Anatomy of the lumbar spinal nerves, sacral and coccygeal nerves

The nerves of the lower back have this common property that some of them go to the muscles of the spine, and some to the abdominal muscles and to the muscles lining the spine, but the three upper nerves, unlike the others, merge with the nerves descending from the brain, and the two lower pairs send large branches towards the legs, and the branch from the third pair and the branch from the beginning of the nerve of the sacral bone merge with them. However, these two branches do not go further than the knee joint and diverge in its muscles, while other nerves bypass them and go to the legs.

The nerves of the thighs and legs differ from the nerves of the arms in that they do not all converge together, but deviate, going deeper inward, for the way of connecting the humerus with the shoulder blade is not the same as the way of connecting the shoulder with the thigh, and the connection of the arm with the place where the nerves begin is not the same. like the connection of the lyadvea with the beginning of its nerves. These nerves are directed towards the lower leg in different ways: some go along the inner side, others along the outer side, and others go deeper, being hidden under the muscles. Since there is no way for the nerves that grow from the side of the ilium to the legs from the back of the body and from the inner side of the thigh due to the numerous muscles and vessels located there, some of the nerves inherent in the muscles located in the legs are directed and sent into the duct descending to the testicles. They go to the muscles of the iliacus and then go down to the muscles of the knee.

The first pair of sacral nerves merges with the lumbar nerves, as has been said, and the remaining pairs and a single nerve coming from the end of the coccyx are divided in the muscles of the anus and the penis itself, as well as in the muscle of the bladder and uterus, in the lining of the abdominal cavity, in the internal parts pubic bone and in the muscles extending from the sacrum.