T.S. of Pheretima through the Pharyngeal region

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 COMMENTS:

• The section shows organ grade of construction, triploblastic layeration and true coelom. Pharynx is clearly seen. Pharynx is wide pear shaped; thick walled muscle chamber.

• Pharyngeal cavity is dorsoventrally compressed.

• Cuticle is thin, non-cellular, double-layered, indescent and made up of protein, collagen, gelatin and polysaccharides.

• Body wall is composed of cuticle, epidermis, musculature and parietal epithelial layer.

• Epidemis consist of single layered distinct columnar cells with gland cells , supporting cells, basal cells and receptor cells.

• Musculature comprises outer continuous circular muscle fibre and inner longitudinal muscle fibres cut in bundles.

• Pharynx contains visceral epithelial layer, pharyngeal gland cells, musculo-vascular tissue and lumen of pharynx.

• Lumen is divided by incomplete horizontal shelf into upper salivary chamber and lower conducting or ventral chamber. Salivary chamber contains ciliated pharyngeal epithelial layers dorsally.

• From the pharyngeal wall radial muscle strands run outward up to body wall. Their contraction dilute the pharyngeal cavity which works as suction pump.





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