Lecture on Mesoderm Development

Introduction

Topic: Mesoderm development
Process involves transitioning from a bilaminar to a trilaminar disc during gastrulation.

Week 2: Development of bilaminar disc.
- Epiblast layer: Top layer along with the amniotic cavity.
- Hypoblast layer: Below the epiblast layer, adjacent to the yolk sac.
Development of the primitive streak and primitive node.
- Fibroblast Growth Factor 8: Released to initiate cell movement.

Epiblast Cells: Migrate through the primitive streak.
- Replace hypoblast to form the endoderm.
- New layer created between endoderm and epiblast called the mesoderm.
- Remaining epiblast cells turn into ectoderm.
Notochord: Formed by epiblast cells through the primitive node.

Secretes proteins and growth factors like Sonic Hedgehog.
- Induces ectoderm to form the neural tube (neurulation).
- Stimulates mesoderm differentiation into specialized structures.

Paraxial Mesoderm
- Somites Formation: Segment into somites and develop cavities.
  - Dermatomyotome: Further divides into dermatomes and myotomes.
  - Dermatome: Differentiates into the dermis, subcutaneous tissue, and meninges.
  - Myotome: Develops into skeletal muscles.
  - Sclerotome: Forms vertebrae, intervertebral discs, and ribs.
Intermediate Mesoderm
- Renal System: Develops kidneys and ureters.
- Gonads: Formation of testes or ovaries and associated ductal systems.
Lateral Plate Mesoderm
- Somatic and Splanchnic Layers
  - Somatic Layer: Forms parietal layers of body cavities and structure such as the sternum, bones, and cartilage of limbs.
  - Splanchnic Layer: Develops visceral layers, adrenal cortex, lymph nodes, spleen, smooth muscle of the GI tract, and components of the cardiovascular system.