ON THE MODE OF CONNECTION OF THE VENTRAL EXTREMITY OF THE TENTH RIB / 解剖学报

ABSTRACT

The mode of connection of the ventral extremity of the tenth rib fails into two different categories, the floating and the costomarginal, as demonstrated by our studies on 100 consecutive Chinese adult cadavers (50 male, 50 female). Each category again consists of two varieties, i. e., the muscular and stripe types in the floating pattern and the fibrous and articular types in the costo-marginal pattern.The floating pattern occurs bilaterally in 72 cases (72.0?4.49％; 31 male, 41 female) and unilaterally in 12 cases (12.0?3.25％, 10 male, 2 female). It thus shows significantly greater frequencies than the costo-marginal pattern on either side, being more frequent in female cases. In those tenth ribs with anterior end not exceeding the anterior axillary line, the floating pattern amounts to 91.52％. It is also found that in the female the anterior ends of the bilaterally floating tenth ribs generally do not reach the anterior axillary line, and again in this pattern, those with the twelfth rib not palpable to the lateral border of the m. erector spinae arrive at 35.41％. The sternal (manubrium-body) length in the female bilaterally floating pattern has significant differences statistically between those with the twelfth ribs palpable and those without.The costo-marginal pattern accounts for 16 cases (16.0?3.67％; 9 male, 7 female) bilaterally and 12 cases (12.0?3.25％; 10 male, 2 female) unilaterally. The great majority is of the fibrous type, except two sides (1 male, 1 female) being the articular one. Most of the costo-marginal tenth rib have their anterior ends extending beyond the anterior axillary line; furthermore, the twelfth rib may always be touched to the lateral border of the m. erector spinae in this pattern.It is our opinion that the floating pattern may be treated as the normal mode of connection, its occurrence can be rooted to the phylogenetic and ontogenetic backgrounds as well as to the respiratory movements.