Week 2 Embryology 2 Flashcards

1
Q

2 outside layers in the trophoblast during Implantation

A

Cytotrophoblast

syncytiotrophoblast

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2
Q

2 layers in the embryo during implantation

A

Epiblast

Hypoblast

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3
Q

2nd week

A

Implantation
Formation of 2 cavities above and below the bilaminar disc
2 layers in the embryo (epiblast, hypoblast)
2 layers in trophoblast (syncytiotrophoblast, cytotrophoblast

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4
Q

3rd week

A
Extraembryonic Mesoderm (XE)
3rd week, from 2 layers to 3 layers
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5
Q

Extraembryonic (XE) Mesoderm

A

New layer of cells
Derived from epiblast (& yolk sac)
Found between inner lining of cytotrophoblast and yolk sac
Continue to separate embryo from surrounding uterine tissue
New layer will be important in forming the materno-fetal interface (placenta)

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6
Q

Coelom

A

Larger cavity

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7
Q

This gives mechanical and trophic support

A

XE Mesoderm

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8
Q

“Somatic”

A

Body wall, skeletal muscle

-green part of XE mesoderm on drawings

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9
Q

Chorion

A

Fetal contribution to the placenta

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10
Q

Transvaginal Ultrasound

A

Measure diameter of chorionic sac

*beginning of 3rd week can see this on u/s

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11
Q

Time frame early on that you are not susceptible to teratogens

A

Weeks 1 and 2.

dividing zygote, implantation and gastrulation

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12
Q

Time frame for major morphological abnormalities

A

Weeks 3-8

Embryonic Period

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13
Q

Time frame for functional defects and minor morphological abnormalities

A

Weeks 9-38

38 weeks is full term

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14
Q

Embryonic Period

A

All major body systems develop
2D disk to 3D cylinder (take edges of disk and fold to get cylinder)
Folding of the embryo
Craniocaudal folding - CNS (head and tail end fold together)
Lateral folding - amnion/body wall

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15
Q

Cranio

A

head

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16
Q

Caudal

A

tail

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17
Q

Gastrulation

A

Beginning of morphogenesis (development of body form)
Forms a trilaminar embryonic disk
Process that establishes the 3 primary germ layers
These 3 layers give rise to all the tissues and organs of the adult

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18
Q

Morphogenesis

A

Development of body form

Begins to occur during gastrulation

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19
Q

3 primary Germ Layers

A
  1. Endoderm
  2. Mesoderm
  3. Ectoderm
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20
Q

Process that establishes the 3 primary germ layers

A

Gastrulation

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21
Q

Primitive Streak

A

Forms about day 13 or 14
Tail - Caudal end
Narrow line of cells appears on surface of embryonic disk

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22
Q

This is future axis of embryo

A

Primitive Streak

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23
Q

This marks beginning of gastrulation

A

Primitive streak

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24
Q

Buccopharyngeal membrane

A

aka Oropharyngeal membrane

Marks the head end and where mouth will be

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25
Q

The Streak organizes embryo

A

along a craniocaudal axis

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26
Q

Dorsal part of embryo

A

Epiblast

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27
Q

Ventral part of embryo

A

Hypoblast

frontal

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28
Q

Cloacal membrane

A

In embryo

anus

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29
Q

Another possible way to get conjoined twins

A

Two primitive streaks

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30
Q

Elongation of Primitive Streak

A

Forms from a proliferation of epiblast cells
Cells migrate to center of embryo
Streak elongates with cells added to the caudal end

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31
Q

Primitive node and pit

A

Towards the middle of the cell

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32
Q

Primitive streak

A

(groove)

Functions like a sieve, allows them to get underneath

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33
Q

Heart in embryo

A

Starts as a hat, above brain, during folding, moves to correct place

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34
Q

What becomes mesoderm and endoderm

A

Epiblast

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35
Q

Amniotic endoderm and Primitive Ectoderm comes from

A

Epiblast NOT hyphoblast

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36
Q

If primitive streak doesn’t go away by third week…

A

Teratoma
Can have teeth, hair, bone, etc.
Since it comes from all 3 germ layers, can contain anything. Removed after birth, can present some issues Ex. can put strain on heart

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37
Q

Sacrococcygeal Teratoma

A
Remnants of primitive streak
Derivatives of all 3 germ layers
'Common' tumor type in newborn (1:35000)
Bizarre mixture of tissue types (all layers)
Like spina bifida can do fetal surgery
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38
Q

Caudal dysplasia - aka

A

Germ layer problem. Usually fetus is not viable
*Mesoderm problem
Total or parial failure of development of the lower vertebrae including sacrum.
Also known as sacral agenesis, sacral regression, caudal aplasia, caudal regression sequence, sirenomelia - once thought to be all of these.

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39
Q

Caudal dysplasia

A

Caused by abnormal gastrulation
Mesoderm migration is disturbed
In about 16% of cases (relative risk for a child of a diabetic mother: about 1%)

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40
Q

4 classifications of caudal dysgenesis

A
  1. complete absence of the sacrum and lower vertebrae, multiple congenital anomalies and association with maternal diabetes
  2. agenesis of distal sacral or coccygeal segments
  3. hemisacral dysgenesis with presacral teratoma
  4. hemisacral dysgenesis with anterior meningocele
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41
Q

Meningocele

A

Herniation of spinal cord cover

42
Q

Notochord

A

replaces the primitive streak

Forms in middle layer - Mesoderm

43
Q

Notochord Formation

A

Migrating cells also form a median column of cells, posterior to head region
Originally called the notochordal process
Will become the notochord
Also called the chordamesoderm (British)

44
Q

Functions of the Notochord

A

Structure - acts as a rigid axis around which the embryo develops
Skeletal - foundation upon which the vertebral column will form
Forms part of the intervetrebal discs
Induction - will bring about formation of the neural tube (future nervous system)

45
Q

Adult part of the Notochord

A

The disk part of the spinal cord

46
Q

Chordoma

A

Primary malignant bone cancer, usually at base of skull or in sacrum
Develops from remnants of embryonic notochord
Avg age of diagnosis - 49 for skull, 69 for spine
Avg survival - 7 years
Affects men more frequently than women

47
Q

Clival Chordoma

A

Benign but invasive skull base tumors arise from bone and often grow through dura. Most can be debulked through an endonasal approach. Because of their invasivness, many require radiotherapy to control further growth.

48
Q

Clival

A

Brain

49
Q

Primary inductor in embryo

A

Notochord

50
Q

Notochord induces

A

Overlying ectoderm to form neural plate –> neural tube.

Tells ectoderm to become the nervous system

51
Q

Induction of the Nervous System

A

Specific signaling molecules are produced by cells of the notochord that elicit a response in the overlying ectoderm to begin the process of neurulation

52
Q

Induction

A

Organisms are formed by interactions between cells and tissues
When one group of cells/tissues causes another set of cells/tissues to change their fate is called this.

53
Q

When one group of cells/tissues causes another set of cells/tissues to change their fate is called

A

Induction

54
Q

Inducer

A

Group of cells or tissues that send signal in induction

55
Q

Responder

A

Group of cells or tissues that receive signal in induction

56
Q

Cross - talk

A

During Induction when the Inducer and Responder ‘talk’ tack and forth

57
Q

Cell to Cell Signaling

A

Most signaling molecules are proteins synthesized by one cell that diffuses over short distances to contact other cells

Growth and differentiation factors (GDFs)

58
Q

GDFs

A

Growth and Differentiation Factors

59
Q

Neurulation

A

Specific molecules are produced by cells of the notochord that elicit a response in the overlying extoderm to begin the process of neurulation

Separates the ectoderm into two parts

  • Epithelial (surface) ectoderm
  • Neural ectoderm
60
Q

Simple definition of neurulation

A

formation of the neural tube

61
Q

2 parts the ectoderm will be separated into by Neurulation

A
  • Epithelial (surface) ectoderm

* Neural ectoderm

62
Q

4 Steps to Neurulation

A
  1. Thickening of the neural plate
  2. Formation of the neural folds and groove
  3. Convergence of the lateral margins of the neural plate - Neural crest begins to ‘pinch off’ of the neural folds and form other structures
  4. Fusion of the neural plate to form the neural plate
63
Q

Neural Crest

A

Migrates extensively to form a variety of structures throughout the body

64
Q

Epithelial Ectoderm

A

(Surface)
Epidermis, hair, nails, tooth enamel, cutaneous glands (sweat, oil, ceruminous), mammary glands, anterior pituitary, lens of eye, inner ear, sensory nasal epithelium

65
Q

Neuroectoderm

A

Derived from neural plate and neural folds

66
Q

Neuroectoderm Derivatives - Neural tube

A

CNS (brian, spinal cord), retina, pineal body, posterior pituatary

67
Q

Neuroectoderm Derivatives - Neural crest

A

Sensory ganglia and nerves of PNS, Schwann cells, adrenal medulla, pigment cells, pharyngeal arch cartilages. Components of the eye, skull, teeth and skin.
**Some argue this is the fourth germ layer

68
Q

Some argue this is the 4th germ layer

A

Neuroectoderm Neural crest

69
Q

Ectodermal Dysplasia (ED) syndromes

A

Problems with surface ectoderm
Group of about 150 heritable disorders that affect the ectoderm, outer layer of tissue in a developing baby.
When child has at least two types of abnormal extodermal features, the child is identified as being affected by an ‘ED’ syndrome

70
Q

Pigmentary Disorders

A

Neural crest disorders
Diseases of melanocyte development, function and survival
Ex. Piebaldism, Albinism, Vitiligo

71
Q

Piebaldism

A
Pigmentary Disorder (from neural crest issue)
characterized by a congenital white forelock and multiple symmetrical hypopigmented and depigmented areas
72
Q

Albinism

A

Most are autosomal recessive
Global reduction or absence of pigment in skin, hiar and eyes or eyes only (ocular)
Eye conditions often include: nystagmus, strabismus, light sensitivity due to lack of pigment

73
Q

Ocular Albinism

A

Affects only eyes

74
Q

Oculocutaneous Albinism

A

Affects skin, hair and eye

75
Q

Why does albinism have problems with eyes?

A

Need melanin for muscle, so this causes problem

Ex. nystagmus, strabismus

76
Q

Vitiligo

A

Pigmentary Disorder
Loss of melanocytes
Autoimmune disorder
Other support for autosomal dominant iheritance with variable expression and incomplete penetrance

77
Q

Forebrain

A

Prosencephalon

78
Q

Midbrain

A

Mesencephalon

79
Q

Hindbrain

A

Rhombencephalon

80
Q

Metencephalon

A

Pons

81
Q

Myelencephalon

A

Medulla

82
Q

Pons

A

Cerebellum

83
Q

Cerebellum

A

Important for position and movement in space

84
Q

Medulla Oblongata

A

Autonomic control of nervous system and heart beating

85
Q

Spinal Dysraphism

A

(NTDs)

When there is a connection from neural and ectoderm

86
Q

Closure of Neuropores

A

Cranial day 24

Caudal day 27

87
Q

Anencephaly

A

aka Craniorachischisis

Cranial doesn’t close, can be born alive and live for awhile

88
Q

Iniencephaly

A

Folding of head goes wrong so spine is hyperextended
Extreme retroflexion of head, short/absent neck
Facial skin connected directly to the skin of the chest
Do not survive.

89
Q

Encephalocele

A
Bones don't fuse so that some of the contents can herniate
Cranium bifida
Most common in occipital region
*Meningoenephalocele
*meningohydroencephalocele
90
Q

Meningoencephalocele

A

herniation contains meninges and brain

91
Q

Meningohydroencephalocele

A

Herniation contains meninges, brain and ventricular system

92
Q

Arnold-Chiari Malformation

A

Herniation of cerebellar vermis or tonsils through the foramen magnum blocking the flow of CSF
*can be associated with neural tube defect, isn’t one on it’s own

93
Q

Spina Bifida

A

Failure of closure of Caudal Neuropore

94
Q

4 Types of Caudal Neuropore

A
  1. Spina Bifida
  2. S.B. Occulta
  3. S.B. Meningocele
  4. S.B. Meningomyelocele
95
Q

Spina Bifida

A

Failure of neural arches to form
Spectrum disorder. The lower the defect, the better the outcome
Usually: urinary/bowel dysfunction, range of locomotor difficulties and reduced sensation

96
Q

Spina bifida occulta

A

Arches absent, tube is normal

97
Q

Spina bifida meningocele

A

Dura and arachnoid also protrude

98
Q

Spina bifida meningomyelocele

A

Neural tissue also protrudes

99
Q

Dietary and Genetic Affects on NTSs

A

Daily intake of 0.4mg of folic acid (folate) will decrease 70% of neural tube defects

100
Q

Alpha-fetoprotein Testing

A

AFP
Is produced in the fetal liver. In a fetus with open NTD, AFP leaks across the defect into the amniotic fluid and across placenta into the maternal serum.