Summary
The fine structure of the pharynx is presented and demonstrates that the pharyngeal epithelial system is a continuous one. The epithelial lining of the pharyngeal cavity with its characteristic fibrous secretory bodies merges with the outer pharyngeal epithelium at the point of anchorage of the pharynx. A few of these cells are insunk, the nuclei occurring beneath the underlying muscular layers. The nature of the outer epithelium changes towards the free end of the pharynx; the cells become ciliated and in contents come to resemble the inner epithelium which it joins at the tip.
The gut cells merge at a transitional zone with the inner pharyngeal epithelium and at this point both bear microvilli and contain rod-shaped apical bodies. Some of these cells are also insunk. Towards the mouth the epithelium shows a greater degree of insinking and exhibits microapocrine secretion. Both inner and outer epithelia bear sense receptors which are concentrated at the lip.
At the point of pharyngeal insertion, the sub-epithelial tissue resembles planarian parenchyma, but is rich in gland cells. These glands open on to the outer epithelium especially towards the free end of the pharynx.
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References
Best, T. B., M. Morita, andJ. Noel, 1968: Fine structure and function of Planarian goblet cells. J. Ultrastruct. Res.24, 385–397.
Bowen, I. D., 1968: Electron cytochemical studies on autophagy in the gut epithelial cells of the locust,Schistocerca gregaria. Histochem. J.1, 141–151.
—, andP. Davies, 1971: The fine structural distribution of acid phosphatase in the digestive gland ofArion hortensis (Ferl.). Protoplasma73, 73–81.
- T. A.Ryder, and J. A.Thompson, 1973: The fine structure of the planarianPolycelis tennis Ijima: II. The intestine and gastrodermal phagocytosis. (In prep.)
Duve, C. de, andR. Wattiaux, 1966: Functions of lysosomes. Ann. Rev. Physiol.28, 435–492.
Emmelot, P., 1968: Plasma membranes. Excerpta Medica Internat. Cong. Ser.166, 16.
Gibbons, I., andA. V. Grimstone, 1970: On flagellar structures in certain flagellates. J. biophys. biochem. Cytol.7, 697–716.
Ishii, S., 1962: Electron microscopic observations on the planarian tissues. 1. A survey of the pharynx. Fukushima J. Med. Sci.9–10, 51–73.
—, 1964: The ultrastructure of the outer epithelium of the planarian pharynx. Fukushima J. Med. Sci.11, 109–125.
—, 1966: The ultrastructure of the insunk epithelium lining the planarian pharyngeal cavity. J. Ultrastruct. Res.14, 345–355.
Ito, S., 1969: Structure and function of the glycocalyx. Fed. Proc.28, 12–25.
Jennings, J. B., 1957: Studies on the feeding, digestion and food storage in free living flatworms. Biol. Bull.112, 63–80.
—, 1962: Further studies on feeding and digestion in TricladTurbellaria. Biol. Bull.123, 571–581.
—, 1968: Platyhelminthes, Nutrition. In: Chemical zoology (M. Florkin andB. T. Scheer, eds.),2, 640. New York and London: Academic Press.
Lehninger, A. L., 1968: The neuronal membrane. Proc. nat. Acad. Sci. (U.S.A.)60, 1069–1080.
Lentz, T. L., 1967: Rhabdite formation in planaria. The role of microtubules. J. Ultrastruct. Res.17, 114–126.
Macrae, E. K., 1963: Observations on the fine structure of pharyngeal muscle in the planarianDugesia tigrina. J. Cell Biol.18, 651–662.
—, 1967: The fine structure of sensory receptor processes in the auricular epithelium of the planarian,Dugesia tigrina. Z. Zeilforsch.82, 479–494.
Millonig, G., 1961: Advantages of a phosphate buffer for osmium tetroxide solutions in fixation. J. Appl. Phys.32, 1637.
Neutra, M., andC. P. Leblond, 1966: Synthesis of the carbohydrate of mucus in the Golgi complex as shown by electron microscope radiography of goblet cells from rats injected with glucose-H3. J. Cell Biol.30, 119–136.
— — 1969: The Golgi apparatus. Sci. Amer.220, 100–107.
Novikoff, A. B., andW. Y. Shin, 1964: The endoplasmic reticulum on the Golgi zone and its relations to microbodies, Golgi apparatus and autophagic vacuoles in rat liver cells. J. Microscopie3, 187.
Oschman, J. L., 1967: Microtubules in the subepidermal glands ofConvoluta roscoffensis (Acoela, Turbellaria). T. Amer. Micros.86, 159–162.
Rambourg, A., andC. P. Leblond, 1967: Electron microscope observations on the carbohydrate-rich cell coat present at the surface of cells in the rat. J. Cell Biol.32, 27–53.
Reynolds, E. S., 1963: The use of lead citrate at high pH as an electron opaque stain in electron microscopy. J. Cell Biol.17, 208–212.
Silveira, M., andK. R. Porter, 1964: The spermatozoids of flatworms and their microtubular systems. Protoplasma54, 240–265.
Skaer, R. J., 1961: Some aspects of the cytology ofPolycelis nigra. Quart. J. micr. Sci.102, 295–318.
Smith, R. E., andN. G. Farquar, 1966: Lysosome function in the regulation of the secretory process in cells of the anterior pituitary gland. J. Cell Biol.31, 319–347.
Ugolev, A. M., 1960: Parietal (contact) digestion. Bull. exp. Biol. Med.49, 12–17.
Weiss, L., 1963: The mammalian tissue cell surface. Biochem. Soc. Symp.22, 32–50.
Willier, B. H., L. H. Hyman, andS. A. Rifenburgh, 1925: A histochemical study of intracellular digestion in Triclad flatworms. J. Morph.40, 299–340.
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This research was supported by the Scientific Research Council. Grant No. B/RG/086.
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Bowen, I.D., Ryder, T.A. The fine structure of the planarianPolycelis tenuis ijima. Protoplasma 78, 223–241 (1973). https://doi.org/10.1007/BF01275693
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DOI: https://doi.org/10.1007/BF01275693