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#blastocoel

3 public questions tagged with this topic.

amphibian Development-l

The blastocoel in amphibians primarily functions to:

The blastocoel is a fluid-filled cavity formed during cleavage stages by active sodium pumping and tight junction sealing between superficial blastomeres. Positioned between animal cap and vegetal mass, it provides empty space required for involution and migration of mesodermal cells during gastrulation. Without blastocoel, involuting marginal zone cells would have no cavity to move into, preventing archenteron formation. Its roof thins via epiboly while floor consists of large yolky cells. Collapse and replacement by expanding archenteron marks progression of gastrulation and germ layer rearrangement.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 8: Blastocoel function facilitates gastrulation movements.

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chick development-l

Formation of the blastocoel-like cavity in chick occurs between:

Chick blastoderm initially bilaminar with dorsal epiblast epithelium and ventral hypoblast layer of polyingressed cells. Subgerminal cavity appears between them through fluid secretion by epiblast via Na-K-ATPase transport, lifting blastoderm off yolk. This space considered blastocoel-like cavity, homologous to amphibian blastocoel though not fully enclosed. It permits hypoblast migration and later mesoderm spreading after ingression through primitive streak. Cavity roof is epiblast, floor hypoblast, not between hypoblast layers. Definitive endoderm ingressing through streak eventually obliterates cavity when contacting yolk forming gut lining for nutrition.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 12: Blastocoel-like cavity formation between epiblast and hypoblast.

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Fertilization in mammals-iv

Blastocoel formation depends on:

Blastocoel is fluid-filled cavity created within morula to form blastocyst. Its generation depends on establishment of functional epithelium by outer trophectoderm cells sealed by tight junctions. Basolateral Na/K ATPases actively transport sodium ions into intercellular space, creating osmotic gradient. Water follows via aquaporins, expanding microcavities into single blastocoel pushing inner cell mass eccentrically. Calcium is needed earlier for compaction and tight junctions, but sodium flux is direct driver of cavitation. Inhibition of Na/K pump with ouabain or removal of extracellular sodium blocks blastocoel formation, proving sodium gradient central to mammalian blastulation and embryonic fluid homeostasis.

Ref: Kim et al., Nat Comm 1998: Sodium pump mediated blastocoel formation in mammalian preimplantation embryos.

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