Pyramidalis Muscles Research Articles

New Insights Into the Development of the Anterior Abdominal Wall.

PurposeAmong the few studies that have examined the development of the anterior abdominal wall, several are based on incomplete “series”, substituted in many cases by non-human specimens.Material and MethodsIn total, 19 human embryos corresponding to Carnegie stages 15–23, 36 fetuses with estimated gestational ages ranging from 9 weeks to term, and eight neonates were included in this study. All specimens belong to the collection of the Department of Anatomy and Embryology at the Complutense University of Madrid.ResultsThe muscles of the anterior abdominal wall appear in the dorsal region at stages 15 and 16 (33–37 days). At stages 17 and 18 (41–44 days), this muscular mass grows ventrally and splits into two sheets: the external abdominal oblique muscle and the common mass of the internal abdominal oblique, and the transversus abdominis muscles, all of which end ventrally in the primitive condensation of the rectus abdominis. In embryos at stages 19 and 20 (48 days), the anterior abdominal wall continues to show an umbilical hernia in the amniotic cavity. However, a narrow neck is apparent for the first time and there is a wider anterior abdominal wall below the hernia made up of dense mesenchyme tissue without layers and showing the primordia of the umbilical canal. In embryos at stages 21, 22, and 23 (51–57 days), the abdominal muscles and aponeuroses cross the midline (linea alba) covering the rectus abdominis and pyramidalis muscles while the umbilical hernia has shrunk. In fetuses during the 9th and 10th weeks, the umbilical hernia becomes encircled by the rectus abdominis muscle, its aponeurosis, and the three layers of lateral abdominal muscles, which are more developed and covered by Camper's and Scarpa's fasciae. The inguinal canal has a course and relationships like those described in adults, with Hesselbach's ligament.

The topography and morphometrics of the pubic ligaments

BackgroundConflicting anatomical reports and the little attention given to the pubic ligaments impede the interpretation of radiological and clinical examinations on groin pain. Morphometric data on the pubic ligaments are lacking. MethodsThe muscular relations of the symphysis pubis were examined in layered dissection (n = 10), hemipelves (n = 60) and (un)stained plastinated body slices of body donors (n = 3). The sagittal and coronal areas, width, mean and maximum thickness of pubic ligaments were determined. ResultsThe adductor longus, brevis, rectus abdominis and pyramidalis muscles are attached to the anterior pubic ligament (APL). The adductor brevis and gracilis muscle are connected to the inferior pubic ligament (IPL). The IPL and superior pubic ligament (SPL) are thicker than the APL and posterior pubic ligament (PPL). The PPL is the thinnest pubic ligament. The APL has a larger sagittal area in women than in men compared to the IPL. The SPL and IPL are thicker in men compared to women. ConclusionThe APL is the ligamentous anchor for the originating and inserting muscles. Investigations of the pubic ligaments might help to determine symphysis instability or severity of injury and should be included as a further criterion for surgical management.

Morphometry and Frequency of the Pyramidalis Muscle in Adult Humans: A Pyramidalis Muscle's Anatomical Analysis

OBJECTIVES:To verify the pyramidalis muscle’s frequency (bilaterality, unilaterality, or absence) and morphometry (length of the medial border and width of its origin/base) in a sample of the Brazilian population and the anthropometric influence.METHODS:Dissection of 30 cadavers, up to 24h post-mortem.RESULTS:The pyramidalis muscle was present bilaterally and unilaterally in 83.33% and 3.33% of the cadavers, respectively, and absent in 13.33%. The muscles on the right and left sides were symmetrical in length but not in width; the pyramidalis muscles of men were longer, while those of the women were wider. We also found that there was greater variation in the dimensions (length and width) of the men’s muscles. Finally, in this sample of the Brazilian population, the pyramidalis muscle’s unilaterality was more prevalent than in other populations, and its complete absence was less prevalent.CONCLUSIONS:There were no cases of muscle duplication in one or both sides, as described in some studies. Despite all of its morphometric variation, the pyramidalis muscle maintained its triangular shape with longitudinal fibers in every case. Furthermore, no statistically significant correlation was noted between the muscles’ dimensions and person’s age, height, weight, or gender.

Morphometry and Frequency of the Pyramidalis Muscle in Adult Humans

The pyramidalis muscle is a small triangular muscle located in the inferior part of the anterior abdominal wall. It can be bilateral, unilateral, duplicated in one or both sides, or also absent, and its incidence and morphometry vary between populations. Moreover, although its function is not well known, there are still few researches describing that it. Therefore, considering the literary scarceness regarding the pyramidalis and the inexistence of morphometric data of such muscle in Brazil, it becomes considerably relevant collecting that data in brazilian people. Thus, this study describes the pyramidalis muscle morphometry in a sample of brazilian population, verifying its dimensions, frequency, bilaterality, unilaterality, and other anatomical variations that may be found. Then, we compare the values obtained with other studies. With it, besides deepening knowledge about pyramidalis' functions, some medical procedures could be done in a more rationalized way, such as abdominal incisions, e.g. Pfannenstiel, once the pyramidalis' can be used as reference to these incisions; and grafts, once the absence of the pyramidalis doesn't cause notable disfunction.The study comprised 21 cadavers of individuals older than 18 years (SVOC/FMUSP). Each one of them was dissected, exposing the pyramidalis muscles (if present), without releasing it from its original place, allowing to take photos for posterior measuring (pyramidalis medial border length and width in its origin/base) in image processing program Image.Out of the 21 cadavers, 7 were females and 14 males. The pyramidalis muscle was present bilaterally in 16/21 (76.19%) of the cadavers, present unilaterally in 2/21 (9.52%) and absent in 3/21 (14.28%). The size of the medial border of the left and right‐sided pyramidalis ranged from 3.50–10.67 cm; and the size of the pyramidalis basis' length ranged from 0.91–2.93 cm in the left side, and from 1.10–2.50 cm in the right side. The mean size of the medial border of the pyramidalis was 6.30 ± 1.97 cm in the left side and 6.69 ± 2.07 cm in the right side. The mean size of the pyramidalis basis' width was 1.99 ± 0.23 cm in the left side and 1.90 ± 0.35 cm in the right side.We found out that, in this sample, males presented longer and wider Pyramidalis than females. Besides that, the incidence of the pyramidalis in this sample of the brazilian population was one of the lowest, comparing to other populations . And, lastly, comparing the dimensions in women, in the present study the pyramidalis was wider and usually longer than in women from other populations .This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Variation and incidence of agenesis of the pyramidalis muscles in Nigerian males

In recognition of the variations in occurrence, shape and size of the pyramidalis muscle in different races, sexes and nationals and its relevance in flap and graft, this study was carried out to determine the incidence of its agenesis, variation in occurrence, shape and mean values of length and breadth in Nigerian males. A total of 24 male cadavers from the Anatomy Laboratories of different Nigerian Universities were used in this study. Dissection of the lower anterolateral abdominal wall was made to ascertain the presence, shape and size of the muscle. Agenesis occurred in 8.33% of the subjects studied. There was no case of unilateral occurrence or supernumerary presence and the predominant shape was triangular with no difference in shape on either side. The mean values of the length and the breadth for the right pyramidalis muscle were 8.09 0.70 and 1.55 0.28, while the mean values of 7.94 1.71 and 1.6 0.30 were recorded for the left. These differences were found not to be statistically significant (P> 0.05). Our findings suggest that the incidence of agenesis of the pyramidalis muscle in Nigerian males is not common and there are no significant differences in the sizes of the muscle on either size.

Architecture and fiber type of the pyramidalis muscle

The paired pyramidalis muscles are small triangular-shaped muscles that lie between the anterior surface of the rectus abdominus and the posterior surface of the rectus sheath. The precise function of pyramidalis muscles is unclear, but together the muscles are thought to tense the linea alba. The muscles are not always present, or are often unilateral, and vary greatly in size. Their wider inferior margins attach to the pubic symphyses and pubic crests, whereas their narrow superior margins attach to the linea alba. The gross anatomy and innervation of the pyramidalis muscles has been described by others, but their architecture and fiber type have not been determined in previous publications. The purpose of the present paper was therefore to investigate these parameters and place the findings into context for the literature available on this muscle. An example of bilateral pyramidalis muscles was recently encountered in a male cadaver that provided ample tissue for an analysis of its architecture and fiber type. The muscle mass, muscle length, fiber length, and pennation angle of muscle fibers were measured to ascertain physiological cross-sectional area and thereby estimate force production. Fiber type composition was also examined using immunofluorescent labeling. The results show that this is a muscle of mixed fiber type composition, similar to the rectus abdominus, and that the estimated forces generated by this muscle are relatively small.

Ocular morphology of the Leatherback sea turtle (Dermochelys coriacea)

The Leatherback sea turtle is the largest extant reptile and the sole member of the family Dermochelyidae. Here, the eye of this critically endangered marine turtle was investigated to determine the anatomy, optics, and optical sensitivity. Three Leatherback sea turtles, Dermochelys coriacea. The eye is small in proportion to body size of the adult compared to other vertebrates, with prominence of the retractor bulbi and pyramidalis muscles. The nictitans shows extensive folding of the bulbar conjunctiva as an apparent mechanism to increase the surface area for mucus secretion. The intraocular anatomy is consistent with an eye adapted to aquatic vision with minimal curvature of the cornea, a near-spherical lens, deep ciliary cleft and highly vascularized ciliary body. The optical sensitivity, a measure of the sensitivity to light of a given optical system, is higher than in other marine turtles studied but lower than those found in teleost fish that share a habitat with the Leatherback sea turtle. The Leatherback sea turtle shows ocular features that are characteristic of Chelonians with similarities to aquatic mammals. The calculated optical sensitivity suggests that compared to pelagic fishes, for instance, the Leatherback sea turtle eye is not particularly well adapted for vision in dim light even though this species is known to venture into deep, dark waters, and might feed at night.

Anatomical significance of the nerve to the pyramidalis muscle: A morphological study

Characteristics of the nerve to the pyramidalis muscle (NPy), including its origin, course and distribution, were observed (macroscopically) in detail in the present study. The spinal segments that give rise to the nerve vary considerably and involve Th12-L2. The course and distribution of the nerve also vary widely. The NPy is given off from one of the following: (i) the anterior cutaneus branch (Rca) of the intercostals nerve; (ii) the ilioinguinal (li) nerve; or (iii) the genital branch (Rg) of the genitofemoral nerve. The NPy can be classified into nine types according to features of the course and branching pattern of the Rca and li. In three of 67 cases, the pyramidalis muscle had two nerves. Double-innervated pyramidalis muscles received one nerve from a transitional-type Rca (Rcat) and a second nerve derived from one of the superficial Rca (Rcas), li or Rg. The NPy derived from the deep Rca (Rcap; Type 1), Rcat (Type 2) and containing their features as well as the Type 9 (Rcat + li + Rg) reach the muscle from behind. Types 3-8 (not containing features of the Rcap and Rcat) enter the muscle from its surface. The branch that gives off the NPy is determined by the level of segmental origin, with the segmental origin of branches from the Rca (Types 1-4), li (Types 5-6) and Rg (Types 7-9) getting lower in that order. The level of segmental origin of the NPy derived from different Rca becomes lower in the following order: Rcap (Type 1), Rcat (Type 2), Rcas (Type 3), Rcas' (Rcas entering the inguinal canal; Type 4). When the origin of the NPy is from a lower segment, the origin of the boundary nerve (Rcap/Rcas) is also deviated downward. The changes in the NPy are related to the deviation of the entire lumbar plexus.

The Modified Misgav-Ladach versus the Pfannenstiel-Kerr Technique for Cesarean Section: A Randomized Trial

Suturing the uterine wall after cesarean section, begun in the late 19th century, markedly lowered the mortality risk from operative delivery. Pfannenstiel, in 1897, proposed making a curved transverse suprapubic incision in the abdominal skin, and Kerr, in 1926, first described the transverse lower-segment incision accompanied by double-layer uterine wall sutures and peritoneal closure. In 1972, Joel-Cohen described a transverse skin incision made 5 cm above the pubic symphysis along with blunt dissection of the abdominal wall. Subsequently, single-layer suturing of the uterus and not closing the peritoneum were introduced. These innovations and subsequent changes are termed the modified Misgav-Ladach (MML) technique after the major hospital contributing to their development. The investigators planned a prospective, randomized study of 162 patients having transverse lower-uterine-segment cesarean section, 88 of them with the MML technique and 74 by the Pfannenstiel-Kerr method. After making a Pfannenstiel skin incision, the subcutaneous tissue is opened upward in the midline to reach the rectus sheath above the point of insertion of the pyramidalis muscles. The subcutaneous tissue is extended and the rectus muscles separated digitally. The parietal peritoneum is opened at the level of the upper intermuscular space, also digitally. A transverse lower-segment incision 2 to 3 cm in length then is made involving both the peritoneum and myometrium. After dissecting the remaining uterine fibers and opening the fetal membranes, the incision is extended laterally by blunt dissection, and the fetus and placenta are extracted. The uterine fundus may be removed from the abdominal cavity if necessary to aid suturing. The uterine incision is closed by one-layer suturing. The visceral and parietal peritoneum are not sutured. Finally, the rectus sheath is sutured, as is the subcutaneous tissue if it is deeper than 2 cm. There were no significant differences between the two surgical groups in maternal age or weight, gestational age, parity, previous cesarean section, frequency of a nonreassuring fetal sate, or maternal/fetal conditions that contraindicate vaginal delivery. No patient had intraoperative complications or postpartum endometritis, but one woman in the MML group who was taking heparin had serious postoperative bleeding. The MML technique took significantly less time than the Pfannenstiel-Kerr approach. Women in the MML group tended to have less febrile morbidity, but there were no important group differences in analgesic needs, return of bowel function, by the second day, or wound complications. These observations suggest that the MML technique will prove more cost-effective than earlier techniques of cesarean delivery, in part because of a shorter operating time and a lesser need for suture material. Using the more recently developed approach does not appear to compromise the immediate condition of the mother or infant.

Myotube heterogeneity in developing chick craniofacial skeletal muscles.

Avian skeletal muscles consist of myotubes that can be categorized according to contraction and fatigue properties, which are based largely on the types of myosins and metabolic enzymes present in the cells. Most mature muscles in the head are mixed, but they display a variety of ratios and distributions of fast and slow muscle cells. We examine the development of all head muscles in chick and quail embryos, using immunohistochemical assays that distinguish between fast and slow myosin heavy chain (MyHC) isoforms. Some muscles exhibit the mature spatial organization from the onset of primary myotube differentiation (e.g., jaw adductor complex). Many other muscles undergo substantial transformation during the transition from primary to secondary myogenesis, becoming mixed after having started as exclusively slow (e.g., oculorotatory, neck muscles) or fast (e.g., mandibular depressor) myotube populations. A few muscles are comprised exclusively of fast myotubes throughout their development and in the adult (e.g., the quail quadratus and pyramidalis muscles, chick stylohyoideus muscles). Most developing quail and chick head muscles exhibit identical fiber type composition; exceptions include the genioglossal (chick: initially slow, quail: mixed), quadratus and pyramidalis (chick: mixed, quail: fast), and stylohyoid (chick: fast, quail: mixed). The great diversity of spatial and temporal scenarios during myogenesis of head muscles exceeds that observed in the limbs and trunk, and these observations, coupled with the results of precursor mapping studies, make it unlikely that a lineage based model, in which individual myoblasts are restricted to fast or slow fates, is in operation. More likely, spatiotemporal patterning of muscle fiber types is coupled with the interactions that direct the movements of muscle precursors and subsequent segregation of individual muscles from common myogenic condensations. In the head, most of these events are facilitated by connective tissue precursors derived from the neural crest. Whether these influences act upon uncommitted, or biased but not restricted, myogenic mesenchymal cells remains to be tested.

Myotube heterogeneity in developing chick craniofacial skeletal muscles

Avian skeletal muscles consist of myotubes that can be categorized according to contraction and fatigue properties, which are based largely on the types of myosins and metabolic enzymes present in the cells. Most mature muscles in the head are mixed, but they display a variety of ratios and distributions of fast and slow muscle cells. We examine the development of all head muscles in chick and quail embryos, using immunohistochemical assays that distinguish between fast and slow myosin heavy chain (MyHC) isoforms. Some muscles exhibit the mature spatial organization from the onset of primary myotube differentiation (e.g., jaw adductor complex). Many other muscles undergo substantial transformation during the transition from primary to secondary myogenesis, becoming mixed after having started as exclusively slow (e.g., oculorotatory, neck muscles) or fast (e.g., mandibular depressor) myotube populations. A few muscles are comprised exclusively of fast myotubes throughout their development and in the adult (e.g., the quail quadratus and pyramidalis muscles, chick stylohyoideus muscles). Most developing quail and chick head muscles exhibit identical fiber type composition; exceptions include the genioglossal (chick: initially slow, quail: mixed), quadratus and pyramidalis (chick: mixed, quail: fast), and stylohyoid (chick: fast, quail: mixed). The great diversity of spatial and temporal scenarios during myogenesis of head muscles exceeds that observed in the limbs and trunk, and these observations, coupled with the results of precursor mapping studies, make it unlikely that a lineage based model, in which individual myoblasts are restricted to fast or slow fates, is in operation. More likely, spatiotemporal patterning of muscle fiber types is coupled with the interactions that direct the movements of muscle precursors and subsequent segregation of individual muscles from common myogenic condensations. In the head, most of these events are facilitated by connective tissue precursors derived from the neural crest. Whether these influences act upon uncommitted, or biased but not restricted, myogenic mesenchymal cells remains to be tested. Dev Dyn 1999;214:178–194. © 1999 Wiley-Liss, Inc.

Developmental relations between sixth nerve motor neurons and their targets in the chick embryo.

The developmental relations between abducens (VI) nerves and their targets, the lateral rectus, quadratus, and pyramidalis muscles, have been examined in the chick embryo from early neural tube stages through 10 days of incubation. Sites of myoblast origins were determined by microinjection of replication-incompetent retroviruses containing the LacZ reporter into paraxial mesoderm corresponding to somitomeres 3-5. Motor neurons and axons were identified by Bodian staining, immunocytochemistry, and application of DiI and DiO to dissected peripheral nerves. Anlage of the dorsal oblique originate in somitomere 3, close to the ventrolateral margin of the mid-to-caudal mesencephalon. Precursors of the lateral rectus arise deep within somitomere 4, beside the future metencephalon (rhombomere "A"). Quadratus and pyramidalis precursors are located between and partially segregated from these other two anlage. VIth nerve axons exit rhombomeres 5 and 6 via multiple median roots, fasciculate, and by stage 17 have elongated rostrally beneath the hindbrain. Immediately caudal to a mesenchymal pre-muscle condensation located deep to rhombomere 2, the VIth nerve separates into two branches. One branch enters the rostral portion of the condensation, from which quadratus and pyramidalis muscles will segregate. This branch projects exclusively from rhombomere 5 and is the accessory abducens nerve. The other branch enters the caudal, presumptive lateral rectus, region of the condensation. This is the abducens nerve, and it projects from cells located in both rhombomeres 5 and 6. These findings indicate that specific matching of motor nerves with their presumptive targets begins prior to the differentiation and segregation of myogenic populations, and that spatial organization of developing eye muscles is initiated well before they interact with connective tissue precursors derived from the neural crest.

Types of muscle fibers in the extraocular muscles of birds

Eye muscles of the quail, pigeon, sparrow and canary were examined histologically to see if their fibers are differentiated into two or more types, as has been described for mammals. In each oblique and rectus muscle examined, an area along the orbital border was found to be occupied by fibers of small cross-sectional area, and a more extensive central portion predominantly by large-caliber fibers. These fiber populations were separable on the basis of levels of α-glycerophosphate dehydrogenase and reduced nicotinamide adenine dinucleotide diaphorase activity, and to a lesser degree by glycogen content. All fibers stained strongly with the myosin adenosine triphosphatase reaction, the level of the activity being comparable to that in fast-twitch, mammalian limb muscles. The differences in features of location, size and histochemical reaction indicate that the rectus and oblique muscles in birds contain at least two types of fibers. The quadratus and pyramidalis muscles, which serve to advance the nictitating membrane, did not show segregation into zones of fibers, although in the pyramidalis two intermixed fibers were generally of larger size in the pyramidalis. Both fiber types stained darkly with myosin adenosine triphosphatase, suggesting that they were fast-twitch fibers.