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Background: The inferior lumbar triangle of Petit is bounded by the iliac crest, lateral border of the latissimus dorsi and the medial border of the external oblique., Objectives: In the present study, we aimed to quantitatively examine the base, sides, area, and interior angles of the inferior lumbar triangle in the human fetus so as to provide their growth dynamics., Material and Methods: Using anatomical dissection, digital image analysis (NIS-Elements AR 3.0), and statistics (Student's t-test, regression analysis), we measured the base, 2 sides, area and interior angles of Petit's triangle in 35 fetuses of both sexes (16 male, 19 female) aged 14-24 weeks., Results: Neither sex nor laterality differences were found. All the parameters studied increased commensurately with age. The linear functions were computed as follows: y = -0.427 + 0.302 × age for base, y = 1.386 + 0.278 × age for medial side, y = 0.871 + 0.323 × age for lateral side, and y = -13.230 + 1.590 × age for area of the Petit triangle., Conclusions: In terms of geometry, Petit triangle reveals neither male-female nor right-left differences. An increase in both lengths and area of the inferior lumbar triangle follows proportionately. The Petit triangle is an acute one in the human fetus.

Background: The trapezius muscle consists of three parts that are capable of functioning independently. Its superior part together with the levator scapulae and rhomboids elevate the shoulder, the middle part retracts the scapula, while the inferior part lowers the shoulder., Objectives: The present study aimed to supplement numerical data and to provide growth dynamics of the trapezius in the human fetus., Material and Methods: Using methods of anatomical dissection, digital image analysis (NIS Elements AR 3.0), and statistics (Student's t-test, regression analysis), we measured the length, the width and the surface area of the trapezius in 30 fetuses of both sexes (13™ k,17™ … ) aged 13-19 weeks., Results: Neither sex nor laterality differences were found. All the studied parameters of the trapezius increased proportionately with age. The linear functions were computed as follows: y = -103.288 + 10.514 × age (r = 0.957) for total length of the trapezius muscle, y = -67.439 + 6.689 × age (r = 0.856) for length of its descending part, y = -8.493 + 1.033 × age (r = 0.53) for length of its transverse part, y = -27.545 + 2.802 × age (r = 0.791) for length of its ascending part, y = -19.970 + 2.505 × age (r = 0.875) for width of the trapezius muscle, and y = -2670.458 + 212.029 × age (r = 0.915) for its surface area., Conclusions: Neither sex nor laterality differences exist in the numerical data of the trapezius muscle in the human fetus. The descending part of trapezius is the longest, while its transverse part is the shortest. The growth dynamics of the fetal trapezius muscle follows proportionately.

Background: The triceps brachii muscle, the strongest extensor of the elbow joint, is characterized by the three heads: long, lateral and medial., Objectives: In the present study we aimed to examine the linear parameters (length, width) of the fetal triceps brachii muscle and to provide their growth dynamics., Material and Methods: Using anatomical dissection, digital image analysis (Multiscan v.14.02), and statistics (Student's t-test, regression analysis) we measured in mm the length and width of the triceps brachii in 30 fetuses of both sexes (12♂,18♀) aged 12-29 weeks., Results: Neither sex nor laterality differences were found. All the parameters studied increased proportionately with age. The linear functions were computed as follows: y = 6.797 + 2.079 x Age (r = 0.886) for length of the long head's belly, y = - 0.041 + 0.215 × Age (r = 0.786) for width of the long head's belly, y = 1.889 + 0.174 × Age (r = 0.796) for length of the long head's proximal tendon, y = 0.158 + 0.052 × Age (r = 0.864) for width of the long head's proximal tendon, y = 5.270 + 1.809 × Age (r = 0.855) for length of the lateral head's belly, y = 0.348 + 0.284 × A ge (r = 0.829) for width of the lateral head's belly, y = 0.942 + 1.837 × Age (r = 0.839) for length of the medial head's belly, y = 0.314 + 0.234 × Age (r = 0.852) for width of the medial head's belly, y = - 3.191 + 0.984 × Age (r = 0.929) for lenght of the common tendon, and y = - 0.478 + 0.133 × Age (r = 0.933) for width of the common tendon., Conclusions: Neither male-female nor right-left differences are observed in morphometric parameters of the triceps brachii muscle. The long head's belly is the thinnest, while the lateral head's belly is the widest one. The long head is the longest and the medial head is the shortest one. The developmental dynamics of the triceps brachii muscle follow proportionately.