Female mammals give birth through the pelvis, a strong skeletal support structure of the lower limbs. At the bottom of the pelvis, two bones are joined together at the pubic symphysis. This is a cartilaginous joint that is relatively immovable. During birth, relaxin acts on this cartilaginous joint to allow the widening of the birth canal.
Figure 1. The Pelvic Girdle, with pubic symphsis labelled
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Relaxin is produced in granulocytes in the corpus lutueum. It has also been observed in several other places including the placenta, uterus and endometrium. Relaxin has also been found in the testes of some male animals. In males, the role of this hormone is not known. In females, the overall effect is a more flexible, wider birth canal.
Research suggests that relaxin works by cutting collagen and inducing its breakdown in the pubic symphysis. A synthetic form has been developed for the treatment of scleroderma (a connective tissue disease that causes the skin to become tight and thick).
Research suggests that relaxin works by cutting collagen and inducing its breakdown in the pubic symphysis. A synthetic form has been developed for the treatment of scleroderma (a connective tissue disease that causes the skin to become tight and thick).
References
1. Anderson LL, Bast JD, Melampy RM. Relaxin in ovarian tissue during different reproductive stages in the rat. J Endocrinol 59:371–372, 1973
2. Sherwood OD, Crnekovic VE, Gordon WL, Rutherford JE. Radio-immunoassay of relaxin throughout pregnancy and during parturition in the rat. Endocrinology 107:691–698, 1980.
3. Perl E, Catchpole HR, (1950). "Changes induced in the connective tissue of the pubic symphysis of the guinea pig with estrogen and relaxin", Arch Pathol (chic), 50(2): 233-239
