Bifid Rib: Anatomical Considerations in Three Cases

The present study involved a detailed investigation of 3 cases of bifid rib, focusing on anatomical features, and classified them into 2 types. The bifid ribs were in the right fourth rib of all 3 male cadavers. The upper intercostal spaces of the fourth bifid rib were considerably narrowed, whereas the lower intercostal spaces were widened. Although the size and shape of the bifid space between the upper and lower divisions of the bifid rib were different, the intercostal muscles were present in the bifid space in all cases. The third anterior intercostal artery from the internal thoracic artery supplied the bifid space in all cases. In 2 cases, the fourth intercostal nerve ran along the inferior margin of the fourth bifid rib and innervated the muscles of the bifid space. In the third case, there was another branch from the third intercostal nerve supplying the muscles of the bifid space as well as the fourth intercostal nerve. The bifid ribs are associated with other diseases or develop accidentally or sporadically. Knowledge of this malformation is needed for the differential diagnosis with other diseases, such as a chest wall tumor or costal fracture.     

Mechanical effect of muscle spindles in the canine external intercostal muscles

High-frequency mechanical vibration of the ribcage increases afferent activity from external intercostal muscle spindles, but the effect of this procedure on the mechanical behaviour of the respiratory system is unknown. In the present study, we have measured the changes in external intercostal muscle length and the craniocaudal displacement of the ribs during ribcage vibration (40 Hz) in anaesthetized dogs. With vibration, external intercostal inspiratory activity increased by ∼50 %, but the respiratory changes in muscle length and rib displacement were unaltered. A similar response was obtained after the muscles in the caudal segments of the ribcage were sectioned and the caudally oriented force exerted by these muscles on the rib was removed, thus suggesting that activation of external intercostal muscle spindles by vibration generates little tension. Prompted by this observation, we also examined the role played by the external intercostal muscle spindles in determining the respiratory displacement of the ribs during breathing against high inspiratory airflow resistances. Although resistances consistently elicited prominent reflex increases in external intercostal inspiratory activity, the normal inspiratory cranial displacement of the ribs was reversed into an inspiratory caudal displacement. Also, this caudal rib displacement was essentially unchanged after section of the external intercostal muscles, whereas it was clearly enhanced after denervation of the parasternal intercostals. These findings indicate that stretch reflexes in external intercostal muscles confer insufficient tension on the muscles to significantly modify the mechanical behaviour of the respiratory system.     

A study on the communication between the pectoral nerve and the extramural nerve branches of the intercostal nerves]

Kumaki et al. (1979) defined the extramural nerve as the rudimentary sensory nerve which appeared on the upper thoracic wall; it branched off the root of the lateral cutaneous nerve of the second, third or fourth intercostal nerve, ran inferomedially adhering to the fascia of the intercostalis externus muscle and ended supplying the membrane covering the adjacent rib. They also stated that the extramural nerve (Rxm) occasionally became a cutaneous nerve which pierced the pectoralis muscles and supplied the skin covering the thoracic wall similar to the lateral cutaneous nerve (Rcl) or the anterior cutaneous nerve (Rca). Further, they proposed that the muscular nerves to the obliquus externus abdominis muscle which are usually situated below the fifth rib might be considered a part of this Rxm series. Although the definition of Rxm is still not widely accepted, Rxm is thought to be a key morphological factor influencing the variations of peripheral nerve arrangement on the thoracic wall. In the student course of gross anatomy dissection at Iwate Medical University School of Medicine during the years 1987-1991, three cases of Rxm communicating with the pectoral nerve and supplying the pectoralis major muscle were observed. Some cases have been reported in which Rcl innervates part of the pectoral muscles. However, the communication between the pectoral nerve and Rxm has not yet been discussed. Therefore, to clarify the morphological significance of the communication between Rxm and the pectoral nerve, the branching pattern and the distribution of the pectoral nerves were extensively investigated and the intramuscular nerve supply of some pectoral nerves, especially the pectoral nerves which communicated with Rxm, was examined in detail under a stereomicroscope. The results are summarized as follows: 1. In the first case, Rxm of the second intercostal nerve originated from Rcl, ran inferomedially adhering to the fascia of the intercostalis externus muscle and pierced the origin of the pectoralis minor muscle at the third intercostal space. Then Rxm turned superolaterally to communicate with a pectoral nerve which originated from the loop composed of the lateral and medial pectoral nerves and passed inferior to the pectoralis minor muscle. After communication, the pectoral nerve with Rxm supplied the caudalmost part of the sternocostal portion of the pectoralis major muscle. In the second case, a similar branch of Rxm of the second intercostal nerve passed inferior to the pectoralis minor muscle.(ABSTRACT TRUNCATED AT 400 WORDS)     

Nerve supply to and the true nature of anterior supracostal muscle: three cases of the anterior supracostal muscle innervated by the external muscular branch of the first intercostal nerve having lateral cutaneous branch

316 body-halves were examined in order to clarify nerve supply to human anterior supracostal muscle and to reveal the true nature of this particular muscle. 14 body-halves were found to have this muscle. It was innervated by the external muscular branch of the first intercostal nerve having lateral cutaneous branch in 3 out of 14 cases, and by the external muscular branch of the first intercostal nerve lacking lateral cutaneous branch in the remaining 11. As the former 3 cases have not been reported yet, we have examined the anatomy of these muscles in detail, and nerve supply to the anterior supracostal muscle and the true nature of this muscle were discussed in the present study. As a result, it was found that the anterior supracostal muscle is innervated essentially by an element of the components of the external muscular branch, and the muscle is derived from the first external intercostal muscle or rarely from the first and second external intercostal muscles. Moreover, it was inferred that the frequency of occurrence of the anterior supracostal muscle innervated by the intercostal nerve having lateral cutaneous branch is very low.     

犬肋骨肌瓣的应用解剖与气管成型及气管再造的实验研究

目的：对犬肋骨肌瓣与肌瓣环进行解剖学观察,并以此组织瓣进行气管成型与气管再造动物实验。方法：将犬的第３肋间血管灌注后观察其分布情况。将第３肋骨民上下肋间肌修整成带肌瓣蒂的肋骨瓣、骨肌瓣环,分别行胸内气管成型与环形替代术。结果：犬的肋骨肌瓣、瓣环血供均良好。第３肋间动脉、静有多个分支在胸腊民骨膜之间上行分布玩具闰肋间肌。实验获得满意效果,气管成型手术的犬与非手术犬一样正常活动。气管再造的１８条犬中１     

Scalenus muscles in macaque monkeys

The attachment and innervation of the scalenus muscles in both sides of two Japanese monkeys and a rhesus monkey were observed to discuss their morphological significance while comparing their findings in humans. The scalenus ventralis muscle in macaques had almost the same attachments as the scalenus anterior muscle in humans and was innervated by the cervical nerve branches, which were lower in spinal segment than in humans and had a close relationship with the branches to the intertransversus ventralis muscles. Furthermore, the scalenus ventralis muscle was penetrated by the phrenic nerve in all cases observed. The posterior part of the scalenus muscle in macaques (the scalenus dorsalis muscle) was divided into short (the scalenus dorsalis brevis) and long (the scalenus dorsalis longus) parts according to their attachments. The former was attached to the transverse processes of the lowest two cervical vertebrae and the first rib, whereas the latter was attached to the 3rd-5th ribs. It is notable that the scalenus dorsalis muscles in macaques were innervated by branches from the long thoracic nerve in addition to direct branches from the cervical nerve roots. In addition, the scalenus dorsalis longus was supplied by twigs from the lateral cutaneous branches of the 2nd and 3rd intercostal nerves. This indicates that the scalenus dorsalis muscles contain a muscular component derived from the upper limb girdle musculature, unlike the human scalenus muscles, which have been considered to belong to the cervical trunk muscles.     

Coupling between the ribs and the lung in dogs

In contrast to the conventional theory, the external and internal intercostal muscles show marked rostrocaudal gradients in their actions on the lung. We hypothesized that these gradients are the result of a non-uniform coupling between the ribs and the lung. Rib displacements ( X _r) and the changes in airway opening pressure ( P _a,o) were thus measured in anaesthetized, pancuronium-treated, supine dogs while loads were applied in the cranial direction to individual pairs of odd-numbered ribs and in the caudal direction to individual pairs of even-numbered ribs. During cranial loading, X _r induced by a given load increased gradually with increasing rib number. The decrease in P _a,o also increased from the third to the fifth rib pair but then decreased markedly to the eleventh pair. A similar pattern was observed during caudal loading, although X _r and Δ P _a,o were smaller. These results were then combined to calculate the net X _r and the net Δ P _a,o that a hypothetical intercostal muscle lying parallel to the longitudinal body axis would produce in different interspaces. The net X _r was cranial in all interspaces. However, whereas the net Δ P _a,o was negative in the cranial interspaces, it was positive in the caudal interspaces. These observations confirm that the coupling between the ribs and the lung varies from the top to the base of the ribcage. This coupling confers to both the external and the internal intercostal muscles an inspiratory action on the lung in the cranial interspaces and an expiratory action in the caudal interspaces.     

犬肋骨膜肌瓣食管成型术的应用解剖及实验研究

目的：为带血供的骨膜肋间肌瓣食管成型术提供解剖学和形态学基础。方法：取１０条犬的肋骨膜肌瓣标本,将其上的第７肋间血管灌注后观察分布情况。手术先切除部分第７肋骨,然后将保留的骨膜和上下肋间肌修整成一个带血管蒂的骨膜肌瓣。瓣上８．５～１２．５ｃｍ,宽４．５ｃｍ,以此肌瓣修复１／２直径４ｃｍ长的食管缺损。结果：带蒂的骨膜肌瓣由肋间动脉的两条主干分支供血,具有良好的血运。尽管处死犬检查手术修复部位轻度狭窄     

前锯肌间隙阻滞的解剖学观察及其临床意义

目的　观察测量前锯肌间隙美兰溶液扩散范围及神经分布, 为该间隙神经阻滞提供解剖学依据。 方法　选用4具尸体,应用超声引导技术,采用Blanco穿刺入路,在胸壁两侧腋中线4、5肋间,注入含美兰染料的液体（0.4 ml/kg）至前锯肌间隙,约10 min后逐层分离至该间隙,观察美兰液体的扩散范围、染料沉积后界限以及该范围内的神经分布。 结果　观察8侧前锯肌,逐层掀开胸大肌和胸小肌后,清晰显露前锯肌间隙的蓝染区域及区域内蓝染的2~6肋间神经的外侧皮支、胸长神经和胸背神经。中位数M(P25, P75)描述8个前锯肌筋膜间隙注射扩散范围测量结果,腋前线11.35（10.45,12.15）cm,腋中线12.6(12.12,13.15)cm,腋后线11.1(10.70,12.05)cm,平乳头线9.8(9.12,10.65)cm。头侧扩散至第2肋腋前线占75%,腋中线占87.5%,腋后线占87.5%;扩散至第3肋腋前线占25%,腋中线占12.5%,腋后线占12.5%。 结论　前锯肌间隙美兰溶液扩散范围解剖测量研究提示临床应用此方法进行前锯肌间隙神经阻滞,可阻滞前锯肌间隙内的2~6肋间神经外侧皮支、胸长神经和胸背神经,满足胸前外侧壁手术的麻醉和镇痛。     

The individuality of chest wall motion in tetraplegia

We have studied the motion of the chest wall in eight supine tetraplegic subjects using optical contour mapping. Measurements were obtained during quiet breathing, exaggerated breathing, during the course of a deep inspiration and during static inspiratory efforts. The pattern of motion showed a high degree of individual variability which did not appear to be related to the age of the patient, the duration of injury or the presence of intercostal muscle spasticity. By contrast, it did appear to be related to the presence of bony rib cage stiffness, and possibly the action of the neck accessory muscles. The pattern of rib cage motion in tetraplegia is more complex than conventionally thought.     

Postnatal development of parvalbumin immunoreactivity in striated muscles of the rat

The presence of parvalbumin, a calcium-binding protein, has been correlated with the maturation of locomotor activity in developing striated muscle. In the present study, postnatal parvalbumin immunoreactivity is examined in the tibialis anterior, intercostal, diaphragm and intrinsic muscles of the tongue of the rat to gather a better understanding of the different developmental patterns. Parvalbumin immunoreactivity appears in the anterior tibialis muscle by day 4, and reaches an adult checkerboard pattern 2 days later. In contrast, parvalbumin immunoreactivity in the intrinsic muscles of the tongue, and in diaphragm and intercostal muscles, which are active near birth, does not appear until the 2nd week. Therefore, these features suggest that parvalbumin immunoreaction is not exclusively dependent on functional activity. In addition, the finding that differences in parvalbumin expression do not correlate in time with the differentiation of fiber types as judged by myosin ATPase activity, suggests that myosin and parvalbumin might be regulated by different mechanisms.     

Do segmental reflexes play a role in the distribution of external intercostal EMG activity in the rabbit?

External intercostal muscle is considered as an inspiratory muscle. Its electromyographic (EMG) activity is exquisitely sensitive to proprioceptive afferents and is predominant in zones with the greatest respiratory effect. In the current series of studies, we assessed the contribution of segmental reflexes to this particular distribution of activity in anesthetized rabbits. We first established a parallel between gradients of activity and mechanical advantage. The sensitivity of external intercostal EMG activity to rib displacement was then assessed in the 3rd and 5th interspaces and in the dorsal, middle and ventral muscle bundles of the 3rd interspace. Finally, persistence of the dorso-ventral gradient was tested after a dorsal rhizotomy (interspaces 3-5). There were no differences in the sensitivity to rib motion in the studied positions. After rhizotomy, the dorso-ventral gradient of activity persisted at rest and with inspiratory resistive loading. We, therefore, conclude that the neuromechanical matching of respiratory drive in the external intercostal muscles is not the result of segmental reflexes.     

A Taiwanese with a pair of sternalis muscles.

A pair of sternalis muscles have been found on both sides of the chest in an adult Taiwanese male. The muscles are located superficial to the medial part of the pectoralis major, arising from the sternum and are inserted into the sheaths of the rectus abdominis. They are innervated by the intercostal nerve. It should be emphasized that the sternalis muscle is rarely found in Taiwan.     

腹前外侧群肌的肌内神经分布模式

目的 揭示腹前外侧群肌的肌内神经分布模式,探讨其临床意义。 方法 取经甲醛固定的12具24侧中国成年尸体的腹前外侧群肌,行改良的Sihler染色。 结果 腹前外侧群肌的神经绝大多数源于节段性分布的胸神经。腹外斜肌各肌齿有独立的神经支配,在髂前上棘和髂结节之间的髂嵴上方有一纵向神经密集带。腹内斜肌腹股沟韧带中点上方有一纵向神经密集带,髂嵴上方有一横向神经密集带。腹横肌髂前上棘与第8、9肋软骨连结处之间有一弧形的神经密集带。腹直肌各肌腹中部有一横向神经密集带,上3个肌腹有独立神经支配。 结论 腹外斜肌和腹直肌可分出神经肌肉亚部;各肌内的神经密集带应被考虑为肉毒毒素A注射和局部麻醉的最佳靶点部位,不宜设为腹壁手术的切口部位。     

Breathing power of respiratory muscles in single-lung transplanted emphysematic patients

Single-lung transplantation may induce asynchronous performance between the respiratory muscles of the chest. The objective of this study was to investigate the influence of a single transplanted lung on respiratory muscle mechanics. The force and power of the sternomastoid, external intercostal and external oblique muscles were evaluated throughout a range of respiratory maneuvers in emphysematic patients with a single transplanted lung and compared with that of healthy subjects. A significant differences was observed between the force, work and power of the muscles on the two sides of the chest in emphysematic patients (P<0.05). The control group demonstrated higher averaged maximal force, work and power. The total work done during either inspiration or expiration by the external intercostal and external oblique muscles on the side of the transplanted lung were higher compared with that of the native lung side and compared with the control group. The asynchrony between the lungs after single-lung transplant leads to asynchronous muscle force and work and lesser muscle strength compared to healthy subjects.     

Are the external and internal intercostal muscles synergist or antagonist in the cat?

The electrical activity of the external and internal intercostal muscles was recorded in decerebrated cats during eupnea and in the course of dyspnoea artificially induced to reinforce the inspiratory or expiratory central drive. In the cephalic part of the thorax (1st-5th ribs) the lateral part of the external and internal intercostal muscles are synergist and inspiratory. In the caudal part of the thorax (9th-13th ribs) these muscles are also synergist but expiratory. In the intermediate part (5th-9th ribs) the intercostal muscles are antagonist, the external ones are inspiratory and the internal ones are expiratory.     

The human musculus obliquus externus abdominis innervated by ramus muscularis externus of intercostal nerves

Each of the uppermost slips of the bilateral M. obliquus externus abdominis originated from the fifth rib and was innervated from its inner surface by the Ramus muscularis externus of the fifth intercostal nerve, in one corpse. Furthermore, the slip originating from the sixth rib of the right M. obliquus externus abdominis was innervated not only by the lateral cutaneous branches of the sixth and seventh intercostal nerves from its outer surface, but also by the Ramus muscularis externus of the sixth intercostal nerve from its inner surface. The slip originating from the fifth rib was given us an aspect in appearance as if it were the uppermost slip of origin of this muscle, but its true nature is considered to be the M. obliquus abdominis externus profundus from the viewpoint of its innervating nerve and pattern. In addition, the slip originating from the sixth rib is considered to be a substance formed by the dorsal adhesion of the M. obliquus abdominis externus profundus originating from the sixth rib to the slip of the M. obliquus externus abdominis originating from the same rib.