Lecture - Mesoderm Development: Difference between revisions
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{{Carnegie stages}} | {{Carnegie stages}} | ||
=== Somitogenesis== | |||
[[Somitogenesis]] | |||
{| border="0" | |||
|-bgcolor="CEDFF2" | |||
| width="40" |<center>'''Stage'''</center> | |||
| width="65" |<center>'''Days''' (approx)</center> | |||
| width="101" |<center>'''Size'''</center> <center>(mm)</center> | |||
| width="100" |<center>'''Images<br />'''(not to scale)</center> | |||
| width="400" |<center>'''Events'''</center> | |||
|- | |||
| width="40" |<center>[[Carnegie_stage_7|'''7''']]</center> | |||
| width="65" |<center> 15 - 17 </center><center>([[week 3|'''week 3''']])</center> | |||
| width="101" |<center> 0.4</center> | |||
| width="100" bgcolor="#000000" |<center>[[File:Stage7_features.jpg|60px|Link=Carnegie_stage_7]]</center> | |||
| width="400" | [[gastrulation]], [[notochord|notochordal process]] | |||
|-bgcolor="F5FAFF" | |||
| width="40" |<center>[[Carnegie_stage_8|'''8''']]</center> | |||
| width="65" |<center> 17 - 19</center> | |||
| width="101" |<center> 1.0 - 1.5</center> | |||
| width="100" bgcolor="#000000" |<center>[[File:Stage8_bf4.jpg|60px|Link=Carnegie_stage_8]]</center> | |||
| width="400" |primitive pit, notochordal canal | |||
|- | |||
| width="40" |<center>[[Carnegie_stage_9|'''9''']]</center> | |||
| width="65" |<center> 19 - 21</center> | |||
| width="101" |<center> 1.5 - 2.5</center> | |||
| width="100" bgcolor="#000000" |<center>[[File:Stage9_dorsal.jpg|60px|Link=Carnegie_stage_9]]</center> | |||
| width="400" |'''Somite Number 1 - 3''' neural folds, cardiac primordium, head fold | |||
|-bgcolor="F5FAFF" | |||
| width="40" |<center>[[Carnegie_stage_10|'''10''']]</center> | |||
| width="65" |<center> 22 - 23 </center><center>([[week 4|'''week 4''']])</center> | |||
| width="101" |<center> 2 - 3.5</center> | |||
| width="100" bgcolor="#000000" |<center>[[File:Stage10_bf4b.jpg|60px|Link=Carnegie_stage_10]]</center> | |||
| width="400" |'''Somite Number 4 - 12''' neural fold fuses | |||
|- | |||
| width="40" |<center>[[Carnegie_stage_11|'''11''']]</center> | |||
| width="65" |<center> 23 - 26</center> | |||
| width="101" |<center> 2.5 - 4.5</center> | |||
| width="100" bgcolor="#000000" |<center>[[File:Stage11 bf7b.jpg|60px|Link=Carnegie_stage_11]]</center> | |||
| width="400" |'''Somite Number 13 - 20''' rostral neuropore closes | |||
|-bgcolor="F5FAFF" | |||
| width="40" |<center>[[Carnegie_stage_12|'''12''']]</center> | |||
| width="65" |<center> 26 - 30</center> | |||
| width="101" |<center> 3 - 5</center> | |||
| width="100" bgcolor="#000000" |<center>[[File:Stage12 bf5b.jpg|60px|Link=Carnegie_stage_12]]</center> | |||
| width="400" |'''Somite Number 21 - 29''' caudal neuropore closes | |||
|- | |||
| width="40" |<center>[[Carnegie_stage_13|'''13''']]</center> | |||
| width="65" |<center> 28 - 32 </center>([[week 5|'''week 5''']]) | |||
| width="101" |<center> 4 - 6</center> | |||
| width="100" bgcolor="#000000" |<center>[[File:Stage13 bf2c.jpg|60px|Link=Carnegie_stage_13]]</center> | |||
| width="400" |'''Somite Number 30''' leg buds, lens placode, pharyngeal arches | |||
|- bgcolor="#CCFFCC" | |||
| colspan="5" width="376" height="18" |<center> [[Carnegie_stage_13_-_serial_sections|Stage 13/14 shown in serial embryo sections]] series of Embryology Program</center> | |||
|} | |||
{{2011ANAT2341}} | {{2011ANAT2341}} |
Revision as of 16:35, 8 August 2011
Objectives
- Understanding of events during the third week of development
- Understanding the process of early somite development
- Understanding the process of body cavity formation
- Brief understanding of the future fate of mesoderm components
- Brief understanding of early heart formation
Notochord (Axial mesoderm)
Mesoderm
- generated from epiblast cells migrating through the primitive streak
- epiblast cells expressing fibroblast growth factor (FGF2)
- forms a layer between ectoderm and endoderm with notochord down midline
- present before neural tube formation
- divides initially into 3 components
- Paraxial mesoderm - somites - musculoskeletal structures
- Intermediate mesoderm - kidney
- Lateral plate mesoderm - body wall structures
Mesoderm Development
The four images below beginning at week 3 show cross-sections of the trilaminar embryo and the sequence of mesoderm development.
Mesenchyme
- Embryonic connective tissue, describes the cell morphology (Histology is not epithelial organization)
- epithelial to mesenchymal transitions
- mesenchymal to epithelial transitions
Paraxial Mesoderm
Somite Formation
Early somite induction signals in the mouse |
- ball forms through epithelialization and interactions (cell-cell, cell-extracellular matrix, ECM) fibronectin, laminin
- has 2 populations of cells - peripheral columnar and central mesenchymal
- early somite has cavity- somitocoel, cavity is lost during growth
- somite enclosed by ECM connected to nearby tissues
Somite Specification
- Different segmental level somites have to generate different segmental body structures?
- somite has to form different tissues?
- Somite Differentiation
- Compartmentalization accompanied by altered patterns of expression of Pax genes within the somite
Somite initially forms 2 main components
- ventromedial- sclerotome forms vertebral body and intervertebral disc
- dorsolateral - dermomyotome forms dermis and skeletal muscle
Somite Axial Specification
- rostro-caudal axis appears regulated by Pax/Hox expression, family of DNA binding transcription factors
- Movie: Somite Development
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"
Dermomyotome
- later divides into dorsal dermatome and ventral myotome
- (MH - This topic of muscle and skeleton development will be covered in 2 later lectures Musculoskeletal Development and Limb Development)
- lateral myotome edge migrates at level of limbs
- upper limb first then lower
- mixes with somatic mesoderm
- dermotome continues to contribute cells to myotome
Myotome
- Myotome component of Somite
- epaxial myotome (dorsomedial quarter) forms the dorsal epimere (erector spinae)
- hypaxial myotome (dorsolateral quarter) forms the ventral hypomere, 3 primary muscle layers which are different at neck, thorax and abdomen
Muscle
- Myoblast determining transcription factor MyoD is first expressed in the dorsomedial quadrant of the still epithelial somite whose cells are not yet definitely committed
- basic Helix Loop Helix
- from myotome
Muscle Development Abnormalities
- Duchenne Muscular Dystrophy
- Embryonic muscle development normal and changes occur postnatally
- X-linked dystrophy, large gene encoding cytoskeletal protein - Dystrophin
- progressive wasting of muscle, die late teens
- Becker Muscular Dystrophy, milder form, adult onset
Axial Segmentation - Somite Specification Signals
Intermediate Mesoderm
|
Lateral Plate Development
- lying at the surrounding edge of he embryonic disc
- a cavity begins in this week to form within the mesoderm itself
Intraembryonic Coelom
- small spaces (vacuoles) begin appearing within the lateral plate mesoderm
- small spaces enlarge forming a single cavity within the lateral plate mesoderm
- divides lateral plate mesoderm into 2 parts at about day 18-19
- this cavity is called the Intraembryonic Coelom
- coelom is a general term for a "cavity" and can lie within the embryo (intraembryonic) and outside the embryo (extraembryonic)
- later anatomical spaces within the embryo and fetus can also be described as coeloms
- when the embryonic disc folds the intraembryonic coelom will form all 3 major body cavities:
- Pericardial
- Pleural
- Peritoneal
Somatic Mesoderm
The intraembryonic coelom divides the lateral plate into 2 portions
- closest to ectoderm
- body wall osteogenic, chrondrogenic and fibrogenic
- except ribs and scapula
Splanchnic Mesoderm
- closest to endoderm
- heart, smooth muscle of gastrointestinal tract (GIT) and blood vessels
- Carnegie Stages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | About Stages | Timeline
= Somitogenesis
(not to scale) |
||||
gastrulation, notochordal process | ||||
primitive pit, notochordal canal | ||||
Somite Number 1 - 3 neural folds, cardiac primordium, head fold | ||||
Somite Number 4 - 12 neural fold fuses | ||||
Somite Number 13 - 20 rostral neuropore closes | ||||
Somite Number 21 - 29 caudal neuropore closes | ||||
Somite Number 30 leg buds, lens placode, pharyngeal arches | ||||
Co-ordinator Note
Dr Mark Hill |
ANAT2341 Embryology S2 2011
|
Course Content 2011
2011 Timetable: | Embryology Introduction | Fertilization | Cell Division/Fertilization | Week 1 and 2 Development | Week 3 Development | Week 1 to 3 | Mesoderm Development | Ectoderm, Early Neural, Neural Crest | Trilaminar Embryo to Early Embryo | Early Vascular Development | Placenta | Vascular and Placenta | Endoderm, Early Gastrointestinal | Respiratory Development | Endoderm and Respiratory | Head Development | Neural Crest Development | Head and Neural Crest | Musculoskeletal Development | Limb Development | Musculoskeletal | Renal Development | Genital | Kidney and Genital | Sensory | Stem Cells | Stem Cells | Endocrine Development | Endocrine | Heart | Integumentary Development | Heart and Integumentary | Fetal | Birth and Revision | Fetal
Glossary Links
- Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link
Cite this page: Hill, M.A. (2024, June 2) Embryology Lecture - Mesoderm Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Lecture_-_Mesoderm_Development
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G