Excretory system

The morphology and ultrastructure of the cestode musculature has been reviewed by Lumsden Hildreth (458) and Lumsden Specian (462). A cestode muscle cell consists of two portions (a) the non-contractile cytoplasmic portion or myocyton containing the nucleus and usually packed with glycogen and (b) the myofibril portion containing myofilaments (presumably actin and myosin) (Fig. 2.7). The myocyton is generally positioned some distance from the myofibrils to which it is connected by tendrillar processes (462). The latter appear to be connected to 

Although some species of cestodes (e.g. Hymenolepis diminuta, p. 236) undergo diurnal migrations within the intestine - and therefore their suckers may not always be in a state of sustained contraction - others (e.g. Echinococcus granulosus) apparently remain in the same place and appear to be able to maintain contraction. How this is achieved physiologically is not known, but it has been speculated that this may operate through a catch muscle mechanism (as in lamellibranchs) or by the involvement of special stretch receptors (796). 

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Wippersteg V, Ribeiro F, Liedtke S et al (2003) The uptake of Texas Red-BSA in the excretory system of schistosomes and its colocalisation with ER60 promoter-induced GFP in transiently transformed adult males. Int J Parasitol 33 1139-1143... 

Lee, D.L. (1970) The fine structure of the excretory system in adult Nippostrongylus brasiliensis (Nematoda) and a suggested function for the excretory glands . Tissue and Cell1 , 225-231. 

Each hormone is the center of a hormonal regulation system. Specialized glandular cells synthesize the hormone from precursors, store it in many cases, and release it into the bloodstream when needed (biosynthesis). For transport, the poorly water-soluble lipophilic hormones are bound to plasma proteins known as hormone carriers. To stop the effects of the hormone again, it is inactivated by enzymatic reactions, most of which take place in the liver (metabolism). Finally, the hormone and its metabolites are expelled via the excretory system, usually in the kidney (excretion). All of these processes affect the concentration of the hormone and thus contribute to regulation of the hormonal signal. 

Hemoperfusion is like hemodialysis except that blood is circulated extracorporeally through a column with adsorbent material like resin or charcoal, which binds molecules electrostatically. The molecules likely to be removed are characterized as poorly dialyzable, lipid-soluble, protein bound. Among the indications for hemoperfusion in the management of poisoning include the presence of a poison in a patient with impairment of excretory system (i.e. damaged kidneys), intoxication of a drug known to produce delayed toxicity or metabolized to a more toxic metabolite (i.e. paraquat or methotrexate), deterioration of the clinical state of the poisoned patient despite conservative therapy (i.e. convulsions or cardiac arrhythmias following theophylline intoxication), or development of coma as a complication. 

Pellegrini M, Pantano S, Lucchini F, Fumi M, Forabosco A (1997) Emx2 developmental expression in the primordia of the reproductive and excretory systems. Anal Embryo (Bert), 196 427-433. 

The processes of selective reabsorption of nutrients and xenobiotics goes on within the complex tubule system. 98-99% of filtered materials (salts, water, sugars, amino acids) are eventually reabsorbed by passive or active transport. Biomolecules such as glucose and amino acids are entirely reabsorbed if their concentrations are within the normal range in the blood. However, should the concentrations be higher than normal, those molecules might not be completely reabsorbed because they have exceeded the ability of the nephron transport systems to accommodate them. This is referred to as exceeding the renal threshold. Urine is therefore a convenient body fluid to assay for the initial assessment of metabolic or excretory system malfunctions. 

The body of flatworms (phylum Platyhehninthes) consists of two external cell layers (endoderm and ectoderm) with a third layer between. A distinct excretory system is present. In addition to a nerve net resembling that of the Cnidaria, there are a cerebral ganglion and distinct eyes. One large group of flat-worms, the planaiians (typically about 15 mm in length, Fig. 1-14), inhabit freshwater streams. They are said to be the simplest creatures in which behavior can be studied. 

Malmberg, C. (1970) The excretory systems and the marginal hooks as a basis for the systematics of Cyrodactylus (Trematoda, Monogenea). Arkiv for Zoologi Serie 2 23, 235. 

Mecozzi, B., Rossi, A., Lazzaretti, P., Kady, M., Kaiser, S., Valle, C., Cioli, D. and Klinkert, M.Q. (2000) Molecular cloning of Schistosoma mansoni calcineurin subunits and immunolocalization to the excretory system. Molecular and Biochemical Parasitology 11 0, 333-343. 

Superimposed on these records are markings of environmental perturbations which sometimes inhibit, and sometimes accelerate carbonate deposition. In the final analysis, however, there has to be an answer, why organisms respond in such a systematic fashion. In all probability these phenomena are connected to the high demand for calcium at all levels of the cell regulatory system. Only at times of lower activities or when the calcium pool runs over will the excretory system package and export the surplus calcium to the periphery of the cell where it may be utilized in carbonate deposition. 

Based on the observations of Marinelli et al. (1953), immediately after accidental exposure of humans to radium-226 (as the sulfate), the major deposit of radium was in the lungs. This deposition decreased with an average half-life of 118 days ( 30 days). Elimination from the lungs via the systemic circulation results in a continuous deposition in the skeleton as well as distribution to soft tissue and the excretory system. In addition, some of the radium salt may have been coughed up and swallowed during the exposure episode. 

Heme degradation Bile pigments exist in both the plant and animal kingdoms, and are formed by breakdown of the cyclic tetrapyrrole structure of heme. In animals this pathway is an excretory system by which the heme from the hemoglobin of aging red blood cells, and other hemoproteins, is removed from the body. In the plant kingdom, however, heme is broken down to form bile pigments... 

Figure 24-4 Cut-away view showing the lacrimal excretory system. Tears drain through the punctum (A) and eventually under the inferior turbinate bone of the nose. Dimensions of the canaliculi serve as references for probing and irrigation. B, canaliculus C, common canaliculus. (Redrawn with permission from Jones LT. Ophthalmic anatomy a manual with some clinical appHcations. 1. The orbital adnexa. Am Acad Ophthalmol 1970 70.)...

A complex invertebrate also has a circulatory system to carry dissolved oxygen to and remove carbon dioxide from each of the millions of cells that make up its body. To feed these cells, the animal has a digestive system that takes food into the body and breaks it down, then turns the nutrients over to the circulatory system for delivery. To keep blood flowing to all of the cells on a full-time basis, a muscular heart powers the circulatory system. An excretory system takes care of removing wastes from cells. All of these body systems are... 

Cholestasis (stoppage or suppression of the flow of bile) is associated with retention of bile within the excretory system. 

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