Outer Longitudinal Smooth Muscle Layer Research Articles

Temporal and spatial development of intestinal smooth muscle layers of human embryos and fetuses.

The sequential occurrence of three layers of smooth muscle layers (SML) in human embryos and fetus is not known. Here, we investigated the process of gut SML development in human embryos and fetuses and compared the morphology of SML in fetuses and neonates. The H&E, Masson trichrome staining, and Immunohistochemistry were conducted on 6-12 gestation week human embryos and fetuses and on normal neonatal intestine. We showed that no lumen was seen in 6-7th gestation week embryonic gut, neither gut wall nor SML was developed in this period. In 8-9th gestation week embryonic and fetal gut, primitive inner circular SML (IC-SML) was identified in a narrow and discontinuous gut lumen with some vacuoles. In 10th gestation week fetal gut, the outer longitudinal SML (OL-SML) in gut wall was clearly identifiable, both the inner and outer SML expressed α-SMA. In 11-12th gestation week fetal gut, in addition to the IC-SML and OL-SML, the muscularis mucosae started to develop as revealed by α-SMA immune-reactivity beneath the developing mucosal epithelial layer. Comparing with the gut of fetuses of 11-12th week of gestation, the muscularis mucosae, IC-SML, and OL-SML of neonatal intestine displayed different morphology, including branching into glands of lamina propria in mucosa and increased thickness. In conclusions, in the human developing gut between week-8 to week-12 of gestation, the IC-SML develops and forms at week-8, followed by the formation of OL-SML at week-10, and the muscularis mucosae develops and forms last at week-12.

Morphology of the Uterotubal Junction of the Cheetah (Acinonyx jubatus).

Less than 7,000 cheetahs survive in the wild. Captive breeding has proved notoriously difficult. The uterotubal junction acts as major barrier and regulator to the passage of sperm. This study describes the morphology of the uterotubal junction of the cheetah. Reproductive tracts were obtained from seven cheetahs that succumbed from natural causes or were euthanized for humane reasons. The uterotubal junction was isolated and examined macroscopically and microscopically. The extramural isthmus made a characteristic 90° bend before entering the mesometrial border of the uterus close to its tip. The intramural isthmus had approximately four primary folds lined by nonciliated cuboidal to low cuboidal epithelium. The Tunica muscularis was robust, merged with its uterine counterparts and consisted of an inner circular layer and outer longitudinal smooth muscle layer. The uterine ostium opened via a muscular and glandular papilla that projected from the apex of the uterine lumen. A sharply demarcated circular zone of simple columnar epithelial cells surrounded the uterine ostium and separated the simple cuboidal to low cuboidal cells of the isthmus and uterine epithelium from each other. Branched tubulo-alveolar glands, some with dilated lumens, were present in the papilla and sometimes extended into the adjacent endometrium. These glands might act as sperm storage areas, and could easily be confused with cystic endometrial hyperplasia. Low transverse endometrial ridges surrounded the papilla and extended caudally for a short distance before disappearing. The uterine glands were lined by a simple cuboidal epithelium. Anat Rec, 302:1855-1864, 2019. © 2019 American Association for Anatomy.

Morphological features of the distal ileum and ceca of the common pigeon (Columba livia)

Background to the study: Common pigeon ( Columba livia ) is widely distributed worldwide and feeds mainly on grains or seeds and insects and small invertebrates. Some studies have demonstrated variations in the morphology and function of avian alimentary tract. Methods: Ten apparently healthy adult common pigeons were examined in this study. Following euthanasia, gross and histological techniques were used to investigate the morphology of the distal ileum and ceca of common pigeon. Results: At the ileo-ceco-rectal junction, the tunica muscularis of the distal ileum exhibited a thickened layer of oblique smooth muscle fibers positioned between the middle circular and outer longitudinal smooth muscle layers. The ceca of the common pigeon were paired, small (approximately 0.33 cm), blind-ended sacs situated at acute angles with the distal ileum. Histologically, each cecum exhibited a lamina propria-submucosa that contained aggregates of lymphocytes and few glandular acini throughout the length of the organ. Conclusion: It was suggested that the ceca of the common pigeon may be important in immunological response of the bird to invasion by antigens while playing some roles in the digestion of food materials. Moreover, the thickened oblique layer of smooth muscle fibers in the wall of the distal ileum may serve to regulate the passage of materials through the ileo-ceco-rectal orifice. Keywords: Cecum, common pigeon, distal ileum, lamina propria‑submucosa, sphincter

Embryonic Diffrentiation of the Colon of One Humped Camel (Camelus Dromedarius): A Histomorphology

A study involving histomorphological differentiation was conducted on the colon of 35 foetuses (both sex) of the one-humped camel collected from the Sokoto metropolitan abattoir, over a period of five months at different gestational ages. The approximate age of the fetuses was estimated and categorized into first, second and third trimester. Grossly, the color of the large intestine was whitish at first trimester and grayish to white in second and third trimester. The colon was divided into three main portions namely the ascending colon, the coiled and the descending part which formed the long part of the colon in second and third trimesters. At first trimester the coiled part was not differentiated but divided into two parts such as the centripetal and centrifugal part at second and third trimester. Histological observation of the tissues in this study revealed a complete structure of the tubular organ. The colon was found to consist of four layers namely: Tunica mucosa, Tunica sub mucosa, Tunica muscularis and Tunica serosa. The epithelium of the Tunica mucosa was stratified squamous epithelium with varying degree of stratification at first trimester and transformed to low columnar /cuboidal epithelium at second trimester. At third trimester, the epithelium was simple columnar epithelium. The lamina propria mucosa was found absent at first trimester but prominent at second and third trimester. The Lamina muscularis mucosa was found prominent at third trimester but not identified at first and second trimester. At first trimester of age tunica submucosa was prominent while at second trimester, it consisted of connective tissue cells and fibres scattered all over the layers with preliminary blood vessels. The cells and fibres were undifferentiated at this stage. There was no evidence of lymphatic nodular cells within the layer. At third trimester of age, the connective tissues and blood vessels were found prominent and the lymphatic nodular cells were found throughout the length of the colon. The tunica muscularis of camel colon consist of inner skeletal and outer longitudinal smooth muscle layers. At first trimester this layer did not differentiate into these two zones but only longitudinal orientation of smooth muscle layer. At second trimester, the layers of two zones with clear demarcation were observed. A thin layer of connective tissue comprising of undifferentiated cells lined the colon externally was observed in all the stages of development. Based on the above findings, it showed that development of the camels’ colon was histologically in succession and different from other domestic animals by having an extensive skeletal muscle at the tunica muscularis.

Histopathological and immunohistochemical study of the wall of spermatic veins and its potential role in the development of varicocele testis

IntroductionVaricocele is defined as a pathological alteration in the venous circulation of the testis which appears almost exclusively on the left side.The aim of current work was to compare the normal structure of the wall of the veins of the pampiniform plexus and also to highlight the occurrence of any structural alterations in these veins in cases of primary varicocele through a combined histopathologic and immunohistochemical study. MethodsHistopathological examination and immunohistochemical studies using monoclonal antibodies against CD31 (a marker for endothelial cells) and neurofilament-200 (NF-200) (nerve fiber marker) were performed on spermatic vein fragments of 30 varicocele patients and 30 normal spermatic veins obtained from patients undergoing inguinal herniectomy. ResultsNormal spermatic veins showed an inner circular smooth muscle (SM) layer in the tunica media, and an outer longitudinal SM layer in the tunica adventitia. Grade I varicocele cases, showed an increase in the connective tissue of the adventitia and of the tunica media, which increased proportional to the degree of varicocele. The outer longitudinal smooth muscle layer of the large spermatic veins was significantly degraded in the presence of varicocele grades I and II, and did not even exist in varicocele grade III. Immunostaining for CD31 and NF-200 revealed that vasa vasorum and nerve fibers were decreased in the wall of large spermatic veins in patients with grades I and II varicocele, and were minimal to absent in patients with grade III varicocele. ConclusionThe wall of pampiniform plexus veins is a complex structure of smooth muscle organization, inner circular and outer longitudinal fibers which is important for providing an effective blood transport through the pampiniform plexus. This mechanism is obviously damaged in varicocele patients.

Postnatal development of excitatory innervations in longitudinal smooth muscle of the chicken anterior mesenteric artery

Aims The anterior mesenteric artery of chickens contains a well-developed outer longitudinal smooth muscle layer in addition to an inner circular layer. Cholinergic and purinergic neurons play crucial roles in excitatory transmission at the longitudinal smooth muscle. The aim of this study was to clarify postnatal development of excitatory neurotransmission of the longitudinal smooth muscle. Main methods Membrane potentials of smooth muscle were recorded with a microelectrode technique. Perivascular nerves were stimulated by applying electrical field stimulation (EFS). Key findings Histological examination showed that longitudinal smooth muscles exist in the artery at birth. EFS failed to evoke membrane response in 1-day-old chickens, though it caused depolarization (excitatory junction potential; EJP) in 12-week-old chickens. However, exogenous application of acetylcholine (ACh) or ATP produced depolarization in longitudinal smooth muscle of 1-day-old chickens, suggesting that responsiveness of smooth muscle to excitatory neurotransmitters is already established at birth. In preparations isolated from 10-day-old chickens, EFS caused EJP, which was totally blocked by atropine but not by a non-specific purinoceptor antagonist, suramin. Several purinoceptor subtypes including P2Y1, which may be related to depolarizing response in smooth muscle of adult chickens, were expressed in the anterior mesenteric artery of 10-day-old chickens. Significance Excitatory innervation in longitudinal smooth muscle of the chicken anterior mesenteric artery is not established at birth but develops during the early postnatal period. Moreover, development of cholinergic excitatory innervation precedes that of purinergic excitatory innervation, although receptors that mediate purinergic control are already expressed in smooth muscle.

Stress-strain distribution in the human stomach

A biomechanical model of the human stomach is proposed, that is based on detailed biological data of the structure and function of the organ. The process of electromechanical conjugation and the spread of the electromechanical wave along the stomach wall were analyzed numerically. Results revealed patterns of stress-strain distribution in the organ. Thus the fundus, the body and the antrum of the organ always experience biaxial stress-strain states, while the cardia and the pylorus undergo uniaxial loading. The circular smooth muscle layer produced greater total forces throughout in comparison to the outer longitudinal smooth muscle layer. The body of the organ along the lesser curvature and the cardia-fundus areas were overstressed compare to other regions. Although the theoretical results resemble qualitatively patterns of electrical and mechanical activity observed in vivo and in vitro there is currently no affirmative experimental evidence to provide a detailed quantitative comparison of the results.

P2X purinoceptors mediate an endothelium‐dependent hyperpolarization in longitudinal smooth muscle of anterior mesenteric artery in young chickens

The chicken anterior mesenteric artery contains an outer longitudinal smooth muscle layer, whose neural regulation remains to be elucidated. ATP evokes a depolarization in the smooth muscle through P2Y purinoceptors. However, there may be an additional inhibitory regulation because blockade of P2Y purinoceptors converts the depolarization to hyperpolarization. The objective of the present study was to examine the mechanism underlying this hyperpolarization. Membrane potentials of longitudinal smooth muscle of the chicken mesenteric artery were recorded with a microelectrode technique. Perivascular nerves were stimulated by applying electrical field stimulation (EFS). EFS induced a hyperpolarization in preparations obtained from 5-week-old chickens, whereas it evoked a depolarization in those from 12-week-old chickens. The EFS-evoked hyperpolarization in 5-week-old chickens was blocked by a non-specific purinoceptor antagonist, suramin, and by a specific P2X purinoceptor antagonist, pyridoxal phosphate-6-azophenyl-2',4'-disulphonic acid. Desensitization of the P2X purinoceptor with its agonist alpha,beta-MeATP significantly suppressed EFS-evoked hyperpolarization. Blockade of the P2Y purinoceptor did not affect EFS-evoked hyperpolarization. The application of the NOS inhibitor Nomega-nitro-L-arginine methyl ester or the removal of the endothelium inhibited the hyperpolarization. The application of the nitric oxide (NO) donor sodium nitroprusside mimicked the hyperpolarization. Reverse transcriptase-PCR showed that P2X purinoceptors are expressed in the endothelium of the anterior mesenteric artery. Hyperpolarization in the longitudinal smooth muscle of the chicken anterior mesenteric artery was induced by ATP. ATP released from perivascular nerves may act on P2X purinoceptors in the endothelium and thereby stimulate NO production.

Resolving the three-dimensional myoarchitecture of bovine esophageal wall with diffusion spectrum imaging and tractography

In order to determine the three-dimensional (3D) resolved muscular anatomy of the mammalian esophagus, we have examined its myoarchitecture with diffusion spectrum magnetic resonance imaging (DSI) and tractography. DSI measures diffusion displacement as a function of magnetic gradients of varied direction and intensity and displays the displacement profile as a 3D contour per voxel. In tractography, the orientation vectors of maximum diffusion/voxel are identified, and intervoxel associations are constructed by a streamline algorithm based on angular similarity in order to generate mesoscale myofiber tracts. We demonstrate that the proximal body of the esophagus consists of helically aligned crossing fiber populations that overlap between layers in the form of a "zipper" region along the length of the tissue. With increasingly distal position along the length of the tissue, helix angle and skeletal muscle prevalence are reduced such that fibers align themselves in the most distal location into distinct inner circular and outer longitudinal smooth muscle layers. We conclude that esophageal myoanatomy consists of crossing myofibers exhibiting a decreasing degree of helicity as a function of axial position and propose that this unique geometric construct provides a mechanism to resist distension and promote aboral flow.

A nude mouse xenograft model of fetal intestine development and differentiation.

This report describes a novel in vivo model of intestinal differentiation. Fourteen day, undifferentiated fetal rat small intestine, stripped of the major part of its mesenchyme, suspended in a type I collagen gel and then xenografted into a nude mouse, undergoes small intestinal morphogenesis and cytodifferentiation. All four major epithelial lineages, namely Paneth, goblet, columnar and endocrine are present. Double-label nonisotopic in situ hybridization, employing biotinylated and digoxigenin-labelled whole rat DNA and whole mouse DNA probes, was performed to distinguish donor cells from host cell types. The outer longitudinal smooth muscle layer, and the major part of the lamina propria, including pericryptal fibroblasts, are of host mouse origin; the inner circular smooth muscle layer is of donor rat origin. Cells of the muscularis propria and lamina propria acquired smooth muscle alpha-actin, presumably under the influence of the donor endoderm. Furthermore, this xenograft develops a host vascular network, and cells with the morphological appearance of lymphocytes are present within the intestinal epithelium. The production of chemotactic factors by the endoderm is postulated because grafting of collagen gel alone results in a minimal invasion by stromal cells which do not express smooth muscle alpha-actin.

Autoradiographical localization of oxytocin binding sites on ovine oviduct and uterus throughout the oestrous cycle.

A highly specific oxytocin receptor ligand, 125I-labelled d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH9(2)] vasotocin (125I-OTA), was used to localize high affinity oxytocin receptors in ovine uterine and oviduct tissues throughout the oestrous cycle. The pattern of binding revealed by in vitro autoradiography correlated well with the results of the homogenate receptor assays using the same ligand and with previous binding assays using the tritiated ligand. At oestrus, specific 125I-OTA binding was evident on the luminal epithelium of the caruncular and intercaruncular regions, on the epithelial cells lining the secretory uterine glands and in the stroma underlying the caruncular epithelium. In the myometrium diffuse labelling was evident in the outer longitudinal smooth muscle layer. At Day 4 of the cycle, binding to the stroma was diffuse and virtually absent from the glandular epithelium. No specific binding was evident in either tissue at Day 12 of the luteal phase, but by Day 14, prior to the decrease in peripheral progesterone concentrations, binding was again apparent on the luminal epithelium only. Specific binding to the oviduct was localized to the smooth muscle layer of the isthmus region of oestrous ewes and was not detected at any other stage of the oestrous cycle. These studies extend our knowledge of the distribution of oxytocin binding sites in uterine and oviduct tissues throughout the oestrous cycle and suggest that oxytocin has an important role in stimulating oviduct and uterine motility at a time crucial to successful egg collection and/or sperm embryo transport.

Localization of the Sites of Synthesis and Action of Insulin-Like Growth Factor-I in the Rat Uterus

In this report we have used in situ hybridization to localize insulin-like growth factor-I (IGF-I) expression in the uterus and have examined the effects of exogenous IGF on 3H-methyl thymidine incorporation into DNA, in uterine sections in organ culture. IGF-I mRNA was detected in all layers of the uterus but was particularly abundant in the outer longitudinal smooth muscle layer. Although IGF-I mRNA was detectable in untreated, immature rat uteri, the abundance in each layer of the uterus was increased after 17 beta-estradiol (E2) administration. A similar increase was seen in uteri from ovariectomized, hypophysectomized rats treated with E2. IGF-I when added to uterine sections in organ culture had no significant effect on DNA synthesis in the absence of E2. However, a dose-dependent increase in DNA synthesis was seen in the presence of E2. The half-maximal and maximal responses required 1 and 10 ng IGF-I, respectively. Autoradiographic localization of 3H-methyl thymidine incorporation into DNA demonstrated that the majority of the DNA synthesis occurred in the stromal layer. These findings are consistent with the hypothesis that IGF-I may function as a paracrine growth factor, mediating stromal-myometrial cell interaction.

Histological and ultrastructural specialization of the digestive tract of the intestinal air breather hoplosternum thoracatum (teleost).

The digestive tract of Hoplosternum thoracatum consists of an esophagus, gastric area, anterior digestive intestine with elaborate folds, digestive intestine with decreasing folds and thin, smooth-surfaced respiratory intestine. The upper tract has a mucoid columnar lining which is gently folded, whereas the gastric area has numerous pits opening into the tubular secretory glands. Striated muscle comprises the anterior muscularis but is replaced by inner circular and outer longitudinal smooth muscle layers in the gastric region. The digestive intestinal mucosa is elaborately folded, consisting of columnar cells with prominent brush borders. Mucosa, submucosa, circular and longitudinal muscularis and serosa layers are present throughout the tract. Goblet cells occur in both the digestive and respiratory intestine. Major changes that appear in the respiratory intestine are a drastic reduction in mucosa epithelial thickness and the penetration of an elaborate capillary bed into the epithelium. The other basic layers are not significantly reduced in thickness. The air-blood barrier consists of the thin epithelium, basement lamina and very thin capillary endothelium. Regional cellular composition and ultrastructural features are correlated with respective digestive and respiratory functions.