesis in the embryo

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11
Q

what is vasculogenesis?

A

process in which the primitive blood vessels form within the blood islands via fusion of endothelial cells (angioblasts)

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12
Q

what is the main event of week three of embryonic development?

A

gastrulation (formation of 3 embryonic germ layers)

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13
Q

what is gastrulation?

A

bilaminar embryo is transformed into a trilaminar embryo and the formation of three embryonic germ layers: embryonic ectoderm, mesoderm, and endoderm

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14
Q

at what end of the embryonic disk does gastrulation begin at? (caudal or cranial)

A

caudal

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15
Q

when does gastrulation begin (day number)

A

day 15

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16
Q

How does gastrulation start? (what is the first thing to begin to develop)

A

primitive streak

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17
Q

what does structures does the primitive streak consist of?

A

primitive groove + primitive node

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18
Q

what types of cells make up the primitive streak?

A

proliferating epiblasts

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19
Q

where is the primitive pit found?

A

it is the depression in the primitive node

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20
Q

what does the first wave of migrating epiblast cells through the primitive groove (during gastrulation) form?

A

embryonic endoderm (displaces the hypoblast)

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21
Q

what does the second wave of migrating epiblast cells through the primitive groove (during gastrulation) form?

A

embryonic mesoderm (moves between the endoderm and epiblast)

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22
Q

what does the remaining epiblast cells that don’t migrate during the first or second wave during gastrulation form?

A

embryonic ectoderm

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23
Q

what cells make up the primitive pit? what is their function?

A

ciliated cells; their cilia protrude toward the ventral side of the embryo and constantly rorate creating nodal flow to the left

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24
Q

Towards which side is nodal flow created? how?

A

to the left; via the ciliated cells in the primitive pit constantly rotating

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25
Q

what is responsible for the left-right embryo asymmetry?

A

the leftward gradient of the signaling protein Nodal (secreted by the primitive node)

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26
Q

what protein is secreted by the primitive node? what is it’s function?

A

nodal; its a signaling protein responsible for the left-right embryo asymmetry

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27
Q

where do the ectoderm and endoderm tightly adhere during gastrulation?

A

at the buccopharyngeal (oropharyngeal) membrane and at the cloacal membrane

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28
Q

Do the buccopharyngeal and cloacal membrane have any intervening mesoderm?

A

NO! they are only made up of tightly adhering ectoderm and endoderm

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29
Q

what does the buccopharyngeal membrane define? what future cavity does it make?

A

defines the cranial end of the embryo; gives rise to the future oral cavity (mouth)

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30
Q

what does the cloacal membrane define? what future cavity does it give rise to?

A

defines the caudal end of the embryo; gives rise to future cloaca (anus and urethra)

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31
Q

what is the notochord process?

A

a hollow tube, which grows cranially from the primitive pit between the ectoderm and endoderm until is it blocked by the prechordal plate

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32
Q

When does the notochord process stop growing?

A

once it reaches the prechordal plate

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33
Q

what is the prechordal plate? where is it located?

A

a condensation of the mesoderm, adjacent to the the buccopharyngeal membrane

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34
Q

What is the notochordal canal?

A

the hollow center of the notochordal process which is continuous with primitive pit

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35
Q

what makes up the notochord plate

A

the notochordal canal unzipped and fused with the endoderm

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36
Q

what is the neuroenteric canal?

A

a transient canal, which temporarily links the amniotic cavity with the yolk sac through the notochordal canal

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37
Q

As the three germ layers are established, the cells of the notochordal plate begin to proliferate and separate from the _________, forming the ________.

A

endoderm; definitive notochord

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38
Q

what does the notochord get incorporated into after notocord transformation?

A

vertebral bodies of the vertebral column during axial skeleton development

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39
Q

What are the main functions of the notochord?

A
  1. defines the dorsal-ventral and left-right axes of the embryo
  2. provides midline patterning signals for the surrounding tissues
  3. serves as a major skeletal element of the developing embryo
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40
Q

which cells make up the neural ectoderm?

A

epiblasts closest to the midline of the ectoderm layer

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41
Q

which cells make up the surface ectoderm?

A

epiblasts closes to the lateral surfaces of the ectoderm layer

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42
Q

what does the neural ectoderm give rise to?

A
  1. brain
  2. spinal cord
  3. all cranial and spinal MOTOR neurons
  4. retina
  5. neurohypophysis
  6. epithelium and muscles of the iris
  7. epithelium of the ciliary body of the eye
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43
Q

from which germ layer does the epithelium of the ciliary body of the eye arise from?

A

neural ectoderm

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44
Q

which germ layer gives rise to the epithelium and muscles of the iris?

A

neural ectoderm

45
Q

which germ layer gives rise to the neurohypophysis?

A

neural ectoderm

46
Q

which germ layer gives rise to the retina

A

neural ectoderm

47
Q

which germ layer gives rise to all of the MOTOR cranial and spinal neurons?

A

neural ectoderm

48
Q

which germ layer gives rise to the spinal cord and brain?

A

neural ectoderm

49
Q

which germ layer gives rise to the epidermis and its appendages?

A

surface ectoderm

50
Q

which germ layer gives rise to the epithelial lining of the cornea and conjunctiva?

A

surface ectoderm

51
Q

which germ layer gives rise to the epithelial lining of the external ear?

A

surface ectoderm

52
Q

which germ layer gives rise to the epithelial lining of the mouth and appendages?

A

surface ectoderm

53
Q

which germ layer gives rise to the proctodeal epithelium and epithelium of terminal male urethra?

A

surface ectoderm

54
Q

where are the cells that make up the mesoderm found?

A

between the ectoderm and endoderm during gastrulation

55
Q

what layers does the mesoderm differentiate into?

A

paraxial, intermediate, and lateral mesoderm

56
Q

Where is the paraxial mesoderm located?

A

caudal to the otic vesicles

57
Q

what forms the somites?

A

paraxial mesoderm segmentation

58
Q

what are somites?

A

symmetrical condensations of mesenchymal cells on both sides of the developing neural tube

59
Q

are all parts of the paraxial mesoderm segmented? If not, what area(s) are not?

A

No! The area cranial to the otic vesicles remains unsegmented

60
Q

what are the four specialized regions of the somite?

A
  1. dermotome
  2. myotome
  3. lateral somite
  4. sclerotome
61
Q

which region of the somite loses its compact organization first?

A

the sclerotome

62
Q

where do the sclerotome cells migrate toward?

A

toward the notochord and neural tube

63
Q

what do the sclerotomal cells form?

A

the vertebral column (later in development)

64
Q

what area of the somite gives rise to the dermatome, myotome, and lateral somite regions?

A

dorsal portion of the somite

65
Q

what does the dermatome give rise to?

A

dermis of the skin over the dorsal region of the trunk

66
Q

what does the lateral somite give rise to?

A

ALL voluntary striated muscles of the body wall and limbs (hypaxial muscles)

67
Q

what does the myotome give rise to?

A

segmented muscles of the axial skeletome (epaxial muscles)

68
Q

what does the unsegmented area of the paraxial mesoderm give rise to?

A

straiated muscles of the head

69
Q

What does the intermediate mesoderm give rise to

A

connective tissue and the smooth muscle cells of the gonads, urinary system, and reproductive tracts

70
Q

what layers of mesoder does the lateral mesoderm divide into?

A

somatic (parietal) and splanchnic (visceral) mesoderm

71
Q

where is somatic mesoderm found?

A

adjacent to the surface of the ectoderm

72
Q

where is splanchnic mesoderm found?

A

adjacent to the endoderm

73
Q

what makes up somatopleure?

A

surface ectoderm + somatic mesoderm

74
Q

what makes up splanchnopleure?

A

visceral mesoderm + endoderm

75
Q

which germ layer (specific) gives rise to the skeleton of the limbs?

A

somatic mesoderm

76
Q

which germ layer (specific) gives rise to the connective tissues of the limbs and trunk?

A

somatic mesoderm

77
Q

which germ layer (specific) gives rise to the dermis of the ventral body wall and limbs?

A

somatic mesoderm

78
Q

which germ layer (specific) gives rise to the connective tissues of the external genitalia?

A

somatic mesoderm

79
Q

which germ layer (specific) gives rise to the smooth muscle and connective tissue of the blood vessels?

A

somatic mesoderm

80
Q

which germ layer (specific) gives rise to the smooth muscle and connective tissues of the intestinal tract, associated glands, and abdominal mesenteries?

A

visceral mesoderm

81
Q

which germ layer (specific) gives rise to the smooth muscle and connective tissues of the respiratory tract and associated glands?

A

visceral mesoderm

82
Q

which germ layer (specific) gives rise to the smooth muscles and connective tissues of the blood vessels?

A

visceral mesoderm

83
Q

which germ layer (specific) gives rise to the cardiac muscle?

A

visceral mesoderm

84
Q

where do the first blood islands appear?

A

in the splanchnopleuric mesoderm surrounding the definitive yolk sac

85
Q

how is primitive vasculature formed?

A

the angioblasts of blood islands differentiate into the endothelial cells that fuse to form primitive vasculature filled with primitive blood (found within the yolk sac)

86
Q

where is primitive vasculature found?

A

within the yolk sac

87
Q

where are hemangioblasts found?

A

in the blood islands

88
Q

where are the definitive hematpoeitic stem cells formed?

A

within the hemangiogenic mesoderm

89
Q

what do angioblasts originating within the hemangiogenic mesoderm form?

A

endothelial lining of the vessels (including aorta and heart)

90
Q

where are primitive hematpoeitic stem cells formed?

A

within the blood islands located in the walls of the definitive yolk sac

91
Q

what do definitive hematpoeitic stem cells give rise to?

A

the embryonic liver

92
Q

what is the function of the embryonic liver? how does this change after birth?

A

it is the main site of hematopoiesis during embryonic development; after birth, hematopoiesis shifts to the bone marrow

93
Q

what does the septum transversum give rise to?

A

the mesenchyme of the developing liver, epicardium, the central portions of the diaphragm, and the esophageal mesentery

94
Q

what does the endoderm give rise to largely?

A

epithelial lining of the developing gut and its appendages (foregut, midgut, hindgut, and allantois)

95
Q

what germ layer gives rise to the epithelial lining of the gut?

A

endoderm

96
Q

what germ layer gives rise to the epithelial lining of the respiratory tract?

A

endoderm

97
Q

what germ layer gives rise to the hepatocytes of the liver?

A

endoderm

98
Q

what germ layer gives rise to the bilary tract?

A

endoderm

99
Q

what germ layer gives rise to the endocrine and exocrine cells of the pancreas?

A

endoderm

100
Q

what germ layer gives rise to the epithelium of the middle ear and auditory tube?

A

endoderm

101
Q

what germ layer gives rise to the urinary bladder

A

endoderm

102
Q

what germ layer gives rise to the epithelial lining of the vagina?

A

endoderm

103
Q

what germ layer gives rise to the epithelial lining of the urethra?

A

endoderm

104
Q

what germ layer gives rise to the secretory cells of the prostate and urethral glands?

A

endoderm

105
Q

what is primary ciliary dyskinesia (PCD)?

A

a rare autosomal recessive genetic disorder in which genetic mutations affect genes encoding various proteins comprising motile cilia; results in cilia which do not rotate, causing disruption of leftward flow of fluid in the primitive node during gastrulation, leading to disruption in the normal signaling cascade responsible for the establishment of left-right body asymmetry

106
Q

what is a common result of primary ciliary dyskinesia (PCD)?

A

sius inversus– karatagener syndrome

107
Q

what is sius inversus– karatagener syndrome?

A

a PCD where the laterality of the internal organs is the mirror-image of normal

108
Q

what are PCD symptoms?

A
  1. susceptibility to chronic recurrent respiratory infections due to absent mucus clearance from the resp. system
  2. infertility in both males and females (due to diminished sperm motility in males or defective ciliary action in the fallopian tubes in females)
109
Q

what is situs ambiguus?

A

organ placement is neither typical (situs solitus) nor totally reversed (situs inversus)

Embryology (16 decks)

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