S8600021 at 00:19, 11 August 2011

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	{{2011Lab3}}		{{2011Lab3}}
	~~===Folding===~~
	~~Endoderm, mesoderm and ectoderm layers. There are two major folding processes that take place during this time.~~
	# Folding of the whole embryonic disc ventrally, separates the endoderm to form the epithelial lining of the gut. Folding of the embryonic disc occurs ventrally around the notochord, which forms a rod-like region running rostro-caudally in the midline.
	~~# Folding of the ecoderm will form a neural groove, then closing to form a neural tube, separating the neural ectoderm from the embryo surface ectoderm.~~

	~~===Mesoderm Segmentation===~~
	~~Different regions of mesoderm form early intermediate structures.~~
	# [[S#somitogenesis\|Somitogenesis]] - when part of the mesoderm layer segments during week 3 to form balls of mesoderm called somites. The later migration of cells forms the mesoderm germ layer. An embryonic connective tissue ([[M#mesenchyme\|mesenchyme]]) which forms nearly all the connective tissues of the body (the head is different). Somitogenesis is when part of this layer segments during week 3 to form balls of mesoderm called somites.
	# [[I#intraembryonic coelom\|Intraembryonic coelom]] - Within the embryonic disc lateral plate mesoderm a space (coelom) forms, it lies within the embryo and so is called the '''intraembryonic coelom'''. This single "horseshoe-shaped" space will form the 3 major body cavities: '''pericardial''' (around the heart), '''pleural''' (around the lungs) and '''peritoneal''' (around the GIT and visceral organs).

	~~===Ectoderm Segmentation===~~
	~~The central portion of the embryonic disc forms the neural plate, the edge of this plate forms neural crest and the edge forms the epitheium of the skin. This will be covered in week 4.~~

	~~<gallery>~~
	~~File:Stage7-sem2.jpg\|Stage 7~~
	~~File:Stage8_SEM1.jpg\|Stage 8~~
	~~File:Stage9 sem4c.jpg\|Stage 9~~

	~~</gallery>~~

	==Folding==		==Folding==

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S8600021: Created page with "{{2011Lab3}} ===Folding=== Endoderm, mesoderm and ectoderm layers. There are two major folding processes that take place during this time. # Folding of the whole embryonic disc v..."

2011-08-11T00:09:44Z

Created page with "{{2011Lab3}} ===Folding=== Endoderm, mesoderm and ectoderm layers. There are two major folding processes that take place during this time. # Folding of the whole embryonic disc v..."

New page

{{2011Lab3}}
===Folding===
Endoderm, mesoderm and ectoderm layers. There are two major folding processes that take place during this time.
# Folding of the whole embryonic disc ventrally, separates the endoderm to form the epithelial lining of the gut. Folding of the embryonic disc occurs ventrally around the notochord, which forms a rod-like region running rostro-caudally in the midline.
# Folding of the ecoderm will form a neural groove, then closing to form a neural tube, separating the neural ectoderm from the embryo surface ectoderm.

===Mesoderm Segmentation===
Different regions of mesoderm form early intermediate structures.
# [[S#somitogenesis|Somitogenesis]] - when part of the mesoderm layer segments during week 3 to form balls of mesoderm called somites. The later migration of cells forms the mesoderm germ layer. An embryonic connective tissue ([[M#mesenchyme|mesenchyme]]) which forms nearly all the connective tissues of the body (the head is different). Somitogenesis is when part of this layer segments during week 3 to form balls of mesoderm called somites.
# [[I#intraembryonic coelom|Intraembryonic coelom]] - Within the embryonic disc lateral plate mesoderm a space (coelom) forms, it lies within the embryo and so is called the '''intraembryonic coelom'''. This single "horseshoe-shaped" space will form the 3 major body cavities: '''pericardial''' (around the heart), '''pleural''' (around the lungs) and '''peritoneal''' (around the GIT and visceral organs).

===Ectoderm Segmentation===
The central portion of the embryonic disc forms the neural plate, the edge of this plate forms neural crest and the edge forms the epitheium of the skin. This will be covered in week 4.

<gallery>
File:Stage7-sem2.jpg|Stage 7
File:Stage8_SEM1.jpg|Stage 8
File:Stage9 sem4c.jpg|Stage 9

</gallery>

==Folding==

There are two major folding processes that take place during this time.

# Folding of the ecoderm will form a [[N#neural groove|neural groove]], then closing to form a [[N#neural tube|neural tube]], separating the neural ectoderm from the embryo surface ectoderm.
# Folding of the whole embryonic disc ventrally, separates the endoderm to form the epithelial lining of the gut. Folding of the [[E#embryonic disc|embryonic disc]] occurs ventrally around the [[N#notochord|notochord]], which forms a rod-like region running rostro-caudally in the midline.

[[File:Amnion 001 icon.jpg|120px|link=Development Animation - Amniotic Cavity]] [[File:Week3_folding icon.jpg|120px|link=Development Animation - Week 3]]

In relation to the notochord:

* '''Laterally''' (either side of the notochord) lies mesoderm.
* '''Rostrally''' (above the notochord end) lies the [[B#buccopharyngeal membrane|buccopharyngeal membrane]], above this again is the mesoderm region forming the heart.
* '''Caudally''' (below the notochord end) lies the primitive streak (where gastrulation occurred), below this again is the [[C#cloacal membrane|cloacal membrane]].
* '''Dorsally''' (above the notochord) lies the neural tube then ectoderm.
* '''Ventrally''' (beneath the notochord) lies the mesoderm then endoderm.

The ventral endoderm (shown yellow) has grown to line a space called the yolk sac. Folding of the [[E#embryonic disc|embryonic disc]] "pinches off" part of this yolk sac forming the first primative GIT.

[[File:Endoderm_cartoon.jpg]] [[File:Endoderm_002_icon.jpg|90px|link=Development_Animation_-_Endoderm 1]]

==Mesoderm==
'''Mesoderm''' means the "middle layer" and it is from this layer that nearly all the bodies connective tissues are derived. In early mesoderm development a number of transient structures will form and then be lost as tissue structure is patterned and organised. Humans are vertebrates, with a "backbone", and the first mesoderm structure we will see form after the notochord will be '''[[S#somite|somites]]'''.

Facts: Week 4, 22 - 23 days, 2 - 3.5 mm, Somite Number 4 - 12

View: This is a dorsal view of the human embryo, the amniotic membrane has been removed. Top embryo is an early stage 10, bottom is late stage 10.

<gallery>
File:Stage10 bf4b.jpg|Early stage 10
File:Stage10 bf5b.jpg|Late stage 10
File:Stage10 bf6b.jpg|Labeled stage 10
</gallery>

<gallery>
Image:Mesoderm cartoon1.gif|trilaminar embryo
Image:Mesoderm cartoon2.gif|mesoderm regions
Image:Mesoderm cartoon3.gif|somite coelom
Image:Mesoderm cartoon4.gif|neural tube and neural crest
</gallery>

===Mesoderm Development===

# [[E#epiblast|epiblast]] -> mesoderm + [[A#axial mesoderm|axial mesoderm]] ([[N#notochord|notochord]])
# [[L#lateral plate|lateral plate]] + [[P#paraxial mesoderm|paraxial mesoderm]] + [[A#axial mesoderm|axial mesoderm]]
# [[L#lateral plate|lateral plate]] + [[I#intermediate mesoderm|intermediate mesoderm]] + [[S#somite|somites]] (body), [[P#paraxial mesoderm|paraxial mesoderm]] (head) + [[A#axial mesoderm|axial mesoderm]]
# [[S#somatic mesoderm|somatic mesoderm]] + [[I#intraembryonic coelom|intraembryonic coelom]] + [[S#splanchnic mesoderm|splanchnic mesoderm]] + [[I#intermediate mesoderm|intermediate mesoderm]] + [[S#somite|somites]] (body), [[P#paraxial mesoderm|paraxial mesoderm]] (head) + [[A#axial mesoderm|axial mesoderm]]

===Axial Mesoderm===
[[File:Sonic_hedgehog_expression.jpg|thumb|Notochord secreting sonic hedgehog]]
{|
| [[Image:Stage7 notochord.jpg|left|200px|Stage 7 notochord]]
|
The notochord
# mechanical role in embryonic disc folding
# molecular role in patterning surrounding tissues

'''Adult''' - contributes to the [[N#nucleus pulposus|nucleus pulposus]] of the intervertebral disc
|-
|}

===Paraxial Mesoderm===
{|
| [[Image:Stage7_paraxial-mesoderm.jpg|right|200px|Stage 7 paraxial mesoderm]]
|
* differentiates rostro-caudally (head to tail)
* remains unsegmented in the head region.
* segments in the body region to form pairs of somites along the length of the embryo.

'''Adult''' - contributes vertebral column (vertebra and IVD), dermis of the skin, skeletal muscle of body and limbs
|-
|}

===Intermediate Mesoderm===
{|
| [[Image:Stage7_intermediate-mesoderm.jpg|right|200px|Stage 7 intermediate mesoderm]]
|
* named by position (between paraxial and lateral plate)
* differentiates rostro-caudally (head to tail)
* forms 3 sets of "kidneys" in sequence
# [[P#pronephros|pronephros]]
# [[M#mesonephros|mesonephros]]
# [[M#metanephros|metanephros]]

'''Adult''' - [[M#metanephros|metanephros]] forms the kidney
|-
|}

===Lateral Plate Mesoderm===

{|
| [[Image:Stage7_lateral-plate.jpg|right|200px|Stage 7 lateral plate]]
|
* a "horseshoe shaped" space forms in the middle
* [[S#somatic mesoderm|somatic mesoderm]] - closest to ectoderm
* space - forms the 3 body cavities (pericardial, pleural, peritoneal)
* [[S#splanchnic mesoderm|splanchnic mesoderm]] - closest to endoderm

'''Adult''' - body and limb connective tissues, gastrointestinal tract (connective tissues, muscle, organs), heart

|-
|}

===Somite Development===

[[File:Stage11 sem100c.jpg|stage 11 Embryo]]

Somite initially forms 2 main components
* ventromedial- [[S#sclerotome|sclerotome]] forms vertebral body and intervertebral disc
* dorsolateral - [[D#dermomyotome|dermomyotome]] forms dermis and skeletal muscle

<gallery>
Image:Somite cartoon1.png|paraxial mesoderm
Image:Somite cartoon2.png|early somite
Image:Somite cartoon3.png|[[S#sclerotome|sclerotome]] and [[D#dermomyotome|dermomyotome]]
Image:Somite cartoon4.png|[[D#dermatome|dermatome]] and [[M#myotome|myotome]]
</gallery>

===Sclerotome===
{|
|-
| [[File:Vertabra 003 icon.jpg|200px|link=Development_Animation_-_Vertebra]]
|
* sclerotome from somites at the same segmental level contribute the right and left half of each vertebral and intervertebral element
* sclerotome later becomes subdivided into rostral and caudal halves (separated by [[V#von Ebner's fissure|von Ebner's fissure]])
* half somites contribute to a single vertebral level body
* other half intervertebral disc
* therefore final vertebral segmentation “shifts”
|-
|}

===Myotome===
{|
| [[File:Somite cartoon5.png|left|200px|epaxial and hypaxial muscles]]
|
Forms 2 muscle groups in body and limbs
* Body - [[E#epaxial muscle|epaxial]] and [[H#hypaxial muscle|hypaxial muscle]] groups
* Limbs - flexor and extensor muscles
|-
| [[File:Somite 001 icon.jpg|200px|link=Development_Animation_-_Somite_Musculoskeletal]]
| Development of the sclerotome and myotome components of the somite.
|-
|}

===Dermatome===
* connective tissue underlying epidermis
* begins as a dorsal thickening
* spreads throughout the body

'''Note''' - Dermatome is the term also used clinically postnatally to describe the region of skin supplied by a single spinal nerve.

==Week 2 and 3 Movies==

{| border='0px'

|-
| [[File:Week2_001 icon.jpg|90px|link=Development_Animation_-_Implantation]]
| [[File:Mesoderm 001 icon.jpg|90px|link=Development_Animation_-_Mesoderm]]
| [[File:Chorion 001 icon.jpg|90px|link=Development Animation - Chorionic Cavity]]
| [[File:Amnion 001 icon.jpg|90px|link=Development Animation - Amniotic Cavity]]
| [[File:Week3_folding icon.jpg|90px|link=Development Animation - Week 3]]
|-
| [[Development_Animation_-_Implantation|Implantation]]
| [[Development_Animation_-_Mesoderm|Mesoderm]]
| [[Development Animation - Chorionic Cavity|Chorionic Cavity]]
| [[Development Animation - Amniotic Cavity|Amniotic Cavity]]
| [[Development_Animation_-_Week 3|Week 3]]
|-
|}

===Embryo Stages and Events===
{| class="prettytable"
| width= "50px" |'''Day'''
| width= "100px" |'''Stage'''
| '''Event'''

|-
| <center>15</center>
|
|

|-
| <center>16</center>
| [[Carnegie stage 7|Stage 7]]
| [[Image:Stage7.jpg|120px|left]] '''Primitive node''' (Hensen's node, primitive knot) The small circular region located at the cranial end of the primitive streak, where gastrulation occurs, and is a controller of this process. The second role is to act as an initial generator of the left-right (L-R) body axis.

|-
| <center>17</center>
|  
|  

|-
| <center>18</center>
| [[Carnegie stage 8|Stage 8]]
| [[Image:Stage8_human.jpg|120px|left]] [[Neural System Development]] neurogenesis, neural groove and folds are first seen

|-
| <center>19</center>
|  
| [[Image:Stage8_SEM1.jpg|120px|left]]

|-
| <center>20</center>
| [[Carnegie stage 9|Stage 9]]
| [[File:Stage9_bf1c.jpg|200px|link=Carnegie stage 9]] [[Musculoskeletal System Development]] somitogenesis - first somites form and continue to be added in sequence caudally

[[Neural System Development]] - three main divisions of the brain, which are not cerebral vesicles, can be distinguished while the neural groove is still completely open

|-
| <center>21</center>
|  
| [[Cardiovascular System Development]] cardiogenesis - week 3 begins as paired heart tubes.

|}
{{2011Lab3}}

2011 Lab 3 - Week 3 - Revision history

S8600021 at 00:19, 11 August 2011

S8600021 at 00:18, 11 August 2011

S8600021: Created page with "{{2011Lab3}} ===Folding=== Endoderm, mesoderm and ectoderm layers. There are two major folding processes that take place during this time. # Folding of the whole embryonic disc v..."