• Neuroglia Classification:
• Astrocytes: Metabolic and blood-brain barrier support (ectodermal).
• Oligodendrocytes: Myelin sheath synthesis in CNS (ectodermal).
• Ependymal cells: Ventricular lining and CSF circulation (ectodermal).
• Microglia:
• The resident phagocytic macrophages of the central nervous system.
• Derived from embryonic yolk sac mesoderm, they scavenge cellular debris, foreign pathogens, and damaged synapses.
• nalysis:
• (Microglia): Correct CNS macrophage.

Correct option: (3) Microglia

• Pre-Implantation Embryonic Development:

• Morula Formation (A): Cleavage divisions produce a solid spherical ball of $16 - 32$ blastomeres.
• Compaction (B): Blastomeres flatten and form tight intercellular junctions, creating distinct inner and outer cell populations.
• Blastulation (C): Fluid accumulation forms a blastocoel cavity, distinguishing the inner cell mass (embryoblast) and trophoblast.
• Zona Hatching (D): The blastocyst sheds the surrounding non-cellular zona pellucida envelope.
• Blastocyst Elongation (E): In domestic ruminants and pigs, the hatched spherical blastocyst elongates into a filamentous conceptus.
  • Sequence:

• nalysis:
• (A, B, C, D, E): Correct chronological order.

Correct option: (1) A,B,C,D.E

• Histology of the Peritoneum:
• The peritoneum (parietal and visceral) is a serous membrane enclosing the abdominopelvic cavity and abdominal viscera.
• It consists of a single continuous layer of flattened polygonal cells termed mesothelium, which is a Simple Squamous Epithelium, supported by a thin submesothelial lamina propria of loose connective tissue.
• nalysis:
• (Simple squamous epithelium): Correct.

Correct option: (1) Simple sqamous epithelium

• Histomorphology of the Thymus:
• The thymus is divided into outer cortical and inner medullary zones.
• The diagnostic histological hallmark of the thymic medulla is the presence of Hassall's corpuscles (Thymic corpuscles).
• They are concentric, eosinophilic, whorled structures composed of clustered, degenerating type VI thymic epithelial reticular cells that synthesize thymic stromal lymphopoietin (TSLP) to instruct regulatory T cell (Treg) differentiation.
• nalysis:
• (Thymus): Correct organ.

Correct option: (3) Thymus