Josep Nebot-Cegarra

Biceps brachii muscle attached to the extensor carpi radialis brevis muscle: an unreported anatomical variation in humans.

We report a new muscular variation in humans. It consisted of a biceps brachii muscle attached to the extensor carpi radialis brevis muscle by means of an accessory fasciculus. It was a trapezoid tendinous connection band that arose from the terminal tendon of the biceps brachii muscle and ended in the internal margin of the extensor carpi radialis brevis muscle. This intermuscular connection band was the external slip of the insertion tendon of the biceps brachii muscle, which was also attached by means of two other fascicles to the radial tuberosity (intermediate slip) and the flexor digitorum superficialis muscle (internal slip). This variation was observed in only one of the sixty upper limbs examined.

Factors involved in the ‘rotation’ of the human embryonic stomach around its longitudinal axis: computer-assisted morphometric analysis

The majority of studies as to whether gastric and nongastric factors are involved in the ‘rotation’ of the human embryonic stomach around its longitudinal axis have been morphological. The aim of this study was to analyse, with morphometric support, the influence on the angular modifications during gastric rotation of the simultaneous changes of the gastric walls and mesenteric growth, and the volumes of organs adjacent to the stomach (right, left and posterior groups). Computer imaging techniques were applied on cross sections of a graded series of 10 human embryos (from Carnegie stage (CS) 11) and 2 fetuses. A clockwise gastric rotation occurred during the embryonic period. The most rapid angular modifications took place from CS 11 to 16, after the rotation became oscillatory with angular changes in clockwise and anticlockwise directions, reaching the highest value at CS 18 (at the supraomental part of the stomach: 54.37°; at the omental part: 68.03°); after this period the angular values tended to stabilise. The predominant growth of the left gastric wall over the right and the changes in the width of the gastric mesentery were the most persistent factors involved in the modifications of the transverse gastric angle during the embryonic period although without relationship to their direction. During the increasing angular phases, clockwise rotation was promoted by the decrease of the volume of any group of organs adjacent to the stomach. When the volume of the left and posterior groups increased simultaneously, clockwise or anticlockwise angular directional change was related to the respective decrease or increase adjacent organ volume to the right. We conclude that the stomach of the human embryo undergoes heterogeneous and multifactorial rotation as a consequence of the overall increase in gastric wall growth to the left and the increase of gastric mobility produced by the previous mesenteric enlargement, and that the rotational direction results from the forces exerted on the stomach and the gastric mesenteries by the adjacent organs.

Cellular proliferation in the urorectal septation complex of the human embryo at Carnegie stages 13-18 : a nuclear area-based morphometric analysis

In order to analyse the patterns of cellular proliferation both in the mesenchyme of the urorectal septum (URS) and in the adjacent territories (posterior urogenital mesenchyme, anterior intestinal mesenchyme and cloacal folds mesenchyme), as well as their contribution to the process of cloacal division, a computer‐assisted method was used to obtain the nuclear area of 3874 mesenchymal cells from camera lucida drawings of nuclear contours of selected sections of human embryos [Carnegie stages (CSs) 13–18]. Based on changes in the size of the nucleus during the cellular cycle, we considered proliferating cells in each territory to be those with a nuclear area over the 75th percentile. The URS showed increasing cell proliferation, with proliferation patterns that coincided closely with cloacal folds mesenchyme, and with less overall proliferation than urogenital and intestinal mesenchymes. Furthermore, at CS 18, we observed the beginning of the rupture in the cloacal membrane; however, no fusion has been demonstrated either between the URS and the cloacal membrane or between the cloacal folds. The results suggest that cloacal division depends on a morphogenetic complex where the URS adjacent territories could determine septal displacement at the time that their mesenchymes could be partially incorporated within the proliferating URS.

Accessory fasciculi of the human pronator teres muscle: Incidence, morphological characteristics and relation to the median nerve

The purpose of this study is to determine the incidence of the accessory fasciculi of the pronator teres muscle and to evaluate the predispositional role of its morphological characteristics to median nerve entrapment. The accessory fasciculi of the pronator teres muscle have been found in 8.3% of 60 upper extremities which were studied. These fasciculi arose from the tendon of the brachialis muscle (5.0%), from the radial tendon of the biceps brachii muscle (3.3%), from the Gantzers muscle (1.6%) or from the flexor digitorum superficialis muscle (1.6%). They were slips of origin of the deep head of the pronator teres muscle. They represented the deep head, when there was no other origin slip, or they were additional origin slips when the deep head also had a coronoid origin. Only the accessory fasciculi that represented the deep head and the accessory fasciculi located inside to the coronoid fasciculus were related directly to the median nerve. Three characteristics of these accessory fasciculi adjacent to the median nerve could be considered to be factors that predispose to the nerve entrapment: 1) the location dorsal to the superficial head of the pronator teres muscle, because it increases the area of contact with the median nerve; 2) the location between the superficial head and the coronoid fasciculus, because it reduces the space occupied by the median nerve; and 3) the tendinous nature of considerable segments of short accessory fasciculi because they are less extensible.