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Embryology Term 1 > Intro Embryology > Flashcards

Intro Embryology Flashcards

1
Q

What signifies the beginning of Gastrulation?

A

The formation of the primitive streak

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2
Q

The primitive streak becomes which end of the embryo?

A

The caudal end

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3
Q

What happens during Gastrulation?

A
  • Formation of the trilaminar disc
  • Cells from epiblast migrate towards the primitive streak, break off, and dive under it, ending up between the epiblast and hypoblast
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4
Q

What do streak cells produce that downregulates E-cadherin, allowing the epiblast cells to migrate?

A

FGF8

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5
Q

What two layers do the invaginated cells become during gastrulation?

A

Endoderm and mesoderm

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6
Q

What is the source of all three germ layers (endoderm, mesoderm, ectoderm)?

A

The Epiblast

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7
Q

What becomes of the epiblast cells that invaginate at the primitive node and proceed directly rostrally? What do we call these cells?

A

They form the notocord. Called Prenotochordal cells.

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8
Q

What two layers make up the notochordal plate?

A

Ectoderm and mesoderm

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9
Q

When does the notochordal plate become the definitive notochord?

A

When the hypoblast is replaced by endodermal cells moving in from the primitive streak

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10
Q

What becomes of the notochord in adults?

A
  • disappears
  • probably serves as scaffolding for Formation of vertebrae
  • Nucleus pulposus
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11
Q

What forms if the connection of the endoderm to the ectoderm at the notochordal plate does not separate and form mesoderm between?

A

a neurenteric canal

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12
Q

What induces neurulation?

A

Appearance of the notochord

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13
Q

What is the neural plate?

A
  • forms at beginning of neurulation

- a thickening of the ectoderm in response to signals form the notochord

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14
Q

What are the cells of the neural plate called?

A

the neuroectoderm

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15
Q

When do somites appear?

A

20 days

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16
Q

What are neural folds?

A

-elevated edges of neural plate, which move towards the midline to fuse, creating the neural tube

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17
Q

When do the neural folds form?

A

Week 3

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18
Q

What is the depression of the mid region between the neural folds called?

A

the neural groove

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19
Q

How is the neural tube created?

A

it is formed by the fusion of the edges of the neural folds

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20
Q

Where does folding of the neural tube begin?

A

in the 5th somite

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21
Q

When does the caudal neuropore of the neural tube finish forming?

A

e27

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22
Q

What becomes the forebrain and midbrain?

A

The cranial neural plate

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23
Q

When does the cranial neuropore close?

A

e25

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24
Q

What two conditions are results of failure of the caudal neuropore to close?

A
  • Spina bifida

- Spina bifida occulta

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25
What two conditions are results of failure of the cranial neuropore to close?
- Anencephaly | - Encephalocele
26
Where does the neural crest come from?
The crests of the neural folds of the ectoderm
27
What occurs during week 1 of early development?
- Ovulation - Fertilization - Cleavage - Morula, Blastocyst - Implantation
28
What anatomical structure sweeps the female oocyte into the fallopian tube?
Fimbriae
29
Where does fertilization occur in humans?
The ampullary region of the fallopian tube
30
What are the three steps of fertilization?
1. Capacitation2. Acrosome reaction3. Fusion of sperm and oocyte membranes
31
What is capacitation?
-Sperm conditioning-allows Sperm to enter zona radiata
32
What is the acrosome reaction?
-a protein reaction induced after Sperm binds to the zona pellucida
33
How can STD's influence the successful migration of the fertilized egg?
- Purulent infection in the fallopian tubes | - can cause narrowing or occlusion of the fallopian tube
34
After how many days post fertilization does the morula form?
3 days
35
What do the inner cells of the morula form?
The embryo
36
What to the outer cells of the morula form?
The trophoblast
37
When is the embryo considered a blastocyst?
When a cavity forms
38
What does it mean for the blastocyst to 'hatch'?
The blastocyst is surrounded by zona pellucida. It hatches from the zona pellucida so that it may impant into the endometrium
39
How many days after fertilization does it take for the blastocyst to form?
5 days
40
What causes placenta previa?
Implantation of the blastocyst near the cervix
41
What two layers does the trophoblast differentiate into?
1. Cytotrophoblast (Inner)2. Syncytiotrophoblast (Outer)
42
What does the Syncytiotrophoblast do?
- Makes HCG | - Erodes into maternal endometrium
43
What does Human Chorionic Gonadotropin (HGC) do?
-Its a glycoprotein that maintains the corpus luteum to maintain progesterone production
44
What is a hydratiform mole?
A benign abnormal growth of the trophoblast
45
What two layers does the embryoblast differentiate into?
1. Hypoblast2. Epiblast
46
What two cavities are formed in week 2 of embryonic development?
1. Chorionic Cavity2. Amniotic Cavity
47
What two layers are formed by the extra-embryonic mesoderm?
1. Extra-embryonic somatopleuric mesoderm2. Extra-embryonic splanchnopleuric mesoderm
48
Which extra-embryonic mesoderm is next to the yolk sac?
Splanchopleuric
49
What cavity is contained between the splanchopleuric and somatopleuric mesoderm?
Chorionic cavity
50
What produces cells that migrate along the inside of the exocoelomic membrane and create the secondary/definitive yolk sac?
The Hypoblast
51
What embryonic structure gives rise to the umbilical cord, and from what tissue does this structure derive?
The connecting stalk, from the extraembryonic mesoderm
52
What does the TGF-Beta family do in gastrulation?
Induces formation of the primitive streak
53
What initially secretes Shh in gastrulation? Then what secretes it?
The primitive noteThenNotochord and floorplate of neural tube
54
What does Shh induce?
- formation of the neural plate | - Gradient is a major factor in differentiation of several types of cells
55
What secretes BMP*4?
The roof plate of the neural tube
56
What results from BMP*4 expression?
Ventralization of the mesoderm
57
What transcription factors cause the left sided differentiation of cells?
- Shh - Nodal - Lefty
58
What activates nodal and lefty expression?
-shh
59
How do cells know which side is left?
cilia in nodal cells beat right to left, creating a flow of amniotic fluid
60
What transcription factor is expressed on the right side of the developing embryo?
Snail
61
What is situs inversus?
Embryo develops as a mirror image of normal-No symptoms in complete cases
62
What is a teratoma?
a true tumor composed of multiple tissues foreign to the part where it arises, contains all three germ lines
63
What is a malignant sacrococcygeal Teratoma called?
Yolk sac tumor
64
What gene regulates dorsal mesoderm formation in the mid and caudal embryo?
Brachyury (T) gene
65
What is the result of deficiency in Brachyury gene?
Caudal dysgenesis or Caudal regression
66
What is imperforate anus?
a common and less severe form of caudal regression
67
What is the paraxial mesoderm?
The lateral edge of the primitive node and cranial end of the primitive streak
68
What does the paraxial mesoderm form?
Somitomeres
69
What are somitomeres?
- rounded, whorl-like structures that are paired | - form somites
70
What embryonic day are somites clear?
E20
71
How many pairs of somites are added per day?
3
72
What tissues develop from the Mesoderm?
- Cartilage, bone, muscle - Blood & lymph - Walls of Blood vessels and heart-Genitourinary system-Spleen
73
What happens to somites in the 4th embryonic week?
- Their ventral and medial Walls loosen to become a sclerotome - dorsal wall forms dermamyotome
74
What does the sclerotome become?
bones
75
What does the dermamyotome become?
Muscle and Dermis (Not epidermis)
76
What happens to the dorsomedial portion of the dermamyotome?
it migrates inside to become back muscles
77
What happens to the dorsolateral portion of the dermamyotome?
migrates to become the precursor of limb and body wall musculature
78
From where does the dermis arise?
The paraxial mesoderm
79
What does the intermediate mesoderm become?
Urogenital structures
80
What are the two layers that the lateral plate mesoderm becomes?
1) Somatic/parietal mesoderm2) Splanchnic/visceral mesoderm
81
What cavity is formed by the two layers of the lateral plate mesoderm?
Intraembryonic Body cavity
82
What becomes of the visceral layer of the lateral plate mesoderm?
it will cover organs
83
What becomes of the parietal layer of the lateral plate mesoderm?
it will line the intraembryonic cavity, forming the lateral and ventral body wall
84
What is the main organ derived from the endoderm?
The GI tract
85
How much should a fetus weigh after 40 weeks of gestation?
3 kg
86
What are the functions of the placenta?
- Exchange of gases - Exchange of nutrients and electrolytes - Transmission of maternal antibodies - Hormone production
87
What three things are present in the primitive umbilical ring?
1. Connecting stalk2. Yolk "stalk" (Connection w/ yolk sac)3. Connection to chorionic cavity

Embryology Term 1 (4 decks)

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