Fimbriae (common pili) and flagella on the surface of bacterial cells. Left: dividing Shigella enclosed in fimbriae. The structures are probably involved in the bacterium's ability to adhere to the intestinal surface. Right: dividing pair of Salmonella displaying both its peritrichous flagella and its fimbriae.
Relaxin's peak is reached during the 14 weeks of the first trimester and at delivery. It is known to mediate the hemodynamic changes that occur during pregnancy, such as increased cardiac output, increased renal blood flow, and increased arterial compliance.
The hormone relaxin is the second explanation for low back pain. During pregnancy, the hormone relaxin is present in 10 times its normal concentration in the female body. Relaxin is good in the sense that its function â as you might guess from the name â is to relax the joints in the pelvis so the baby has room to pass through the birth canal. Unfortunately, relaxin also causes abnormal motion in many other joints of the body, causing inflammation and pain.