Mesoderm/endoderm

Regions of mesoderm

1. Central trunk: chordamesoderm formed from notochord: patterns neural tube and established AP axis

2. To the side of notochord: Semitic mesoderm. Forms the somites

3. Itnermediate mesoderm urogenital system

4. Lateral palate mesoderm: lateral to the Semitic mesoderm forms heart blood vessels and gives rise to circulatory system

Cell types of the somite

1. Somites formed by epithelial cells creating a block of mesenchyme cell core

2. When somites first seperate from presomitic meso they are capable of any somite derived fate

3. As somite matures EMT is undergone committing cells

4. Two major cells in somite not :scleratome and dermamyotome

   1. Ventromedial=scleratome forms vertebrae ribs and tendons

   2. Epithelial portion=dermamyotome forms muscles

Establishing parasail mesoderm and cells fates on AP axis

1. Mesodermal subtypes are specifies along mediolateral axis by BMP gradient


1. More lateral = more bmp
2. Noggincan be used as an inhibitor of BMP who in is from notochord then from Semitic mesoderm

vertebrae formation

1. Notochord induces surrounding cels to release epimorphin that attracts scleratome cells around neural tube where they condense and differentiate Into cartilage

2. More dorsal cells over the top of nerual tube form spinous process of vertebrae are induced by platelet derived growth factor from the scleratome cells\

3. Motor neurons from the neural tube grow laterally and innervate new muscles

4. Scleratome splits into aA/P regions

5. Anterior segments of each scleratome recombine with posterior forming vertebral rudiments

6. The arthrotome creates the synovial joints between the vertebra and if it is removed there is fusion within the spine

Formation of the heart field

1. Heart progenitor cells migrate through the streak forming two groups of lateral plate mesoderm

2. Cardio genie mesoderm= heart field begins specification during migration

3. First heart field appears forming the scaffold of developing heart

   1. Progenitor cells use the midline to form the primary heart tube that gives rise to muscular region of left and right ventricle

4. The progenitors of teh second heart field add cells to both anterior and posterior ends of the heart tube

5. Posterior end forms atria and entry to heart

Specification of cardio genie mesoderm

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1. Specified by interactions with pharyngeal endoderm And notochord

2. BMP from anterior endoderm promotes heart cells o form

3. The notochord then secretes chord in and noggin that blocks bmp from the center of the embryo and noggin secreting cells in myotonic keep heart from forming within the somites