Gametogenesis and Embryonic Development

Gametogenesis

• Process by which gametes (sperm and egg cells) are formed
• Involves meiosis, resulting in haploid cells with unique genetic material
• Spermatogenesis:
  • Occurs in testes
  • Produces four haploid sperm cells from one diploid spermatogonium
• Oogenesis:
  • Occurs in ovaries
  • Produces one haploid egg cell from one diploid oogonium
  • Involves unequal cytokinesis, resulting in a large egg cell and smaller polar bodies

Morula

• Stage in embryonic development that occurs 3-4 days after fertilization
• Characterized by:
  • A solid ball of 16-32 cells (blastomeres)
  • Cells are compact and tightly packed
  • No visible cavities or differentiation
• Morula stage is critical for:
  • Compaction of cells
  • Establishment of cell-cell contacts
  • Preparation for further development

Gastrulation

• Stage in embryonic development that occurs 5-7 days after fertilization
• Characterized by:
  • Series of complex cellular movements
  • Formation of three primary germ layers:
    • Ectoderm
    • Mesoderm
    • Endoderm
  • Establishment of anterior-posterior and dorsal-ventral axes
• Gastrulation is critical for:
  • Formation of embryonic layers and tissues
  • Establishment of body plan and organization

Organogenesis

• Stage in embryonic development that occurs 3-8 weeks after fertilization
• Characterized by:
  • Formation of organs and organ systems
  • Differentiation of tissues and cells
  • Morphogenesis of body structures
• Organogenesis is critical for:
  • Development of functional organs and systems
  • Establishment of body shape and form

Morphogenesis

• Process by which tissues and organs take shape and form
• Involves:
  • Cellular differentiation and migration
  • Changes in cell shape and adhesion
  • Pattern formation and tissue interactions
• Morphogenesis is critical for:
  • Formation of complex body structures
  • Establishment of tissue and organ architecture
  • Development of functional organs and systems

Gametogenesis

• Gametes (sperm and egg cells) are formed through meiosis, resulting in haploid cells with unique genetic material
• Spermatogenesis:
  • Occurs in testes
  • Produces four haploid sperm cells from one diploid spermatogonium
• Oogenesis:
  • Occurs in ovaries
  • Produces one haploid egg cell from one diploid oogonium
  • Involves unequal cytokinesis, resulting in a large egg cell and smaller polar bodies

Embryonic Development

Morula

• Stage occurs 3-4 days after fertilization
• Characterized by a solid ball of 16-32 compact and tightly packed cells (blastomeres) with no visible cavities or differentiation
• Critical for compaction of cells, establishment of cell-cell contacts, and preparation for further development

Gastrulation

• Stage occurs 5-7 days after fertilization
• Characterized by a series of complex cellular movements, forming three primary germ layers:
  • Ectoderm
  • Mesoderm
  • Endoderm
• Establishes anterior-posterior and dorsal-ventral axes, critical for formation of embryonic layers and tissues, and establishment of body plan and organization

Organogenesis

• Stage occurs 3-8 weeks after fertilization
• Characterized by formation of organs and organ systems, differentiation of tissues and cells, and morphogenesis of body structures
• Critical for development of functional organs and systems, and establishment of body shape and form

Morphogenesis

• Process by which tissues and organs take shape and form
• Involves cellular differentiation and migration, changes in cell shape and adhesion, and pattern formation and tissue interactions
• Critical for formation of complex body structures, establishment of tissue and organ architecture, and development of functional organs and systems

Cardiovascular System Development

• The cardiovascular system is the 1st major system to function in the embryo.
• The heart begins beating rhythmically as early as day 22 and pumps blood by days 24 to 25.

Origin of Cardiac Progenitor Cells

• Cardiac progenitor cells are derived from intraembryonic mesoderm.
• These cells emerge from the cranial 1/3 of the primitive streak during early gastrulation.

Migration of Cardiac Progenitor Cells

• The progenitor cells migrate in a cranial-lateral direction and become localized on either side of the primitive streak.
• The cranial lateral plate mesoderm on both sides contains cardiac progenitor cells (cardiogenic cells).

Formation of the Cardiac Crescent

• The progenitor cells in the cranial lateral plate mesoderm migrate cranially and form an arch over the developing head fold.
• This arch is called the cardiac crescent.

Primary Heart Field

• The primary heart field is formed by the 16-18th day.
• Cells in the cardiac crescent constitute the primary heart field.
• The primary heart field forms part of the primordial heart, including:
  • Atria
  • Left ventricle
  • Most part of the right ventricle