DEVELOPMENT OF MESODERM,
DEVELOPMENT OF MESODERM,
DEVELOPMENT OF MESODERM,
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<strong>DEVELOPMENT</strong> <strong>OF</strong> <strong>MESODERM</strong>,<br />
PARAXIAL <strong>MESODERM</strong> AND<br />
SCLEROMYOTOME AND FORMATION <strong>OF</strong> CARTILAGES<br />
LEARNING OBJECTIVES<br />
At the end of lecture students should be able to know,<br />
What is gastrulation.<br />
Development of mesoderm.<br />
Somitogenesis.<br />
Formation of cartilage.<br />
GASTRULATION(<br />
Week 3-8)<br />
• Gastulation is the process<br />
which establishes the<br />
formation of three germ<br />
layered embryo:<br />
– Ectoderm<br />
– Mesoderm<br />
– Endoderm<br />
• Formation of trilaminar<br />
embryonic disc by day 21.<br />
THE THREE GERM LAYERS<br />
The three germ layers are the derivatives of epiblast<br />
The three germ layers give rise to all the tissues and organs of the body.
<strong>DEVELOPMENT</strong> <strong>OF</strong> <strong>MESODERM</strong><br />
Paraxial mesoderm<br />
Intermediate mesoderm<br />
Lateral mesoderm
PARAXIAL <strong>MESODERM</strong><br />
Thick plate of mesoderm located on each side of midline<br />
Becomes organized into segments called somatomeres in cranio-caudal<br />
sequence.<br />
INTERMEDIATE <strong>MESODERM</strong>
Longitudinal dorsal ridge of mesoderm located between paraxial and lateral<br />
mesoderm<br />
This ridge forms the Urogenital ridge<br />
Urogenital ridge forms the future kidneys and gonads<br />
LATERAL <strong>MESODERM</strong><br />
Thin plate of mesoderm located along the lateral side of embryo.<br />
Large spaces develop in the lateral plate mesoderm and coalesce to form<br />
intraembryonic coelom<br />
Intraembryonic coelom divides lateral mesoderm into:<br />
Intraembryonic somatic mesoderm<br />
Intraembryonic visceral mesoderm<br />
SOMITOGENESIS<br />
Process of segmentation development of<br />
axial system vertebrae, muscles and
innervations.<br />
Somites form from paraxial mesoderm in<br />
anterior-posterior gradient, begins at<br />
neurulation.<br />
Two parallel columns of mesodermal cells<br />
form along the longitudinal axis, on each<br />
side of the notochord and neural tube.<br />
Transverse fissures form in the<br />
columns forming somitomeres in cranio caudal direction.<br />
SOMITOMERES
Somitomere 1-7 do not form somites, but contribute mesoderm to<br />
pharyngeal arches<br />
The remaining somitomeres condense in cranio-caudal sequence forming<br />
41-42 pairs of somites.<br />
SOMITES
Somites differentialte into:<br />
Sclerotome<br />
Forms cartilage and bone component of veebral column<br />
Myotome<br />
Forms epimeric and hypomeric muscles<br />
Dermatome<br />
Forms dermis and subcutaneous area of skin<br />
SUMMARY <strong>OF</strong> <strong>MESODERM</strong>AL <strong>DEVELOPMENT</strong><br />
FORMATION <strong>OF</strong> CARTILAGE<br />
Cartilage is derived from mesenchyme<br />
Avascular mesenchyme contains stem cells embedded in a delicate collagen<br />
matrix
CHONDROBLAST<br />
Mesenchyme cells begin to differentiate into protochondral cells<br />
Protochondral cells divide to produce chondroblasts<br />
CARTILAGE <strong>DEVELOPMENT</strong>
The center fills with chondroblasts as the top and bottom edges continue to<br />
differentiate.<br />
Stem cells remain on the edges<br />
Chondroblasts remain in the center and produce cartilage matrix.<br />
Stem cells at the edges produce fibroblasts and make the fibrous<br />
perichondrium<br />
Chondroblasts in the center continue to divide
THANK YOU
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