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Cell Biology Block 2 > Bilaminar To Trilaminar Stages > Flashcards

Bilaminar To Trilaminar Stages Flashcards

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1
Q

Cytotrophoblast differentiates into what two layers?

A

Epiblast layer - adjacent to aminotic cavity

Hypoblast - adjacent to the blastocyst cavity

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2
Q

Amniotic cavity function?

Location?

What is the surrounding location like?

A

Amniotic sac; protection

First appears within the epiblast as a small cavity and it grows larger

Endometrial stroma- because edematous and highly vascularized

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3
Q

__ + ___ = primitive yolk sac

A

Hypoblast + Heusers membrane

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4
Q

Function of sinusoids?

When are sinusoids formed?

A

They are filled with blood; exchange of nutrients (but never exchange of blood)

When synciotrophoblasts erode maternal capillaries

~ Day 11/12

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5
Q

What is the decidual rection

A

Thickening of the endometrium around the gestational sac

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6
Q

__ + ___ = primary villi

Purpose?

A

Cellular column + syncytial covering; surface defect is closed now

Increase surface area to increase supply of nutrients, oxygen, and waste removal

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7
Q

When is the secondary yolk sac formed?

A

Day 13

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8
Q

DAY 13

Epiblasts form?

Hypoblast forms?

A

Epiblast: floor of amniotic cavity
Hypoblast: roof of secondary yolk sac

~bilaminar germ disc

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9
Q

Prechordal plate is

A

Future mouth

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10
Q

So in summary, what is developed during the second week?

A

Decidual reaction, primary yolk sac, extraembryonic coelom (cavity), secondary yolk sac, amniotic cavity, bilaminar germ disc (epiblast/hypoblast) and prechordal plate

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11
Q

Migration of cells of epiblast forms?

When does it appear? Disappear?

Significance?

A

Primitive streak

Appears on day 15-16; disappears on day 26

Helps in identifying craniocaudal axis of embryo

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12
Q

Difference between what is happening at the cranial and caudal ends during invagination

A

Cranial - differentiation

Caudal- gastrulation (primitive streak continues to form mesoderm

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13
Q
  1. Cranial end of primitive streak gives rise to?
  2. Midstreak?
  3. Caudal end?
A
  1. Paraxial mesoderm (head and somite)(somite= skeletal muscle, dermatomes and cartilage)
  2. Intermediate mesoderm (kidney and gonads)
  3. Lateral plate mesoderm (splanchnic, somatic, extra embryonic)
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14
Q

Define gastrulation

What does it begin with?

What is the gastrula?

A

Process by which bilaminar embryonic discs convert to trilaminar embryonic discs; formation of embryonic mesoderm and endoderm

Begins with formation of the primitive streak

Embryo

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15
Q
  1. What does FGF8 stand for?
  2. What is it synthesized by?
  3. FGF8 controls what two processes?
  4. FGF8 downregulates? Which normally does?
A
  1. Fibroblast growth factor 8
  2. Streak cells
  3. Cell migration and specification
  4. E-cadherin which normally binds epiblast cells together
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16
Q

How do FGF8 control cell specification into mesoderm?

A

By regulating Brachyury (T) expression

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17
Q
  1. What do cells in the germ layers give rise to?

2. What is the source of all the germ layers?

A
  1. All of the tissues and organs in the embryo

2. Epiblast

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18
Q

The prechordal plate itself forms what two things?

Later, the prechordal plate is important for what?

What later becomes of the oropharyngeal membrane?

A

Notochord and oropharyngeal membrane

Induction of the forebrain

Its layers represent the future opening of the oral cavity

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19
Q

What is the extent of the notochord

A

In midline from prechordal plate caudally to the primitive streak

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20
Q

Neural cells proliferate beginning at which end?

When the notochord gets detached from embryonic endoderm, what does endoderm form?

A

Cranial and begins to fold

Roof of yolk sac

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21
Q

Notochord is basis for developing?

Remnants of notochord is?

Notochord induces overlying ectoderm to form?

A

Axial skeleton

Nucleus pulposus

Neural plate

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22
Q

What is the cloacal membrane?

A

Covers embryonic cloaca during development of urinary and reproductive organs

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23
Q

What is allantois?

What is it involved with

A

Small diverticulum from posterior wall of yolk sac

Involved with abnormality of bladder development

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24
Q

Derivatives of ectoderm

A

CNS, PNS, sensory of ear, nose and eye, epidermis, subcutaneous glands, mammary glands, pituitary gland, and enamel of teeth

25
Q

Derivatives of endoderm

A

Liver, pancreas, parathyroid glands, thymus, thyroid, tonsils, auditory tube, and epithelial linings of GI, respiratory tract, urinary bladder/urethra

26
Q

Derivatives of mesoderm

A

Spleen, cortical portion of suprarenal gland, kidneys, gonads, blood and lymph cells, walls of heart, striated and smooth muscles, and supporting tissue (connective tissue, cartilage, bone)

27
Q

The anterior visceral endoderm expresses genes. What are the genes and what are they important for?

What do they inhibit?

A

Three transcription factors- OTX2, LIM1, and HESX1. Important for head formation; disfunction in these genes will make the body unable to develop axis’s

Inhibit nodal (a growth factor) in order to establish cranial end embryo before gastrulation

28
Q

Function of BMP4 and FGF?

A

Cause mesoderm to be ventralized which contributes to the formation of kidneys, blood and body wall mesoderm

29
Q

What blocks BMP4?

Why?

A

Genes expressed by the node; if not, all mesoderm would be ventralized (so node is considered the organizer)

30
Q
  1. What 3 things antagonize the activity of BMP4?

2. What does this cause?

A
  1. Chordin, noggin, and follistatin
  2. Causes cranial mesoderm is dorsalized into notocord, somites, and somitomeres; also important for neural induction in the cranial region
31
Q

Function of HNF-3 beta

What would happen without HNF-3beta

A

Maintains the node and later induces regional specificity in the forebrain and midbrain

Embryos fail to gastrulate properly and lack midbrain/forebrain structures

32
Q

What acts as an inhibitor of BMP4?

Contributes to regulation of?

A

Goosecoid; head development

33
Q

Brachyury encodes a transcription factor that causes?

So absence of Brachyury results in?

A

Mesoderm formation in the middle and caudal regions

Shortening of embryonic axis (caudal dysgenesis)

34
Q

When the primitive streak appears, what is secreted and what does it do?

A

FGF8 is secreted by cells in the node and primitive streak to induce expression of Nodal

35
Q

How is left and right sidedness established?

A

Nodal expression is restricted to the left side of the embryo by accumulation of serotonin (5-HT) on the left

36
Q

High concentration of 5-HT on left activates expression of? Which does what?

Name 3 genes that are involved in establishing the midline and prevent Nodal expression from crossing over to the right side

A

MAD3- restricts nodal expression to the left side of the primitive node

SHH, Lefty1 and ZIC3

37
Q

Lefty2 upregulates PITX2 which is ?

So a defect in this gene would look like what in the body?

A

A master gene that establishes left sidedness for heart, stomach, and gut primordia

For example, if the heart was on the right side instead of the left (if gene is expressed ectopically)

38
Q
  1. 5HT is a neurotransmitter that helps establish ?

2. Issues with 5HGT signaling are seen in patients that?

A
  1. Laterality (heterotaxy)

2. Take SSRIs (antidepressants)(selective serotonin reuptake inhibitors)

39
Q

Cells that migrate to the following areas become?

  1. Epiblast cells that enter through cranial region?
  2. To the lateral edges of the node?
  3. Through the midstreak
  4. Through caudal part of streak?
  5. Caudalmost part of streak?
A
  1. Notochord
  2. Paraxial mesoderm (somites and somitomeres)
  3. Intermediate mesoderm (urogenital)
  4. Lateral plate mesoderm (body wall)
  5. Extraembryonic mesoderm (primitive yolk sac, hypoblast)
40
Q

Cartilage cells are formed from?

A

Folding and invagination of surface cells

41
Q

What does it mean that the embryo develops cephalocaudally?

A

Gastrulation is continuing in caudal segments while cranial structures are differentiating

42
Q

Differentiation into blood vessels and blood cells happens during which week?

When does heart begin to beat?

A

Third week

Fourth week (primary villus to tertiary villus)

43
Q

Conjoined heads/head duplication would be caused by?

A

Overexpression of goosecoid

44
Q

What is situs inversus?

A

Condition where the organs of the thorax and abdomen are transposed or reversed

45
Q

Sacrococcygeal teratoma?

A

Remnants of primitive streak persist in the sacrococcygeal region

46
Q

Function of FGF8?

What increases the expression of FGF8?

Name another function of nodal gene

A

Expresses nodal gene from primitive node but only on the left side

Serotonin (5-HT)

It initiates and maintains the primitive streak (same as HNF 3 beta)

47
Q

So serotonin expresses FGF 8 which expresses nodal and ___ which expresses ___

A

Nodal and lefty 1 express PITX2 which is responsible for left sidedness

~absence in any of these can lead to situs inversus

48
Q

Why does serotonin not work on the right side?

A

MAD is present on the right side which destroys it. But it is not present on the left side

49
Q

What is the only gene present on the right side?

A

Snail

50
Q

What is located on the notochord that prevents left sided genes from going over to the right side

A

Shh

51
Q

Absence of HNF 3 beta will stop what two things?

A

Will prevent gastrulation and formation of forebrain/midbrain

52
Q

4 genes for head formation

A

OTX2, LIM1, HESX1, cerebrus

53
Q

What do homeobox genes do

A

Separate forebrain/midbrain/hindbrain

54
Q

Main function of BMP4

Same family as ?

A

Ventralization of mesoderm

Nodal gene

55
Q

Why does BMP4 need to be controlled

What 3 genes control BMP4

A

Or else it will ventralize all mesoderm

Chordin, noggin, and follistatin

56
Q

What activates chordin?

A

Goosecoid (important for head development)

57
Q

What is brachyury gene responsible for?

What is it under the control of?

Absence of brachyury leads to

A

Dorsalization of middle and caudal mesoderm

FGF8

Caudal dysgenesis (lower part of spine is abnormal)

58
Q

If primitive streak does not close what can happen

A

Sacrococcygeal tetratoma

59
Q

Primitive streak grows in what direction

A

Cranial to caudal

Cell Biology Block 2 (10 decks)

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