Talk:2010 BGD Practical 6 - Week 3: Difference between revisions

Latest revision as of 00:01, 10 October 2010

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).

The mesoderm adjacennt to the endoderm is now called the splanchnic mesoderm which forms the connective tissue and muscular wall of the GIT.

Note intraembryonic coelomic cavity communicates with extraembryonic coelom (space outside the embryo) through portals (holes) initially on lateral margin of embryonic disc.

Week 3

Week 3 - Embryonic disc

Week 3 - Carnegie stage 7 | 8 | 9

Gastrulation

Trilaminar embryo

Somitogenesis

Neurogenesis

Week 3

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 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.

Early stage 10
Late stage 10
Labeled stage 10

trilaminar embryo
mesoderm regions
somite coelom
neural tube and neural crest

Mesoderm organization: lateral plate - intermediate mesoderm - paraxial mesoderm - axial mesoderm - paraxial mesoderm - intermediate mesoderm - lateral plate

Stage 7 paraxial mesoderm
Stage 7 intermediate mesoderm
Stage 7 lateral plate

Axial Mesoderm

notochord

mechanical role in embryonic disc folding
molecular role in patterning surrounding tissues

Stage 7 embryonic disc
Stage 7 primitive-streak-node
Stage 7 cloacal-oral-membranes
Stage 7 notochord

Adult - contributes to the nucleus pulposis of the intervertebral disc

Paraxial Mesoderm

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

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

pronephros
mesonephros
metanephros

Adult - metanephros forms the kidney

Lateral Plate Mesoderm

Stage 7 lateral plate

a "horseshoe shaped" space forms in the middle
somatic mesoderm - closest to ectoderm
space - forms the 3 body cavities (pericardial, pleural, peritoneal)
splanchnic mesoderm - closest to endoderm

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

Somite Development

Somite initially forms 2 main components

ventromedial- sclerotome forms vertebral body and intervertebral disc
dorsolateral - dermomyotome forms dermis and skeletal muscle

paraxial mesoderm
early somite
sclerotome and dermomyotome
dermatome and myotome
epaxial and hypaxial muscles

Sclerotome

sclerotome later becomes subdivided
- rostral and caudal halves separated laterally by von Ebner's fissure
half somites contribute to a single vertebral level body
other half intervertebral disc
therefore final vertebral segmentation “shifts”

Myotome

Body - epaxial and hypaxial muscles
Limbs - flexor and extensor muscles

Dermatome

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

@@ Line 1: / Line 1: @@
+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).
+The mesoderm adjacennt to the endoderm is now called the '''splanchnic mesoderm''' which forms the connective tissue and muscular wall of the GIT.
+Note intraembryonic coelomic cavity communicates with extraembryonic coelom (space outside the embryo) through portals (holes) initially on lateral margin of embryonic disc.
 == Week 3 ==
 [[Image:Stage7 features.jpg|thumb|Week 3 - Embryonic disc]]
@@ Line 10: / Line 20: @@
 * [[Neurogenesis]]
+==Week 3==
+'''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 organization:''' lateral plate - intermediate mesoderm - paraxial mesoderm - axial mesoderm - paraxial mesoderm - intermediate mesoderm - lateral plate
+<gallery>
+Image:Stage7_paraxial-mesoderm.jpg|Stage 7 paraxial mesoderm
+Image:Stage7_intermediate-mesoderm.jpg|Stage 7 intermediate mesoderm
+Image:Stage7_lateral-plate.jpg|Stage 7 lateral plate
+</gallery>
+===Axial Mesoderm===
+* notochord
+# mechanical role in embryonic disc folding
+# molecular role in patterning surrounding tissues
+<gallery>
+Image:Stage7_800x700px.jpg|Stage 7 embryonic disc
+Image:Stage7_primitive-streak-node.jpg|Stage 7 primitive-streak-node
+Image:Stage7_cloacal-oral-membranes.jpg|Stage 7 cloacal-oral-membranes
+Image:Stage7 notochord.jpg|Stage 7 notochord
+</gallery>
+'''Adult''' - contributes to the nucleus pulposis of the intervertebral disc
+===Paraxial Mesoderm===
+[[Image:Stage7_paraxial-mesoderm.jpg|thumb|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|thumb|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
+# pronephros
+# mesonephros
+# metanephros
+'''Adult''' - metanephros forms the kidney
+===Lateral Plate Mesoderm===
+[[Image:Stage7_lateral-plate.jpg|thumb|Stage 7 lateral plate]]
+* a "horseshoe shaped" space forms in the middle
+* somatic mesoderm - closest to ectoderm
+* space - forms the 3 body cavities (pericardial, pleural, peritoneal)
+* splanchnic mesoderm - closest to endoderm
+'''Adult''' - body 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- sclerotome forms vertebral body and intervertebral disc
+* dorsolateral - dermomyotome forms dermis and skeletal muscle
+<gallery>
+Image:Somite cartoon1.png|paraxial mesoderm
+Image:Somite cartoon2.png|early somite
+Image:Somite cartoon3.png|sclerotome and dermomyotome
+Image:Somite cartoon4.png|dermatome and myotome
+Image:Somite cartoon5.png|epaxial and hypaxial muscles
+</gallery>
+===Sclerotome===
+* sclerotome later becomes subdivided
+** rostral and caudal halves separated laterally by von Ebner's fissure
+* half somites contribute to a single vertebral level body
+* other half intervertebral disc
+* therefore final vertebral segmentation “shifts”
+===Myotome===
+* Body - epaxial and hypaxial muscles
+* Limbs - flexor and extensor muscles
+===Dermatome===
+* connective tissue underlying epidermis
+* begins as a dorsal thickening
+* spreads throughout the body
+[[File:Mesoderm 001 icon.jpg|160px|link=Development_Animation_-_Mesoderm]] [[File:Somite 001 icon.jpg|160px|link=Development_Animation_-_Somite_Musculoskeletal]]  [[File:Vertabra 003 icon.jpg|160px|link=Development_Animation_-_Vertebra]]