[Taenia and appendicitis, or taenia appendicitis].
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Adult↗
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[Treatment of Taenia saginata and Taenia solium with atebrin administered through a duodenal tube].
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Adolescent↗
[Treatment of infections by Hymenolepis nana, Taenia saginata, Taenia solium and Diphyllobothrium pacificum with praziquantel (Embay 8440) (author's transl)].
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Diphyllobothriasis↗
Pig as a favorable animal for Taenia saginata asiatica infection.
The epidemiology of Taenia saginata in some parts of Asia is confusing, in that beef does not appear to be the source of infection. In some areas, beef is either not available or not eaten raw, whereas pork at times is eaten uncooked. In light of this situation, we have exposed pigs and other animals to infection with strains of T. saginata to establish their ability to serve as intermediate hosts. Eggs of Taiwan Taenia, Korea Taenia, Indonesia Taenia, Thailand Taenia, Philippines Taenia, Ethiopia Taenia, and Madagascar Taenia were fed to 83 pigs of three strains: 43 Small-Ear Miniature (SEM), 34 Landrace Small-Ear Miniature (L-SEM), and 6 Duroc-Yorkshire-Landrace (DYL). We also fed the eggs to 10 Holstein calves, 17 Sannean goats, and 4 monkeys (Macaca cyclopis). We succeeded in infecting SEM (infection rate 88%, cysticercus recovery rate 19.1%), L-SEM (83%, 1.1%), and DYL (100%, 0.3%) pigs with Taiwan Taenia; SEM (100%, 1.7%), L-SEM (100%, 5.6%), and DYL (100%, 0.06%) pigs with Korea Taenia; SEM (100%, 22%) and L-SEM (100%, 1.6%) pigs with Indonesia Taenia; SEM (75%, 0.06%) pigs with Thailand Taenia SEM (100%, 11%) pigs with Philippines Taenia; SEM (80%, 0.005%) pigs with Ethiopia Taenia; SEM (100%, 0.2%) pigs with Madagascar Taenia. Holstein calves became infected with Taenia from Taiwan (100%, 1.1%), Korea (100%, 0.03%), Thailand (100%, 0.2%), and the Philippines (100%, 6%); however, the cysticerci of Taenia from Korea, Thailand, and the Philippines were degenerated and/or calcified. Sannean goats became infected with Taenia from Taiwan (33%, 0.01%) and Korea (50%, 0.02%), while monkeys became infected with Taenia from Taiwan (50%, 0.01%). However, the cysticerci were degenerated and/ or calcified. Therefore, these strains of pig seem to be favorable animal models for experimental studies of T. saginata-like tapeworms, with the SEM pig the most favorable.
Animals↗
NADH dehydrogenase subunit 1 and cytochrome c oxidase subunit I sequences compared for members of the genus Taenia (Cestoda).
Nine members of the genus Taenia (Taenia taeniaeformis, Taenia hydatigena, Taenia pisiformis, Taenia ovis, Taenia multiceps, Taenia serialis, Taenia saginata, Taenia solium and the Asian Taenia) were characterised by their mitochondrial NADH dehydrogenase subunit 1 gene sequences and their genetic relationships were compared with those derived from the cytochrome c oxidase subunit 1 sequence data. The extent of inter-taxon sequence difference in NADH dehydrogenase subunit 1 (approximately 5.9-30.8%) was usually greater than in cytochrome c oxidase subunit 1 (approximately 2.5-18%). Although topology of the phenograms derived from NADH dehydrogenase subunit 1 and cytochrome c oxidase subunit 1 sequence data differed, there was concordance in that T. multiceps, T. serialis (of canids), T. saginata and the Asian Taenia (of humans) were genetically most similar, and those four members were genetically more similar to T. ovis and T. solium than they were to T. hydatigena and T. pisiformis (of canids) or T. taeniaeformis (of cats). The NADH dehydrogenase subunit 1 sequence data may prove useful in studies of the systematics and population genetic structure of the Taeniidae.
Animals↗
Genetic characterization of the Asian Taenia, a newly described taeniid cestode of humans.
Recent studies on the epidemiologic pattern of taeniasis in Southeast Asia have indicated the existence of a third form of human Taenia, distinguishable from Taenia saginata and T. solium. Originally termed Taiwan Taenia, and first described in Taiwanese aboriginals, this newly recognized taeniid is now generally referred to as Asian Taenia since it has since been recorded in a number of other Asian countries. Here we have used a genetic yardstick approach to determine whether the Asian Taenia should most appropriately be considered as a new, distinct species or as a subspecies, strain, or variant of T. saginata, which previous studies have shown it closely resembles. Sequence variation in the 28S rRNA and mitochondrial cytochrome c oxidase I (COI) genes of a range of taeniid cestodes and the COI and rDNA internal transcribed spacer I polymerase chain reaction (PCR) restriction fragment length polymorphism (RFLP) pattern differences in the Asian Taenia, T. saginata, and T. solium were used as markers of genetic identity. The PCR-RFLP approaches proved useful for rapid and unambiguous discrimination of Asian Taenia from the other two human species, whereas the mitochondrial and nuclear sequence comparisons indicate that the Asian Taenia is much more closely related to T. saginata than recognized taeniid species are to each other. The results support earlier conclusions that the Asian Taenia is a genetically distinct entity but is closely related to T. saginata, and suggest that its taxonomic classification as a subspecies or strain of T. saginata is more appropriate than formal designation as a new species. The very close relationship between Asian Taenia and T. saginata has public health implications in that the Asian form is unlikely to be an important cause of human cysticercosis because T. saginata cysticercosis, if it occurs at all in humans, is an extremely rare phenomenon.
Amino Acid Sequence↗
Inhibitory action of PPADS on relaxant responses to adenine nucleotides or electrical field stimulation in guinea-pig taenia coli and rat duodenum.
1. The effect of pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) on the relaxant response to adenine nucleotides was examined in the carbachol-contracted guinea-pig taenia coli and rat duodenum, two tissues possessing P2y-purinoceptors. In addition, in the taenia coli PPADS was investigated for its effect on relaxations evoked by adenosine, noradrenaline and electrical field stimulation. In order to assess the selectivity of PPADS between P2-purinoceptor blockade and ectonucleotidase activity, its influence on ATP degradation was studied in guinea-pig taenia coli. 2. The resulting rank order of potency for the adenine nucleotides in guinea-pig taenia coli was: 2-methylthio ATP >> ATP > alpha,beta-methylene ATP with the respective pD2-values 7.96 +/- 0.08 (n = 23), 6.27 +/- 0.12 (n = 21) and 5.88 +/- 0.04 (n = 24). 3. In guinea-pig taenia coli, PPADS (10-100 microM) caused a consistent dextral shift of the concentration-response curve (CRC) of 2-methylthio ATP and ATP resulting in a biphasic Schild plot. A substantial shift was only observed at 100 microM PPADS, the respective pA2-values at this particular concentration were 5.26 +/- 0.16 (n = 5) and 5.15 +/- 0.13 (n = 6). Lower concentrations of PPADS (3-30 microM) antagonized the relaxant effects to alpha,beta-methylene ATP in a surmountable manner. An extensive shift of the CRC was produced only by 30 microM PPADS (pA2 = 5.97 +/- 0.08, n = 6), and the Schild plot was again biphasic. 4. The relaxant responses to electrical field stimulation (80 V, 0.3 ms, 5 s, 0.5-16 Hz) in guinea-pigtaenia coli were concentration-dependently inhibited by PPADS (10-100 microM).5. In guinea-pig taenia coli, the potency of ATP in inducing relaxation appeared to be independent of its rate of degradation by ecto-nucleotidases, since the Km-value (366 microM) obtained in the enzyme assay was much higher than the functional EC50-value (0.45 microM) of ATP. PPADS (3-100 microM) was only weakly active in inhibiting ecto-nucleotidase activity leaving a residual activity of 81.8 +/- 5.1% at 100 microM.Enzyme inhibition by PPADS was concentration-independent and non-competitive.6. In rat duodenum, the rank order of potency was: 2-methylthio ATP >ATP> >alpha,beta-methylene ATP,the respective pD2-values being 6.98 +/- 0.04 (n = 76), 6.26 +/- 0.02 (n = 6) and 4.83 +/- 0.02 (n = 6). Among these agonists, 2-methylthio ATP displayed the lowest apparent efficacy.7. The CRC of 2-methylthio ATP in rat duodenum was shifted to the right by PPADS (10-100 microM) ina concentration-dependent manner, and Schild analysis gave a pA2-value of 5.09 +/- 0.06 (slope = 1.02,n=14).8 PPADS was without any effect on the carbachol-induced contraction in guinea-pig taenia coli or rat duodenum and on the relaxation to noradrenaline or adenosine in guinea-pig taenia coli.9 In conclusion, the antagonistic properties of PPADS at the taenia coli and rat duodenum P2y-purinoceptors were different from those recently described at the P2x-subtype: inhibition of P2y-purinoceptor-mediated responses was observed at higher concentrations (3-100 microM vs. 1-10 (30) microM).Furthermore, we conclude that in addition to the classical P2y-subtype, which is largely PPADS-resistant,the guinea-pig taenia coli may be endowed with a distinct relaxation-mediating P2-purinoceptor subtype which is sensitive to PPADS.
Adenosine↗
Effects of external cations on calcium efflux from single cells of the guinea-pig taenia coli and porcine coronary artery.
1. Single smooth muscle cells were prepared from the guinea-pig taenia coli and the porcine coronary artery by treatment with collagenase, in order to measure the 45Ca flux with special reference to the effects of external cations. 2. In excess [K]o solution, cell suspensions prepared from both tissues showed an increased 45Ca uptake within 3-5 min. In Na-free solution, the cells prepared from taenia coli, but not from coronary artery showed an increased 45Ca uptake. The Ca uptake of the cells paralleled with the tension increase recorded from tissues of both species. 3. The efflux of 45Ca into Ca-free EGTA containing solution was markedly increased by [Na]o in cells from the taenia coli, but not in cells from the coronary artery. 4. The [Na]o-activated 45Ca efflux from cells of the taenia coli was slightly larger in Ca-free solution than in the Ca-containing (10)-4) M) solution. Depolarization of membranes produced by excess [K]o did not effect the [Na]o-activated 45Ca efflux. 5. Increase in [Na]i by treatment with K-free solution suppressed the [Na]o-activated 45Ca efflux in the taenia coli. Re-addition of [K]o reactivated the [Na]o-activated 45Ca efflux. This re-activation was blocked by ouabain. 6. The efflux of 45Ca was slightly activated by [Ca]o in cells from the taenia coli. This [ca]o-activated 45Ca efflux was larger in Na-free solution than in Na-containing solution, thus suggesting interactions between [Na]o and [Ca]o on the Ca efflux. 7. In cells from the taenia coli, 45Ca efflux could still be observed in nominally Na-and Ca-free solution. This residual 45Ca efflux made a large contribution to the total 45Ca efflux. 8. When 45Ca uptake was measured in Na-free (Tris) solution, the [Na]o-activated, [Ca]o-activated and residual 45Ca effluxes of cells from the taenia coli were accelerated, non-selectively. 9. These results obtained with cells prepared from the guinea-pig taenia coli are comparable to the Ca2+ efflux mechanism seen in the squid axon. However, maintenance of low concentrations of [Ca]i seems to require not only the above three 45Ca efflux mechanisms, but also Ca sequestering mechanisms in the cell.
Animals↗
Experimental infection of Indonesia Taenia (Samosir strain) in domestic animals.
Three 58-day old Small-Ear-Miniature (SEM) pigs, six 36-day old Landrace-Small-Ear-Miniature (L-SEM) pigs, and two 5-day old Holstein calves were each fed 3000 or 30,000 Indonesia Taenia (Samosir strain) eggs and sacrificed 27-195 days after inoculation. A total of 4922 cysticerci were recovered only from the livers of the three SEM pigs (1977 cysticerci) and six L-SEM pigs (2945 cysticerci). The infection rate in pigs was 100%. Cysticerci recovery rates of SEM and L-SEM pigs were 22.0% and 1.6%, respectively. Calves were not susceptible to Indonesia Taenia. More cysticerci were found in the liver parenchyma (L-SEM, 66.4%; SEM, 76.2%) than on the liver surface (L-SEM, 33.6%; SEM, 23.8%) of the infected animals. Most (99.86%) of the cysticerci recovered from the livers of L-SEM pigs were degenerated or calcified but 77.9% of those in the livers of SEM pigs were mature and only 22.1% were degenerated or calcified. Measurements of length, width, diameters of protoscolex, rostellum, and sucker and hooklet pattern indicated that Indonesia Taenia is very similar to Taiwan Taenia and very different from Taenia saginata and Taenia solium. The present findings indicate that Indonesia Taenia and Taiwan Taenia may be the same new species.
Animals↗
A phylogenetic hypothesis for species of the genus Taenia (Eucestoda : Taeniidae).
Cladistic analysis of a numerical data matrix describing 27 characters for species of Taenia resulted in 4 most parsimonious phylogenetic trees (174 steps; consistency index = 0.28; homoplasy index = 0.72; retention index = 0.48). Monophyly for Taenia is diagnosed by the metacestode that is either a cysticercus or a form derived from a bladder-like larva; no other unequivocal synapomorphies are evident. Tree structure provides no support for recognition of a diversity of tribes or genera within the Taeniinae: Fimbriotaeniini and Taeniini have no phylogenetic basis. Hydatigera, Fimbriotaenia, Fossor, Monordotaenia, Multiceps, Taeniarhynchus, Tetratirotaenia must be subsumed within Taenia as synonyms. Taenia saginata and Taenia asiatica are sister species and distantly related to Taenia solium. Cospeciation with respect to carnivorous definitive hosts and Taenia appears to be limited. Although felids are putative ancestral hosts, contemporary associations appear to have resulted from extensive host-switching among felids, canids, hyaenids, and others. In contrast, relationships with herbivorous intermediate hosts are indicative of more pervasive coevolution; rodents as intermediate hosts are postulated as ancestral for the Taeniidae, Taenia + Echinococcus. Patterns appear consistent with rapid shifts between phylogenetically unrelated carnivores but among those that historically exploited a common prey resource within communities in specific biogeographic regions.
Animals↗
The differentiation of a newly described Asian taeniid from Taenia saginata using enzymatically amplified non-transcribed ribosomal DNA repeat sequences.
A newly described Asian taeniid which is morphologically indistinguishable from adult Taenia saginata has been identified in the aboriginal population of Taiwan. Hybridization patterns of restriction enzyme digested genomic DNA isolated from "Taiwan" Taenia and Taenia saginata revealed distinct variations between these cestodes. We have demonstrated by Southern blot analysis of ribosomal DNA fragments that Taiwan Taenia and T. saginata differ in a 2.4 kb fragment present in Bam HI digested DNA from T. saginata but absent from Taiwan Taenia DNA. The unique 2.4 kb sequence from T. saginata, as well as a partially homologous 3.1 kb fragment found in both Taiwan Taenia and T. saginata, contain sequences shown to be complementary to the 3'-end of the large ribosomal DNA subunit and to a large portion of the non-transcribed ribosomal DNA repeat. These fragments were subcloned into pUC 13 plasmid DNA, restriction enzyme mapped and partially sequenced. Two oligonucleotides complementary to regions on both the 2.4 kb and the 3.1 kb fragments were synthesized which generate 1.0 kb and 0.29 kb fragments specific for Taiwan Taenia and T. saginata, respectively, when used as primers during enzymatic amplification of cestode genomic DNA. Using this technique, we have been able to determine the identify of either cestode from a single proglottid with less than 200 ng of genomic DNA per reaction and further demonstrate that Taiwan Taenia exists in other parts of Eastern Asia.
Animals↗
Relaxation of depolarized guinea pig taenia caecum induced by some antispasmodics.
Taenia isolated from the guinea pig caecum were used for the experiments. No inhibitory response of the depolarized taenia to isoprenaline was observed during the significant increase of cyclic AMP level. These observations suggest that the total tissue level of cyclic AMP is not an important determinant of relaxation in the depolarized taenia. Antispasmodics, such as papaverine, benactyzine and Aspaminol (1,1-diphenyl-3-piperidino-butanol hydrochloride) relaxed the depolarized taenia, while the depolarized taenia was not relaxed by concentrations of dibutyryl cyclic AMP sufficient to relax the polarized taenia. Ca uptake by the depolarized taenia was inhibited by papaverine, benactyzine and Aspaminol but not by isoprenaline and dibutyryl cyclic AMP. These results indicate that relaxation of the depolarized taenia induced by the antispasmodics used was mainly due to inhibition of Ca uptake.
Animals↗
Effects of lesions of nucleus taeniae on appetitive and consummatory aspects of male sexual behavior in Japanese quail.
Neurochemical, hodological and functional criteria suggest that the nucleus taeniae and parts of the adjacent archistriatum represent the avian homologue of parts of the mammalian amygdaloid complex. It has been proposed in particular that the nucleus taeniae is the homologue of the mammalian medial amygdala. In male quail, relatively large lesions to the posterior/medial archistriatum selectively decrease the expression of appetitive sexual behavior in a manner reminiscent of similar manipulations involving the medial amygdala in mammals. We investigated the effects of discrete lesions restricted to nucleus taeniae and of lesions to an adjacent part of the archistriatum (pars intermedium ventralis, AIv) on the expression of appetitive (ASB) and consummatory (CSB) aspects of male sexual behavior. ASB was measured by a learned social proximity response (after copulation a male quail stands in front of a window providing visual access to a female) and by the frequency of rhythmic cloacal sphincter movements. CSB was assessed by the frequency of mount attempts (MA) and cloacal contact movements (CCM). Lesions confined to nucleus taeniae and to AIv did not influence the acquisition or the maintenance of the two responses indicative of ASB. In contrast, lesions of nucleus taeniae significantly increased the occurrence frequencies of MA and CCM when administered before the beginning of behavior testing and increased the frequency of MA only when performed on sexually experienced subjects. No effect of AIv lesions could be detected. The discrepancy between these results and previous experiments in quail might reflect procedural differences, but more probably differences in locations of the lesions that were restricted in the current study to the anterior part of taeniae. Those in the Thompson study were in the posterior part of this nucleus. These findings indicate that there is a larger degree of functional heterogeneity in the nucleus taeniae than previously thought. The effects of taeniae lesions suggest that this nucleus, similar to the medial amygdala in mammals, might be implicated in the control of sexual satiety.
Amygdala↗
Experimental infection of Thailand Taenia (Chiengmai strain) in domestic animals.
Twenty-five gravid proglottides of a Thailand Taenia were obtained from a patient in Chiengmai, Thailand, and brought to our laboratory. The tapeworm was determined to be T. saginata-like by counting uterine branches (mean number 16, range 12-19 on each side). The eggs from these proglottides remained infective under storage at room temperature for 14 days followed by refrigeration (4-8 degrees C) for 131 days. Eight Small-Ear-Miniature pigs and two Holstein calves were each fed with 3000 eggs and sacrificed 12-76 days afterwards. Six pigs became infected and 16 cysticerci were recovered from the livers. Thirteen degenerated/calcified cysticerci were also recovered from the livers of the two calves. More cysticerci were found in the liver parenchyma (55%) than on the liver surface (45%) of the infected animals. Measurements of length, width, diameters of protoscolex, rostellum and sucker and hooklet pattern show that Thailand Taenia is similar to Taenia from Taiwan, Korea and Indonesia but different from T. saginata and T. solium. These findings indicate that Thailand Taenia, Taiwan Taenia, Korea Taenia, and Indonesia Taenia may be of the same species or sub-species.
Animals↗
Detection of Taenia hydatigena copro-antigens by ELISA in dogs.
A sandwich-ELISA was developed for the detection of soluble Taenia hydatigena antigens in fecal samples of dogs. Affinity-purified polyclonal catching antibodies and alkaline phosphatase-conjugated detecting antibodies were employed, which had been obtained from rabbits hyperimmunized with excretory/secretory antigens derived from in vitro maintained adult Taenia hydatigena. The assay allowed the detection of 800 ng T. hydatigena antigen g-1 of feces as a lower limit. Six helminth-free dogs were each infected with 10 T. hydatigena cysticerci isolated from Swiss sheep. After prepatent periods ranging from 57 to 71 days, the dogs started to excrete Taenia eggs and/or proglottids. The ELISA detected Taenia antigens in all six dogs during the prepatent period starting individually between Day 18 and 45 post-infection (p.i.). Anthelmintic treatment of three dogs at Day 95 p.i. resulted in elimination of the cestodes and within the 5 following days in the disappearance of Taenia antigens from feces. The specificity of the assay was evaluated by testing crude antigens derived from helminths or bacteria. Four Taenia species showed cross-reactivity at concentrations of 5 micrograms protein ml-1. Conversely, no cross-reactions occurred with various antigen batches derived from Echinococcus granulosus, E. multilocularis, Dipylidium caninum, Mesocestoides corti, Diphyllobothrium sp., Toxocara canis and bacterial antigens (Salmonella and Escherichia). Moreover, fecal samples from dogs naturally infected with T. canis (n: 13), hookworms (n: 2), Trichuris vulpis (n: 13) and of 10 dogs with mixed infections with these three nematode groups were tested, and results confirmed the high degree of specificity. The Taenia antigens detectable by this ELISA remained immunologically stable in native feces stored at +25 degrees, +4 degrees or at -20 degrees C for at least 5 days.
Animals↗
Experimental studies of Korea Taenia (Cheju strain) infection in domestic animals.
In the present study, one DYL pig (five-day old), four L-SEM pigs (37-day old), three SEM pigs (44-day old), one Holstein calf (eight-day old) and two Sannean goats (five-day old) were each fed 1000, 30,000, or 380,000 eggs of the Korea Taenia (Cheju strain) and were sacrificed 16-105 days after inoculation. All DYL, L-SEM, and SEM pigs and the Holstein calf were susceptible to Korea Taenia, and one of the two Sannean goats became infected. The cysticerci recovery rates for L-SEM, SEM and DYL pigs, Holstein calf, and Sannean goat were 5.6, 1.7, 0.06, 0.03 and 0.02% respectively. Cysticerci were recovered only from the livers of the infected animals, and more cysticerci were found in the parenchyma (51%) than on the surface of the liver (49%). Immature cysticerci were first observed on day 16 after infection, mature ones on day 29, and degenerated or calcified cysticerci on day 30. Inoculation of a huge number (380,000) of Korea Taenia eggs lead to early degeneration or calcification of the cysticerci. The length, the width, and the diameters of protoscolex, rostellum, and sucker of the cysticerci were largely proportional to the period of inoculation. The measurements and patterns of the hooklets indicate that Korea Taenia is very similar to Taiwan Taenia but is different from T. saginata and T. solium. The results of the present study provide evidence that Korea Taenia and Taiwan Taenia may be of the same species.
Animals↗
The Asian Taenia and the possibility of cysticercosis.
In certain Asian countries, a third form of human Taenia, also known as the Asian Taenia, has been discovered. This Asian Taenia seems to be an intermediate between Taenia solium and T. saginata since in morphological terms it is similar to T. saginata, yet biologically, as it uses the same intermediate host (pigs), it is more akin to T. solium. Taenia solium causes human cysticercosis, while T. saginata does not. It is not known whether the Asian taeniid is able to develop to the larval stage in humans or not. The arguments proposed by those authors who consider it unlikely that the Asian Taenia causes human cysticercosis are: (a) its molecular similarities with T. saginata; (b) the absence of cases of human cysticercosis in populations where the Asian adult is highly prevalent; and (c) the unsupporting results derived from an experimental infestation study. These three arguments are debated, although bearing in mind that at present there is still no clear scientific data to support that human cysticercosis can be caused by the Asian Taenia.
Animals↗
Why are taeniae, haustra, and semilunar folds differentiated in the gastrointestinal tract of mammals, including man?
When a small change, either contraction or dilation, of the surface area of a digestive tube coincides with a considerable change in internal volume, this can be considered an effective influence of surface on volume. This study discusses the effects of anatomical differences between those types of digestive tracts where the longitudinal musculature is reduced to small bands, the taeniae, and those where such differentiations are not found. With the help of a geometric model the efficiency of transport (eta = net volume expelled aborally / volume of the tube) from haustra in tubes with two, three, four, and six taeniae was determined. It could be shown that efficiency of transport from haustra decreases when the number of taeniae increases. The second model applies the program "Surface Evolver" (author K.A. Brakke). The program is applied to investigate the relationships between changes in surface area of tubes with different numbers of taeniae (0, 2, 3, 4, and 6) and the respective changes of the internal volumes of tubes. Both haustra formation and formation of semilunar folds between haustra are considered. Tubes with two or three taeniae reduce their internal volume more efficiently than all others, namely, with a relatively small reduction of the surface area and contraction of the Tunica muscularis at a relatively low rate. In addition to chemical and mechanical decomposition of digesta the gastrointestinal tube has three tasks: propagation, storage, and retention of digesta. A tube without taeniae, i.e., with a complete longitudinal muscular layer, propagates contents with peristaltic movements. Storage can take place in areas of the tract with a dilated cross-section. Finally, folds can retain digesta. In many sections of the gastrointestinal tract folds are differentiated as permanent structures. However, folds formed with relatively little contraction of the musculature, i.e., little change in the surface area, represent an effective means of retention and thus of flow regulation. Tubes with taeniae and semilunar folds are adaptations for this effective type of regulation of digesta transit through the tract.
Animals↗